The morning-after pill is a type of emergency contraception that can help prevent pregnancy after unprotected sex or if a method of birth control does not work correctly. It is effective when used as directed, but like any medication, it may cause side effects. Being aware of possible side effects can help you feel more prepared when deciding on 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).

Some common side effects include:

• Heavier or lighter periods
• Spotting or bleeding between periods
• Nausea
• Vomiting
• Dizziness
• Headache
• Breast tenderness
• Tiredness
• Abdominal discomfort

These are not all of the possible side effects. Speak to your healthcare provider if you experience any side effects that are bothering you or won’t go away.

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 these medications 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?

Both Plan B and ella can temporarily affect your menstrual cycle. Your next period may be early, late, heavier, or lighter than usual. 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 or your method of birth control did not work as expected, 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.

Clinically reviewed and updated June 2026.