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Blood work decoded · specialized markers
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In one pass A routine checkup measures blood lipids, glucose, liver enzymes and kidney function: the body's big board.
Educational content, not medical advice — consult a clinician.
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Chapter 1
Six markers beyond the routine
A routine checkup measures blood lipids, glucose, liver enzymes and kidney function: the body's big board. Some markers are not in the routine package, yet they often explain why the big board looks the way it does.
This story covers six: the butterfly-shaped thyroid gland at the front of the neck, the hormones made by the sex glands, the vitamin D your skin makes in sunlight, the store of iron kept in the liver, a way station on the route of protein metabolism, and a protein the liver makes in a hurry when there is inflammation.
They have two things in common.
First, they cross-check the big board. When the thyroid slows down, cholesterol and creep up. When insulin stays high for a long time, the liver makes less of the protein that binds testosterone. When iron runs low, the marker of long-term blood glucose reads falsely high and makes you think your glucose metabolism is in trouble.
Second, they depend more on context. The same number means different things at 30 and at 75. The same total testosterone, paired with a high or a low level of that binding protein, can mean very different amounts actually able to enter cells.
The rules for reading them are the same as for a routine checkup: an arrow is not a verdict, patterns matter more than single values, trends matter more than snapshots, and nutrition is the foundation, not a replacement for medical care.
This story covers six: the butterfly-shaped thyroid gland at the front of the neck, the hormones made by the sex glands, the vitamin D your skin makes in sunlight, the store of iron kept in the liver, a way station on the route of protein metabolism, and a protein the liver makes in a hurry when there is inflammation.
They have two things in common.
First, they cross-check the big board. When the thyroid slows down, cholesterol and creep up. When insulin stays high for a long time, the liver makes less of the protein that binds testosterone. When iron runs low, the marker of long-term blood glucose reads falsely high and makes you think your glucose metabolism is in trouble.
Second, they depend more on context. The same number means different things at 30 and at 75. The same total testosterone, paired with a high or a low level of that binding protein, can mean very different amounts actually able to enter cells.
The rules for reading them are the same as for a routine checkup: an arrow is not a verdict, patterns matter more than single values, trends matter more than snapshots, and nutrition is the foundation, not a replacement for medical care.
Background · What these markers are called on the report
These are the names you will see on the report:Thyroid function: (thyroid-stimulating hormone), (free T4, free thyroxine), (free T3, free triiodothyronine), TPOAb (thyroid peroxidase antibody)Sex hormones: total testosterone, (sex hormone-binding globulin), , and and (two hormones from the pituitary that drive the sex glands)Vitamin D: (25-hydroxyvitamin D)Iron stores: and transferrin saturation (TSAT): sometimes printed as HcyInflammation: (high-sensitivity C-reactive protein)
Three examples of how they cross-check routine chemistry. A raised TSH (subclinical hypothyroidism) by itself pushes up cholesterol and and worsens (an estimate of insulin resistance from fasting glucose and insulin). A low SHBG is both a result of insulin resistance and something that changes how free testosterone and estradiol should be read. A low ferritin makes (glycated hemoglobin, a reflection of average blood glucose over two to three months) read falsely high, so you may think your blood glucose is the problem. These markers are not isolated; they are closely tied to the string of metabolic markers in a routine checkup: lipids, glucose and liver enzymes.
Why their reading depends more on context: a TSH of 4.5 means different things in a 30-year-old and a 75-year-old; a total testosterone of 450 ng/dL gives very different free testosterone depending on whether SHBG is high or low; a ferritin of 40 means different things in men and in women.
Chapter 2
Reading thyroid tests
The thyroid sits at the front of your neck, shaped like a butterfly. The hormone it makes is the body's throttle: how fast cells burn fuel, how fast the heart beats, how warm you are all follow its lead.
This is the point most often read backwards: is not made by the thyroid; it is the pituitary shouting. The pituitary keeps tasting whether there is enough thyroid hormone in the blood. If there is not, it shouts TSH louder to push the thyroid to work harder. So when the thyroid slacks, TSH is high: a high TSH usually means hypothyroidism, not hyperthyroidism. The other way round, when the thyroid runs out of control and pours out hormone, the pituitary goes quiet and TSH falls very low.
