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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 time. It can help identify inflammation in your body.

Quick summary

["ESR helps doctors check for inflammation, often used in conditions like infections, autoimmune diseases, or after injuries."]

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

Key facts at a glance

LOINC
7297-5
Short code
Eggplant IgG Qn
Synonyms
Eggplant IgG Qn
Category
chemistry
Sample
serum
Container
Red-top tube (SST)
Units
N/A
Fasting
false
Population
adult
Sex
all
Age range
18–65 years
CPT
82784
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) clump together and sink to the bottom of a test tube over one hour. This clumping, called erythrocyte aggregation, is influenced by proteins like fibrinogen and inflammation markers. Higher ESR often indicates inflammation, though it can also be influenced by factors like age, sex, and hydration levels.

Why ESR Might Be Ordered

Your doctor may order an ESR to monitor conditions like rheumatoid arthritis, lupus, infections, or after surgery to check for healing progress. It’s also used to screen for hidden inflammation in conditions like cancer or heart disease.

How ESR Results Are Interpreted

ESR results alone don’t diagnose a condition—they’re part of a broader picture. Doctors compare your ESR to your symptoms, other test results, and medical history. While ESR can be elevated in inflammation, it can also be normal even when inflammation is present.

What to Expect Before or After the Test

This test is quick and painless. You’ll provide a blood sample, usually from your arm, and the lab will analyze it. No special preparation is needed, but tell your doctor about any medications or conditions that might affect results.

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Short name

ESR

Frequently asked questions

Can ESR results be affected by what I eat or drink?
Diet and hydration can slightly influence ESR, but the effect is usually minor. Avoiding heavy meals or caffeine before the test may help, but it’s not a strict requirement.
Is ESR the same as C-reactive protein (CRP)?
No, ESR and CRP are different. ESR measures red blood cell settling speed, while CRP is a protein in blood that rises with inflammation. Both are inflammation markers but serve different purposes in diagnosis.
When might my doctor order ESR repeatedly?
Your doctor may repeat ESR tests to monitor chronic conditions (like arthritis) or track response to treatment. It’s also used in follow-ups for conditions where inflammation is suspected but not confirmed.
  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