The estrogen in combination hormonal birth control methods sometimes raises the risk of blood clots. These blood clots could be in a leg (deep vein thrombosis) or in a lung (pulmonary embolism). But the risk for blood clots is overall very low with hormonal birth control.
Birth control pills
In the past, combination birth control pills had a higher dose of estrogen. The higher dose raised the risk of blood clots. Now birth control pills have a lower dose of estrogen. So the risk is lower. Pregnancy actually raises the risk of blood clots more than taking a birth control pill does.
Some combination birth control pills contain types of progestin that can raise the risk of blood clots. Talk to your doctor about the risk of blood clots when deciding which pill is right for you.
Birth control pills are usually stopped within 1 month of major surgery to lower the risk of a blood clot. But this can raise the risk of getting pregnant. You will need to use a backup method of birth control, such as a condom, or not have vaginal sex to prevent pregnancy.
The birth control patch
The patch delivers more estrogen than the low-dose birth control pills do. The U.S. Food and Drug Administration (FDA) warns that using the patch makes you slightly more likely to get blood clots in the legs and lungs than if you use birth control pills. Talk to your doctor about your risks before you use the patch.
Things that can increase your risk for a blood clot
Some of the things that can increase your risk for a blood clot include:
Slowed blood flow
When blood doesn't flow normally, clots are more likely to develop. Reduced blood flow may result from long-term bed rest, such as after a surgery, injury, or serious illness. Or it may result from sitting for a long time, especially when traveling long distances.
Abnormal clotting
Some people have blood that clots too easily or too quickly. Things that may cause increased clotting include:
- Having certain blood problems that make blood clot too easily. This is a problem that may run in families.
- Having certain health problems, such as cancer, heart failure, stroke, or severe infection.
- Being pregnant. The risk of getting blood clots increases both during pregnancy and shortly after delivery or after a cesarean section.
- Using hormonal forms of birth control, gender-affirming hormone therapy, or hormone therapy for menopause.
- Smoking.
Injury to the blood vessel wall
Blood is more likely to clot in veins and arteries shortly after they are injured. Injury can be caused by a recent medical procedure or surgery that involved your legs, hips, belly, or brain. Or it can be caused by an injury, such as a broken hip.