what does esr mean in a blood test

ESR stands for erythrocyte sedimentation rate, which is a blood test that measures how quickly red blood cells settle or sink to the bottom of a test tube. Normally, red blood cells sink slowly, but inflammation can cause them to stick together in clumps, which are heavier than single cells and sink faster. The ESR test measures the distance red blood cells fall in a test tube in one hour, and a higher ESR rate means higher levels of inflammation. However, an ESR test alone cannot diagnose what condition is causing the inflammation, and other tests are almost always needed. An ESR test may be ordered if you have symptoms like unexplained fever, muscle pain, joint pain, headache, or other vague symptoms that cannot be explained. It can help confirm a diagnosis of certain conditions, including giant cell arteritis, polymyalgia rheumatica, and rheumatoid arthritis. An ESR test is usually performed with a sample of blood that is drawn from a vein in your arm, and there is no special test preparation required.