Functional Lab Reference Ranges — 31 Biomarkers

Metabolic

Glucose

Glucose control is foundational. Elevated fasting glucose indicates insulin resistance. the root of metabolic dysfunction. even when it's still inside the standard range.

Functional

70–90 mg/dL fasting

Standard

70–100 mg/dL

Insulin (Fasting)

Elevated fasting insulin is the earliest sign of metabolic dysfunction, appearing years before glucose rises. Drives inflammation, fat storage, and hormonal disruption.

Functional

2–5 mIU/L

Standard

2–12 mIU/L

HbA1c

Three-month average of blood glucose. Reveals chronic glucose dysregulation that a single fasting glucose reading misses. Metabolic damage accelerates above 5.3.

Functional

<5.3%

Standard

<5.7%

Lipid Panel

The relationships between lipids matter far more than any single number. TG:HDL ratio and Total Cholesterol:HDL ratio are the meaningful signals. Low HDL is a stronger risk predictor than high LDL in isolation.

Functional

Ratios & context

Standard

Individual cutoffs

Thyroid

TSH

Standard range is dangerously wide. Values above 2.0 often indicate subclinical hypothyroidism with real, measurable symptoms. fatigue, weight gain, cold intolerance. that get dismissed because the number is "normal."

Functional

1.0–2.0 mIU/L

Standard

0.45–4.5 mIU/L

Free T4

Measures circulating thyroid hormone available for conversion. Low-normal Free T4 often correlates with fatigue, weight resistance, and cold intolerance even when TSH appears acceptable.

Functional

1.0–1.5 ng/dL

Standard

0.8–1.8 ng/dL

Free T3

The active form of thyroid hormone. Low T3 despite normal TSH and T4 indicates poor conversion. common in chronic stress, inflammation, and nutrient deficiency. This is the number that actually matters at the cellular level.

Functional

3.0–4.0 pg/mL

Standard

2.3–4.2 pg/mL

Reverse T3

Elevated Reverse T3 blocks Free T3 receptors and slows metabolism at the cellular level even when all other thyroid markers appear normal. This is the most commonly missed thyroid marker.

Functional

<15 ng/dL

Standard

9.2–24.1 ng/dL

TPO Antibodies

Detects autoimmune thyroiditis (Hashimoto's). A positive result indicates immune system activity against the thyroid even when TSH reads normal. Early detection allows meaningful intervention.

Functional

Negative

Standard

Positive or negative

Thyroglobulin Antibodies

Second autoimmune thyroid marker. Some Hashimoto's cases are TPO-negative but Tg-positive. both must be run to catch the full picture. Running only TPO misses a meaningful percentage of cases.

Functional

Negative

Standard

Positive or negative

Hormonal

Testosterone (Total)

Standard ranges are too wide. Low-normal testosterone drives fatigue, poor recovery, and loss of muscle mass even when the number is flagged as "normal." Optimal function requires more than just being inside the range.

Functional

500–800 ng/dL (M)

Standard

300–1000 ng/dL

Free Testosterone

Only free testosterone is biologically active. Low free T despite normal total testosterone indicates elevated SHBG or poor conversion. not a production problem. This distinction changes the entire protocol.

Functional

>25 pg/mL (M)

Standard

9–30 pg/mL

Estradiol (Sensitive)

Standard estradiol assays are not sensitive enough for men or low-range women. The sensitive assay is required for accurate interpretation. In men, high estradiol is as problematic as low testosterone.

Functional

20–30 pg/mL (M)

Standard

Varies by lab

Progesterone

For women, must be drawn mid-luteal (day 19–21). Low progesterone relative to estradiol drives estrogen dominance symptoms even when both appear individually "normal."

Functional

>10 ng/mL mid-luteal

Standard

Individual cutoff only

SHBG

Sex hormone binding globulin binds sex hormones and reduces bioavailability. Elevated SHBG suppresses free testosterone and free estradiol. Commonly elevated in hyperthyroidism and low in insulin resistance.

Functional

25–40 nmol/L (M)

Standard

24–122 nmol/L

LH / FSH

Pituitary signals that drive gonadal hormone production. Elevated LH and FSH with low sex hormones indicates primary gonadal failure. Low LH and FSH with low sex hormones indicates central suppression. The direction changes everything.

Functional

Context-dependent

Standard

Varies by sex/phase

PSA (Men)

Prostate-specific antigen. Included in the male panel as a baseline. Essential for monitoring if hormone optimization is pursued.

Functional

<1.5 ng/mL (under 50)

Standard

<4.0 ng/mL

Adrenal

Cortisol (AM)

Morning cortisol below 10 indicates adrenal insufficiency. Above 13 indicates chronic HPA axis dysregulation. The functional window is narrow and the standard range is so wide as to be nearly useless.

Functional

10–13 mcg/dL

Standard

5–23 mcg/dL

DHEA-S

Marker of adrenal reserve. Low DHEA-S despite normal cortisol indicates adrenal fatigue and reduced stress resilience. Chronically low in high-stress individuals regardless of cortisol output.

Functional

300–500 mcg/dL (M)

Standard

30–400 mcg/dL

Micronutrient

Iron (Serum)

Low iron causes fatigue, poor recovery, and hair loss. High iron drives oxidative stress and organ damage. The functional window is significantly narrower than standard ranges suggest.

Functional

70–100 mcg/dL

Standard

60–170 mcg/dL

Ferritin

Iron storage protein and direct input into ATP production. Below 80 impairs energy production. Above 250 drives oxidative stress. Both extremes are problematic and both are commonly missed.

Functional

50–150 ng/mL (M)

Standard

12–150 ng/mL

Magnesium (RBC)

Serum magnesium reflects only 1% of total body magnesium and is nearly useless as a functional marker. RBC magnesium is the meaningful measurement. Low RBC magnesium drives muscle cramps, poor sleep, anxiety, and hormonal disruption.

Functional

2.2–2.6 mg/dL

Standard

1.7–2.2 mg/dL

Zinc

Zinc deficiency impairs immune function, wound healing, and hormone metabolism. Often severely depleted in chronically stressed individuals. Low zinc suppresses testosterone production.

Functional

70–100 mcg/dL

Standard

60–120 mcg/dL

Vitamin B12

Low-normal B12 (200–400 pg/mL) causes fatigue, brain fog, mood instability, and peripheral neuropathy. The functional threshold is 500+, not the standard floor of 200.

Functional

>500 pg/mL

Standard

>200 pg/mL

Folate

Folate deficiency impairs methylation, DNA synthesis, and neurotransmitter production. Low-normal folate correlates with persistent fatigue and mood instability.

Functional

>9 ng/mL

Standard

>5.4 ng/mL

Vitamin D

Vitamin D functions as a hormone, not just a vitamin. Below 55 ng/mL impairs immune function, mood, bone health, and recovery. The standard floor of 30 is a deficiency threshold. not an optimization target.

Functional

>55 ng/mL

Standard

>30 ng/mL

Inflammation & Cardiovascular

hs-CRP

High-sensitivity C-reactive protein is the most practical marker of systemic inflammation. Chronic low-grade inflammation (values between 1–3 mg/L) drives cardiovascular risk, accelerated aging, and hormonal disruption years before anything shows up clinically.

Functional

<1.0 mg/L

Standard

<3.0 mg/L

Homocysteine

Independent cardiovascular risk factor that reflects methylation status and vascular health. Vascular damage begins above 8 mcmol/L. not the standard cutoff of 15. High homocysteine indicates B-vitamin deficiency and poor methylation.

Functional

<8 mcmol/L

Standard

<15 mcmol/L

Liver & Protein

Albumin

Marker of protein status and liver synthetic function. Low albumin indicates poor nutritional status or hepatic stress. Required to accurately interpret calcium and other albumin-bound markers.

Functional

3.5–4.5 g/dL

Standard

3.5–5.0 g/dL

ALT / AST

Liver enzymes. Even low-normal elevation indicates early fatty liver or hepatic inflammation. The functional threshold is below 25 U/L. not the standard 40. Elevation here often predates metabolic disease by years.

Functional

<25 U/L

Standard

<40 U/L

GGT

Gamma-glutamyl transferase is a highly sensitive marker of oxidative stress and metabolic dysfunction. Elevated GGT predicts metabolic disease, liver stress, and cardiovascular risk well before other liver markers move.

Functional

<30 U/L

Standard

<55 U/L

What we track and why.

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