According to WebMD, a high sedimentation rate may be caused by an autoimmune disease, cancer, an infection, joint inflammation, pregnancy, Graves' disease or a viral infection. The sedimentation rate blood tests indirectly measure the amount of inflammation present in the body.
A sedimentation blood test measures the amount of time it takes for red blood cells to settle into a test tube. After an hour, the amount of red blood cells that has settled into the bottom of the test tube is measured. A high sedimentation rate indicates that a high concentration of red blood cells settled to the bottom of the test tube within the hour, states WebMD.