Emergency Contraception After Unprotected Sex: Options, Timing, Safety & Next Steps
If you have had unprotected sex or your contraception failed and you do not want to become pregnant, emergency contraception can reduce the chance of pregnancy.
The important thing is not to panic or spend too much time trying to calculate exactly where you are in your menstrual cycle. Emergency contraception is time-sensitive, and the available options differ in how long after intercourse they can be used and how well they work at different times.
Emergency contraception includes emergency contraceptive pills and the copper intrauterine device (IUD). The copper IUD is the most effective emergency contraceptive option. Oral options include ulipristal acetate and levonorgestrel.
Emergency contraception is intended to prevent a pregnancy from occurring after an episode of unprotected sex. It does not terminate an established pregnancy.
Emergency contraception at a glance
Use emergency contraception as soon as possible after unprotected sex.
Emergency contraceptive pills can be used within 5 days (120 hours), although their effectiveness varies by type and timing.
Ulipristal acetate maintains effectiveness better than levonorgestrel during days 3–5.
A copper IUD is the most effective form of emergency contraception and can also provide ongoing contraception.
Emergency contraception does not protect against sexually transmitted infections (STIs).
Emergency contraceptive pills do not cause permanent infertility.
Emergency contraception does not provide ongoing protection for later unprotected intercourse.
A pregnancy test may be appropriate if expected menstrual bleeding does not occur or about 3 weeks after emergency contraception when advised by clinical guidance.
First: work out how much time has passed
The first practical question is:
When did the unprotected sex or contraceptive failure happen?
You do not need to know the exact time of ovulation before seeking emergency contraception.
Within the first 24 hours
Several emergency contraception options may still be available. Acting promptly is useful because oral emergency contraception generally works better when taken sooner.
1–3 days afterward
Emergency contraceptive pills remain an option. Levonorgestrel is most effective when taken early, while ulipristal can also be used during this period.
3–5 days afterward
The distinction between the pills becomes particularly important. CDC guidance reports similar effectiveness for ulipristal and levonorgestrel during the first three days, but ulipristal has been observed to be more effective than levonorgestrel during days 3–5.
A copper IUD is another option when medically appropriate.
More than 5 days afterward
The usual five-day emergency-contraception window has passed for oral emergency contraceptive pills. A copper IUD may sometimes still be considered when the timing of ovulation can be estimated; CDC guidance allows placement more than five days after intercourse when placement is no more than five days after ovulation. This requires assessment by a qualified healthcare professional.
If more than five days have passed, professional advice is particularly useful rather than assuming that no options remain.
The main emergency contraception options
1. Ulipristal acetate
Ulipristal acetate is a 30 mg emergency contraceptive pill.
It acts through progesterone-receptor activity and is thought to prevent or delay ovulation. It can be used up to five days after unprotected sex and retains effectiveness better than levonorgestrel later in the five-day window.
One important consideration is what you do afterward.
Because ulipristal interacts with progestin-containing hormonal contraception, CDC recommends waiting at least 5 days before starting or resuming hormonal contraception. Barrier protection or abstinence is then needed for the appropriate period after the regular method is started.
2. Levonorgestrel
Levonorgestrel is a progestin-type emergency contraceptive pill, commonly provided as a single 1.5 mg dose.
It primarily works by preventing or delaying ovulation. It should be taken as soon as possible after unprotected sex. Although it can retain some effectiveness through five days, its effectiveness decreases with increasing time after intercourse.
Unlike ulipristal, regular hormonal contraception can generally be started or resumed immediately after levonorgestrel emergency contraception. CDC recommends barrier protection or abstinence for the required backup period while the regular method becomes effective.
3. Copper IUD
A copper IUD is inserted into the uterus by a qualified healthcare professional.
It is the most effective emergency contraception. WHO reports that a copper IUD inserted within 120 hours of unprotected intercourse is more than 99% effective at preventing pregnancy. It can then remain in place as an ongoing contraceptive method if the person wishes to continue using it.
The copper IUD does not depend on taking a pill correctly and its emergency use is not affected by body weight in the same way that oral emergency contraception may be.
However, it is not appropriate for everyone. A clinician must consider the person's medical history and whether there are conditions that make IUD insertion unsuitable. For example, an IUD should not be inserted as emergency contraception in someone who is already pregnant, and certain pelvic infections or other medical circumstances require particular consideration.
Does emergency contraception work after ovulation?
This is one of the most important limitations.
Oral emergency contraceptive pills work mainly by preventing or delaying ovulation. If ovulation has already occurred, their ability to prevent pregnancy is limited because the main target of the medication has already passed.
The difficulty is that most people cannot determine the exact day of ovulation simply by looking at their menstrual calendar.
For this reason, do not delay seeking emergency contraception because you are unsure whether you have already ovulated.
The copper IUD works differently and has a different role in emergency contraception.
Can body weight affect emergency contraception?
