Emergency contraception
Levonorgestrel within 72 hours, ulipristal within 120 hours, and the copper IUD is the most effective of all.
A 24-year-old married woman had unprotected intercourse about 72 hours ago. She has two children and doesn't want another pregnancy now. She weighs 78 kg and takes carbamazepine for epilepsy. Her period is regular; she is on day 14 of her cycle.
Which method works best for her, and what are the pitfalls with the tablets?
- Pregnancy test if period late or unsureEmergency contraception doesn't end an existing pregnancy.
- Copper IUD is most effectiveUp to 5 days after sex, or 5 days after the earliest likely ovulation.
- LevonorgestrelWithin 72 hours, less effective as time passes.
- UlipristalWithin 120 hours, more effective than levonorgestrel.
- Weight over 70 kg or BMI over 26Copper IUD, ulipristal, or double-dose levonorgestrel 3 mg.
- Enzyme-inducing drugsCopper IUD preferred, or levonorgestrel 3 mg.
- Plan regular contraceptionAnd a pregnancy test in 3 weeks.
- Possible sexual assault
- Under 18 or vulnerable (safeguarding)
- Severe abdominal pain or missed period later (ectopic)
- Recurrent requests (offer long-term contraception)
- Existing pregnancy
- Ectopic pregnancy later
- Sexual assault or coercion
- STI risk
- Drug interactions
| Copper IUD | Up to 120 hours after sex, most effective, also long-term contraception |
| Levonorgestrel | 1.5 mg within 72 hours, 3 mg if weight over 70 kg, BMI over 26, or enzyme inducers |
| Ulipristal | 30 mg within 120 hours, not with enzyme inducers |
| Vomiting within 3 hours | Repeat the dose |
| After ulipristal | Wait 5 days before starting hormonal contraception |
| Pregnancy test | 3 weeks after |
Check every dose against a current drug reference and your hospital protocol.
On this page
How each method works
| Method | How it works | Time limit | Effectiveness |
|---|---|---|---|
| Copper IUD | Copper is toxic to sperm and eggs; prevents implantation | 5 days | Most effective (over 99%) |
| Ulipristal acetate 30 mg | Delays ovulation, even close to the LH surge | 5 days (120 hours) | More effective than levonorgestrel |
| Levonorgestrel 1.5 mg | Delays ovulation; less effective once the LH surge has started | 3 days (72 hours) | Less effective, falls with time |
Choosing a method
Copper IUD within 5 days
Ulipristal 30 mg
Levonorgestrel 1.5 mg (3 mg if over 70 kg, BMI over 26, or enzyme inducers)
- Copper IUD, or levonorgestrel 3 mg
- not ulipristal
Interactions and pitfalls
- Enzyme inducers (carbamazepine, phenytoin, rifampicin, St John's wort, some HIV drugs) reduce hormonal methods.
- Ulipristal and progestogens cancel each other: after ulipristal, wait 5 days before starting or restarting hormonal contraception (use condoms meanwhile). Don't give levonorgestrel within 5 days of ulipristal.
- Drugs that reduce stomach acid (PPIs) may reduce ulipristal absorption.
- Breastfeeding: levonorgestrel is fine; after ulipristal, express and discard milk for a week per product advice.
- Vomiting within 3 hours of the tablet: repeat the dose (or use a copper IUD).
After emergency contraception
- Next period may be early or late.
- Pregnancy test in 3 weeks, or sooner if the period is late or unusual.
- Severe lower abdominal pain or unusual bleeding: come back (ectopic).
- Start regular contraception: copper IUD, implant, injection, pill or condoms.
- Offer STI testing if at risk.
Safeguarding
- Ask sensitively whether sex was consensual. Possible sexual assault: follow the hospital and medicolegal process, with forensic examination and support.
- Young or vulnerable patients: follow child protection and safeguarding procedures.
Treatment
Ulipristal acetate 30 mg single dose (within 120 hours) and copper IUD insertion are given per local availability and training.
Common mistakes
- Not offering the copper IUD (the most effective option).
- Giving standard-dose levonorgestrel to a woman over 70 kg or on enzyme inducers.
- Giving ulipristal to someone on carbamazepine.
- Starting the pill the same day as ulipristal.
- Forgetting the pregnancy test in 3 weeks.
- Not asking about consent and safety.
Frequently asked questions
How long after sex does emergency contraception work?
Copper IUD and ulipristal up to 5 days; levonorgestrel up to 3 days. The sooner, the better.
Does emergency contraception work for heavier women?
Levonorgestrel is less effective over 70 kg or BMI over 26, so a double dose (3 mg), ulipristal or a copper IUD is used.
Which emergency contraception is most effective?
The copper IUD, which can also be kept as long-term contraception.
Can emergency contraception cause an abortion?
