Acute kidney injury (AKI) is a broad clinical syndrome comprising acute kidney diseases, non-specific and extrarenal patho-logical conditions. Definition and staging of AKI according to KDIGO classification are based on preceding RIFLE and AKIN criteria and studies on risk relationships. Diagnosis of chronic kidney disease (CKD) is assessed on base of the cause of disease, glomerular filtration rate and albuminuria categories. KDIGO classification of CKD divides stage 3 into two categories G3a and G3b with different risk profiles. CKD-EPI equation for estimating eGFR should be implemented in biochemical laboratories.