Hematocrit

Hematocrit is the percentage of your total blood volume made up of red blood cells. It rises with training adaptation, altitude, dehydration, and anything that boosts red cell production.

Reference range

Male: 38–50 % (optimal ≤ 50 %)
Female: 35–45 % (optimal ≤ 45 %)

Watch points

Critical: at or above 54 %
High: at or above 52 %
Borderline: at or above 50 %

Same thresholds apply to men and women in this table.

Why hard-training athletes watch it

Volume-driven training raises hematocrit naturally, and dehydration on a cut can push a single reading up without any real change in red cell mass. A high reading after a hard block or a dehydrated draw is common and usually resolves — it's a rising trend across draws that matters, not one number.

When to retest

Redraw fasted and well-hydrated, at the same time of day as your last panel — a reading taken dehydrated or right after training isn't comparable to one taken under normal conditions.

Talk to your clinician

Hydrate well, and ask your clinician about donating a unit of blood — it drops hematocrit fast. A reading above the reference band is worth a conversation with your clinician, not a self-diagnosis — hydration status and training block both move this number.