The morning-after pill can help prevent pregnancy following unprotected sex, but it can also lead to side effects. It’s important to be aware of these side effects so that you can make an informed decision about emergency contraception.

There are two main types of morning-after pills: the over-the-counter female contraceptive levonorgestrel (Plan B One-Step, Take Action and other brand names) and the prescription medication ulipristal acetate (ella). The potential side effects of each drug vary.

Common Plan B pill side effects can include:

• Heavier or lighter periods
• Early or late periods
• Nausea
• Lower abdominal cramps
• Dizziness
• Headache
• Breast tenderness
• Vomiting

Some commonly reported side effects of ella include:

• Early or late periods
• Headache
• Nausea
• Abdominal pain
• Menstrual cramps
• Fatigue
• Dizziness

Most women won’t develop every potential side effect associated with the morning-after pill. Some women don’t experience side effects at all from emergency contraception.

Generally, the morning-after pill is well-tolerated, and any associated side effects tend to be mild. In rare cases, women may be allergic to ingredients in Plan B or ella and develop a serious allergic reaction.

If you have additional questions about emergency contraception, the following answers may be helpful:

Does Plan B make you bleed?

Irregular bleeding or spotting can occur after taking Plan B. The medication may also cause your period to come early, resulting in unexpected bleeding. Similar side effects may also occur with ella.

How long will Plan B side effects last?

Plan B One-Step side effects usually resolve within a few days. If they last longer, contact your healthcare provider.

Can Plan B change your cycle?

The hormone present in Plan B, progestin, can cause changes in your menstrual cycle. You may skip your period or have a late or early period after taking it. Women may also experience menstrual cycle changes after taking ella, a selective progesterone receptor modulator. If your period is late or abnormal, you should contact your healthcare provider to advise you on next steps.

Can Plan B make your period late?

Plan B, as well as ella, can make a menstrual period late in some women. However, if your period is more than a week late, there is a possibility that you could be pregnant, so you should talk to your healthcare provider, and you may want to take a pregnancy test.

If you’ve had unprotected sex, talk to your healthcare provider. They can help you weigh the benefits and risks of the morning-after pill. They can also recommend the right form of emergency contraception for you.

Published July 2024.