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Erythrocyte Sedimentation Rate (ESR) - Serum

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

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

Quick summary

["ESR helps doctors check for inflammation, often used alongside other tests to diagnose conditions like infections or autoimmune diseases."]

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

Key facts at a glance

LOINC
23233-0
Short code
Mite Skin Sedimentation
Synonyms
Mite Skin Sedimentation
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Ref low
0
Ref high
17
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
Method
sedimentation
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 ESR Measures

ESR measures the rate at which red blood cells (RBCs) fall to the bottom of a test tube over a specific period, typically 1 hour. This rate can be influenced by factors like the presence of proteins (such as fibrinogen) that help RBCs clump together, making them settle faster. The test does not directly measure the amount of inflammation but is often used as a general indicator.

Why It’s Done

Doctors may order an ESR to help diagnose or monitor conditions such as infections, autoimmune diseases (like rheumatoid arthritis), inflammatory diseases (like lupus), or other conditions causing chronic inflammation. It can also be used to assess the effectiveness of treatments for these conditions.

How It’s Done

A small blood sample is drawn from a vein, usually in your arm. The blood is placed in a test 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. The result is reported in millimeters per hour (mm/h).

What the Results Mean

ESR results can vary based on age, sex, and overall health. Higher ESR levels may suggest inflammation or infection, while lower levels may indicate no inflammation or a less active condition. However, ESR alone is not a definitive test for diagnosing any specific condition and should be interpreted alongside other clinical findings and tests.

Reference range

NCBI: NSE 0-17 ng/mLN/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

ESR

Frequently asked questions

What causes an elevated ESR?
Elevated ESR levels can be caused by a variety of conditions, including infections (like pneumonia or tuberculosis), autoimmune diseases (like lupus or rheumatoid arthritis), inflammatory diseases (such as inflammatory bowel disease), or other health issues like cancer or anemia. It’s important to note that ESR can also be influenced by factors like smoking, pregnancy, or certain medications.
What causes a normal or low ESR?
A normal or low ESR may indicate no active inflammation in your body. It can also occur in people with certain genetic conditions, older adults, or those who are not experiencing acute illness. However, a low ESR does not necessarily mean there is no underlying health concern, so further evaluation may be needed if symptoms persist.
How often should I get this test?
The frequency of ESR testing depends on your medical condition and why the test was ordered. If you have a chronic condition like rheumatoid arthritis, your doctor may recommend regular monitoring. If you are asymptomatic and the test was done for screening or routine check-ups, it may not be repeated unless symptoms or other test results suggest a need for follow-up.
  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