Caffeine-induced hypokalemia: a case report.

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Background: With an increase in the global popularity of coffee, caffeine is one of the most consumed ingredients of modern times. However, the consumption of massive amounts of caffeine can lead to severe hypokalemia.Case presentation: A 29-year-old man without a specific past medical history was admitted to our hospital with recurrent episodes of sudden and severe lower-extremity weakness. Laboratory tests revealed low serum potassium concentration (2.6-2.9 mmol/L) and low urine osmolality (100-130 mOsm/kgH₂O) in three such prior episodes. Urinary potassium/urinary creatinine ratio was 12 and 16 mmol/gCr, respectively. The patient was not under medication with laxatives, diuretics, or herbal remedies. Through an in-depth interview, we found that the patient consumed large amounts of caffeine-containing beverages daily, which included > 15 cups of coffee, soda, and various kinds of tea. After the cessation of coffee intake and concomitant intravenous potassium replacement, the symptoms rapidly resolved, and the serum potassium level normalized.Conclusions: An increased intracellular shift of potassium and increased loss of potassium in urine due to the diuretic action have been suggested to be the causes of caffeine-induced hypokalemia. In cases of recurring hypokalemia of unknown cause, high caffeine intake should be considered.