Every blood test report comes with a reference range printed next to your result. If your number falls within the range, it gets a neutral checkmark. If it falls outside, it gets a flag.
But those reference ranges are not health targets — they are statistical norms derived from the tested population. Being "in range" means you are not obviously sick. It does not mean you are optimally healthy. And for many markers, the difference between normal and optimal is where the most important health information lives.
This guide covers every common blood test marker, with both standard reference ranges and optimal targets. If you want the interpretation method rather than the raw numbers, start with how to read your blood test results.
Complete blood count (CBC)
| Marker | Normal range (men) | Normal range (women) | Optimal |
|---|---|---|---|
| RBC | 4.5–5.5 M/µL | 4.0–5.0 M/µL | Mid-range |
| Hemoglobin | 13.5–17.5 g/dL | 12.0–16.0 g/dL | 14–16 (M), 12.5–14.5 (F) |
| Hematocrit | 38.3–48.6% | 35.5–44.9% | Mid-range |
| MCV | 80–100 fL | 80–100 fL | 85–95 fL |
| WBC | 4,000–11,000/µL | 4,000–11,000/µL | 4,500–7,500/µL |
| Platelets | 150,000–400,000/µL | 150,000–400,000/µL | 180,000–300,000/µL |
| RDW | 11.5–14.5% | 11.5–14.5% | Below 13% |
If a flagged value has you worried, is my blood test result actually bad? explains how to read the flag.
Key insight: RDW (red cell distribution width) above 14.5% is associated with increased all-cause mortality in multiple studies, making it an underappreciated longevity marker.
Metabolic panel
| Marker | Normal range | Optimal (longevity) |
|---|---|---|
| Fasting glucose | 70–99 mg/dL | 75–90 mg/dL |
| HbA1c | Below 5.7% | 4.8–5.3% |
| Fasting insulin | 2.6–24.9 µIU/mL | 3–6 µIU/mL |
| HOMA-IR | Below 2.5 (calculated) | Below 1.5 |
| BUN | 7–20 mg/dL | 10–18 mg/dL |
| Creatinine | 0.7–1.3 mg/dL (M), 0.6–1.1 (F) | Stable over time |
| eGFR | Above 60 mL/min | Above 90 mL/min |
| Cystatin C | 0.6–1.0 mg/L | Below 0.9 mg/L |
| Uric acid | 3.5–7.2 mg/dL (M), 2.6–6.0 (F) | Below 6.0 (M), Below 5.0 (F) |
| Sodium | 136–145 mEq/L | Mid-range |
| Potassium | 3.5–5.0 mEq/L | 4.0–4.5 mEq/L |
| Calcium | 8.5–10.5 mg/dL | 9.0–10.0 mg/dL |
Key insight: Fasting insulin is the earliest metabolic warning sign. A fasting glucose of 90 with fasting insulin of 15 looks "normal" on paper but signals insulin resistance through HOMA-IR calculation.
Lipid panel
| Marker | Normal range | Optimal (longevity) |
|---|---|---|
| Total cholesterol | Below 200 mg/dL | Context-dependent |
| LDL-C | Below 100 mg/dL | Below 70 mg/dL (if high risk) |
| HDL-C | Above 40 (M), Above 50 (F) | Above 55 (M), Above 65 (F) |
| Triglycerides | Below 150 mg/dL | Below 100 mg/dL |
| ApoB | Below 130 mg/dL | Below 80 mg/dL (conservative), Below 60 (aggressive) |
| Lp(a) | Below 30 mg/dL | Below 30 mg/dL (genetically fixed) |
| Non-HDL-C | Below 130 mg/dL | Below 100 mg/dL |
Key ratios:
- Total cholesterol / HDL: below 3.5 ideal
- Triglyceride / HDL: below 2.0 optimal (best proxy for insulin resistance on a standard panel)
- LDL / HDL: below 2.5 good
Key insight: ApoB is the single best lipid marker for cardiovascular risk — better than LDL-C. Lp(a) should be tested once in every adult's lifetime.
