Metabolic acidosis is defined as a decrease of bicarbonates in the blood, below normal range, with a reduction of blood pH. It is a common disorder in chronic kidney disease (CKD). Clinically apparent fairly late (GFR < 30 ml/min/m2), although usually mild, it can have adverse effects on important functions of the human body. In the article the pathomechanism of metabolic acidosis in CKD, its influence on human body and treatment is shortly reviewed.