When you start birth control how long until its effective

• Oral birth control takes seven days to become effective at preventing pregnancy. 
• Missing two days or more of the pill will put you at risk of getting pregnant. 
• Copper IUDs work immediately after insertion and can even prevent pregnancy five days after unprotected sex.

Doctors recommend waiting at least one week before having sex after starting a birth control method, because in many cases, it's not instantly effective. How quickly your birth control will start protecting you against pregnancy depends on the method and where you are in your menstrual cycle. 

"For most methods of contraception, it takes some time before becoming effective given their mechanism of action in preventing pregnancy, so during that time, it is important to use a backup method of contraception or practice abstinence," says Tania Basu Serna, MD, MPH, associate professor of obstetrics and gynecology at the University of California, San Francisco.

Here's how long it takes before common birth control methods become effective against pregnancy.

How long does it take for your birth control to start working?

Generally, you need to abstain from sex or use back-up contraceptives (such as external and internal condoms or diaphragms) for about a week to prevent pregnancy. 

Oral contraceptives

To prevent pregnancy, you should use condoms for at least seven days after starting hormonal birth control pills (i.e. the estrogen-progesterone pill or progesterone-only pills). 

"Contraceptive pills can also be started on the first day of the menstrual cycle, and if this is the method of initiation, then delaying intercourse or using a back-up method is not necessary," says Anne Banfield, MD, FACOG, national young physician-at-large at the American College of Obstetricians and Gynecologists and director of Women's Health Services at Davis Medical Center.

Copper intrauterine device (IUD)

Paragard is the only brand of copper IUD in the United States. "It isn't necessary to wait to have sex after starting the Paragard IUD because it is immediately effective upon insertion," says Banfield. 

Hormonal IUD, patch, and implant

If you started using the transdermal patch (Xulane), birth control implant (Nexplanon), or hormonal IUD (Kyleena, Liletta, Mirena, and Skyla) within the first five days of your period, there's no need for back-up contraceptives. Outside of that time frame, you'd have to use the barrier method for the seven days after starting your birth control.

Hormonal injection

You need to use a form of barrier contraception for at least seven days after receiving the hormonal injection (Depo-Provera). If you had the shot within the first week of your period, a back-up birth control won't be necessary.

"Irregular periods on birth control does not necessarily mean the method is not working since side effects of different contraceptive methods are oftentimes irregular bleeding," says Serna. However, if you are concerned about your abnormal vaginal bleeding, you can consult your health care provider for medical advice.

What happens if you miss a birth control dose?  

If you miss taking the pill for two days or more, you are no longer protected against pregnancy. When you restart a birth control packet, you need to use a backup contraceptive for seven days. 

In order for the hormonal injection to be effective, experts typically recommend that you get a shot every 10 to 12 weeks. If you wait longer than 15 weeks to get your next shot, then you're at higher risk of pregnancy and should use a backup method, like condoms, for seven days following your next injection.

The steps to take if you miss your birth control patch differs depending on your patch week and the number of days you missed before applying a new one. To help you find out what to do next, you can take Planned Parenthood's missed birth control patch quiz.

Insider's takeaway

Some birth control methods, like a copper IUD, protect you against pregnancy quicker than others, depending on the kind of contraceptive and where you are in your menstrual cycle. To minimize your risk of pregnancy, use back-up contraceptives like external and internal condoms or diaphragms during the first seven days of a new birth control method. 

"The menstrual cycle does not affect when you can start taking birth control, but it does affect when it will provide maximum effect," says Banfield. "Since contraception (other than condoms) does not prevent sexually transmitted infections (STIs), continuing either male or female condoms for STI prevention should always be considered."

Carla Delgado

Freelance Reporter, Insider Reviews

Carla is a Filipino freelance health & culture journalist with bylines in Insider, Architectural Digest, Elemental, Observer, and Mental Floss. Outside of writing, she works for local theatre productions as a stage manager and assistant sound operator. Learn more about how our team of experts tests and reviews products at Insider here.

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