[Oral contraceptive lowers serum magnesium].

The effect of an oral contraceptive on serum magnesium was assessed in a group of 32 women, mean age 24.2 years, attending a family planning clinic. The pill contained ethinyl estradiol 0.03 mg and levonorgestrel 0.15 mg. As in pregnancy and during estrogen replacement in postmenopausal women, the contraceptive pill lowered serum magnesium (from a mean of 0.82 mmol/l, to 0.61 mmol/l in 6 months). Larger studies may determine whether routine dietary magnesium supplementation is necessary in oral contraception.