ESR (Erythrocyte Sedimentation Rate)

ESR (erythrocyte sedimentation rate) is a simple blood test that measures how quickly red blood cells settle to the bottom of a tube over one hour. When inflammation is present in the body, certain proteins cause red cells to settle more quickly, so a faster rate suggests inflammation. This makes ESR a useful general marker for detecting and monitoring inflammation.

What it can help assess

• Detecting inflammation: a raised ESR indicates inflammation somewhere in the body, although it does not identify the exact location or cause
• Monitoring inflammatory conditions: it is widely used to track the activity of conditions such as arthritis and other autoimmune diseases, and to monitor response to treatment
• Supporting the investigation of infections and other illnesses, alongside your symptoms and other tests

An important note on interpretation

ESR is a non-specific test, meaning it tells you that inflammation may be present but not what is causing it. Levels can rise with infection, inflammation, and many other conditions, and can also be affected by factors such as age, sex, pregnancy, and anaemia. For this reason, the result is always interpreted alongside your symptoms and other clinical information, and a raised result usually means further assessment is needed rather than giving a diagnosis on its own.

Why it matters

ESR is a long-established and valuable test for picking up inflammation that might otherwise go unnoticed, and for tracking known inflammatory conditions over time. It is often used together with other markers, such as CRP, to build a fuller picture. Any raised or abnormal result should be discussed with your GP, who can consider the likely cause in the context of your overall health.