The Hct blood test measures hematocrit, which is the percentage of red blood cells in the blood. This value helps assess oxygen-carrying capacity and is commonly used to support the diagnosis of conditions like anemia and dehydration.
Hematocrit (Hct) levels can reflect the amount of hemoglobin in red blood cells, with low values often linked to anemia or nutrient deficiencies. High levels are usually associated with dehydration, low blood oxygen, or conditions that increase red blood cell production.
The Hct blood test is not diagnostic on its own and is typically evaluated with other blood test results and clinical findings. Normal ranges vary by age and sex, and abnormal results may indicate issues such as bleeding, malnutrition, lung disease, or pregnancy-related changes.
Reference ranges
Hematocrit reference ranges can vary depending on the lab, age, sex, pregnancy status, and other factors. In general, normal hematocrit levels are about:
- Women: 35% to 45%
- Men: 40% to 50%
- Children: varies by age, but often around 32% to 44%
During pregnancy, hematocrit levels may be lower due to increased blood volume.
Hematocrit results should be interpreted alongside other results from a complete blood count (CBC), as well as the patient’s symptoms and physical exam. Small changes in hematocrit are not always clinically significant, so results should be evaluated by the ordering provider.
Low Hct
Low Hct levels may indicate:
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Anemia
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Bleeding
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Malnutrition
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Deficiencies in vitamin B12, folate, or iron
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Leukemia
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Excessive hydration
During pregnancy, a low hematocrit may suggest anemia, particularly when ferritin and hemoglobin levels are also low.
According to the CDC, anemia during pregnancy can increase the risk of maternal and fetal complications, including premature delivery and other adverse outcomes. Although anemia during pregnancy is relatively common in pregnancy, it should be properly evaluated and managed.
High Hct
Elevated Hct levels are often caused by reduced plasma volume (less water in the blood), as seen with dehydration. In these cases, red blood cell and hemoglobin levels are typically also increased.
Hct may also be elevated in conditions such as lung disease, congenital heart disease, chronic low blood oxygen levels, or polycythemia (excess red blood cell production).