What are the most common birth control side effects?

Not every woman has side effects from birth control, but the most common ones are menstrual cycle changes, an increased risk of blood clots, and lack of protection against sexually transmitted infections (STIs).

Menstrual cycle changes

The “period” you have while taking a combined oral contraceptive is not actually a true period, rather it is a withdrawal bleed that occurs because the levels of hormones in your body have dropped for a short period of time.

Your "period” while on birth control pills is usually lighter than normal and women taking extended or continuous cycle pills (such as Seasonique, Seasonale, Amethyst) skip it entirely. Spotting (drops of blood or a dark brown discharge) or irregular bleeding is also commonly reported, particularly when first starting a hormonal contraceptive. This may be worse with extended- or continuous-cycle birth control pills or with progestin-only pills.

An increased risk of blood clots

Birth control pills that contain estrogen and progestin increase a woman’s risk of developing a blood clot by about three to four times, although this risk is still significantly smaller than the risk of blood clots associated with pregnancy. The risk is higher in women over the age of 35 who smoke, and these women should not take combined estrogen/progestin contraceptives. A progestin called drospirenone (found in Yaz, Yasmin, and several other pills) is linked to a higher risk for blood clots.

Lack of protection against sexually transmitted infections (STIs)

Only a condom can protect against STIs and these should be used in conjunction with hormonal methods of birth control.

Weight gain

The early oral contraceptive pills were notorious for making a woman gain weight. However, there is no evidence that modern-day birth control pills cause weight gain. Some may initially cause slight fluid retention, but that is generally minimal and resolves within two to three months.

Other common side effects

Breast pain or tenderness, low mood or depression, fatigue, a headache, nausea, and vaginal dryness have also been reported. Most of these side effects resolve with continued use.

Birth control pills have come a long way since they were first developed in the 1960s. Today’s pills contain much lower levels of hormones and are considered a very safe and effective way to prevent pregnancy in women.

For more information see What are the benefits and risks of taking birth control pills?