Hi Dr Kate,
I've heard that a chemical in grapefruit juice blocks the absorption of some medications. I've been on birth control for a month, and generally eat one grapefruit a day. Could this lower the effectiveness of the pill?
You're right, grapefruit juice can interact with some medications - but your birth control pill is fine. Only anti-seizure meds, certain strange antibiotics and St. John's Wort have been found to lower the pill's effectiveness. If anything, your pill will be more effective (in a sense) because it will absorb more slowly, leading to higher hormone levels in your blood. So f you're going to continue to eat a grapefruit each day, I'd let your gyno know, so she can keep you on the lowest possible dose pill.
Keep up the healthy eating!