Hematocrit (Hct)
Hematocrit (Hct) is a measure of the proportion of blood volume occupied by formed elements (mainly red blood cells) relative to total blood volume. It is expressed as a percentage or fraction (L/L) and reflects the blood's oxygen-carrying capacity.
Normal hematocrit values:
- Men: 40–50% (0.40–0.50 L/L)
- Women: 36–46% (0.36–0.46 L/L)
- Children: 32–44% (depending on age)
- Newborns: up to 60%
Causes of increased hematocrit:
- Dehydration (vomiting, diarrhea, burns, fluid loss)
- Chronic hypoxia (high altitude, smoking, lung diseases)
- Polycythemia (increased red blood cell production)
- Shock states, blood thickening
Causes of decreased hematocrit:
- Anemias (especially iron and B12 deficiency)
- Hyperhydration (excess fluid intake or infusion therapy)
- Blood loss (acute or chronic)
- Pregnancy (physiological decrease due to increased plasma volume)
- Chronic inflammatory processes
Why hematocrit is measured:
- To assess the degree of anemia or dehydration
- To diagnose fluid balance disorders
- To monitor blood, heart, kidney, and lung diseases
- As part of a complete blood count and in emergency conditions
How the test is performed:
- Blood is drawn from a finger or vein, fasting
- It is important to avoid physical exertion, smoking, and alcohol 24 hours before the test
Important to know:
- High hematocrit increases blood viscosity and may promote thrombosis.
- Low hematocrit indicates reduced oxygen-carrying capacity and may cause weakness, fatigue, dizziness.
- Hematocrit is always analyzed together with hemoglobin and red blood cell count for accurate blood status assessment.