Urinary fractional excretion potassium is high or inappropriately normal in the context of hypokalaemia, and high levels of urinary sodium and chloride are observed. Other clinical indicators include elevated serum renin and aldosterone in the bloodstream, and metabolic alkalosis. The symptomatic features of this syndrome are highly variable ranging from asymptomatic to mild manifestations (weakness, cramps) to severe symptoms (tetany, paralysis, rhabdomyolysis). Symptom severity is multi-factorial, with phenotypic expression varying amongst individuals within the same family. Genetic testing is another measure of identifying the underlying mutations which cause the pathologic symptoms of the disease. This mode of testing is available at select laboratories.Work-up to exclude the differential diagnosis of the electrolyte abnormalities is key. In Gitelman syndrome hypocalciuria is present, and a urine calcium:creatinine ratio may help distinguish it from Bartter syndrome as the two disorders can be clinically indistinguishable. Additionally in Bartter syndrome maximal urine concentrating ability is lost. Laxative abuse can mimic the serum electrolyte abnormalities, but fractional excretion of potassium will be low
Diuretic abuse could be suspected if urinary chloride excretion varies by time of day but may require a diuretic assay to detect
Surreptitious vomiting can cause metabolic alkalosis and hypokalaemia, but urinary chloride levels will be low
Medication history; Proton-pump inhibitors can cause an isolated hypomagnesaemia phenotype, and aminoglycosides such as gentamicin can cause a transient metabolic alkalosis with hypokalaemia and hypomagnesaemia that resolves 2–6 weeks after drug termination.
Primary aldosteronism will cause metabolic alkalosis and hypokalaemia, but hypertension will be present and serum renin will be low
EAST syndrome, though neurological features will predominate
Renal cysts and diabetes syndrome can cause hypomagnesaemia and hypocalcuria, but is distinguished by early onset chronic kidney disease and an autosomal dominant inheritance pattern of renal cysts and/or diabetes

Treatment
Most asymptomatic individuals with Gitelman syndrome can be monitored without medical treatment. Dietary modification of a high salt diet incorporated with, potassium and magnesium supplementation to normalize blood levels is the mainstay of treatment. Large doses of potassium and magnesium are often necessary to adequately replace the electrolytes lost in the urine. Diarrhea is a common side effect of oral magnesium which can make replacement by mouth difficult but dividing the dose to 3-4 times a day is better tolerated. Severe deficits of potassium and magnesium require intravenous replacement. If low blood potassium levels are not sufficiently replaced with replacement by mouth, aldosterone antagonists (such as spironolactone or eplerenone) or epithelial sodium channel blockers such as amiloride can be used to decrease urinary wasting of potassium.In patients with early onset of the disease such as infants and children, indomethacin is the drug of choice utilized to treat growth disturbances. Indomethacin in a study by Blanchard et al. 2015 was shown to increase serum potassium levels, and decrease renin concentration. Adverse effects of indomethacin include a decrease in the glomerular filtration rate, and gastrointestinal disturbances.Cardiac evaluation is promoted in the prevention of dysrhythmias and monitoring of QT interval activity.