This is a great question with a complicated answer - the short answer is that we aren't sure. The hormones that are in these birth control options can dissolve in the fats of the body so increased fat stores may lower the amount that are available to help prevent unwanted pregnancy. Additionally, excess bodily fat may produce related hormones and change how your body breaks down, responds to, or processes the hormones in birth control pills, patches, and rings.

There aren't clear answers to exactly how much less effective these medicines are in patients who are obese, but based on evidence about emergency contraception (in which some types are less effective in obese patients) we presume that birth control pills, patch and ring may be moderately less effective.

If unintended pregnancy is a major concern we recommend considering other options that may not be effected by weight such as the copper intrauterine device (IUD). Also, you can combine some options like using a condom with your current method to provide additional protection.

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