Medically reviewed by Jessica Swirble, PharmD
Last updated on 5/24/2024

Drug Information | Side Effects | Use & Dosage | Request a Prescription

The use of Plan B can lead to various side effects in some individuals.

Common mild side effects of Plan B use include:

• Increased menstrual bleeding
  
• Nausea
  
• Headache
  
• Fatigue
  
• Vomiting
  
• Dizziness
  
• Abdominal pain
  
• Breast tenderness
  
• Changes in the menstrual cycle (delayed or late period)
  
  

More severe side effects of Plan B use can include:

• Allergic reactions (symptoms include skin rash, hives, difficulty breathing, swelling, hoarseness)
  
• Ectopic pregnancy (symptoms may appear as severe abdominal pain 3-5 weeks after taking Plan B)
  
  

If you experience any severe or concerning side effects while taking Plan B, contact your healthcare provider right away. Ectopic pregnancies, in particular, are medical emergencies that require immediate attention. If you experience severe abdominal pain several weeks after taking Plan B, seek medical attention.

Tell your healthcare provider about any existing medical conditions, allergies, or other medications you are taking before starting treatment with Plan B. This includes prescription drugs, over-the-counter medications, and dietary supplements, as they may interact with Plan B.

Tell your provider if you are taking these medications or supplements:

• Efavirenz
  
• Rifampin
  
• Bosentan
  
• Griseofulvin
  
• Topiramate
  
• Anticonvulsant medications
  
• Medications for HIV
  
• Herbal products (especially St. John’s wort)
  
  

Do not use Plan B if you are pregnant, planning to become pregnant, or breastfeeding.

Take Plan B exactly as directed on the package or as prescribed by your healthcare provider. It is most effective when taken as soon as possible after unprotected sex or birth control failure.

Plan B may cause side effects such as nausea, fatigue, or headache, so monitor your health and report any severe or persistent symptoms to your doctor.

In case of a Plan B overdose, seek medical attention immediately. Symptoms of overdose may include severe nausea or vomiting, sudden abdominal pain, or extreme tiredness. If you suspect an overdose, contact the poison control helpline at 1-800-222-1222 or call emergency services.