Emergency contraceptive pill
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Emergency contraceptive pills help prevent pregnancy after unprotected sex, a missed/failed contraceptive method, or sexual assault. They work best as soon as possible and do not end an established pregnancy.
Options
- Levonorgestrel 1.5 mg: Take as soon as possible, ideally within 72 hours, but it can be used up to 5 days after sex. Often available without prescription.
- Ulipristal acetate 30 mg: Use within 5 days. It is generally more effective than levonorgestrel on days 3-5, and may work better at higher body weight. It may require a prescription depending on where you live.
- Copper IUD: Not a pill, but the most effective emergency option if inserted within 5 days, and it provides long-term contraception afterward. CDC guidance notes that ulipristal and levonorgestrel have similar effectiveness within 3 days, while ulipristal performs better at 3-5 days.
After taking it
- If you vomit within 3 hours, contact a pharmacist or clinician because another dose may be needed.
- With ulipristal, wait 5 days before starting or restarting hormonal contraception, then use condoms or avoid sex until you have used the hormonal method for 7 days.
- With levonorgestrel, you can start or resume regular hormonal contraception immediately, but use condoms or avoid sex for 7 days.
- Take a home pregnancy test 3 weeks after the unprotected sex, or sooner if your period is more than a week late.
Common effects include nausea, tiredness, headache, breast tenderness, spotting, or a period that comes earlier or later. Emergency contraception does not protect against STIs and should not replace a regular contraceptive plan. CDC emergency-contraception recommendations advise taking emergency contraceptive pills as soon as possible, within 5 days.
Seek urgent care if you develop severe one-sided lower abdominal pain, fainting, or unusual heavy bleeding, especially if a pregnancy test is positive.
Text reference: Lippincott Illustrated Reviews: Pharmacology, p. 849.
Which emergency contraception option is best for my situation?
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The safest choice depends mainly on timing, pregnancy risk, body weight, medicines, and whether you want ongoing contraception.
Asking for Preferences
When was the most recent unprotected vaginal sex or contraceptive failure? · Which factors apply? Select all that apply. · Would you consider a same-week clinic visit for an IUD, which can also provide ongoing contraception?
Emergency contraceptive pills help prevent pregnancy after unprotected sex, a missed/failed contraceptive method, or sexual assault. They work best as soon as possible and do not end an established pregnancy.
Options
- Levonorgestrel 1.5 mg: Take as soon as possible, ideally within 72 hours, but it can be used up to 5 days after sex. Often available without prescription.
- Ulipristal acetate 30 mg: Use within 5 days. It is generally more effective than levonorgestrel on days 3-5, and may work better at higher body weight. It may require a prescription depending on where you live.
- Copper IUD: Not a pill, but the most effective emergency option if inserted within 5 days, and it provides long-term contraception afterward. CDC guidance notes that ulipristal and levonorgestrel have similar effectiveness within 3 days, while ulipristal performs better at 3-5 days.
After taking it
- If you vomit within 3 hours, contact a pharmacist or clinician because another dose may be needed.
- With ulipristal, wait 5 days before starting or restarting hormonal contraception, then use condoms or avoid sex until you have used the hormonal method for 7 days.
- With levonorgestrel, you can start or resume regular hormonal contraception immediately, but use condoms or avoid sex for 7 days.
- Take a home pregnancy test 3 weeks after the unprotected sex, or sooner if your period is more than a week late.
Common effects include nausea, tiredness, headache, breast tenderness, spotting, or a period that comes earlier or later. Emergency contraception does not protect against STIs and should not replace a regular contraceptive plan. CDC emergency-contraception recommendations advise taking emergency contraceptive pills as soon as possible, within 5 days.
Seek urgent care if you develop severe one-sided lower abdominal pain, fainting, or unusual heavy bleeding, especially if a pregnancy test is positive.
*Text reference: Lippincott Illustrated Reviews: Pharmacology, p. 849.*The safest choice depends mainly on timing, pregnancy risk, body weight, medicines, and whether you want ongoing contraception.To recommend the best option, tell me:
-
How long ago was the unprotected sex or contraception failure?
- Under 72 hours
- 3-5 days
- More than 5 days
-
Are you taking medicines for seizures, tuberculosis, or HIV, or St John's wort?
-
Would you consider a copper IUD if you can get a clinic appointment within 5 days?
Quick guide: if it was within 5 days, a copper IUD is most effective; otherwise ulipristal 30 mg is usually the strongest pill option, especially at 3-5 days. Levonorgestrel 1.5 mg is a good accessible option if taken as soon as possible, particularly within 72 hours.
What are side effects of levonorgestrel 1.5mg
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levonorgestrel emergency contraception adverse effects
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levonorgestrel 1.5 mg emergency contraception side effects FDA label vomiting 2025
Common, temporary side effects of levonorgestrel 1.5 mg emergency contraception include:
- Nausea or occasional vomiting
- Lower abdominal cramps/pain
- Tiredness
- Headache
- Dizziness
- Breast tenderness
- Diarrhea
- Spotting or bleeding before the next period
- Your next period may be earlier or later, and lighter or heavier than usual
Most settle within a day or two. Nausea and vomiting occur less often with levonorgestrel than with older combined-hormone emergency-contraception regimens. ROSEN's Emergency Medicine: Concepts and Clinical Practice reports nausea, headache, and irregular menstrual bleeding as expected effects.
