Levonorgestrel

What levonorgestrel is and how it works

Levonorgestrel is a hormone-based emergency contraceptive ('morning-after pill') taken as a single tablet to help prevent pregnancy after unprotected sex or a contraceptive failure (such as a missed pill or broken condom). (1) (2)

Levonorgestrel does not carry a boxed warning, but there are real things to know: it works best the sooner it is taken after unprotected sex (up to 72 hours), it does not end an existing pregnancy, it does not protect against sexually transmitted infections, and if you do become pregnant after taking it, your prescriber should consider whether the pregnancy could be ectopic (outside the womb). It is not intended as a regular, ongoing contraceptive method.

Mechanism of action: how levonorgestrel works

Levonorgestrel is a synthetic progestogen that works mainly by inhibiting or delaying ovulation and interfering with fertilisation if intercourse has occurred in the pre-ovulatory phase; it is not effective once implantation has already begun. (3) (2) (6)

What levonorgestrel is used for

Before taking levonorgestrel

Do not take / not appropriate for

• Do not take levonorgestrel if you are pregnant or think you might already be pregnant -- it will not end an existing pregnancy. (all countries) (1) (6)
• Do not take levonorgestrel if you are allergic to levonorgestrel or any of its ingredients. (all countries) (6)

Tell your clinician about

• If you have had a previous ectopic pregnancy or a previous episode of salpingitis (a type of pelvic infection).
• If you have any condition that could affect absorption, such as severe vomiting, severe diarrhoea, or Crohn's disease.
• If you have severe liver problems.
• If you have used any enzyme-inducing medicine (such as certain anticonvulsants, rifampicin, or St. John's Wort) in the last 4 weeks.
• Your age, if you are a young person seeking emergency contraception, since data are more limited in younger teenagers.

How to take levonorgestrel

• Take one tablet by mouth as soon as possible after unprotected sex -- it works best within 12 hours but can still help for up to 72 hours.
• If you vomit within 3 hours of taking the tablet, take another tablet as soon as possible, or contact your pharmacist or clinician for a replacement dose.
• Use a barrier method (such as condoms) for the rest of your cycle until your next period, and consider starting or restarting a regular contraceptive method.
• Contact your prescriber if your next period is more than 7 days late, is unusually light, or you have severe lower abdominal pain -- to check you are not pregnant and to rule out an ectopic pregnancy.

Procedures and treatment changes

Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5) (6)

Missed dose

Levonorgestrel emergency contraception is a single, one-time dose rather than an ongoing regular medicine, so there is no 'missed dose' in the usual sense -- take it as soon as possible after unprotected sex, within the 72-hour window.

Overdose

No serious harmful effects have been established from taking more than the recommended dose. If you have concerns after taking more than directed, contact your pharmacist, prescriber, or local poison control for advice. (2)

Side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms.

Serious warnings

Interactions

• Enzyme-inducing medicines (such as rifampicin, certain anticonvulsants including carbamazepine and phenytoin, barbiturates, ritonavir, rifabutin, griseofulvin, and St. John's Wort) can reduce levonorgestrel's effectiveness by speeding up its breakdown in the body -- tell your pharmacist or prescriber if you have used any of these in the last 4 weeks, since a higher dose or a non-hormonal option (copper IUD) may be recommended instead. (2) (6)
• Efavirenz (an HIV medicine) has been shown to reduce levonorgestrel blood levels by around 50%, which may reduce effectiveness. (6)

Pregnancy, breastfeeding, kidney/liver function, age

Monitoring

Before starting

• Confirm the timing of unprotected intercourse (within 72 hours)
• History of ectopic pregnancy or pelvic infection (salpingitis)
• Any recent use of enzyme-inducing medicines
• Whether pregnancy is already suspected

During treatment

• Watch for severe lower abdominal pain or an unusually delayed/light period, which may need prompt evaluation for ectopic pregnancy.
• Consider follow-up with a pharmacist or clinician to confirm effectiveness and discuss ongoing contraception.

Storage

Store at room temperature, in the original packaging, out of reach of children.

Frequently asked questions

References

1. PLAN B ONE-STEP (levonorgestrel) tablet, 1.5 mg -- full prescribing informationU.S. Food and Drug Administration / DailyMed (NIH), full prescribing information · United States · accessed 2026-07-30 · source 1
2. Levonorgestrel 1.5mg Tablets -- Summary of Product Characteristicselectronic medicines compendium (emc), United Kingdom -- Lupin Healthcare (UK) Limited · United Kingdom · accessed 2026-07-30 · source 2
3. Levonorgestrel and ulipristal remain suitable emergency contraceptives for all women, regardless of bodyweight -- EMA review conclusionEuropean Medicines Agency (EMA), Article 31 referral · European Union · accessed 2026-07-30 · source 3
4. Emergency contraception -- Canadian Contraception Consensus (background on Health Canada authorisation)Health Canada / Society of Obstetricians and Gynaecologists of Canada (SOGC) clinical practice guidance · Canada · accessed 2026-07-30 · source 4
5. Levonorgestrel 1.5 mg and 0.75 mg, oral emergency contraceptive -- TGA safety alertTherapeutic Goods Administration (TGA), Australia · Australia · accessed 2026-07-30 · source 5
6. Levonorgestrel-1 (levonorgestrel 1.5 mg tablet) -- New Zealand Data SheetMedsafe (New Zealand regulator) · New Zealand · accessed 2026-07-30 · source 6

Brand names by country

Single-ingredient levonorgestrel names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries