Hematocrit

Routine annual

also hct

What it isThe percentage of total blood volume occupied by red blood cells, after spinning the sample down in a centrifuge.

DoesCaptures the same information as RBC count and hemoglobin but in a different form; helps assess blood viscosity.

GoodMid-range hematocrit balances oxygen-carrying capacity against blood viscosity.

BadLow hematocrit signals anemia. High hematocrit increases blood viscosity and clotting risk — common with testosterone therapy, sleep apnea, smoking, and high altitude.

Standard

Men 38.8–50%; women 34.9–44.5%.

Optimal

42–47% men, 38–43% women (narrow target)

Modifiers

Dehydration falsely raises it; over-hydration falsely lowers it; rises with TRT and altitude.

How to optimize

Lifestyle: Hydrate; treat sleep apnea; quit smoking; in TRT, monitor and consider therapeutic phlebotomy.
Diet: Same as hemoglobin — iron, B12, folate, protein.
Supplements: Iron (only if deficient).
Peptides: —
Drugs: Therapeutic phlebotomy for elevated hematocrit; treat underlying cause for low.

within Blood Cells