If you vomit within 2 hours of taking the tablet, speak with a pharmacist or clinician promptly because you may need another dose, as indicated in the FDA prescribing information.
Take a pregnancy test if your period is more than 1 week late, or about 3 weeks after the unprotected sex. Get urgent medical assessment for severe or worsening one-sided lower-abdominal pain, fainting, or unusually heavy bleeding, particularly if pregnancy is possible.
When should I take a pregnancy test after levonorgestrel?
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CDC emergency contraception levonorgestrel pregnancy test 3 weeks period delayed
Take a home pregnancy test 3 weeks after the unprotected sex or after taking levonorgestrel emergency contraception.
Test earlier if your next period is more than 1 week later than expected. Levonorgestrel can make the next period earlier, later, lighter, heavier, or cause spotting, so bleeding alone is not a reliable confirmation.
If the test is negative but you still have no period after a few days, repeat it or see a clinician. Seek urgent care for a positive test plus severe one-sided lower-abdominal pain, fainting, shoulder-tip pain, or heavy bleeding. The CDC guidance advises pregnancy testing if there is no withdrawal bleed within 3 weeks.
How long it takes to act
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levonorgestrel emergency contraception mechanism delay ovulation how soon takes effect official guidance
Levonorgestrel starts being absorbed soon after you take it and acts by delaying or preventing ovulation if ovulation has not happened yet. There is no sensation that tells you it is working.
The key point is to take it immediately after unprotected sex. It works best within 24 hours and is intended for use within 72 hours. It does not protect you from unprotected sex later in the same cycle, so use condoms or avoid sex until your regular contraception is effective.
It is much less likely to work if ovulation has already occurred, and it does not affect an established pregnancy. The FDA explanation states that it works before egg release by stopping or delaying ovulation.
How effective is levonorgestrel at different times?
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levonorgestrel emergency contraception efficacy timing
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levonorgestrel emergency contraception effectiveness 24 48 72 120 hours evidence WHO CDC
Effectiveness declines the longer you wait, so take levonorgestrel 1.5 mg immediately.
| Time since unprotected sex | Expected effectiveness |
|---|---|
| Within 24 hours | Highest effectiveness |
| 24-48 hours | Still effective, but less than in the first day |
| 48-72 hours | Can still help, but effectiveness continues to decline |
| 72-120 hours (3-5 days) | May still reduce pregnancy risk, but is less reliable. Ulipristal or a copper IUD is generally a better option if available |
A single percentage for each day is not reliable because effectiveness depends strongly on whether ovulation was about to occur. Levonorgestrel works mainly by delaying ovulation, so it may not work if ovulation has already happened.
Across studies, levonorgestrel emergency contraception has been associated with pregnancy rates of roughly 1.2%-2.1% among users, but this is not the same as a personal chance of pregnancy and varies by timing and cycle day. The CDC guidance reports that pregnancy rates are higher when pills are taken after 3 days, particularly at days 4-5. The WHO summary recommends using any emergency contraceptive pill as early as possible.
If it has been more than 72 hours, seek ulipristal acetate or a copper IUD promptly if possible. Take a pregnancy test 3 weeks after the unprotected sex.
How does levonorgestrel compare with ulipristal?
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ulipristal levonorgestrel emergency contraception
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CDC emergency contraception ulipristal acetate compared levonorgestrel 5 days contraception after use
| Feature | Levonorgestrel 1.5 mg | Ulipristal acetate 30 mg |
|---|---|---|
| Best use window | Best within 72 hours, though may have some effect up to 5 days | Effective up to 5 days |
| Effectiveness | Works best the sooner it is taken; effectiveness falls after day 3 | Generally more effective, especially on days 3-5 |
| How it works | Delays or prevents ovulation if it has not occurred | Delays ovulation, including closer to the time of ovulation |
| Access | Often available over the counter | Often prescription-only, depending on country |
| Starting regular hormonal contraception | You can start or resume it immediately | Wait 5 days before starting/resuming hormonal contraception |
| Back-up protection | Use condoms or avoid sex for 7 days after starting/resuming contraception | After waiting 5 days, use condoms or avoid sex for 7 days after starting/resuming contraception |
| Side effects | Both can cause nausea, headache, cramps, fatigue, breast tenderness, spotting, and a changed next period | Similar side effects |
| Can they be combined? | No | No. Do not take ulipristal and levonorgestrel within 5 days of each other. |
Practical choice
- If it has been 0-72 hours and levonorgestrel is available now, take it now rather than delaying to find ulipristal.
- If it has been 72-120 hours, ulipristal is usually preferred if you can get it promptly.
- If you may be close to ovulation, or have a higher body weight/BMI, ulipristal is often favored, though the evidence on weight is not fully consistent.
- If you use hormonal birth control and need to restart it immediately, levonorgestrel may be more convenient because ulipristal requires the 5-day wait.
- If you take certain enzyme-inducing medicines, such as some anti-seizure medicines, rifampicin/rifabutin for TB, some HIV medicines, or St John's wort, both pills can be less effective. A copper IUD within 5 days is the most effective emergency method and is not affected by these medicines.
Neither pill works after pregnancy is established, and neither protects against STIs. Take a pregnancy test 3 weeks after the unprotected sex if you have not had a normal period. The CDC emergency contraception guidance and ACOG comparison both report that ulipristal is more effective than levonorgestrel at 3-5 days after sex.
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