Erythrocyte Sedimentation Rate (ESR)
Also known as: Sed rate, Westergren ESR, Sedimentation rate
ESR measures how quickly red blood cells settle in a tube — inflammation makes them clump and fall faster. It is a non-specific but clinically useful marker for detecting and monitoring inflammatory conditions.
Venous blood (Westergren tube or EDTA)
1–2 hours
Not required
Inflammation & Infection
Reference Ranges
| Measurement | Reference Range | Unit |
|---|---|---|
| Men (< 50 years) | ≤ 15 | mm/hr |
| Men (> 50 years) | ≤ 20 | mm/hr |
| Women (< 50 years) | ≤ 20 | mm/hr |
| Women (> 50 years) | ≤ 30 | mm/hr |
Reference ranges are typical adult values. Your laboratory may use slightly different intervals — always use your lab's reported reference.
What This Test Measures
During inflammation, fibrinogen and other acute-phase proteins coat red blood cells, causing them to clump (rouleaux formation) and fall more quickly. The ESR records how many millimetres the RBCs fall in one hour. It reflects systemic inflammation but does not identify the cause — it is always interpreted alongside clinical context and other tests.
When Is This Test Ordered?
- Screening for and monitoring rheumatoid arthritis, temporal arteritis, or polymyalgia rheumatica
- Detecting occult infection or chronic inflammatory disease
- Monitoring inflammatory bowel disease activity
- Evaluating unexplained fever or weight loss
- Suspected multiple myeloma (ESR often extremely high)
When Results Are High
Above 100 mm/hr strongly suggests a serious pathology: multiple myeloma, other malignancies, severe autoimmune disease, or major infection. Moderate elevation (30–100 mm/hr) is non-specific and requires clinical correlation. Temporal arteritis is an important emergency cause in elderly patients — ESR often exceeds 50 mm/hr.
When Results Are Low
A very low or zero ESR can occur in polycythaemia (too many RBCs) or sickle cell disease — cells do not clump normally in these conditions. Otherwise, low ESR simply means low inflammation.
ESR vs CRP: when to use each
CRP rises within 6–12 hours and normalises quickly — ideal for tracking acute changes. ESR rises over 24–48 hours and normalises slowly over weeks — useful for monitoring chronic or recurrent disease. In temporal arteritis, both are used together; a normal ESR with a normal CRP makes the diagnosis unlikely.
In multiple myeloma, the ESR is a classic finding (often above 100 mm/hr) because the abnormal immunoglobulins dramatically coat red blood cells. CRP may be only modestly elevated in the same patient.
Factors That Can Affect Your Result
- Pregnancy — ESR rises progressively through all trimesters
- Anaemia falsely raises ESR (fewer cells, faster fall)
- Polycythaemia falsely lowers ESR
- High fibrinogen from any cause raises ESR
- Sickle cell disease — abnormal cells resist clumping, lowering ESR
- Room temperature — samples must be processed within 2 hours or ESR is unreliable
Tracking This Test Over Time
In temporal arteritis and polymyalgia rheumatica, ESR is used to monitor corticosteroid response. A falling ESR as the steroid dose is tapered confirms disease control. A rise warns of relapse before symptoms fully return.
Track your ESR in LoomsRelated Tests
CRP
CRP is a protein released by the liver in response to inflammation. Depending on which assay is ordered, it serves as either a sensitive general inflammation marker (standard CRP) or a cardiovascular risk predictor (high-sensitivity CRP, hs-CRP).
CBC
A CBC measures all three types of blood cells — red cells, white cells, and platelets — along with haemoglobin and haematocrit. It is one of the most ordered tests in medicine because it screens for dozens of conditions in a single draw.
Ferritin
Ferritin is the body's primary iron storage protein and the most sensitive blood test for detecting iron deficiency — it falls before haemoglobin or serum iron does. But it is also an acute-phase reactant, which means inflammation can mask deficiency.
Medical disclaimer
This page is for educational purposes only and does not constitute medical advice. Reference ranges vary between laboratories, and results must be interpreted in the context of your symptoms, history, and other tests. Always discuss your results with your healthcare provider. Content reviewed by the Looms medical team, 2026-06-01.