The thyroid mostly makes (thyroxine), the storage form. In the tissues it loses one iodine atom and becomes (triiodothyronine), the form that does the work. So TSH has to be read together with free T4 and T3 to tell which situation you are in.
When to see a doctor: TSH > 10 (treatment to be considered); TSH > 20 or < 0.01 (clearly abnormal); symptoms of an overactive thyroid (palpitations, weight loss, feeling too hot); pregnancy or planning a pregnancy (TSH targets are stricter); thyroid nodules (see Thyroid Nodules).
This is the point most often read backwards: is not made by the thyroid; it is the pituitary shouting. The pituitary keeps tasting whether there is enough thyroid hormone in the blood. If there is not, it shouts TSH louder to push the thyroid to work harder. So when the thyroid slacks, TSH is high: a high TSH usually means hypothyroidism, not hyperthyroidism. The other way round, when the thyroid runs out of control and pours out hormone, the pituitary goes quiet and TSH falls very low.
The thyroid mostly makes (thyroxine), the storage form. In the tissues it loses one iodine atom and becomes (triiodothyronine), the form that does the work. So TSH has to be read together with free T4 and T3 to tell which situation you are in.
When to see a doctor: TSH > 10 (treatment to be considered); TSH > 20 or < 0.01 (clearly abnormal); symptoms of an overactive thyroid (palpitations, weight loss, feeling too hot); pregnancy or planning a pregnancy (TSH targets are stricter); thyroid nodules (see Thyroid Nodules).
Clinical · Four patterns of TSH and FT4
(thyroid-stimulating hormone): 0.4–4.0 mIU/L is the usual range (some labs use 0.5–5.0). The four patterns:High TSH, low : primary hypothyroidism (the thyroid is slacking and the pituitary is shouting)High TSH, normal FT4: subclinical hypothyroidism (the thyroid is straining but still coping)Low TSH, high FT4 or : hyperthyroidism (the thyroid is out of control and the pituitary has gone quiet)Low TSH, normal FT4: subclinical hyperthyroidism
FT4 (free thyroxine): 0.8–1.8 ng/dL (10–23 pmol/L). It reflects the storage hormone the thyroid releases.
FT3 (free triiodothyronine): 2.3–4.2 pg/mL (3.5–6.5 pmol/L). This is the active form, made when tissues convert T4.
TPOAb (thyroid peroxidase antibody): about 90% of people with Hashimoto's thyroiditis (the most common cause of autoimmune hypothyroidism) test positive for it. Read it the other way round with care: a positive antibody does not mean you already have hypothyroidism. Among people who are TPOAb-positive with a normal TSH, about 2–5% a year progress to clinical hypothyroidism.
Key pitfalls:
Whether to treat a TSH between 4.5 and 10 (subclinical hypothyroidism) is debated. The gist of the 2014 American Thyroid Association (ATA) guideline: consider levothyroxine if TSH is > 10, or if there are symptoms, an enlarged thyroid or abnormal blood lipids; if TSH is < 10 and there are no symptoms, watching first is reasonable.Hypothyroidism itself raises cholesterol and . If your blood lipids are high, check TSH first to rule out this secondary form of lipid disorder.Pregnancy, acute illness and some drugs (glucocorticoids, dopamine) can temporarily suppress TSH, so do not make a diagnosis in those situations.
In practice · What nutrition can do for the thyroid
What nutrition can do:Iodine: 150 µg a day for adults; 220 µg in pregnancy, which is the US recommended amount (the World Health Organization gives about 250 µg for pregnancy). Do not overdo iodine; too much also disturbs the thyroid.Selenium: 100–200 µg a day may help in Hashimoto's thyroiditis. Toulis 2010's found that TPOAb fell after selenium; but the antibody is a , and whether its fall translates into better thyroid function or symptoms is not clear.Iron: iron deficiency impairs the making of thyroid hormone.Zinc: also takes part in thyroid-hormone metabolism.
The premise to keep in mind: these nutrients hold things back when they are lacking; they do not make things better when you add more. For people who are not deficient, there is no evidence that extra supplements help.
Chapter 3
Why free hormone levels matter
The biggest pitfall in reading sex hormones is looking only at total testosterone.
