Hematocrit (HCT)
Hematocrit measures the proportion of your blood that is made up of red blood cells. It is closely related to hemoglobin — when one is low, the other usually is too. Hematocrit helps doctors assess anemia, dehydration, and blood disorders, and is part of every complete blood count (CBC).
Reference Ranges
Male
38.3 – 48.6
%
Female
35.5 – 44.9
%
Child
35 – 45
%
Ages 6–12
Reference ranges may vary by laboratory. Always compare with the range printed on your lab report.
What Low Levels Mean
Low hematocrit indicates anemia or overhydration. Symptoms include fatigue, weakness, and paleness. Causes overlap with low hemoglobin — iron deficiency, chronic disease, blood loss, or nutritional deficiencies.
What High Levels Mean
High hematocrit can result from dehydration (most common), chronic lung disease, living at high altitude, or polycythemia vera. Thicker blood flows less easily and raises clot risk.
Frequently Asked Questions
What is the difference between hemoglobin and hematocrit?
Hemoglobin measures the actual protein that carries oxygen, while hematocrit measures the percentage of blood volume occupied by red blood cells. They usually move in the same direction — if one is low, the other typically is too.
Can dehydration affect hematocrit?
Yes. Dehydration reduces plasma volume, which concentrates red blood cells and artificially raises hematocrit. Drinking adequate fluids before a blood test gives a more accurate reading.
What hematocrit level is dangerous?
Below 25% is considered severe anemia and may require transfusion. Above 55% significantly increases clot risk and needs investigation. Both extremes require prompt medical attention.
This information is for educational purposes only and should not replace professional medical advice. Always consult your doctor for interpretation of your test results.
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