In this article six patients with hypokalemic metabolic alkalosis, classified as Bartter or Gitelman syndrome are presented. Both syndromes result from different gene mutation inducing impaired function of the transporters involved in sodium, chloride and potassium reapsorption in thick ascending limb of the loop of Henle and distal convoluted tubules. These syndromes typically present with hypokalemia, metabolic alkalosis, hyperreninemic hyperaldosteronism without hypertension, polyuria and muscle weakness. Other clinical characteristics may vary considerably, depending on the gene expression. Correct diagnosis is only possible using expensive and not-routinely available genetic testing. Routine laboratory tests, especially those considering serum and urine electrolytes, can help in recognizing these syndromes and therefore in timely beginning of treatment. The most important distinctive laboratory findings are serum magnesium concentration and urine calcium excretion. In Bartter syndrome typically there is hypercalciuria with or without hypomagnesemia, while in Gitelman syndrome typical findings are hypocalciuria and hypomagnesemia. Recognizing and treating these patients is important due to possible increased morbidity and mortality induced by severe electrolyte imbalance.