Body weight or BMI may affect the effectiveness of emergency contraceptive pills.
CDC's 2024 guidance states that ECPs might be less effective in people with obesity, particularly compared with people with lower BMI, but obesity is not considered a safety reason to withhold emergency contraception.
This is an important distinction:
Possible reduction in effectiveness is not the same as increased toxicity or danger.
If body weight may be a concern, a healthcare professional can discuss the available options, including whether a copper IUD is appropriate.
Do not delay emergency contraception while trying to calculate whether your BMI changes your eligibility.
What medicines can interfere with emergency contraception?
Some medicines can increase the activity of liver enzymes that process hormonal medicines. This can potentially reduce the effectiveness of some oral emergency contraception.
Examples may include certain:
antiseizure medicines
tuberculosis medicines
HIV medicines
other enzyme-inducing medicines
The exact medicine matters. Do not assume that every prescription medicine interferes with emergency contraception.
Tell the pharmacist, doctor, or other healthcare professional about all regular medicines and supplements you take.
This is particularly important if you take medicines for epilepsy, tuberculosis, HIV, or other conditions that may involve enzyme-inducing drugs.
What if you are breastfeeding?
Breastfeeding does not automatically rule out emergency contraception.
CDC's current medical-eligibility guidance classifies breastfeeding as compatible with levonorgestrel, ulipristal and copper-IUD emergency contraception. However, the evidence is not identical for the different options. CDC notes that levonorgestrel passes into breast milk in minimal quantities, while ulipristal and its active metabolite are also detectable in milk but evidence about effects on breastfed infants is limited.
Because product labeling and clinical recommendations can differ between countries, a breastfeeding person should check the specific product information or speak with a pharmacist or clinician.
What side effects can occur?
Emergency contraceptive pills are generally well tolerated.
Short-term effects can include:
nausea
headache
dizziness
tiredness
breast tenderness
abdominal discomfort
spotting or changes in menstrual bleeding
Your next period may come earlier or later than expected, and its flow may be different from usual. A change in bleeding does not by itself prove that emergency contraception has failed.
The copper IUD has a different side-effect profile. Some users experience increased menstrual bleeding or cramping, particularly during the first months after insertion.
What if you vomit after taking the emergency contraceptive pill?
If vomiting occurs soon after taking an emergency contraceptive pill, some of the medicine may not have been absorbed.
CDC recommends taking another dose as soon as possible when vomiting occurs within 3 hours of taking an emergency contraceptive pill. A pharmacist or healthcare professional can help determine the appropriate repeat dose.
Do not take repeated extra tablets simply because you are worried that a larger dose will work better.
What happens to your next period?
Temporary menstrual changes are common after emergency contraception.
Your next period may:
arrive earlier
arrive later
be lighter
be heavier
include spotting
These changes can occur because emergency contraception can temporarily alter the timing of ovulation and the menstrual cycle.
However, a late period can also occur because pregnancy happened despite emergency contraception. Therefore, menstrual changes should not be used alone to decide whether the method worked.
When should you take a pregnancy test?
Consider pregnancy testing when:
your expected period is substantially late
pregnancy symptoms develop
you are concerned that emergency contraception may have failed
about 3 weeks have passed after emergency contraception and expected bleeding has not occurred, particularly following CDC guidance for follow-up after ECP use.
A positive pregnancy test after emergency contraception does not mean that the emergency contraceptive pill caused the pregnancy or harmed it. Available evidence does not show that inadvertent ECP exposure during early pregnancy causes poor pregnancy outcomes at a high rate.
If a pregnancy test is positive, arrange appropriate medical care.
Emergency contraception does not protect against later sex
This is easy to misunderstand.
Suppose you take an emergency contraceptive pill after unprotected sex on Monday and then have unprotected sex again on Wednesday.
The Wednesday episode creates a new pregnancy risk.
Emergency contraceptive pills should therefore not be treated as protection for the remainder of the menstrual cycle.
Use condoms or an appropriate ongoing contraceptive method for subsequent sex.
Starting regular contraception after emergency contraception
The instructions depend on which emergency contraceptive pill you used.
After levonorgestrel
Regular hormonal contraception can generally be started or resumed immediately.
Use condoms or avoid intercourse for the appropriate backup period for your regular contraceptive method. CDC recommends seven days of barrier protection or abstinence for many methods.
After ulipristal
Wait at least 5 days before starting or restarting hormonal contraception because progestins may interfere with ulipristal's action.
After starting or restarting the regular method, continue condoms or abstinence for the required backup period.
Because backup requirements differ among contraceptive methods, follow the instructions for the specific method rather than applying one rule to every form of contraception.
Emergency contraception and sexually transmitted infections
Emergency contraception does not prevent STIs, including HIV.
If the sexual exposure may have involved STI or HIV risk, emergency contraception addresses only pregnancy prevention.
Condoms can reduce the risk of STI transmission when used correctly and consistently. CDC also notes that HIV prevention may involve other measures, including HIV post-exposure or pre-exposure prevention depending on the circumstances.
