Acid-base balance must be maintained in the body fluid. This balance can easily be upset by pathological conditions such as infection, inappropriate use of medications, or trauma—resulting in an acid-base imbalance that can be more detrimental to the outcome of the patient’s health than the initial cause of the person’s illness.

The hydrogen ion (H⁺) concentration in body fluids is very small, around 0.0000001 mg/L or 10⁻⁷. Because the H⁺ concentration is so low, the power of hydrogen (pH) is expressed as the negative logarithm, 10⁻⁷, with the neutral point of a pH of 7.0 in the clinical setting. The pH value is inversely related to the hydrogen ion concentration; therefore as the pH decreases the solution becomes more concentrated with H⁺ and as the pH rises the solution becomes less concentrated with H⁺. In the body, fluids with a pH < 7.40 are considered to be acidic; those with a pH > 7.40 are alkaline.