How can birth control pills lower my vitamin B12 levels?

The evidence that birth control pills may lower vitamin B12 levels is mixed. Some studies don't show drops in vitamin B12 levels in women who take birth control pills for as long as six months. Other studies show reductions in vitamin B12 levels in women who take birth control pills but in most cases not enough to cause symptoms of vitamin B12 deficiency.

Some of the studies showing a drop in vitamin B12 were done years ago, when levels of hormones in birth control pills, particularly estrogen, were much higher than they are in today's pills. Talk to your doctor about whether you need to be concerned about your vitamin B12 level.