Hematocrit
Also called HCT, packed cell volume, PCV
Hematocrit is a blood test that measures how much of your blood is made up of red blood cells, the cells that carry oxygen from the lungs to the rest of the body. It is usually reported as part of a complete blood count (CBC), often alongside hemoglobin.
A low hematocrit can point to anemia, where there are too few red cells. A high hematocrit can reflect dehydration or polycythemia, also called erythrocytosis, in which there are too many red cells and the blood becomes thicker than normal.
Why it matters after 45
Testosterone helps the body make new red blood cells, so hematocrit is one of the main safety markers around testosterone therapy. The American Urological Association says hemoglobin and hematocrit should be measured before therapy is offered and that men should be told about the increased risk of polycythemia, with hematocrit checked again periodically during treatment. The Endocrine Society lists an elevated hematocrit among the reasons not to start testosterone therapy. How a result is interpreted, and what is ruled out first, is covered in the article linked below.
Where it comes up
Related terms
References
- MedlinePlus. Hematocrit Test. U.S. National Library of Medicine. https://medlineplus.gov/lab-tests/hematocrit-test/
- American Urological Association. Evaluation and Management of Testosterone Deficiency (AUA Guideline). https://www.auanet.org/guidelines-and-quality/guidelines/testosterone-deficiency-guideline
- Endocrine Society. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline, 2018. https://www.endocrine.org/clinical-practice-guidelines/testosterone-therapy
- MedlinePlus. Testosterone Levels Test. U.S. National Library of Medicine. https://medlineplus.gov/lab-tests/testosterone-levels-test/
Definitions here are educational and are not medical advice. They explain what a term means; the pages linked above cover what it means for you, and a clinician reviews your own results. Editorial & medical review policy · All glossary terms