Emergency Contraceptive Pill: When to Take It, Side Effects & Period Changes
Understand emergency contraception timing, levonorgestrel versus ulipristal, vomiting, side effects, pregnancy testing and when to seek care.
When a condom breaks or contraception fails
A broken condom, missed birth-control pill or unexpected unprotected sex can be stressful. If emergency contraception may be needed, seeking advice quickly matters more than waiting until the next morning. The best option depends on timing, current medication and circumstances.
When might you need emergency contraception?
It may be needed after unprotected sex, condom failure, certain missed regular pills, a delayed injection or sexual assault. Missing a regular pill does not always mean emergency contraception is needed; the type of pill and timing matter.
72 hours or 120 hours: which option?
Levonorgestrel (LNG) emergency contraception is usually taken within 72 hours (three days). Ulipristal acetate (UPA) can be taken within 120 hours (five days), and may be more effective between 72 and 120 hours. A copper IUD placed within five days by a trained professional is the most effective emergency method, over 99% effective. Ask a clinician about remaining options even when time has passed.
Does the morning-after pill cause an abortion?
No. Emergency contraceptive pills mainly prevent or delay ovulation. They do not end an established pregnancy. No oral emergency method is guaranteed to prevent pregnancy.
What if you vomit or take other medication?
Vomiting within about two or three hours may mean another dose is needed. Contact a pharmacist promptly rather than guessing. Some medicines used for seizures or tuberculosis can reduce effectiveness, so mention all medicines you take.
Sex after taking the pill and restarting contraception
Emergency contraception taken for one episode does not protect against later unprotected sex. Use condoms. After UPA, guidance generally recommends waiting five days before restarting or starting a progestogen-containing contraceptive method; additional protection may then be required until it becomes effective.
Breastfeeding and updated UPA advice
In January 2025, FSRH updated guidance to state that breastfeeding interruption is generally not needed after a single dose of UPA used for emergency contraception. Older guidance suggesting a week of interruption is no longer the current FSRH recommendation. Discuss individual circumstances with your clinician.
Side effects, bleeding and your next period
Temporary nausea, headache, tiredness, mild abdominal pain, breast tenderness and spotting can occur. The next period can arrive earlier or later than expected. Consider testing if the period is more than seven days late or unusually light, and take a pregnancy test three weeks after the last unprotected sex.
How often can emergency pills be used?
There is no universal fixed number of times per month that applies to every person and product. Repeated use may affect bleeding patterns but is not known to damage future fertility. If you need emergency contraception often, a reliable regular method is preferable.
When urgent medical attention is needed
Sudden severe or one-sided pelvic pain, fainting, shoulder-tip pain or heavy bleeding requires urgent assessment, including for possible ectopic pregnancy. Emergency contraception does not protect against sexually transmitted infections.
Frequently Asked Questions
How soon should emergency contraception be taken?
Usually within 72 hours for LNG or 120 hours for UPA; seek advice promptly.
Does it cause an abortion?
No. Emergency pills do not end an established pregnancy.
What if I vomit after taking it?
Contact a pharmacist if you vomit within two to three hours because another dose may be needed.
Can it delay my period?
Yes. Test three weeks after the last unprotected sex; seek advice about a period more than seven days late.
Will repeated use cause infertility?
No known damage to future fertility, though irregular bleeding can occur.
Should breastfeeding stop after UPA?
Updated 2025 FSRH advice says interruption is generally unnecessary after a single emergency-contraception dose.
Does it prevent STIs?
No, condoms and appropriate testing remain important.
Sources
- World Health Organization — Emergency contraception
- NHS — How to take the emergency contraceptive pill
- FSRH — UPA and breastfeeding (2025)
- Prothom Alo — Gynecologist discussion
This article is educational and does not replace individual medical advice.
