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The morning-after pill

After unprotected sex or a broken condom, the first reflex is often to rush to the pharmacy. Your body and your health matter: take the time to understand before you decide.

What is the morning-after pill?

It is a form of "emergency contraception": a drug taken after sex to try to prevent pregnancy. Two kinds are available in Canada:

  • Levonorgestrel (Plan B and similar products): one tablet, sold without a prescription,1 to be taken as soon as possible, within 72 hours.2 In 2014 Health Canada said it is less effective in women who weigh 75 to 80 kg and ineffective above 80 kg.3
  • Ulipristal (ella): one tablet, obtained from a pharmacist or a doctor, usable up to 5 days after sex.4

How does it work?

Its main effect is to delay or prevent ovulation.2,4 It does not end a pregnancy that is already implanted in the uterus.2

Can it also prevent an embryo that has already been conceived from implanting in the uterus? The manufacturer and major medical bodies say no.2,5 Some researchers, however, say this cannot be ruled out.6 Since the life of a new human being begins at conception, those who share this concern consider such an effect equivalent to a very early abortion.

Should I take it?

A woman can only become pregnant during about six days in each cycle, ending on the day of ovulation.7 That day is often hard to know for sure. The morning-after pill contains 1.5 mg of levonorgestrel, 10 to 15 times the amount in one combined birth-control pill.2,8 If you are already pregnant from an earlier encounter, it is of no use.2

It does not protect against sexually transmitted infections (STIs) either.

Possible side effects

Nausea, stomach pain, tiredness, headache, irregular bleeding, tender breasts, dizziness. These effects usually pass. If your period is more than a week late, take a pregnancy test.2

Wondering whether you're pregnant? Call us at 1-855-871-4442. We'll refer you to a pregnancy resource centre near you that offers free tests.

This information is general and does not replace the advice of a pharmacist or doctor.

Sources

  1. Canadian Medical Association Journal (CMAJ), 2008: Canada approves off-the-shelf sale of levonorgestrel, three years after removing the prescription requirement. https://www.cmaj.ca/content/178/13/1645
  2. Plan B patient information, approved November 15, 2024 (French version): one 1.5 mg levonorgestrel tablet, taken as soon as possible within 72 hours; works by preventing the release of an egg; not effective once pregnancy is established; side effects (nausea, abdominal pain, fatigue, headache, irregular bleeding, breast tenderness, dizziness); take a pregnancy test if the period is a week late. https://planb.ca/assets/pdf/planb-patient-medication-information-fr.pdf
  3. Health Canada advisory, March 26, 2014 (French version): levonorgestrel emergency contraceptives are less effective in women weighing 75 to 80 kg (165 to 176 lb) and ineffective in women weighing more than 80 kg (176 lb). https://recalls-rappels.canada.ca/fr/avis-rappel/contraceptifs-oraux-urgence-porteront-mises-en-garde-indiquant-leur-efficacite-reduite
  4. ella (ulipristal) product monograph, revised February 16, 2023 (French version): taken within 120 hours (5 days); works mainly by delaying or preventing ovulation. https://pdf.hres.ca/dpd_pm/00069759.PDF
  5. International Federation of Gynecology and Obstetrics (FIGO) and International Consortium for Emergency Contraception (ICEC), joint statement: levonorgestrel pills “cannot prevent implantation of a fertilized egg.” https://www.figo.org/mechanism-action-emergency-contraception
  6. R. Peck, W. Rella, J. Tudela, J. Aznar and B. Mozzanega, “Does levonorgestrel emergency contraceptive have a post-fertilization effect?,” Linacre Quarterly, February 2016: the authors estimate ovulation is prevented in under 15% of cases, and that observed effects “may suggest” a post-fertilization effect. https://pubmed.ncbi.nlm.nih.gov/27833181/
  7. A. J. Wilcox, C. R. Weinberg and D. D. Baird, “Timing of sexual intercourse in relation to ovulation,” New England Journal of Medicine, December 7, 1995: nearly all pregnancies come from intercourse during the six days ending on the day of ovulation. https://pubmed.ncbi.nlm.nih.gov/7477165/
  8. World Health Organization, Family Planning: A Global Handbook for Providers, ch. 3: a combined birth-control pill contains 0.1 to 0.15 mg of levonorgestrel, against 1.5 mg in the morning-after pill. https://fphandbook.org/node/2781

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