No. It works by delaying ovulation (tablets) or preventing fertilisation and implantation (copper IUD). It doesn't end an established pregnancy.
Test yourself
Exam-style questions on this guide, from our two question banks. Choose an answer to see why each option is right or wrong.
1. Which emergency contraceptive method is most effective?
Answer: Copper IUD. The copper IUD can be inserted up to 5 days after sex and is the most effective.
- Levonorgestrel 1.5 mg: Less effective.
- Condom: Not emergency.
- Combined pill: Not used.
- Ulipristal 30 mg: Less effective than the IUD.
2. A woman weighing 80 kg requests levonorgestrel emergency contraception. What dose?
Answer: 3 mg. Double-dose levonorgestrel (3 mg) for weight over 70 kg or BMI over 26.
- 6 mg: Too high.
- 1.5 mg: Less effective over 70 kg.
- Not allowed: It can be used at double dose.
- 0.75 mg: Too low.
3. A woman on carbamazepine needs emergency contraception. Which is preferred?
Answer: Copper IUD. Enzyme inducers reduce hormonal EC; copper IUD preferred, or levonorgestrel 3 mg.
- No method works: IUD works.
- Progesterone-only pill: Not emergency.
- Standard levonorgestrel 1.5 mg: Reduced effect.
- Ulipristal: Reduced by enzyme inducers.
4. A woman had unprotected intercourse 96 hours ago and declines an IUD. Which oral emergency contraceptive is effective up to 120 hours?
Answer: Ulipristal acetate 30 mg. Emergency contraception: copper IUD (most effective, up to 5 days after intercourse or expected ovulation; ongoing contraception); ulipristal acetate 30 mg (selective progesterone receptor modulator, up to 120 h, delays ovulation even close to LH surge; reduced effect if progestogen started within 5 days — wait 5 days before starting hormonal contraception; breastfeeding — express and discard for 1 week); levonorgestrel 1.5 mg (up to 72 h, licensed; less effective with BMI > 26/weight > 70 kg — consider double dose). Enzyme inducers reduce oral EC efficacy — use copper IUD.
- Levonorgestrel 1.5 mg: Levonorgestrel is licensed up to 72 hours.
- Combined pill (Yuzpe): The Yuzpe regimen is less effective with more nausea.
- Mifepristone 200 mg for abortion: This is not an emergency contraceptive regimen.
5. A woman wants long-acting non-hormonal contraception. Which is a contraindication to a copper IUD?
Answer: Current PID. Copper IUD (WHO MEC): effective 10–12 years; mechanism — toxic to sperm/ova, inflammatory endometrial reaction; most effective emergency contraception (within 5 days). Contraindications (MEC 4): current PID/purulent cervicitis/chlamydia/gonorrhoea, pregnancy, unexplained vaginal bleeding, cervical/endometrial cancer, distorted cavity, Wilson disease, puerperal sepsis. Side effects: heavier, more painful periods. Nulliparity/adolescence are MEC 2 (fine).
- Nulliparity: Nulliparity is not a contraindication.
- Age under 20 years: Age under 20 is not a contraindication.
- Previous caesarean: A previous caesarean is not a contraindication.
6. Which hormone surge triggers ovulation, and about how long before ovulation does it occur?
Answer: LH surge, about 24–36 hours before. Rising oestrogen from the dominant follicle switches from negative to positive feedback, causing an LH surge about 24–36 hours before ovulation (ovulation kits detect this). LH completes meiosis I, stimulates prostaglandins and proteases that rupture the follicle, and starts luteinisation.
- FSH fall, 1 week before: FSH rises slightly with LH.
- Progesterone surge, 3 days before: Progesterone rises after ovulation.
- Oestrogen fall, at ovulation: Oestrogen peaks before the LH surge.
- Prolactin surge, 12 hours before: Not involved.
7. A baby boy has kinky, brittle hair, hypotonia, seizures and arterial tortuosity. Which element's transport is defective?
Answer: Copper. Menkes disease (X-linked, ATP7A) impairs copper absorption, so copper-dependent enzymes fail: lysyl oxidase (weak collagen, tortuous vessels), cytochrome oxidase, tyrosinase (pale hair), dopamine β-hydroxylase. Wilson disease (ATP7B) is the opposite: copper overload. Zinc deficiency causes acrodermatitis enteropathica.
- Zinc: Acrodermatitis, poor healing.
- Iron: Anaemia.
- Selenium: Keshan cardiomyopathy.
- Iodine: Goitre, cretinism.
References and dose sources
- FSRH — Emergency Contraception guideline
- NICE CKS — Contraception: emergency
- Levonorgestrel (emergency contraception) dosing: Drugs.com: Levonorgestrel dosage (see also our levonorgestrel (emergency contraception) dose page)
International guidance is linked where it reflects good practice. Where your hospital’s protocol differs, follow your hospital.