Emergency Contraception: Which One, and When
Levonelle, ellaOne and the copper coil compared on timing, effectiveness and body weight — and the five-day rule that trips up pill users.
Part of the Complete Contraception Guide.
Key fact: The copper coil is the most effective emergency contraception and works up to five days after sex. Of the two tablets, ellaOne (ulipristal) covers 120 hours and Levonelle (levonorgestrel) is licensed to 72 hours. Sooner is better in every case.
The three options and their time limits
There are three forms of emergency contraception in the UK, and they are not interchangeable. Timing, body weight, what other hormones you have taken recently, and what you want to use afterwards all push the decision one way or the other.
| Copper coil (Cu-IUD) | Ulipristal acetate | Levonorgestrel | |
|---|---|---|---|
| Time limit | 5 days after sex, or 5 days after the earliest likely ovulation — whichever is later | 120 hours (5 days) | Licensed to 72 hours (3 days) |
| How it works | Copper is toxic to sperm and prevents implantation | Delays the release of the egg | Delays the release of the egg |
| Effectiveness | The most effective option, and not weight-dependent | More effective than levonorgestrel, particularly later in the window | Falls away with time; little evidence of effect beyond 96 hours |
| Ongoing cover | Stays in place as contraception for up to 5–10 years | None — a single act only | None — a single act only |
| Available as | A fitting at a clinic or GP | ellaOne | Levonelle |
Why the coil is the most effective
Guidance recommends that the copper coil be offered to anyone eligible, because it is more effective than either tablet and its effectiveness does not vary with body weight or with what hormones you have taken recently. It also solves the next problem at the same time, because it stays in as ongoing contraception.
Its window is also wider than people assume. It can be fitted within five days of the first unprotected sex in that cycle, or within five days of the earliest likely date of ovulation — whichever comes later. In practice that means a coil is sometimes still an option when both tablets are out of time. It needs a clinic appointment, which is the practical limitation rather than any clinical one.
Levonelle (levonorgestrel)
A single 1.5mg tablet, licensed for use up to 72 hours after unprotected sex. It works by delaying ovulation, which is also why it does nothing if ovulation has already happened.
- Most effective taken as soon as possible, and noticeably less effective as the three days pass
- You can restart or start hormonal contraception immediately afterwards, which is its main practical advantage over ulipristal
- A double dose (3mg) is advised if your BMI is over 26 or your weight is over 70kg, or if you take an enzyme-inducing medicine
- Beyond 96 hours there is little evidence of benefit, so later than that the conversation moves to ulipristal or a coil
ellaOne (ulipristal acetate)
A single 30mg tablet licensed to 120 hours — five days. It is more effective than levonorgestrel overall, and the gap widens later in the window and around the time of ovulation, which is precisely when emergency contraception is most needed.
The trade-off is hormonal interference in both directions. Ulipristal competes with progestogen at the same receptor, so:
- It may work less well if you have taken a progestogen in the preceding seven days — including your own pill
- Taking a progestogen in the five days afterwards can reduce its effect, which is the reason for the waiting period below
- Doubling the dose is not recommended, even at higher body weight or on enzyme inducers — unlike levonorgestrel
Weight, BMI and dose
Body weight affects oral emergency contraception, and this is not widely known.
>70kgor BMI over 26 — consider a double dose of levonorgestrel (3mg)
>85kgor BMI over 30 — effectiveness of oral emergency contraception is unknown
0effect of body weight on the copper coil
At the higher end, a coil is the option that does not carry this uncertainty. If a coil is not acceptable or available, a tablet is still far better than nothing — the point is to raise weight with the prescriber so the dose is right, not to be deterred.
The five-day rule that catches people out
After ulipristal (ellaOne) you must wait five days before starting or restarting hormonal contraception — the pill, the patch, the ring, the implant or the injection — and use condoms or avoid sex throughout those five days and for the usual additional days after restarting. Starting your pill the next morning, which feels like the responsible thing to do, can undo the ulipristal you have just taken.
Levonorgestrel has no such restriction: you can pick your pill straight back up. For someone who is on the pill and intends to carry on with it, that difference genuinely matters and is worth raising at the point of supply. If you have already missed pills, the missed pill rules set out how many days of condoms you need once you restart.
