At a Glance
Hematocrit (HCT), also reported as packed cell volume (PCV), is the share of your blood's volume taken up by red blood cells, given as a percentage. It is usually measured as part of a complete blood count (CBC), from a whole-blood sample.
The interval stored on this page is 37.5 to 51%, and every result here is flagged against it. It matches the interval on Labcorp's sample CBC report for a 15-year-old male patient. It is not a range for everyone. Mayo Clinic Laboratories publishes 38.3 to 48.6% for males aged 18 and over and 35.5 to 44.9% for females aged 18 and over. If you are a woman, the interval printed on your own report is the one to read your result against; if you are pregnant, see the pregnancy section below.
A proportion, not a count
StatPearls describes hematocrit as the volume of packed red cells relative to whole blood. Because it is a share, it can change for two different reasons:
- The red cells change. Fewer red cells (anemia, blood loss) lower it; more red cells (polycythemia, or the body's response to low oxygen) raise it.
- The plasma around them changes. Less plasma concentrates the red cells and raises the figure; MedlinePlus names dehydration as the most common cause of a high hematocrit. More plasma dilutes them and lowers it, which is why it can be lower in pregnancy.
StatPearls notes that hematocrit is used with the red cell count and hemoglobin to identify anemia and polycythemia.
The range on your report depends on your sex and age
| Males | Females | |
|---|---|---|
| Mayo Clinic Laboratories, 18 and over | 38.3–48.6% | 35.5–44.9% |
| StatPearls, healthy adults | 40–54% | 36–48% |
The interval stored on this page, 37.5–51%, is applied to everyone. It matches the interval on Labcorp's sample CBC report for a 15-year-old male patient; no Labcorp female interval was read for this page.
The figures differ between sources by a few percentage points, and in both sources that give separate ranges the female range sits lower than the male one; StatPearls states that adult males have a higher hematocrit than adult females. Children have their own intervals: Mayo publishes separate ranges by age, and StatPearls notes newborns have a high hematocrit.
MedlinePlus adds that normal levels vary with age, sex, smoking and the altitude where you live. StatPearls notes that people living at high altitude have a higher hematocrit, as do smokers and people with chronic obstructive pulmonary disease, because of chronic low oxygen.
What this means on this page: a woman's result from 35.5% to just under 37.5% is flagged low here while sitting inside Mayo's female range; a woman's result above 44.9% and up to 51% is not flagged here although it is above Mayo's female range; a man's result from 37.5% to just under 38.3% is not flagged here although it is below Mayo's male range; and a man's result above 48.6% and up to 51% is not flagged here although it is above Mayo's male range.
How to read your result
These steps read a single adult result against the intervals in the table. If you are pregnant, skip to the pregnancy section below; different thresholds apply.
Below 35.5%. Flagged low here, and below Mayo's adult range for both sexes. A low hematocrit means fewer red cells (anemia, blood loss) or more fluid diluting them.
35.5 to under 37.5%. Flagged low here. For a woman this is inside Mayo's female range (35.5 to 44.9), and from 36 inside StatPearls' female range. For a man it is below Mayo's male range, which starts at 38.3, and below StatPearls', which starts at 40.
37.5 to under 38.3%. Inside the stored interval. For a woman, inside Mayo's and StatPearls' female ranges. For a man, just below Mayo's male range and below StatPearls'.
38.3 to 44.9%. Inside the stored interval and inside Mayo's ranges for both sexes. For a man below 40, still below StatPearls' male range.
Above 44.9, up to 48.6%. Inside the stored interval and Mayo's male range. For a woman, above Mayo's female range; inside StatPearls' female range only up to 48, and above it above 48.
Above 48.6, up to 51%. Inside the stored interval, so not flagged here, but above Mayo's male and female ranges and, for a woman, above StatPearls' female range. For a man, inside StatPearls' male range, which runs to 54.
Above 51%. Flagged high here, and above Mayo's adult ranges for both sexes. For a man, still inside StatPearls' male range up to 54, and above it beyond that. A high hematocrit means the red cells take up more of the blood than usual, either because there are more of them or because there is less plasma; MedlinePlus names dehydration as the most common cause.
If you are pregnant
A CBC analyzer does not know you are pregnant, so it may compare your result against a non-pregnant interval. The American College of Obstetricians and Gynecologists defines anemia in pregnancy as a hematocrit below 33% in the first trimester, below 32% in the second and below 33% in the third, all below the lower limit applied on this page.
A fall through pregnancy is expected rather than abnormal. Plasma volume expands by 40–50% against a 15–25% rise in red cell mass, so the concentration drops, and hemoglobin falls by roughly 1–2 g/dL by the late second trimester before stabilizing. The obstetric literature calls that pattern physiologic anemia of pregnancy.
