The percentage of blood volume made up of red blood cells. Anabolic steroids stimulate red cell production, and a hematocrit above the normal range thickens the blood and raises the risk of clots, stroke and heart attack.
Hematocrit is one of the two markers, with HDL cholesterol, that change most reliably with anabolic steroid use. It rises over months and falls after stopping. Elevated hematocrit is among the most common reasons physicians pause testosterone therapy. Dehydration and living at altitude also raise it, so the sample should be taken well hydrated.
This article is for information and education only. It is not medical advice and does not replace a consultation with a physician. Anabolic-androgenic steroids are prescription medicines in most countries and are controlled substances in many. Check the law where you live.