Is my Hematocrit normal?
Free blood test checker · Standard + longevity-optimal ranges
What is a normal Hematocrit level?
Hematocrit is the percentage of blood volume made up of red blood cells. Normal range is 36-52% (varies by sex: men 38.3-48.6%, women 35.5-44.9%). Low hematocrit indicates anemia; high hematocrit increases blood viscosity and clotting risk. Hematocrit below 30% is critically low and may require transfusion.
| Range | Values |
|---|---|
| Standard Reference | 36–52 % |
| Low Risk | < 30 % |
What causes abnormal Hematocrit levels?
Low hematocrit is caused by iron deficiency anemia, B12/folate deficiency, chronic disease, blood loss, kidney disease, bone marrow disorders, and overhydration. High hematocrit is caused by dehydration (most common acute cause), polycythemia vera, chronic hypoxia (COPD, sleep apnea, high altitude), smoking, testosterone replacement therapy, and erythropoietin abuse.
When should you see a doctor?
See your doctor if hematocrit is below 30% (critical anemia, may need transfusion) or above 52%. Men on testosterone replacement therapy should monitor hematocrit every 3-6 months — if it exceeds 54%, dose reduction or phlebotomy is typically needed.
Hematocrit and longevity
Hematocrit is a critical safety parameter for men on testosterone replacement therapy (TRT), which is increasingly common in the longevity and optimization community. TRT stimulates erythropoiesis and can push hematocrit above 54%, significantly increasing thrombotic risk. Regular monitoring and therapeutic phlebotomy when needed are essential. Beyond TRT, hematocrit optimization supports oxygen delivery and exercise capacity — both pillars of healthy aging.
Where to get a Hematocrit test
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Related biomarkers
These biomarkers are often tested alongside Hematocrit for a more complete picture.
Frequently asked questions
What is a normal hematocrit level?
How are hematocrit and hemoglobin related?
Why is high hematocrit dangerous?
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Sources: Reference ranges based on AHA/ACC, ADA, and AACE clinical guidelines. Biological variation data from Ricos/Westgard database. Longevity-optimal ranges reflect targets used by preventive and functional medicine practitioners.
Last reviewed: April 2026. This tool provides general health information and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your healthcare provider about your specific results.