Caffeine and hypokalemia:
Excessive caffeine intake can lead to severe hypokalemia (low serum potassium levels) due to the diuretic effect of caffeine. (28)
Caffeine and calcium:
Caffeine consumption increases calcium excretion in the urine and may increase the risk of kidney stones. A positive relationship between caffeine consumption and urine calcium levels in with and without kidney stones was found. The study examined 39 participants who had kidney stones but had normal levels of calcium in their body, and nine participants who had no stones and normal amounts of calcium. Consuming caffeine increased the amount of calcium in both group’s urine but not the amount of oxalate, molecule that can link up with calcium and crystallize causing stones. The researchers stated that the risk of getting calcium oxalate stones increased from 2.4 to 3.1 in those who had stones and from 1.7 to 2.5 in those who had no stones. (30)