Human blood pH measures the acidity or alkalinity of the blood. The normal range for human blood pH is 7.35 to 7.45, which is slightly alkaline. A lower-than-normal pH indicates acidosis, while a higher-than-normal pH indicates alkalosis. The pH of human blood varies with age, sex, and health status. For example, newborns tend to have a higher pH, while adults tend to have a slightly lower pH.