If you are sick afterwards
If you vomit within three hours of taking either tablet, the dose may not have been absorbed and another dose is needed. Beyond three hours, absorption is complete and there is nothing to repeat.
Nausea is a recognised effect of both. If you are prone to it, taking the tablet with food helps, and it is worth knowing the three-hour threshold in advance rather than working it out afterwards.
When to take a pregnancy test
Test at least 21 days after the last unprotected sex. Testing earlier risks a false reassurance, because there may not yet be enough hCG to detect.
Emergency contraception often shifts the timing of your next bleed, in either direction, so a period that arrives a few days early or late is not in itself evidence of anything. Reasons to test regardless of timing: a period more than seven days late, a bleed that is unusually light or different in character, or any new pregnancy symptoms.
What emergency contraception does not do
- It does not cover future sex. Both tablets act on a single act of intercourse. Sex two days later needs its own cover.
- It is not an abortion and does not end an established pregnancy. Both tablets act by delaying ovulation.
- It does not protect against sexually transmitted infections. If the reason you needed it was a condom failure or sex with a new partner, testing is a separate and reasonable step.
- It is not a method. Repeated use is safe but far less effective than ongoing contraception, and it is a reasonable prompt to look at the options available or the contraception overview.
Enzyme-inducing medicines change the calculation. Drugs that speed up liver metabolism — including some anti-epileptics, rifampicin and St John's wort — reduce the effectiveness of oral emergency contraception. A copper coil is preferred; if a tablet is used, levonorgestrel is doubled and ulipristal is not. See the pill and other medicines.
Frequently Asked Questions
Which is better, Levonelle or ellaOne?
Ulipristal (ellaOne) is more effective overall, and the difference is greatest later in the window and around ovulation. Levonorgestrel has the advantage that you can start or restart hormonal contraception immediately afterwards, and it can be given as a double dose at higher body weight. The copper coil is more effective than either.
How late is too late for the morning after pill?
Levonorgestrel is licensed to 72 hours and there is little evidence it helps beyond 96 hours. Ulipristal covers 120 hours. A copper coil can be fitted within five days of the first unprotected sex in that cycle, or within five days of the earliest likely ovulation, whichever is later, so it is sometimes still an option when the tablets are not.
Does the morning after pill work if you are overweight?
Body weight reduces the effectiveness of oral emergency contraception. A double dose of levonorgestrel is advised above 70kg or BMI 26. Above 85kg or BMI 30 the effectiveness of tablets is not known, and a copper coil, which is unaffected by weight, is the more reliable choice.
Can I start my pill the day after taking ellaOne?
No. Wait five days after ulipristal before starting or restarting hormonal contraception, and use condoms or avoid sex throughout. Starting sooner can reduce the effect of the ulipristal you have just taken. After levonorgestrel you can restart straight away.
When will my period come after emergency contraception?
It may arrive early, on time or late. A shift of a few days in either direction is common and is not a sign of failure. Take a pregnancy test at least 21 days after the unprotected sex, or sooner if your period is more than seven days late or unusually light.
References
- Faculty of Sexual & Reproductive Healthcare. Combined Hormonal Contraception (amended October 2023). fsrh.org
- Faculty of Sexual & Reproductive Healthcare. Progestogen-only Pills (August 2022, amended 2026). fsrh.org
- Faculty of Sexual & Reproductive Healthcare. Emergency Contraception (March 2017, amended 2026). fsrh.org
- Faculty of Sexual & Reproductive Healthcare. Drug Interactions with Hormonal Contraception (May 2022). fsrh.org
- Faculty of Sexual & Reproductive Healthcare. Problematic Bleeding with Hormonal Contraception. fsrh.org
- Faculty of Sexual & Reproductive Healthcare. UK Medical Eligibility Criteria for Contraceptive Use (UKMEC 2025). fsrh.org
- NHS. Contraception. nhs.uk
Medical disclaimer: This article is for informational purposes only and does not constitute medical advice. Contraceptive choice depends on your medical history, and no method described here protects against sexually transmitted infections. Always read the leaflet supplied with your own pill and consult a qualified healthcare professional. In a medical emergency, call 999.