Intestinal calcium absorption in man during lithium therapy.

Intestinal absorption of calcium was determined in 11 patients prior to and after 4 weeks of lithium therapy. In 6 patients the absorption decreased and in 5 patients the absorption increased. The urinary calcium excretion decreased in all patients during lithium therapy, representing a relative reduction of 55%. Serum calcium remained unchanged. These findings indicate a retention of calcium, which probably accumulates in the intracellular space.