Ions hydrogene concentration in fluids and tissues is one of the strict regulated physiological organism variables. Most common man and animal diseases are accompanied with compensated acid-base balance shift development. But diagnosis of metabolic acidosis and alkalosis with blood indices (pH, pCO2, HCO3) doesn't reflect true tissue condition that is connected not only with respiratory and excretion system functioning but with hypercompensation of metabolic processes. Excess organic acid formation in case of metabolic alkalosis formation in tissues directed to support pH leads to acidification, what brings an essential mistake in pathogenesis understanding of such diseases as cardiomyopathy, ischemic cardiac disease, myocardial infarction, hepatitis, collagenosis, caries, peptic ulcer, macula dystrophy, atherosclerosis, virus diseases, radiation damages. Ignorance primary tissue damages doesn't allow to conduct necessary preventive measures and to cure disease. It is suggested to assess development of metabolic acidosis and alkalosis by compensated changes of regulation acid-base homeostasis system, which is the basis of all future damages and development of different diseases against this background.