unwanted effects

Last reviewed 01/2018

Evidence from a randomised controlled trial comparing the effectiveness of hormonal emergency contraceptives showed that various unwanted effects were less common with levonorgestrel than with the Yuzpe regimen (1):

  • nausea (23% vs. 50% of women)
  • vomiting (6% vs. 19% of women)
  • fatigue (17% vs. 29% of women)
  • dizziness (11% vs. 17% of women)

Other unwanted effects that occurred in similar frequencies with both regimens included headache (17% in levonorgestrel group), breast tenderness (11% in levonorgestrel group), and lower abdominal pain (18% in levonorgestrel group).

Less common unwanted effects that occurred with both regimens included irregular bleeding/spotting and diarrhoea.


  • (1) Task Force on Postovulatory Methods of Fertility Regulation (1998). Randomised controlled trial of levonorgestrel versus the Yuzpe regimen of combined oral contraceptives for emergency contraception. Lancet, 352, 428-33.