What is acid in the blood?

General term: Acid has to do with the pH of the blood - a measurement which is done. Our normal pH is 7.35-7.45 or thereabouts. If your pH is less than this then you are "acidotic". It relates your acid-base balance in your bloodstream.

Imbalance: Normally, people have acid production from metabolic activities that goes to blood and gets neutralized by alkali produced by kidneys. In kidney failure, acid is noted in blood since it is not neutralized. Other cases include diabetes type i, chronic diarrhea, certain meds, sepsis with blood infection, and respiratory (ventillatory) failure among other more rare causes.