That is a population expectation, not a reading of your own result: StatPearls states that no specific hemoglobin or hematocrit value can distinguish physiologic anemia from other causes of anemia in pregnancy, iron deficiency included. A low value in pregnancy is for your maternity team to interpret.
If you remember only one thing
Hematocrit is a share of your blood's volume, so it moves with the fluid around your red cells as well as with the red cells themselves, and the range it is compared against depends on your sex and on pregnancy.
Two people, same result
Two adults are each told their hematocrit is 37%.
The first is a woman who is not pregnant. Her result is inside Mayo's female range (35.5 to 44.9) and StatPearls' (36 to 48). On this page, which applies 37.5 to 51%, it is flagged low.
The second is a man. His result is below Mayo's male range (38.3 to 48.6) and below StatPearls' (40 to 54), and it is flagged low here too.
Same number and the same flag on this page, but against the ranges for their own sex only one of them is low. Neither reading says why; that needs the hemoglobin, red cell count and a clinician.
What this result cannot tell you
It cannot tell you why a level is high or low. A high hematocrit can come from more red cells or from less plasma; a low one from fewer red cells or more fluid. The number alone does not separate them.
It cannot tell you what kind of anemia you have, if it is low. It is read with the hemoglobin and red cell count, and Mayo notes that results are interpreted in light of your clinical picture and further testing.
It cannot tell you whether a pregnancy result is expected or not. No specific value distinguishes the normal fall of pregnancy from other causes.
Common interpretation mistakes
Reading the flag without checking whose range it is. The stored interval matches Labcorp's sample CBC report for a 15-year-old male patient; a woman at 36% is inside Mayo's female range.
Treating 51% as the upper limit for women. Mayo's female range ends at 44.9%.
Assuming a high result means a blood disorder. MedlinePlus names dehydration as the most common cause of a high hematocrit.
Treating PCV and HCT as two different tests. They are two names for the same measurement; StatPearls notes hematocrit is also known and reported as packed cell volume.
Comparing a pregnancy result with a non-pregnant range. ACOG defines anemia in pregnancy as a hematocrit below 33%, 32% and 33% by trimester.
Questions your doctor may ask
Whether you have had any bleeding, recent or long-term. Whether you were dehydrated when the sample was taken. Whether you smoke, have a lung or heart condition, or live at high altitude. Whether you are or might be pregnant. And what your hemoglobin and red cell count were on the same report.
Read together with
Hemoglobin and the red blood cell count, which StatPearls names as the parameters hematocrit is read with to identify anemia and polycythemia. The MCHC on the same report is calculated from hemoglobin and hematocrit, so an error in hematocrit carries into it; StatPearls also gives the relationship MCV = hematocrit × 10 ÷ red cell count.
Clinical pearls
Most laboratories use an analyzer, not a spun tube. StatPearls notes that the older manual methods have largely been replaced in most settings by automated analyzers, which report hematocrit with the complete blood count.
Two red cell indices are linked to it by formula. StatPearls gives MCV as hematocrit × 10 ÷ red cell count, and MCHC as hemoglobin ÷ hematocrit × 100.
Where the blood comes from matters slightly. StatPearls notes venous blood reads higher than arterial blood, with no difference between venous and finger-prick samples.
Clinical Takeaway
The interval stored here, 37.5 to 51%, matches Labcorp's sample CBC report for a 15-year-old male patient and is applied to every result; Mayo's adult ranges are 38.3 to 48.6% for males and 35.5 to 44.9% for females, and pregnancy has lower thresholds again. Because hematocrit is a share of blood volume, fluid changes move it as well as red cells do, and dehydration is the most common cause of a high result. A single value is read with the hemoglobin and red cell count, not on its own.
In one sentence
Hematocrit is the share of your blood made of red cells; read it against your own sex's range, and remember that fluid moves it too.
Bottom line
Check whose range your result was flagged against, read it with your hemoglobin and red cell count, and treat a single out-of-range value as a question for follow-up rather than a diagnosis.
Hematocrit (HCT) / Packed Cell Volume (PCV)
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Frequently Asked Questions
What is HCT in a blood test?
What does PCV mean on a blood test?
What is a normal hematocrit?
Is a hematocrit of 37.5 normal?
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Is hematocrit the same as hemoglobin?
All our content is backed by peer-reviewed studies, academic research, and trusted medical sources. We’re committed to accuracy and transparency — see our editorial policy for details.
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Anemia in Pregnancy — ACOG Practice Bulletin Number 233
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Physiology, Maternal Blood — StatPearls
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Complete Blood Cell Count (CBC) with Differential, Blood — test 9109
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CBC With Differential/Platelet — test 005009
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Hematocrit
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Hematocrit Test