Liver panel
| Marker | Normal range | Optimal |
|---|---|---|
| ALT | 7–56 U/L | Below 25 (F), Below 33 (M) |
| AST | 10–40 U/L | Below 25 (F), Below 30 (M) |
| GGT | 0–45 U/L (F), 0–65 (M) | Below 18 (F), Below 25 (M) |
| ALP | 44–147 U/L | 40–100 U/L |
| Bilirubin (total) | 0.1–1.2 mg/dL | 0.3–1.0 mg/dL |
| Albumin | 3.5–5.5 g/dL | 4.2–5.0 g/dL |
Key insight: ALT and GGT in the upper half of "normal" are associated with fatty liver disease and increased cardiovascular risk. The lab-normal thresholds are too generous.
Thyroid panel
| Marker | Normal range | Optimal |
|---|---|---|
| TSH | 0.4–4.0 mIU/L | 0.5–2.5 mIU/L |
| Free T4 | 0.8–1.8 ng/dL | 1.0–1.5 ng/dL |
| Free T3 | 2.0–4.4 pg/mL | 3.0–4.0 pg/mL |
| Anti-TPO | Below 35 IU/mL | Below 9 IU/mL |
Key insight: A TSH of 3.5 is "normal" but may indicate subclinical hypothyroidism, especially if Free T3 is on the lower end. The reference range for TSH has been debated for decades — many endocrinologists argue the upper limit should be 2.5, not 4.0.
Inflammation markers
| Marker | Normal range | Optimal (longevity) |
|---|---|---|
| hs-CRP | Below 3.0 mg/L | Below 1.0 mg/L (ideally below 0.5) |
| Homocysteine | 5–15 µmol/L | Below 10 µmol/L |
| ESR | 0–22 mm/hr (M), 0–29 (F) | Low end of range |
| Ferritin | 12–300 ng/mL (M), 12–150 (F) | 40–100 ng/mL (sweet spot) |
Key insight: hs-CRP below 1.0 mg/L is the longevity target. The JUPITER trial showed that even people with "normal" cholesterol benefit from statin therapy if hs-CRP is above 2.0 — highlighting that inflammation is an independent risk factor.
Hormones
| Marker | Normal range (men) | Normal range (women) | Optimal |
|---|---|---|---|
| Total testosterone | 264–916 ng/dL | 15–70 ng/dL | Upper half of range |
| Free testosterone | 5–21 ng/dL | 0.1–6.4 pg/mL | Upper third of range |
| SHBG | 10–57 nmol/L | 18–144 nmol/L | Mid-range |
| DHEA-S | 80–560 µg/dL (age-dependent) | 35–430 µg/dL (age-dependent) | Upper half for age |
| Cortisol (AM) | 6–23 µg/dL | 6–23 µg/dL | 10–18 µg/dL |
| IGF-1 | Age-dependent | Age-dependent | Lower half of age-range |
Vitamins and minerals
| Marker | Normal range | Optimal |
|---|---|---|
| Vitamin D (25-OH) | 30–100 ng/mL | 40–60 ng/mL |
| Vitamin B12 | 200–900 pg/mL | 500–800 pg/mL |
| Folate | Above 3 ng/mL | Above 10 ng/mL |
| Iron | 60–170 µg/dL (M), 37–145 (F) | Mid-range |
| Ferritin | 12–300 ng/mL (M), 12–150 (F) | 40–100 ng/mL |
| Magnesium (serum) | 1.7–2.2 mg/dL | Above 2.0 mg/dL |
Key insight: Serum magnesium is a poor reflection of total body magnesium (most is intracellular). A "normal" serum magnesium does not rule out deficiency. RBC magnesium is a better test but less commonly available.
How to use this chart
- Compare to YOUR lab's ranges — your lab's printed reference range is the primary comparison. This chart provides context.
- Look at trends, not snapshots — one abnormal value means little. A trending change over 2–3 tests is meaningful.
- Context matters — a marathon runner's blood work looks different from a sedentary person's. Recent illness, medication, exercise, fasting status, and time of day all affect results.
- Normal is not optimal — if you are pursuing health optimization, the "optimal" column is your target. If you are screening for disease, the "normal" column is your baseline.
How Merios helps
Upload any blood test PDF to Merios and we automatically extract the markers on it (Merios recognizes 160+), compare them to both standard and optimal reference ranges, and track your trends over time. See all your numbers in one dashboard alongside your Apple Watch data. Stop guessing what your results mean.
Upload your blood test to Merios →
This article is for informational purposes only and does not constitute medical advice. Reference ranges vary by lab, age, sex, and individual health status. Discuss your results with your physician.