Almost all the testosterone in blood travels held by proteins. About six-tenths is bound to a protein called (sex hormone-binding globulin), nearly four-tenths hangs loosely on albumin, and only about 2% floats free. And only that free sliver can get into cells and do its job. So two people with the same total testosterone, one with a high SHBG and one with a low SHBG, can have very different amounts actually working.
SHBG is made by the liver, and insulin that stays high for a long time holds back the liver's production of SHBG. That is why people with insulin resistance or fatty liver often have a low SHBG, and this thread ties sex hormones to the metabolic markers of a routine checkup.
One safety note: do not start testosterone replacement on your own. Testosterone from outside shuts down your own production and can cause infertility.
When to see a doctor: total testosterone < 200 ng/dL with symptoms; infrequent or absent periods in women together with signs of excess androgen (extra hair growth, acne, hair loss); suspected polycystic ovary syndrome (); erectile dysfunction with low testosterone.
Almost all the testosterone in blood travels held by proteins. About six-tenths is bound to a protein called (sex hormone-binding globulin), nearly four-tenths hangs loosely on albumin, and only about 2% floats free. And only that free sliver can get into cells and do its job. So two people with the same total testosterone, one with a high SHBG and one with a low SHBG, can have very different amounts actually working.
SHBG is made by the liver, and insulin that stays high for a long time holds back the liver's production of SHBG. That is why people with insulin resistance or fatty liver often have a low SHBG, and this thread ties sex hormones to the metabolic markers of a routine checkup.
One safety note: do not start testosterone replacement on your own. Testosterone from outside shuts down your own production and can cause infertility.
When to see a doctor: total testosterone < 200 ng/dL with symptoms; infrequent or absent periods in women together with signs of excess androgen (extra hair growth, acne, hair loss); suspected polycystic ovary syndrome (); erectile dysfunction with low testosterone.
Numbers · Reading a sex-hormone panel line by line
Total testosterone: men 300–1200 ng/dL (10–42 nmol/L); women 20–75 ng/dL. Of total testosterone, 98% is bound to protein: about 60% to and 38% to albumin. Only about 2% is free testosterone, and free testosterone is the form that can enter cells and act.SHBG (sex hormone-binding globulin): 20–60 nmol/L. A high SHBG means low free testosterone (even when the total is normal); a low SHBG means a higher free share. The other way round, a low SHBG is independently associated with insulin resistance in the liver and with metabolic dysfunction-associated steatotic liver disease, (formerly NAFLD; the studies used the old definition of the time): one study observed that men with a low SHBG had about 4 times the risk of developing type 2 diabetes within 5 years. This is an observed association and does not show that a low SHBG causes it.
What changes SHBG:
Lowers it: insulin resistance, fatty liver, obesity, hypothyroidism, glucocorticoids, growth hormoneRaises it: estrogen, pregnancy, oral contraceptives, hyperthyroidism, cirrhosis of the liver, weight loss
: men 10–40 pg/mL; in women it varies across the menstrual cycle (follicular phase 30–100, around ovulation 100–400, luteal phase 50–200 pg/mL), and after menopause it is < 30. In men, estradiol is made mainly from testosterone by the enzyme aromatase, and fat tissue has more of that enzyme (the review by Kelly and Jones 2015).
and : men 3–15 and 5–15 mIU/mL; in women they vary with the cycle, and after menopause they are > 30–40. An LH-to-FSH ratio > 2–3:1 is seen in some people with polycystic ovary syndrome, but it is not part of the diagnostic criteria, and a normal ratio does not rule the condition out.
Late-onset hypogonadism in men (often called male menopause): diagnosis is usually considered only with total testosterone < 300 ng/dL and free testosterone < 65 pg/mL together with symptoms (lower sex drive, fewer morning erections, fatigue, low mood, reduced strength); the cut-offs differ slightly between professional societies. Low numbers without symptoms do not necessarily need treatment. Sleep moves this number too: in a small trial of 10 healthy young men, one week of only 5 hours of sleep a night (compared with 8 hours) lowered daytime testosterone by 10–15% (Leproult 2011).
