How does the birth control patch work?

The birth control patch works exactly like the pill; it’s just a different delivery system. The patch contains estrogen and progestin, as the pill does, and it works to suppress ovulation (same as the pill). There’s no difference in the risk of side effects, like weight gain. 

The primary distinction is that the patch is worn on the skin–anywhere except breasts, genitals, and hands or feet–for a week at a time, while the pill is taken every day. 

Medications administered through a patch are absorbed into the bloodstream slowly by the skin. The patch is just as effective as the pill for non-obese individuals.