Visit 1 (day 1) Participant voluntarily agrees to participate by giving informed written consent. Baseline study assessment is going to be performed fasting: blood count and differential, blood chemistry (liver enzymes, sodium, potassium, calcium, phosphorus, magnesium, chloride, serum amorality, urea and creatinine, lipid panel including cholesterol, triglycerides, HDL and LDL cholesterol, coagulation, uric acid, glucose and insulin, renin activity, aldosterone, GLP1 level, T4 TSH-thyroid stimulating hormone, ADH, BNP) In the 24 h urine collection sodium, chloride and calcium excretion, osmolality, creatinine are going to be measured, glomerular filtration is going to be assessed by creatinine clearance, urin analysis with microscopy is going to be preformed, EKG, kidney ultrasound together with 24-h blood pressure monitor. HOMA2 (The Homeostasis Model Assessment ) index is calculated and a total body water percentage determinated via Bioelectrical Impedance Analysis. All samples of renin activity and aldosterone in a study are going to be taken while being in horizontal position at least for 3 hours. Participants are going to be randomized regarding the glucose tolerance test. First group it the one with fasting glucose 4,5 -5,7 mmol/L and at 2 hour OGTT (the amount of sodium in OGTT fluid used is 0,4 mg of sodium and 0,3 mg of chloride in 0,2 L of water) glucose level below 7.8 mmol/l. The other group is the one with fasting glucose from 5,7 to 7 mmol/l and/or at 2 hour OGTT glucose level form 7.8 mmol/l to 11,1 mmol/L (venous sample). Patients are instructed to come on the next day fasting again.