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Erythrocyte Sedimentation Rate (ESR) – Serum

Published: August 9, 2026Updated: August 16, 2026

This test measures how quickly red blood cells settle in a sample of your blood over a set period. It can help identify inflammation in your body.

Quick summary

["ESR helps detect inflammation, often used alongside other tests to assess conditions like infections, autoimmune diseases, or injuries."]

Medically reviewed by WellAlly Editorial TeamLast reviewed August 16, 2026Editorial policy

Key facts at a glance

LOINC
20924-7
Short code
O+P Stl Sedimentation
Synonyms
O+P Stl Sedimentation
Category
chemistry
Sample
stool
Container
Clean container
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
sedimentation
Specimen volume
5 g
Stability
Refrigerated: 24h, Frozen: 7d
TAT
4–24 hours
Order
routine

What ESR Measures

ESR measures the rate at which red blood cells (RBCs) clump together and sink to the bottom of a test tube over one hour. This clumping is influenced by proteins like fibrinogen in your blood, which can be affected by inflammation. The slower the RBCs settle, the higher the ESR, which may signal underlying inflammation or infection.

Why It’s Done

Your doctor may order an ESR to monitor conditions like rheumatoid arthritis, lupus, or infections. It’s also used to check for signs of inflammation after surgery, injury, or during certain treatments.

How It’s Performed

A small blood sample is drawn from a vein, usually in your arm. The blood is placed in a special tube with an anticoagulant to prevent clotting. The tube is then tilted upright, and the time it takes for the red blood cells to settle is measured.

What to Expect Before or After

There are no special preparations needed. You may feel slight discomfort or bruising at the injection site, but this usually fades quickly. If you have a bleeding disorder or take blood thinners, let your doctor know before the test.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

ESR

Frequently asked questions

When might my ESR be checked?
Your doctor may check your ESR if you have symptoms like joint pain, fever, fatigue, or if they suspect an infection, autoimmune disease, or other inflammatory condition.
What do my ESR results mean?
Your ESR result alone doesn’t diagnose a condition. It’s part of a broader evaluation. Elevated ESR may suggest inflammation, but doctors consider other factors like your medical history, symptoms, and test results to determine the cause.
Can lifestyle changes affect ESR?
Yes, lifestyle factors like diet, exercise, and stress can influence inflammation levels, which may indirectly affect ESR. However, ESR is not a direct measure of lifestyle health and should not replace medical advice or treatment.
  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 16, 2026. · Read our editorial policy