CSU Clinic

Emergency Contraception(Plan B)

What is emergency contraception?

Emergency contraception is a form of birth control. You can use this method if you have had unprotected sex. For example, if your regular birth control fails (the condom breaks during sex), if you forget to take your birth control pills or if you have sex without using any birth control.

Emergency contraception is available from health care providers. It is provided in two ways:

  • Emergency contraception pills (ECPs)
  • Insertion of an IUD (Not available at Health and Wellness Services)

    You may want emergency contraception if

    • His condom broke or slipped
    • You forgot to take your birth control pills
    • Your diaphragm or cervical cap slipped out of place
    • You miscalculated your "safe"days
    • You were not using any birth control
    • You had unprotected vaginal sex

Important! ECPs DO NOT protect against HIV or other sexually transmitted infections. You may want to consider testing for sexually transmitted infections if there is a possibility that unprotected sex put you at risk.

How do I use emergency contraception?

The first kind of emergency contraception, sometimes called the "morning-after pill," is taken in two doses. You can start taking this kind of emergency contraception right away after having unprotected sex. The sooner you take it, the better it works, but you can take the first dose within three days (72 hours) after having unprotected sex. You take the second dose 12 hours after the first. Your doctor may tell you about other ways of taking this medicine.

There is a brand of pills made just for emergency contraception. It is called Plan B (levonorgestrel).

The U.S. Food and Drug Administration also has said that some brands of regular birth control pills are safe for emergency use. The number of pills you take in each dose depends on which brand of pills you are using. To learn more about which pills are safe for emergency use, talk with your doctor.

An IUD that is placed in your uterus within 7 days after unprotected sex also can be used as emergency contraception. An IUD is a small device that can be left in your body for 5 to 10 years. It will prevent pregnancy during that time.

How does emergency contraception work?

Pills used for emergency contraception can prevent your ovaries from releasing an egg, can prevent an egg from being fertilized by sperm or can prevent a fertilized egg from attaching itself to the wall of the uterus. Emergency contraceptive pills are not the same as the medicine known as the "abortion pill." This medicine is taken in the early weeks of pregnancy to end the pregnancy. Pills used as emergency contraception can't end a pregnancy once a fertilized egg has attached itself to the wall of the uterus.

Unlike the morning-after pill, an IUD doesn't stop your ovaries from releasing an egg. The IUD can prevent an egg from being fertilized and it can stop a fertilized egg from attaching itself to the wall of the uterus.

No studies have shown that taking hormones while you are pregnant can hurt your baby. But, if you know you are pregnant, you should not take emergency contraception pills.

How effective is emergency contraception?

Emergency contraception pills can be very effective if they are used in time. If used within 72 hours of unprotected sex, it can reduce the risk of pregnancy by 75% to 89%. It is important to remember that these pills will work best when taken as soon as possible after unprotected sex.

Emergency IUD insertion is also very effective. It can reduce the risk of pregnancy by 99.9% if inserted within 7 days after unprotected sex.

It is important to remember that using this type of contraception regularly is less effective than using ongoing methods of contraception (like contraception pills or diaphragms). Emergency contraception should not be your main type of contraception.

After you take the pills


  • Your next period may be earlier or later than usual.
  • Your flow may be heavier, lighter, more spotty, or the same as usual.
  • If you see another health care provider before you get your period, remember to tell them that you have taken emergency contraception pills.
  • Schedule a follow-up visit with your health care provider if you don't have your period in three weeks or if you have symptoms of pregnancy.
  • Be sure to use another method of contraception if you have intercourse any time before you get your period again.
  • Continue using the birth control method of your choice for as long as you want to avoid pregnancy.

Risks and side effects

  • Nausea
  • Vomiting
  • Headaches
  • Breast tenderness
  • Dizziness
  • Fluid retention
  • Menstrual changes with heavier or lighter bleeding

Side effects associated with the use of ECPs usually taper off one or two days after the second dose has been taken. Frequent use of ECPs may cause periods to become irregular and unpredictable.The side effects of anti-nausea medication may include drowsiness.Please follow the precautions on the package insert.

Who should not use Plan B?

Women who have or have had the following conditions should not use Plan B:

  • An already established pregnancy
  • Blood clots or inflammation of veins in the legs
  • Blood clots in the lungs
  • Unexplained vaginal bleeding
  • Cancer of the breast or reproductive organs
  • Serious liver disease
  • Stroke or heart disease
  • Neurologic migraines

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