The ESR test (erythrocyte sedimentation rate) measures how fast red blood cells settle to the bottom of a thin tube of blood in one hour. When there is inflammation in the body, proteins in the blood make red cells clump together and fall faster, so the ESR rises. It is a cheap, simple test, but it is non-specific: it shows that something is going on, not what it is. This guide explains the two standard methods, the Westergren and Wintrobe methods, normal values and what high or low results mean.
Quick answer: ESR is reported in millimetres per hour (mm/hr). With the Westergren method, a rough upper limit of normal is your age divided by 2 for men, and (age + 10) divided by 2 for women; in young adults it is usually under 15 mm/hr for men and under 20 mm/hr for women. A raised ESR can be caused by infection, autoimmune disease, anemia, pregnancy, kidney disease, some cancers or simply older age, so it is always interpreted with your symptoms and other tests.
Key takeaways
- ✅ ESR rises with inflammation but cannot diagnose any single disease.
- ✅ Westergren is the reference method recommended by the International Council for Standardization in Haematology (ICSH).
- ✅ Women, older adults and pregnant women normally have higher values.
- ✅ A very high ESR (above 100 mm/hr) needs careful investigation.
Principle of the ESR test
Blood mixed with an anticoagulant is left standing in a vertical tube. Red cells are heavier than plasma and slowly sink. Normally they carry a negative charge that keeps them apart. In inflammation, the liver makes more fibrinogen and globulins, which reduce this charge and make red cells stack like coins (rouleaux). These stacks fall faster, so the clear plasma column at the top is longer after one hour. That length, in millimetres, is the ESR.
Westergren vs Wintrobe method
| Westergren method | Wintrobe method |
|---|
| Tube | Long, open tube, 200 mm graduated, about 2.5 mm bore | Shorter tube, 100 mm graduated, about 2.5 to 3 mm bore |
| Anticoagulant | 3.8% sodium citrate (4 parts blood to 1 part citrate) or EDTA blood diluted as per protocol | Undiluted EDTA or double oxalate blood |
| Sensitivity | Better at showing high values because the tube is longer | Less sensitive at high values; the same tube can also give the PCV (hematocrit) |
| Use today | Reference method; most labs and automated analysers are calibrated against it | Older method, still taught and used in some labs |
Procedure (Westergren method)
- Collect venous blood into sodium citrate (or EDTA) as the lab requires and mix gently.
- Fill the Westergren tube to the zero mark without air bubbles.
- Place the tube exactly vertical in the stand, at room temperature, away from vibration and direct sunlight.
- After exactly 60 minutes, read the distance from the top of the plasma to the top of the red cell column in mm.
- Test within a few hours of collection, as delays and refrigeration change the result.
No fasting or special preparation is needed for the patient.
Normal ESR values
| Group | Westergren (approximate upper limit) | Wintrobe |
|---|
| Men under 50 | Up to 15 mm/hr | 0 to 9 mm/hr |
| Women under 50 | Up to 20 mm/hr | 0 to 20 mm/hr |
| Men over 50 | Up to 20 mm/hr | — |
| Women over 50 | Up to 30 mm/hr | — |
| Children | Up to about 10 mm/hr | 0 to 13 mm/hr |
Ranges differ between labs, so use the reference range printed on your report.
Causes of a high ESR
- Infections: tuberculosis, bone and joint infections, endocarditis, pneumonia
- Autoimmune and inflammatory disease: rheumatoid arthritis, lupus, polymyalgia rheumatica, giant cell arteritis (temporal arteritis), inflammatory bowel disease
- Blood and cancer-related: multiple myeloma, lymphoma and some other cancers
- Other: anemia, pregnancy, chronic kidney disease, older age, obesity
An ESR above 100 mm/hr is strongly linked to serious infection, autoimmune disease or cancer and should always be investigated.
Causes of a low ESR
- Polycythaemia (too many red cells)
- Sickle cell disease and other abnormally shaped red cells
- Very low fibrinogen, severe heart failure
- Technical errors, such as a tilted tube or delay in testing
ESR vs CRP
C-reactive protein (CRP) is another marker of inflammation. CRP rises and falls within a day or two, while ESR changes more slowly over days to weeks. Doctors often order both: CRP to track acute infection, and ESR in conditions such as polymyalgia rheumatica, giant cell arteritis and bone infections.
Frequently asked questions
Is a high ESR always serious?
No. Mildly raised ESR is common with minor infections, anemia, pregnancy and ageing. It becomes more significant when it is very high or comes with symptoms such as fever, weight loss or joint pain.
Can ESR diagnose TB?
No. ESR is often raised in TB, but many other conditions raise it too. TB is diagnosed with sputum tests and X-rays.
How quickly does ESR return to normal?
It falls slowly, often over several weeks after the illness settles, so a repeat test too soon may still look high.
Related reading: Complete blood count tests and tuberculosis tests and treatment.
Last updated: September 2026. General health and laboratory information only, not a diagnosis. Please interpret results with a qualified doctor.
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