In practice · What nutrition can do for sex hormones
If is low and there is insulin resistance: improve insulin sensitivity first. That gets closer to the root than boosting testosterone.If total testosterone is low but SHBG is high: free testosterone may be normal, and treatment is not necessarily needed.Zinc deficiency affects testosterone. Prasad 1996 was a very small before-and-after study: when young men's zinc intake was restricted, their testosterone fell clearly, and when older men who were mildly zinc-deficient were given zinc, it rose again. It had no control group, and it shows that making testosterone needs zinc, not that extra zinc raises testosterone in people who already have enough.Low vitamin D may be linked with low testosterone, but the evidence is inconsistent.Sleep 7–9 hours, do strength training, and keep body fat in a moderate range (both too little and too much lower testosterone).Chapter 4
Which vitamin D test to read
Vitamin D is not really a vitamin but the precursor of a hormone, and most of it is not eaten; you make it yourself.
Ultraviolet light striking the skin breaks open a cholesterol-derived molecule in it and turns it into vitamin . The blood carries it to the liver, which attaches a hydroxyl group and makes 25-hydroxyvitamin D, the form the lab test measures. It stays in the blood for weeks (a half-life of about 15 days), so it reflects your status over a period of time, not how long you were in the sun today. Finally the kidney attaches a second hydroxyl group and makes the active form that does the work.
Two things follow that are often confused:
To check vitamin D, test the 25-hydroxy form, not the active one. The active form stays in the blood for only hours, is pushed around by parathyroid hormone and blood calcium, and can even rise when vitamin D is lacking.The farther from the equator, the less you can make in winter. North of 35 degrees latitude, from November to February the sun is too low in the sky and the skin makes almost no vitamin D.
When to see a doctor: < 10 ng/mL (severe deficiency); > 100 (toxicity); osteoporosis or repeated fractures; chronic kidney disease; poor absorption (celiac disease, inflammatory bowel disease, after weight-loss surgery).
Ultraviolet light striking the skin breaks open a cholesterol-derived molecule in it and turns it into vitamin . The blood carries it to the liver, which attaches a hydroxyl group and makes 25-hydroxyvitamin D, the form the lab test measures. It stays in the blood for weeks (a half-life of about 15 days), so it reflects your status over a period of time, not how long you were in the sun today. Finally the kidney attaches a second hydroxyl group and makes the active form that does the work.
Two things follow that are often confused:
To check vitamin D, test the 25-hydroxy form, not the active one. The active form stays in the blood for only hours, is pushed around by parathyroid hormone and blood calcium, and can even rise when vitamin D is lacking.The farther from the equator, the less you can make in winter. North of 35 degrees latitude, from November to February the sun is too low in the sky and the skin makes almost no vitamin D.
When to see a doctor: < 10 ng/mL (severe deficiency); > 100 (toxicity); osteoporosis or repeated fractures; chronic kidney disease; poor absorption (celiac disease, inflammatory bowel disease, after weight-loss surgery).
Numbers · Cutoffs, the active form and a big trial
Reference values (the tiers of the US National Institutes of Health Office of Dietary Supplements, NIH ODS):< 12 ng/mL (30 nmol/L): deficient12–20 ng/mL (30–50 nmol/L): possibly inadequate for some people≥ 20 ng/mL (50 nmol/L): adequate for most people> 50 ng/mL (125 nmol/L): starting to be linked with potential adverse effects> 100 ng/mL (250 nmol/L): potential toxicity
Some lab reports still use the Endocrine Society's line of 30 ng/mL (75 nmol/L) for sufficiency. The US Institute of Medicine (IOM) holds that 20 ng/mL (50 nmol/L) is enough for most people and that 30 ng/mL is not a target everyone needs to reach.
About the active form: the active form made in the kidney is called 1,25(OH)₂D (calcitriol). It should not be used to judge vitamin D status. Its half-life is measured in hours (often given as 4–6 hours; Jones 2008 gives about 15 hours; either way far shorter than the roughly 15 days of the 25-hydroxy form), it is regulated by parathyroid hormone and calcium, and it can even rise when vitamin D is lacking (secondary hyperparathyroidism).
What nutrition can do:
Deficient or inadequate: vitamin (cholecalciferol) works better and lasts longer than D2. A common maintenance dose is 1000–2000 a day; with a deficiency, 2000–4000 IU a day and a recheck after 8–12 weeks, with the exact dose set by a doctor.Food sources are limited: fatty fish (salmon, mackerel, sardines), fortified foods, egg yolks.Magnesium takes part in vitamin D metabolism (both the 25-hydroxylation and the 1-alpha-hydroxylation steps need magnesium as a cofactor), so by the mechanism, a magnesium deficiency should impair the activation of vitamin D.
No deficiency, no need to supplement: the large US randomized VITAL trial (Manson 2019, NEJM, n=25,871) gave vitamin D to middle-aged and older adults and did not reduce cancer or major cardiovascular events. In the same year, the D2d trial gave vitamin D to people with prediabetes and did not significantly reduce new cases of type 2 diabetes. So if you are not deficient, there is no evidence that extra vitamin D prevents these diseases. Vitamin D supplements are for correcting a deficiency, not all-purpose insurance.
Chapter 5
Reading ferritin and its trap
is the container the body stores iron in. Measuring ferritin in the blood is like estimating what is left in a warehouse from outside the wall: usually good enough, but with one big trap.
Ferritin is also an acute-phase protein. As soon as there is inflammation, signals released by immune cells travel in the blood to the liver, and the liver makes an extra batch of ferritin. So infection, chronic inflammation, liver disease and tumors can all push the number up while the body's iron has not increased at all, and a real iron deficiency can be hidden by a cold.
One safety note: men and women past menopause should not take iron without a reason. The body has no active way to get rid of iron, and iron overload damages the liver, the heart and the pancreas.
When to see a doctor: ferritin < 10 ng/mL; hemoglobin < 12 g/dL (women) or < 13.5 (men) with low ferritin; transferrin saturation > 45% with ferritin above 200 (men) or 150 (women), which is the gate for checking iron overload, with no need to wait for a ferritin of 500; ferritin that stays high with no inflammatory cause found; suspected hemochromatosis (family history, darkening of the skin, joint pain, diabetes together with liver disease).
Ferritin is also an acute-phase protein. As soon as there is inflammation, signals released by immune cells travel in the blood to the liver, and the liver makes an extra batch of ferritin. So infection, chronic inflammation, liver disease and tumors can all push the number up while the body's iron has not increased at all, and a real iron deficiency can be hidden by a cold.
One safety note: men and women past menopause should not take iron without a reason. The body has no active way to get rid of iron, and iron overload damages the liver, the heart and the pancreas.
When to see a doctor: ferritin < 10 ng/mL; hemoglobin < 12 g/dL (women) or < 13.5 (men) with low ferritin; transferrin saturation > 45% with ferritin above 200 (men) or 150 (women), which is the gate for checking iron overload, with no need to wait for a ferritin of 500; ferritin that stays high with no inflammatory cause found; suspected hemochromatosis (family history, darkening of the skin, joint pain, diabetes together with liver disease).
Numbers · Reading ferritin and saturation together
Iron has to be read with two numbers together: tells you about the stores, and transferrin saturation tells you how much is in transit. Low ferritin means a deficiency. Ferritin that is not low with a low saturation looks more like inflammation locking iron inside macrophages. Only when both are high do you start thinking about iron overload (hemochromatosis).Reference values:
Men 30–300 ng/mL; women 15–200 ng/mL< 30 ng/mL: iron stores depleted< 15 ng/mL: definite iron deficiency (WHO criterion)With inflammation, adjust: WHO 2020 recommends measuring (and/or another inflammatory protein, AGP) alongside ferritin to interpret it, and the BRINDA project uses a statistical correction by degree of inflammation. One common shortcut is that when CRP is > 5 mg/L, the ferritin cut-off for deficiency is relaxed to < 30; different guidelines give different numbers.
Why ferritin alone is not enough:
Low ferritin: depleted iron stores (possibly before anemia appears)Normal or high ferritin with low transferrin saturation: possibly anemia of inflammation (iron locked inside macrophages and unable to get out). When ferritin is high but saturation is not, the more common causes are inflammation, obesity, fatty liver, alcohol or liver-cell injury rather than iron overload (Adams 2011)High ferritin and high transferrin saturation: check for hemochromatosis. The 2022 guideline of the European Association for the Study of the Liver (EASL) starts the search from raised saturation plus raised ferritin, and the referral line in this story is saturation > 45%
Transferrin saturation (TSAT) = serum iron ÷ total iron-binding capacity (TIBC) × 100, normally 20–50%. Below 20% with low ferritin means iron deficiency; above 45% with high ferritin is a reason to see a doctor about iron overload.
zoller-2022-easl-haemochromatosis
Mechanism · What iron deficiency can look like
Iron deficiency pulls on other markers:Iron deficiency makes (glycated hemoglobin) read falsely high by about 0.2–0.5%, because it changes how red cells and hemoglobin become glycated.Iron deficiency impairs the making of thyroid hormone and slows the conversion of to .Iron deficiency affects the making of dopamine, which is linked with restless legs syndrome.Low without anemia can still bring fatigue, lower exercise tolerance and poor concentration.
What nutrition can do:
Iron deficiency or low ferritin: heme iron (red meat, liver, blood products) is absorbed best; non-heme iron (spinach, beans) is absorbed better with vitamin C; tea, coffee, calcium and calcium supplements taken within 2 hours before or after a meal inhibit iron absorption.Men and women past menopause should not take iron without a reason: for them the risk of supplementing blindly outweighs the benefit. The body has no active way to get rid of iron, and iron overload (for example in hemochromatosis) damages the liver, heart and pancreas.If ferritin is high, look for the cause first (inflammation, liver disease, hemochromatosis). Do not assume a high ferritin means too much iron.
Chapter 6
Homocysteine and the inflammation test
These two markers often sit together at the bottom of the report, but they tell two different stories.
is a way station on the route of protein metabolism. Methionine passes through it as the body handles it, and from there homocysteine is either sent back to methionine or broken down and cleared; both exits need B12, folate and B6 as helpers. When the helpers are short, homocysteine backs up and its level in the blood rises. So the most common, and most easily fixed, cause of a high level is too little B12 or folate, especially in older adults and long-term vegetarians.
is a protein the liver makes in a hurry when there is inflammation. It does not care about the cause: a cold, inflamed gums, hard exercise and autoimmune disease all push it up. So a single high reading says almost nothing. Only when two readings at least two weeks apart are both high does it count as persistent low-grade inflammation.
One safety note: if B12 is low, taking folate alone can put the look of the blood count right while nerve damage carries on. Check B12 first, then decide how to take folate.
When to see a doctor: homocysteine > 30 µmol/L; hs-CRP > 10 mg/L (acute inflammation, which needs a check for infection or autoimmune disease); hs-CRP persistently > 3 together with other cardiovascular risk factors.
is a way station on the route of protein metabolism. Methionine passes through it as the body handles it, and from there homocysteine is either sent back to methionine or broken down and cleared; both exits need B12, folate and B6 as helpers. When the helpers are short, homocysteine backs up and its level in the blood rises. So the most common, and most easily fixed, cause of a high level is too little B12 or folate, especially in older adults and long-term vegetarians.
is a protein the liver makes in a hurry when there is inflammation. It does not care about the cause: a cold, inflamed gums, hard exercise and autoimmune disease all push it up. So a single high reading says almost nothing. Only when two readings at least two weeks apart are both high does it count as persistent low-grade inflammation.
One safety note: if B12 is low, taking folate alone can put the look of the blood count right while nerve damage carries on. Check B12 first, then decide how to take folate.
When to see a doctor: homocysteine > 30 µmol/L; hs-CRP > 10 mg/L (acute inflammation, which needs a check for infection or autoimmune disease); hs-CRP persistently > 3 together with other cardiovascular risk factors.
Evidence · Does lowering homocysteine help?
: normal is 5–15 µmol/L; > 15 is called hyperhomocysteinemia. It is an intermediate of methionine metabolism and can only be processed with the help of B6, B12 and folate as cofactors.The C677T variant of the gene lowers the activity of this enzyme and raises homocysteine; but even in people with two copies of the variant (homozygotes), it is on average only about 25% higher, and folate can correct it.High homocysteine is associated with the risk of cardiovascular disease, stroke and cognitive decline, but whether it is a cause is debated: randomized trials that lowered homocysteine with B vitamins mostly did not reduce cardiovascular events. One exception is the China Stroke Primary Prevention Trial (CSPPT, 2015): in people with high blood pressure, enalapril plus folic acid lowered the risk of a first stroke by 21% in relative terms compared with enalapril alone. The researchers suggested this is linked to low baseline folate in parts of China.Vitamin B12 deficiency is the most common reversible cause of high homocysteine, especially in older adults and vegetarians.
What nutrition can do: B12 (2.4 µg a day; people who absorb it poorly need injections or high oral doses), folate (400 µg a day), B6 (1.3–1.7 mg a day), and betaine (6 g a day lowers homocysteine by about 10–20%, Olthof 2003). But note: if B12 is low, taking folate alone hides the anemia while nerve damage carries on, so check B12 before taking folate.
huo-2015-csppt-folic-acid
Evidence · What a raised hs-CRP does and does not mean
(high-sensitivity C-reactive protein): < 1 mg/L means low cardiovascular risk; 1–3 moderate; > 3 high. It is an acute-phase protein made by the liver and reflects low-grade inflammation throughout the body.hs-CRP is associated with cardiovascular risk, but whether it is a marker of risk or a cause is debated. Mendelian randomization studies (which use inborn genetic differences as a kind of natural random assignment) do not support CRP itself directly causing atherosclerosis.A single high reading means little: a cold, gum inflammation, hard exercise and autoimmune disease all raise it.Only a reading persistently > 3 on two or more occasions (at least 2 weeks apart) is meaningful.Metabolic syndrome itself raises hs-CRP: fat tissue releases (interleukin-6, an inflammatory signal), which stimulates the liver to make more CRP.
What nutrition can do: a Mediterranean-style diet, omega-3 fats ( and ), weight loss, exercise, quitting smoking, limiting alcohol, and treating chronic infections (such as gum disease). Do not take anti-inflammatory supplements to bring CRP down: improving metabolism is what gets at the root.
Chapter 7
How these markers connect
Blood work decoded · routine chemistry reached one conclusion: the string of arrows on routine chemistry is often the many faces of one upstream problem, insulin resistance. The six specialized markers in this story hang on the same web.
Insulin resistance reaches further downstream than routine chemistry. When insulin stays high for a long time, the liver makes less , which rewrites the proportions of free testosterone and . Fat builds up in the liver, and liver enzymes and rise with it. Inflammatory signals from fat tissue make the liver produce more .
Hypothyroidism can masquerade as metabolic syndrome. When the thyroid slows, liver cells carry fewer of the receptors that take back out of the blood, the basal metabolic rate drops, and SHBG falls, so blood lipids, body weight and sex hormones are all dragged along at once. That is why people with abnormal blood lipids should have their thyroid checked first: the problem may be the thyroid, not metabolism.
Iron deficiency can disguise itself as other things. It makes the long-term blood glucose marker read falsely high, slows both the making and the conversion of thyroid hormone, and starves dopamine production, which shows up as fatigue, poor concentration and restless legs.
This is why you read the pattern, not the single value: one arrow may mislead, but a group of arrows points to what is really going on.
Insulin resistance reaches further downstream than routine chemistry. When insulin stays high for a long time, the liver makes less , which rewrites the proportions of free testosterone and . Fat builds up in the liver, and liver enzymes and rise with it. Inflammatory signals from fat tissue make the liver produce more .
Hypothyroidism can masquerade as metabolic syndrome. When the thyroid slows, liver cells carry fewer of the receptors that take back out of the blood, the basal metabolic rate drops, and SHBG falls, so blood lipids, body weight and sex hormones are all dragged along at once. That is why people with abnormal blood lipids should have their thyroid checked first: the problem may be the thyroid, not metabolism.
Iron deficiency can disguise itself as other things. It makes the long-term blood glucose marker read falsely high, slows both the making and the conversion of thyroid hormone, and starves dopamine production, which shows up as fatigue, poor concentration and restless legs.
This is why you read the pattern, not the single value: one arrow may mislead, but a group of arrows points to what is really going on.
Mechanism · Four chains, one by one
Downstream of insulin resistance, beyond routine chemistry:Insulin resistance keeps insulin high, and high insulin holds back the liver's production of . With less SHBG, the proportions of free testosterone and change (a relative excess of androgen in men, and features of polycystic ovary syndrome in women).Insulin resistance drives fat into the liver, and , and (an inflammatory rise, in this case) go up together.Insulin resistance makes the kidneys reabsorb more uric acid, so blood uric acid rises.Insulin resistance makes fat tissue release more , IL-6 stimulates the liver to make more , and hs-CRP rises.People with insulin resistance often have low vitamin D as well; the mechanism is not fully clear, and it may have to do with less time outdoors and vitamin D being diluted in body fat.
