A common pH definition is: a logarithmic scale, from 1 to 14, used to describe the acidity or alkalinity of a solution. Blood & saliva in the human body should be close to 7.4 on the pH scale. A pH level of less than 7 indicates an acidic solution while a pH greater than 7 indicates an alkaline solution. Correctly applying pH testing as a diagnostic to establish a person's acidity levels can indicate potential cause of illness or disease. An over acidic body is an indicator of compromised overall health.