What to Expect from Plan B - The Morning After Pill. When did you have sex without a contraceptive or have a contraceptive accident?

What to Expect

Plan B is a form of Emergency Contraception

plan B is safe and effective. To begin with, make sure you’ve read How plan B works.

You can call the plan B info line anytime 24/7, at 1-888-550-6060 (Canadian residents only).

Although few people experience vomiting with plan B, if you vomit within one hour of taking plan B, you might not have absorbed the medication in the pills. Call your healthcare professional, as you might need another dose.

After you’ve taken plan B, you should get your next period at the expected time, or a few days early or late. You may experience spotting a few days after taking plan B.

While you’re waiting for your next period, abstain from having intercourse or make sure you use a contraceptive.

If you've taken plan B because of missed birth control pills, ask your pharmacist or doctor about the best way for you to restart them. Remember to use another method of contraception, such as condoms, until your birth control is working again.

If your period is over a week late, or you haven’t had a period within three weeks of taking plan B, it is possible that you’re pregnant. Talk to your doctor and have a pregnancy test done.

Good to know: Tell your doctor if you have taken plan B within three days of a Pap test, as it may affect your results.


Side effects of the morning after pill - plan b

It’s very unlikely that you will have any severe reaction to plan B. You may have some temporary side effects that usually pass within 24 hours.

Most common plan b side effects

  • Nausea: 14 to 23% of women
  • Vomiting: About 6% of women
  • Irregular menstrual bleeding: Some women may experience spotting after taking plan B. The majority of women will have their next menstrual period at the expected time or early. When plan B is used repeatedly (more than once within a menstrual cycle, or more than occasional once-a-month use), menstrual changes may occur, including a shorter or longer cycle and a heavier or lighter period.

Less common side effects

Breast tenderness, headache, dizziness, fatigue, lower abdominal pain, and diarrhea. If the symptoms continue for more than 48 hours or are severe, see your health professional.

Unusual - call a health professional

  • Itching and a rash
  • Sudden or unusual cramps or pain in the stomach or belly
  • Migraine or severe headache
  • Any effects that persist or worsen
  • If you vomit within one hour of taking plan B, you may need to take another dose

Some medications can interact with plan B and make it less effective. These include: anticonvulsant drugs (phenytoin, carbamazepine), antibiotics (ampicillin, cotrimoxazole, tetracycline, clarithromycin), rifampicin, acetaminophen.

There are some medical conditions that may mean plan B is not right for you. plan B is not recommended if:
- You have a confirmed pregnancy
- You are allergic to it, or to any of the components of its formulation
- You have abnormal vaginal bleeding

There is no evidence of any long-term impact on your health or future fertility.
For more details, download the abbreviated product monograph (.pdf, 53KB)


Avoid a "next time"

The idea here is not to need plan B again. Plan A is deciding with your doctor which long-term method of contraception you want to go with.


(these percentages reflect each method’s effectiveness when used under ideal conditions)

Female Male % effective
% effective
  99.70 0
Transdermic patch
  99.70 0
Vaginal ring
  99.70 0
Injectable contraceptive
  99.70 0
Intra-Uterine System IUS
  99.90 0
Intra-Uterine Device IUD
  99.20 0
  99.50 0
Contraceptive Sponge
  91 0
  82 0
  94 0
Cervical Cap
  91 0
98 98
99.9 0
Female Condom
  95 N/A
Family Planning
99 0

Don't be afraid to use Plan B when you need to. There are no medical restrictions on taking Plan B more than once but remember that it's indicated for emergency situations, and it should never replace a good plan A.

When it comes to sex, knowledge is power. The more you know about contraception and sexual health, the more you can enjoy it. Start learning at: