Normal, optimal, and the evidence between them.

Metabolism & Metabolomics · µIU/mL

Fasting insulin

Fasting insulin is the hormone level your pancreas holds while you are not eating. It can climb for years while glucose stays normal. Laboratories call anything up to about 20 to 25 µIU/mL normal; the long cohorts put the lowest-risk groups in the single digits.

Grade B · 13 sourcesRead

Mitochondria & Cellular Energy · ng/mL

Ferritin

Ferritin reflects stored iron, and it rises with inflammation whether or not iron is present. Laboratories call a span from about 15 or 30 up to 150 to 400 ng/mL normal. The literature is firm at the low end, where deficiency and symptoms live, and cautionary at the high end, and says little about the middle.

Grade A · 21 sourcesRead

Metabolism & Metabolomics · mg/dL

ApoB

ApoB counts the particles that carry cholesterol into artery walls, one molecule per particle. It predicts heart disease better than LDL cholesterol and explains why two people with the same LDL can carry different risk. Laboratories usually print under 90 mg/dL as desirable; the evidence supports lower is better, by degree of risk and duration.

Grade A · 19 sourcesRead

Metabolism & Metabolomics · %

Hemoglobin A1c

Hemoglobin A1c is the share of your hemoglobin that has glucose attached, a weighted average of blood sugar over about three months. Laboratories call anything under 5.7 percent normal. The cohorts put the lowest-risk group at 5.0 to about 5.4, show diabetes and heart risk climbing from 5.5, and find a puzzling excess of deaths below 5.0.

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Metabolism & Metabolomics · mg/dL

Fasting glucose

Fasting glucose is the diagnostic test for diabetes, and the cutoffs it carries (100 and 126 mg/dL) are agreed by guideline. Inside the normal range the number still carries information: large cohorts place the lowest risk of later diabetes in the low 80s and below, and the lowest mortality in the 80s and low 90s. It is also a late marker, moving years after insulin has.

Grade A · 26 sourcesRead

Metabolism & Metabolomics · mg/dL

Triglycerides

Triglycerides are the fat carried in ApoB particles, mostly VLDL and its remnants, and they rise with carbohydrate, alcohol, weight and insulin resistance. The printed cutoff of 150 mg/dL comes from a 2001 US panel; cohorts show risk rising from the lowest band upward, and Mendelian randomization shows the effect is carried by particle number. They move a lot from day to day, and with meals.

Grade A · 26 sourcesRead

Metabolism & Metabolomics · mg/dL

HDL cholesterol

HDL cholesterol was called the good cholesterol because low values predict heart disease. Laboratories flag under 40 mg/dL in men and under 50 in women as low and 60 or more as high. The cohort curve is U-shaped, with higher mortality at very high values, and genes and trials agree that pushing the number up does not protect anyone.

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Gut-Immune Health · mg/L

hs-CRP

hs-CRP is the liver's response to inflammation anywhere in the body, measured by an assay sensitive enough to read the low values that track cardiovascular risk. Laboratories band it at 1 and 3 mg/L. The cohorts show risk rising with the number; the trials show that treating inflammation prevents events; the genetics show CRP is the messenger, not the cause. Body fat, sleep, gums, smoking and hormones all move it, and one reading is rarely enough.

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Evolutionary Medicine · ng/mL

Vitamin D (25-OH)

25-hydroxyvitamin D measures the body's vitamin D supply from sun, food and supplements. Laboratories print about 30 to 100 ng/mL as normal, the Institute of Medicine says about 20 covers nearly everyone's bone needs, and the large trials of the past decade found that adding vitamin D to replete adults changed no major outcome. The literature is clear at the low end and quiet above it.

Grade A · 24 sourcesRead

Metabolism & Metabolomics · mIU/L

TSH

TSH is the pituitary's signal to the thyroid, and it moves in the opposite direction to thyroid hormone. Laboratories call about 0.4 or 0.45 to 4.0 or 4.5 mIU/L normal. The harm thresholds at both ends are well established; whether the upper half of the range is healthy or merely common is the most argued question in thyroid testing, and this page gives both sides.

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Metabolism & Metabolomics · U/L

ALT

ALT is an enzyme that leaks out of liver cells when they are injured, and in most adults a raised value means fat in the liver rather than hepatitis. The printed reference range is wide because the people used to define it included many with undiagnosed fatty liver. Healthy-population studies put the upper limit near 30 in men and about 20 in women.

Grade A · 25 sourcesRead

Epigenetics · µmol/L

Homocysteine

Homocysteine is an amino acid that builds up when the methylation cycle runs short of folate, B12, riboflavin or B6, or when the kidneys clear it slowly. Laboratories print upper limits from about 11 to 15 µmol/L. In cohorts, risk climbs steadily from about 9 upward; in trials, vitamins that lowered it prevented some strokes and no heart attacks. The number is most useful for what it says about the vitamins and the kidneys behind it.

Grade A · 35 sourcesRead