Hematocrit Test
Overview
A hematocrit (Hct) test is a type of blood test that shows what portion of the blood consists of red blood cells. Red blood cells help move oxygen throughout the body. Doctors use this test, often as part of a complete blood count (CBC), to check for health conditions. Too few or too many red blood cells may signal a problem.
Reasons for Testing
Healthcare teams often order this test to check for a range of health issues. The results help diagnose or monitor conditions such as anemia and infection.
A Low Hematocrit Result May Signal
- Fewer healthy red blood cells (anemia)
- Loss of blood recently or over time
- Not having enough vitamins or minerals
A High Hematocrit Result Can Be Linked To:
- Dehydration
- Polycythemia vera, which causes the body to make too many red blood cells
- Heart or lung problems
- Living at high elevations
Doctors use the test as part of a complete blood count (CBC) to guide treatment decisions and track how well someone responds to care. It plays an important role in identifying changes in overall health.
Getting Ready for the Test
No special steps are needed. People can eat, drink, and take any usual medicines before technicians collect their blood sample.
What to Expect During the Procedure
A healthcare worker uses a small needle to draw blood from a vein in the arm. Some people may notice a pinch or minor discomfort. After the sample, individuals can continue daily activities as usual.
Key Parts Measured
- Red blood cells
- White blood cells (including neutrophils)
- Hemoglobin
- Platelets
- Other blood components
The process checks blood cell count and may serve for whole blood analysis or before a blood transfusion.
Findings
Test Result Reliability
The hematocrit test shows the percentage of red blood cells in a person’s blood. This percentage is known as the hematocrit level. Laboratories display the result as a percentage and compare it to a normal reference range to help doctors understand if it falls within healthy limits.
These limits can differ by population, so each laboratory may have slightly different reference ranges based on people who live in their area. For most adults:
| Group | Typical Range (%) |
|---|---|
| Men | 38.3 – 48.6 |
| Women | 35.5 – 44.9 |
For children under 15, the normal hematocrit range depends on both age and sex.
The normal range, often called the “reference range,” helps health professionals decide if additional tests or follow-up are needed. Minor differences can exist between labs or regions due to differences in the sample population.
Several situations can influence hematocrit results even if a person is healthy. Living at a high altitude or severe dehydration may increase hematocrit. Pregnancy or significant blood loss may lower results. Blood transfusions can temporarily increase hematocrit as well.
Doctors consider these factors when evaluating hematocrit test results to prevent misinterpretation. If a result does not fit a person’s overall health picture, healthcare providers may repeat the test or order other lab tests to get more information.
Consideration List
- High Altitude: May make hematocrit higher than normal.
- Pregnancy: Usually lowers hematocrit.
- Heavy Blood Loss: Can cause a temporary drop.
- Recent Transfusions: May temporarily raise levels.
- Dehydration: Can artificially raise hematocrit.
When hematocrit is outside the typical range, it does not always mean there is a medical problem. Test accuracy depends on many factors, so healthcare providers take a complete look at health and recent events before making decisions.
