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Hematocrit [Volume Fraction] in Blood by Calculation

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

This blood test estimates the hematocrit, which is the percentage of red blood cells in the blood. The result is calculated from other laboratory measurements rather than measured directly.

Quick summary

["A calculated hematocrit helps assess the relative proportion of red blood cells in your blood."]

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

Key facts at a glance

LOINC
41654-5
Short code
Hct VFr BldV Calc
Synonyms
Hct VFr BldV Calc
Category
chemistry
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
calculated
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

What the Test Measures

Hematocrit describes how much of your blood is occupied by red blood cells. Red blood cells carry oxygen from the lungs to tissues throughout the body.

How the Result Is Calculated

The laboratory estimates hematocrit using other results, commonly the red blood cell count and hemoglobin level. The calculation is not the same as measuring packed red blood cells directly.

Why It May Be Ordered

A calculated hematocrit may be used when a directly measured hematocrit is unavailable or cannot be obtained. It can support evaluation of anemia, dehydration, blood loss, and other changes in blood composition.

What Affects the Result

Hydration, recent blood loss, transfusion, pregnancy, altitude, and laboratory measurement differences can affect the components used in the calculation. The calculated value should be interpreted alongside the other results from the same blood sample.

Reference range

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

Specimen: serum

No special preparation usually required. Stay well hydrated. Inform your healthcare provider of all medications and supplements you are taking.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

Calculated hematocrit

Frequently asked questions

Is a calculated hematocrit the same as a directly measured hematocrit?
No. A calculated hematocrit is estimated from other laboratory values, while a directly measured hematocrit is determined by centrifuging or analyzing the blood sample.
Does the test require a blood draw?
Yes. It is calculated using results from a blood sample, so it is usually part of a complete blood count or related laboratory panel.
Can hydration change the hematocrit?
Yes. Changes in body fluid can alter the concentration of red blood cells in the circulation, so hydration status may influence the result.
  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