Why ESR values are different in male and female?

ESR stands for Erythrocyte Sedimentation Rate, a blood test which helps doctors diagnose conditions that can cause inflammation. This test measures the distance red blood cells fall in a test tube in one hour. A Normal value for women is less than 20 mm per hour, while normal for men is less than 15 mm per hour. Since women tend to normally have a smaller number of red blood cells the they can more quickly settle in the tube and therefore "fall" to a lower level.