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Why can oral contraceptives increase the risk of blood clots?

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Blister pack of 28 oral contraceptive pills arranged in four rows, with 21 white active pills followed by 7 orange inactive pills. Arrows indicate the order for taking pills. — birth control A 28-day package of birth control pills.

Oral contraceptives, particularly those containing a combination of estrogen and progestin, are associated with an increased risk of blood clots because they mimic certain hormonal changes that occur during pregnancy.1

While these medications are highly effective at preventing ovulation, they alter the body's hormone balance, which can lead to various physiological changes. Large-scale epidemiological research has documented that users of these pills are more likely to experience blood clots in the veins compared to nonusers. This risk is notably higher in specific groups, such as women over the age of 34 and those who smoke.12

It is important to note that the incidence of such side effects has been significantly reduced over time by decreasing the dosages of estrogen and progesterone in modern contraceptive preparations. If you have concerns about these risks, it is essential to consult a healthcare provider, as they may recommend alternative methods—such as progestin-only pills—for individuals with specific health histories.23