A normal ESR indicates that a human body contains a typical amount of inflammation, according to MedlinePlus. Medical conditions that can cause an abnormal ESR, or erythrocyte sedimentation rate, include pregnancy, thyroid or kidney disease, anemia, and some cancers.
To test the ESR level, a blood sample is taken from a vein inside the elbow or on the back side of the hand, notes MedlinePlus. The blood is tested by a lab to determine how quickly red blood cells sink to the bottom of the specimen. Conditions that sometimes precede an ESR test include muscle pain, some types of arthritis, fevers and other symptoms for which no cause has been found. The test is not used as a diagnosis for specific medical conditions. An abnormal ESR test helps determine a diagnosis but does not indicate on its own that a particular medical condition is present.