An erythrocyte sedimentation rate (ESR) is a type of blood test that measures how quickly

erythrocytes (red blood cells) settle at the bottom of a test tube that contains a blood sample.

Normally, red blood cells settle relatively slowly. A faster-than-normal rate may indicate

inflammation in the body. Inflammation is part of your immune response system. It can be a

reaction to an infection or injury. Inflammation may also be a sign of a chronic disease, an

immune disorder or other medical condition.