How can taking birth control pills affect sexual desire?

Anytime hormone levels are changed, sexual desire can also change; the one definitely impacts the other. However, that impact should change back to normal once the body adjusts to new levels of hormones.

More likely, a change in sexual desire after starting the pill is emotional or psychological. Possibly, conception is desired but ill-advised at this time. That could be depressing. The urge to procreate is very strong. It could be the reverse. The pill is sufficiently reliable so that sexual activity is less risky related to conception and so is enjoyed with more enthusiasm.

Any change in desire that persists for a length of time and creates a problem in the relationship should be investigated with your health care provider.

Although the pill itself contains no testosterone, persuasive research has shown that women who use oral contraceptive pills may develop long-term sexual health problems because their bodies are filled with low amounts of "unbound," or free, testosterone, which is bad news for women as it can potentially lead to continuing negative sexual, metabolic, and mental health consequences, including a flat libido.

Put another way, the birth-control pill increases the number of sex hormone binding globulins (SHBG) so that they attach to testosterone more readily, leaving less testosterone to freely circulate through the body -- making us less horny.