Medical Definition of pH

  • Medical Author:
    William C. Shiel Jr., MD, FACP, FACR

    Dr. Shiel received a Bachelor of Science degree with honors from the University of Notre Dame. There he was involved in research in radiation biology and received the Huisking Scholarship. After graduating from St. Louis University School of Medicine, he completed his Internal Medicine residency and Rheumatology fellowship at the University of California, Irvine. He is board-certified in Internal Medicine and Rheumatology.

pH: A measure of the acidity or alkalinity of a fluid. The pH of any fluid is the measure of its hydrogen ion (H+) concentration relative to that of a given standard solution. The pH may range from 0 to 14, where 0 is most acid, 14 most basic, and 7 is neutral.

Mathematically, the pH is the logarithm (to the base 10) of the reciprocal of the hydrogen ion concentration, [H+]. The pH is approximately equal to the negative logarithm of the H+ ion concentration expressed in molarity.

See also: Blood pH; Urine pH.

Reviewed on 12/21/2018

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