Hematocrit blood test
In short
A typical adult hematocrit result is 35.5 to 44.9 % for women and 38.3 to 48.6 % for men. A slightly high level most often comes from dehydration, smoking or living at high altitude. It usually moves with hemoglobin, so the two are read together. Always read your result against the range printed on your own report.
How much of the blood's volume is red blood cells.
Hematocrit is the share of the blood's volume taken up by red blood cells. It usually moves together with hemoglobin, so doctors read the two side by side. Dehydration can push it up, because the liquid part of the blood shrinks.
Is my Hematocrit high or low?
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Typical range
| For | Range | Unit |
|---|---|---|
| Female | 35.5–44.9 | % |
| Male | 38.3–48.6 | % |
| Female · as a fraction (L/L) | 0.355–0.449 | ratio |
| Male · as a fraction (L/L) | 0.383–0.486 | ratio |
Typical ranges for adults. Labs differ a little, so the range printed next to your result is the one to go by.
If your Hematocrit is high
A slightly high level most often comes from dehydration, smoking or living at high altitude. It usually moves with hemoglobin, so the two are read together.
Common reasons
- Not drinking enough before the test (dehydration)
- Smoking, which pushes the body to make more red cells
- Living at high altitude
- Sleep apnea (breathing pauses in sleep) or a long-term lung condition
- Some hormone treatments, especially male hormone therapy
- Less often: polycythemia vera, a bone marrow condition making too many red cells
If your Hematocrit is low
A low hematocrit usually comes with low hemoglobin, which is called anemia. Mild anemia is common, and the other red cell results usually point to the reason.
Common reasons
- Low iron, often from heavy periods or pregnancy
- Pregnancy, when extra fluid naturally thins the blood
- Low vitamin B12 or folate
- Long-term kidney disease or ongoing inflammation
- Recent bleeding, surgery or blood donation
- Less often: slow, hidden bleeding from the stomach or bowel
- Less often: red cells breaking down early, or a bone marrow problem
What can throw it off
Dehydration raises hematocrit, while pregnancy and IV fluids in hospital lower it.
Questions to take to your appointment
- 1Does my hemoglobin tell the same story?
- 2Could I have been dehydrated when the blood was taken?
- 3Should we repeat it before looking further?
Read together with
Doctors rarely read Hematocrit alone. These usually sit next to it.
Quick answers
What is the hematocrit blood test?
Hematocrit: How much of the blood's volume is red blood cells. Hematocrit is the share of the blood's volume taken up by red blood cells. It usually moves together with hemoglobin, so doctors read the two side by side. Dehydration can push it up, because the liquid part of the blood shrinks.
What is a normal hematocrit level?
For most adults, hematocrit is typically 35.5 to 44.9 % for women and 38.3 to 48.6 % for men. Some countries print it in ratio, so check the unit first. Labs differ a little, so the range printed next to your result is the one to go by.
What does a high hematocrit mean?
A slightly high level most often comes from dehydration, smoking or living at high altitude. It usually moves with hemoglobin, so the two are read together. Common reasons include not drinking enough before the test (dehydration); smoking, which pushes the body to make more red cells; living at high altitude; and sleep apnea (breathing pauses in sleep) or a long-term lung condition. A doctor reads it together with your other results and how you feel.
What does a low hematocrit mean?
A low hematocrit usually comes with low hemoglobin, which is called anemia. Mild anemia is common, and the other red cell results usually point to the reason. Common reasons include low iron, often from heavy periods or pregnancy; pregnancy, when extra fluid naturally thins the blood; low vitamin B12 or folate; and long-term kidney disease or ongoing inflammation.
What can affect my hematocrit result?
Dehydration raises hematocrit, while pregnancy and IV fluids in hospital lower it.
What should I ask my doctor about my hematocrit?
Questions worth taking to the appointment: Does my hemoglobin tell the same story? Could I have been dehydrated when the blood was taken? Should we repeat it before looking further?
What this page can’t do
It reads each number on its own.
Doctors read results together — ALT with AST, ferritin with hemoglobin, TSH with free T4. A pattern says more than any single flag.
It doesn't know you.
Your age, your medicines, how you feel and your last result all change what a number means.
It doesn't remember.
Close this page and your results are gone. That's on purpose: nothing was ever sent to us.
We also make Vita: Health Coach, an app for those parts. It reads your whole report with your medicines and history in mind, answers follow-up questions in plain words, and keeps your reports in one place — for you and for the people you look after.
Vita: Health Coach on the App StoreSources
- Mayo Clinic Laboratories — CBC with differential, reference values
- MedlinePlus — Complete blood count (CBC)
Stuck on a word? See the medical words. How we choose our sources. More about Vita Health Coach.