An ESR (erythrocyte sedimentation rate) test measures how quickly red blood cells settle to the bottom of a tube of blood in one hour. Faster settling suggests inflammation somewhere in the body. Normal ESR rises with age and is higher in women; for men under 50, it is usually 0–15 mm/hr.
What does the ESR test measure?
ESR is one of the oldest and simplest blood tests still in use. A blood sample is placed in a tall, thin tube, and the lab measures how far the red cells have fallen after exactly one hour, in millimetres.
When there is inflammation, the liver releases proteins (such as fibrinogen) that make red cells clump together. Clumped cells are heavier and fall faster, so the ESR goes up. That is why ESR is called a non-specific marker: it shows that inflammation is present, but not where or why.
Doctors in India still use ESR widely for a few practical reasons:
- Investigating long-lasting fever or unexplained weight loss, including when tuberculosis is a possibility.
- Monitoring inflammatory conditions such as rheumatoid arthritis, where trends over weeks matter.
- Supporting other tests: ESR is often ordered with a CBC and CRP to build a fuller picture.
ESR changes slowly, over days to weeks, so it is better for tracking long-term conditions than sudden illness.
ESR normal range (Westergren method)
ESR is naturally higher in pregnancy, older age and anaemia. Ranges vary between labs and methods. Always compare your result with the reference range printed on your own report.
What abnormal results can mean
- Mildly raised ESR: Common with age, anaemia, pregnancy, obesity or a recent minor infection, and often not concerning on its own.
- Moderately to markedly raised ESR: Can suggest infection (including tuberculosis), autoimmune disease such as rheumatoid arthritis, or, less commonly, other serious conditions. Your doctor will look for the cause with further tests.
- Very low ESR: Rarely significant; can occur with some blood conditions such as polycythaemia or sickle cell disease.
Who should get this test?
- People with fever lasting more than a week, night sweats or unexplained weight loss.
- People with joint pain, morning stiffness or muscle aches, especially if persistent.
- People already diagnosed with an inflammatory condition, to monitor treatment.
- As part of a routine checkup, usually alongside a CBC.
- Preparation: No fasting needed.
This page is for general information and is not a substitute for medical advice. Always interpret your results with a qualified doctor.