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Hematocrit

Published: August 9, 2026Updated: August 17, 2026

This test measures the proportion of red blood cells in your blood, which helps assess your blood’s ability to carry oxygen and detect conditions like anemia or polycythemia.

Quick summary

["Hematocrit reflects red blood cell volume and can signal blood disorders or hydration status."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
39227-4
Short code
HEMATOCRITTESTSTATUS
Synonyms
—
Category
hematology
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
36
Ref high
50
Critical range
18 N/A – 60 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
cphs
CPT
85014
Specimen volume
5 mL
Stability
Room temperature: 4h, Refrigerated: 24h, Frozen: 7d
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
4–24 hours
Order
routine

Why It’s Done

Doctors may order a hematocrit test to diagnose or monitor conditions such as anemia (low red blood cells), polycythemia (high red blood cells), dehydration, or blood loss. It’s also used before surgeries, during pregnancy, or if you have symptoms like fatigue or unusual bleeding.

What to Expect

A simple blood draw from a vein in your arm is typically all that’s needed. The test is quick and painless, though you might feel slight discomfort afterward. No special preparation is usually required, but check with your provider if you’re on blood thinners or have a history of clotting issues.

Sample Collection and Processing

Blood is collected in a tube and spun in a centrifuge to separate red blood cells from plasma. The hematocrit percentage is calculated by measuring the red cell layer’s height relative to the total blood volume.

Interpreting Results

Results are compared to general reference ranges, but individual ranges may vary slightly by lab. Low hematocrit may indicate anemia or blood loss, while high levels could signal dehydration, polycythemia, or other conditions. Your provider will discuss findings in context with your symptoms and medical history.

Reference range

Adult males: 38-50%; Females: 36-44%N/A

Specimen: serum

No special preparation required. Stay well hydrated.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

Clinical Significance

Short name

Hematocrit Test

Frequently asked questions

What does a low hematocrit mean?
A low hematocrit often suggests anemia, where your body doesn’t have enough healthy red blood cells to carry oxygen. This could be due to iron deficiency, vitamin deficiencies (like B12 or folate), chronic illness, or blood loss. It may also indicate conditions like kidney disease or autoimmune disorders.
What does a high hematocrit mean?
A high hematocrit may signal polycythemia, where your blood has an excess of red blood cells. This can occur due to dehydration, certain lung diseases, or rare blood disorders. It may also be a side effect of some medications or conditions like chronic obstructive pulmonary disease (COPD).
Can hematocrit change with diet or lifestyle?
Yes, diet and lifestyle can influence hematocrit levels. Eating iron-rich foods (like lean meats, spinach, or fortified cereals) or vitamin B12 and folate (found in leafy greens, beans, and fortified foods) may help maintain healthy red blood cell production. Staying hydrated can also help prevent dehydration-related changes. However, significant shifts often require medical evaluation.
  1. 1
    MedlinePlus — Laboratory TestsSource
  2. 2
    Lab Tests OnlineSource
  3. 3
    Mayo Clinic — Tests & ProceduresSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy