Exenatide effect was studied in 55 human including 38 patients with type 2 diabetes mellitus without signs of diabetic nephropathy and primary renal diseases. Preliminary study with water load in volume from 0.5 to 1% b.w. showed that water load equal to 0.7% b.w. caused significant increase in urine excretion. The rise of diuresis after 10 microg Byetta (exenatide) injection and simultaneous water load of 0.7% of b.w. depended on increase in solute-free water clearance. Thus, exenatide (mimetic of GLP-1) action let us to consider its possible role as component of osmoregulation system in human. This peptide provides high efficiency of renal function in osmotic homeostasis.