Downstream of hypothyroidism, masquerading as metabolic syndrome:
Hypothyroidism leaves liver cells with fewer receptors to take back, so LDL-C and rise.Hypothyroidism lowers the basal metabolic rate, weight goes up and worsens.Hypothyroidism lowers SHBG, which changes how sex hormones should be read.So people with abnormal blood lipids should have checked first: the problem may be the thyroid, not metabolism.
Downstream of iron deficiency, masquerading as other things:
Iron deficiency makes read falsely high, which is easily mistaken for a blood glucose problem.Iron deficiency reduces the making of thyroid hormone and slows the conversion of to , worsening hypothyroidism.Iron deficiency reduces the making of dopamine, bringing fatigue, restless legs and poor concentration.Iron deficiency lowers exercise tolerance, so people move less, which in turn worsens insulin resistance.
Upstream of high :
B12 deficiency (older adults, vegetarians, people on long-term acid-suppressing drugs called proton pump inhibitors) raises homocysteine.Low folate (flour is not fortified with folic acid in parts of China) raises homocysteine.An variant combined with low folate raises homocysteine.Poor kidney function means homocysteine is not cleared.
Chapter 8
Specialist markers to act on
Red flags that need prompt medical care:
> 20 mIU/L (clear hypothyroidism) or < 0.01 (clear hyperthyroidism)Symptoms of an overactive thyroid: palpitations, rapid weight loss, heat intolerance, tremor, atrial fibrillation → the risk of thyroid storm needs to be ruled outMen with total testosterone < 200 ng/dL plus symptomsWomen with absent periods plus signs of excess androgen < 10 ng/mL or > 100Transferrin saturation > 45% with raised (check for hemochromatosis) > 30 µmol/L > 10 mg/L (acute inflammation, infection or autoimmune disease)Any persistent abnormality you cannot explain → see a doctor; do not diagnose yourself
If you take medications (anticoagulants, thyroid hormone, glucose-lowering or blood-pressure drugs and so on), supplements may interact with them, so ask your doctor or pharmacist first.
Disclaimer: this story is health education, not a medical diagnosis or prescription. Discuss any decision about treatment, medication or supplements with your doctor. This project does not replace an in-person consultation and is not responsible for any personal decision based on this content.
> 20 mIU/L (clear hypothyroidism) or < 0.01 (clear hyperthyroidism)Symptoms of an overactive thyroid: palpitations, rapid weight loss, heat intolerance, tremor, atrial fibrillation → the risk of thyroid storm needs to be ruled outMen with total testosterone < 200 ng/dL plus symptomsWomen with absent periods plus signs of excess androgen < 10 ng/mL or > 100Transferrin saturation > 45% with raised (check for hemochromatosis) > 30 µmol/L > 10 mg/L (acute inflammation, infection or autoimmune disease)Any persistent abnormality you cannot explain → see a doctor; do not diagnose yourself
If you take medications (anticoagulants, thyroid hormone, glucose-lowering or blood-pressure drugs and so on), supplements may interact with them, so ask your doctor or pharmacist first.
Disclaimer: this story is health education, not a medical diagnosis or prescription. Discuss any decision about treatment, medication or supplements with your doctor. This project does not replace an in-person consultation and is not responsible for any personal decision based on this content.
In practice · A few honest words about supplements
The supplements mentioned across the two stories on routine chemistry and specialized markers (vitamin , B12, folate, zinc, selenium, magnesium, omega-3, betaine, berberine) are for use when there is a deficiency or a clear reason; not everyone needs them.Do not take something because it might help: too much carries risks, such as iron overload, vitamin D toxicity, too much zinc blocking copper absorption, and hair loss from too much selenium.Supplements fill gaps in a diet; they do not excuse a poor one.If you take medications (especially anticoagulants, thyroid hormone, glucose-lowering or blood-pressure drugs), supplements may interact with them, so ask your doctor or pharmacist first.Together, the two stories should let you pick up a lab report and see not just arrows but patterns: the physiology behind each marker, how the markers connect, what nutrition can do, and when to hand the report to a doctor.
References · 21
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- Institute of Medicine. (2011). Dietary Reference Intakes for Calcium and Vitamin D. National Academies Press. www.ncbi.nlm.nih.gov/books/NBK56070
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