Hematocrit (HCT): What It Is and What Your Results Mean
Hematocrit measures the percentage of your blood volume that is made up of red blood cells. Normal range is 36–44% for women and 40–50% for men. Low hematocrit often indicates anemia, while high hematocrit may suggest dehydration or polycythemia.
What Is Hematocrit?
Hematocrit (HCT) is one of the most commonly ordered blood tests. It tells your doctor what proportion of your blood consists of red blood cells. Since red blood cells carry oxygen throughout your body, hematocrit is a key indicator of your blood's oxygen-carrying capacity.
The test is usually part of a Complete Blood Count (CBC) panel. Your result is expressed as a percentage — for example, a hematocrit of 42% means that 42% of your blood volume is red blood cells.
Normal Hematocrit Ranges
| Category | Range |
|---|---|
| Critically Low | Below 20% |
| Low (Anemia) | 20 – 35% |
| Normal (Women) | 36 – 44% |
| Normal (Men) | 40 – 50% |
| High | 51 – 55% |
| Very High | Above 55% |
What Causes Low Hematocrit?
- Iron deficiency anemia — the most common cause worldwide
- Vitamin B12 or folate deficiency
- Chronic kidney disease — reduced erythropoietin production
- Blood loss — from surgery, injury, or heavy menstruation
- Bone marrow disorders
- Chronic inflammatory conditions
What Causes High Hematocrit?
- Dehydration — concentrates red blood cells, most common cause
- Polycythemia vera — bone marrow overproduces red blood cells
- Chronic lung disease or heart disease
- Living at high altitude
- Smoking
- Use of erythropoietin (EPO)
Look Up Your Hematocrit Value
Select your hematocrit result below to see what it means:
Frequently Asked Questions
Normal hematocrit is 36-44% for women and 40-50% for men. Children and pregnant women may have different reference ranges.
Low hematocrit usually indicates anemia, meaning you have fewer red blood cells than normal. This can be caused by iron deficiency, blood loss, vitamin deficiencies, or chronic disease.
Yes. Dehydration reduces plasma volume, which artificially raises your hematocrit percentage. Proper hydration before testing gives the most accurate result.