After sexual assault, medical care should address more than pregnancy prevention. STI evaluation, HIV prevention, injuries, and emotional support may also be appropriate. WHO specifically recognizes emergency contraception as part of care following sexual assault when pregnancy is possible.
Can emergency contraception cause infertility?
Current evidence does not show that emergency contraceptive pills cause permanent infertility.
Emergency contraception is a temporary intervention. Fertility is not known to be permanently impaired by its use. WHO states that emergency contraceptive medicines do not harm future fertility and do not delay the return of fertility.
The copper IUD is also reversible. Fertility can return after its removal.
Can emergency contraception be used more than once?
Yes, emergency contraception may be needed again if another episode of unprotected sex occurs.
Repeated use of emergency contraceptive pills can produce more temporary menstrual irregularity, but repeated use is not the same as taking a dangerous cumulative dose of hormones.
If emergency contraception is needed frequently, that does not mean someone has done anything wrong. It may simply be useful to discuss whether another contraceptive method would provide more convenient ongoing protection.
The copper IUD is one option because it can provide both emergency contraception and long-term contraception.
Common misunderstandings
“Emergency contraception is an abortion pill.”
No. Emergency contraception is intended to prevent pregnancy before an established pregnancy exists. It does not terminate an established pregnancy.
“Taking extra emergency contraceptive pills makes them work better.”
No. Follow the recommended dose. Taking additional tablets without specific medical instructions does not provide a reliable way to increase effectiveness.
“A late period proves the emergency contraceptive failed.”
No. Emergency contraception can change the timing of menstrual bleeding. A pregnancy test is more useful when pregnancy is a concern.
“Emergency contraception protects against the next time I have sex.”
No. A subsequent episode of unprotected sex can create a new pregnancy risk.
“Emergency contraception protects against STIs.”
No. It is designed for pregnancy prevention, not STI prevention.
“Emergency contraception causes permanent infertility.”
There is no good evidence that emergency contraceptive pills cause permanent infertility.
When should you seek medical evaluation?
Seek prompt medical attention if you develop symptoms such as:
severe or worsening abdominal or pelvic pain
fainting or marked weakness
unusually heavy bleeding
a positive pregnancy test accompanied by significant pain or bleeding
severe symptoms that do not seem consistent with the expected temporary effects of emergency contraception
Do not automatically assume significant pain or heavy bleeding is simply a side effect of the emergency contraceptive pill.
A healthcare professional can assess whether another condition needs to be considered.
A practical way to think about emergency contraception
If unprotected sex or contraceptive failure has occurred:
1. Act promptly.
Do not delay simply because you are uncertain about your menstrual-cycle timing.
2. Work out approximately when the exposure occurred.
The number of hours or days affects the available options.
3. Consider the method.
Ulipristal, levonorgestrel and the copper IUD do not have identical characteristics.
4. Mention important factors.
Tell the pharmacist or clinician if you are breastfeeding, take regular medicines, have relevant medical conditions, or may prefer an ongoing IUD.
5. Follow the instructions for the specific product.
Do not substitute one emergency contraceptive for another without understanding the difference.
6. Plan for later sex.
Emergency contraception does not provide continuing protection against new episodes of unprotected intercourse.
7. Know when to test.
If expected bleeding does not occur or pregnancy remains possible, take a pregnancy test at an appropriate time.
8. Seek care for concerning symptoms.
Severe pain, fainting, heavy bleeding or a positive pregnancy test with concerning symptoms warrants medical evaluation.
Key Takeaways
Emergency contraception can reduce pregnancy risk after unprotected sex or contraceptive failure.
The sooner it is used, the better, although the available options differ in their time windows and effectiveness.
Ulipristal acetate and levonorgestrel are different emergency contraceptive pills.
Ulipristal generally has an advantage over levonorgestrel during days 3–5 after intercourse.
A copper IUD is the most effective emergency contraception and can provide ongoing contraception.
Oral emergency contraception works mainly by preventing or delaying ovulation.
Emergency contraception does not terminate an established pregnancy.
Body weight, medication interactions and breastfeeding can affect which option deserves discussion.
Vomiting within 3 hours of an emergency contraceptive pill may require another dose.
Emergency contraception does not prevent STIs or protect against later unprotected sex.
After ulipristal, hormonal contraception should generally be delayed for at least 5 days.
If pregnancy remains possible, appropriate pregnancy testing and medical follow-up are important.
Medical Disclaimer
This article provides general educational information and does not replace individualized medical advice, diagnosis or treatment. Emergency contraception choices can depend on the time since intercourse, the specific medicine available, other medications, breastfeeding, medical history, body weight, pregnancy status and local clinical guidance. If you need emergency contraception, speak with a qualified doctor, gynecologist, pharmacist or other healthcare professional, particularly if you have medication interactions, significant symptoms, or questions about an IUD.