Ulipristal emergency contraception: how it works, how to take it
Last updated September 3, 2026.
Ulipristal is an emergency contraceptive - it prevents or delays the release of an egg from the ovary. You may know it as Ella. The 5-day option: effective up to 120 hours after unprotected sex, with sooner always better.
What does it treat?
Pregnancy prevention after unprotected sexual intercourse - no birth control, or a method that failed or was used incorrectly. A backup, not a routine method - and no protection against HIV or other sexually transmitted infections.
How do you take it?
One tablet, with or without food, as soon as possible after unprotected sex - it can be taken up to 120 hours (5 days) after, but the sooner the more likely it works. Any time in the cycle, but not more than once in the same cycle. If you vomit within 3 hours, call your doctor - a repeat dose may be needed. After taking it: hormonal birth control can resume 5 days later, with a barrier method in between and until the birth control has run long enough - the two interfere with each other. If your period is more than a week late, take a pregnancy test.
Side effects to know
- Common: painful periods, spotting or bleeding between periods, nausea, tiredness, headache, and dizziness.
- Serious - call your doctor immediately: severe lower abdominal pain 3 to 5 weeks after taking it - the ectopic-pregnancy signal.
Who should not take it?
Anyone already pregnant - it is not intended for that and will not work. It prevents or delays ovulation; it does not end an established pregnancy. If you breastfeed, the guidance is to pause and pump-and-discard - ask your doctor for the current interval. For regular contraception, ongoing methods are the tools.
When is it an emergency?
Severe lower abdominal pain in the weeks after taking it is urgent care - ectopic pregnancy needs same-day evaluation. For an overdose, call Poison Control at 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
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Common questions
How is ulipristal different from levonorgestrel?
The window and the mechanism depth: levonorgestrel works up to 72 hours; ulipristal up to 120 hours (5 days) - and it holds its effectiveness better across those days, especially on days 3 to 5. Both prevent or delay ovulation; neither ends an established pregnancy. Timing decides: as soon as possible, with whichever reaches you first - and past 72 hours, ulipristal is the tablet option.
Why wait 5 days before restarting my birth control pills?
They interfere with each other: ulipristal blocks progesterone's action, and the progestin in birth control competes for the same target - restart too soon and you can undo the emergency dose. The rule: wait 5 days after ulipristal before resuming hormonal contraception, use a barrier method until the hormonal method has run long enough to protect (for most pills, 7 days), and let your pharmacist confirm the count for your specific method.
What if I vomit after taking it?
Inside 3 hours of the dose, call your doctor - the tablet may not have absorbed and a repeat dose may be needed. After 3 hours, it is in. Nausea is common and brief; vomiting inside that window is the only version that matters.
How will I know it worked?
The period is the proof: it may come early or late, heavier or lighter, with some spotting before - all normal. More than a week late: take a pregnancy test. And the one symptom that never waits: severe lower abdominal pain 3 to 5 weeks afterward - the ectopic signal - is immediate medical care.
Can I use it more than once?
Never more than once in the same menstrual cycle - the cycles get scrambled and reliability drops. Reaching for emergency contraception repeatedly is the signal that a regular method would serve you better: the daily, weekly, monthly, and years-long options all out-protect the backup. That is a practical conversation, not a lecture.
Does it protect against infections?
No - pregnancy only, not HIV or other sexually transmitted infections. If the encounter carried infection risk, testing is a separate step worth taking on its own timeline, and barrier methods are the protection that covers both fronts going forward.