Blood health
Hematocrit (Hct)
Hct, packed cell volume (PCV)
Included in every MyHealthspan membership: Focus, Baseline, and Complete.
Compare membershipsRed cells as a share of your blood volume.
Hematocrit measures how much of your blood's volume is taken up by red blood cells. It usually moves in step with hemoglobin and helps assess anemia and conditions where red cells run high.
Hydration can shift this number.
Because hematocrit is a proportion, it also depends on the liquid part of your blood (plasma). If you're dehydrated when your blood is drawn, there's less plasma, so hematocrit can read higher even though your red cells haven't changed. Dehydration is a common reason for a mildly high result.
Pregnancy works the other way. Extra body fluid dilutes the blood and can lower hematocrit.
Drink normally before your blood draw so hematocrit reflects your usual state.
Questions
What else can cause a high hematocrit?
Smoking, living at high altitude, lung or heart conditions, and sleep apnea can raise it. Testosterone therapy and anabolic steroids can too. Rarely, a bone marrow condition that makes too many red cells is responsible.
What does a low hematocrit mean?
A low hematocrit usually points to anemia or blood loss. Your hemoglobin, red cell size measures, and iron results help a clinician work out the likely cause.