9 Side Effects of the Morning-After Pill (& What to Do)

April 2022

The morning-after pill is used to prevent an unwanted pregnancy and is often referred to as “emergency birth control.” A common brand name is Plan B. This pill can cause some side effects like an irregular period or dizziness, which will generally last for a few days and vary from woman to woman. 

The main unpleasant side effects that the morning-after pill can cause include:

  1. Nausea and vomiting
  2. Bleeding between periods
  3. Abdominal pain
  4. Fatigue
  5. Headache
  6. Breast tenderness
  7. Diarrhea
  8. Dizziness
  9. Irregular period, starting earlier or later than usual.

Although more rare, other side effects can also occur, such as urticaria, itchiness, facial swelling, pelvic pain, painful menstruation, or the formation of blisters on the skin.

Side effects can occur in both dosing formats: the single-dose 1.5 mg levonorgestrel pill or the two-dose version of levonorgestrel, each pill containing 0.75 mg. You may alternatively be advised to take 30mg of ulipristal acetate.

What to do

Some side effects can be treated and even prevented, as follows:

1. Nausea and vomiting

You should eat soon after taking Plan b to reduce the any related nausea. If nausea occurs, a home remedy may be prepared and taken, such as ginger or clove tea with cinnamon, or antiemetic medication. 

2. Headache and abdominal pain

If the pill causes side effects like headaches or abdominal pain, painkillers such as acetaminophen are recommended. 

3. Breast tenderness

To relieve breast pain, apply warm compresses or take a warm bath, massaging the breast area. 

4. Diarrhea

In case of diarrhea, drink plenty of fluids and avoid greasy foods, eggs, milk and alcohol, giving preference to black, chamomile or guava leaf tea.

Who cannot take this pill

Plan B should not be taken by men, women who are breastfeeding or pregnant, or if you are allergic to any of its ingredients. 

An appointment with the gynecologist is advisable before using this pill in cases of high blood pressure, cardiovascular conditions, morbid obesity or if you have a history of abnormal vaginal bleeding or bleeding of unknown origin.

Frequently asked questions

Some common questions about the morning-after pill are:

1. How many times can I take the morning-after pill?

This method of contraception should only be used sporadically as it contains a high dose of hormones. In addition, if it is taken more than once in the same month, it can lose its intended effect. Therefore, this pill should only be taken in emergency situations.

2. Can the morning-after pill affect my period?

Yes, although generally speaking, most women who use Plan B have minimal or no significant changes to their menstrual cycle. Nonetheless, changes can last for 5 to 7 days. It is important to highlight the the repetitive or frequent use of the morning-after pill can worsen any menstrual disturbances, making it difficult to identify your fertile days and menstrual phase.

It is also important to note that bleeding usually does not occur immediately after taking the morning-after pill.

3. If Plan B is taken accidentally during pregnancy, is fetal health at risk?

There are no records of the morning-after pill causing teratogenic effects (which affect the growth and development of the fetus) if it is taken in the first trimester.

The same applies if the morning-after pill fails and you become pregnant, as you would have taken the pill way before the fetus’ initial developmental phase, when it is most vulnerable.

4. Is it still possible to get pregnant?

Yes. Although the probability of getting pregnant after taking the morning after pill is very low, it is still possible, especially if: 

  • The levonorgestrel pill isn’t taken within the first 72 hours after unprotected sex, or the ulipristal acetate pill isn’t taken within 120 hours;
  • Taken with antibiotics or other medication that decrease the effect of the pill;
  • Vomiting or diarrhea occur within 4 hours of taking the pill;
  • Ovulation has already occurred;
  • The morning after pill has been taken several times in the same month.

Consult a doctor or pharmacist if vomiting or diarrhea occur within 4 hours of taking the pill because it may be necessary to take a new dose of the pill to have the desired effect.

It’s important to remember that emergency oral contraception doesn’t protect against sexually transmitted diseases.

Was this information helpful?

Edited by Tua Saude editing team in April 2022. Clinical review completed by Flávia Costa - Pharmacist in April 2022.


  • MINISTÉRIO DA SAÚDE BRASIL. ANTICONCEPÇÃO DE EMERGÊNCIA: PERGUNTAS E RESPOSTAS PARA PROFISSIONAIS DE SAÚDE. 2005. Available on: <https://bvsms.saude.gov.br/bvs/publicacoes/caderno3_saude_mulher.pdf>. Access in 22 Dec 2021
  • AGENCIA ESPAÑOLA DE MEDICAMENTOS Y PRODUCTOS SANITARIOS. Ficha técnica Postinor 1,5 mg comprimido. Available on: <https://cima.aemps.es/cima/dochtml/ft/67515/FT_67515.html>. Access in 23 Sep 2021
Clinical review:
Flávia Costa
Graduated in Pharmacy at Centro Universitário Newton Paiva, Brazil, in 2003. Master in Biomedical Sciences at UBI, Portugal.