You've talked to your doctor about birth control. They've written you a prescription. Finally, you have the new pill pack in your hand.
Here's the short answer
You need to take birth control for 7 days in a row for it to start doing its magic.
In other words, you and your partner need to go through a waiting period of 1 week before having unprotected sex (or use a backup method like condoms in the meantime).
Here's the long answer (you're welcome)
That was too easy, right? Well, the answer of 7 days doesn't change. But here are the details so you know what's really happening.
First, let's get the terms straight:
The medical term for any form of birth control is contraception (this could be condoms, birth control pills, the patch, you name it).
Contraceptive methods that have hormones in them are called hormonal birth control methods. These methods include birth control pills (oral contraceptives) or even long-acting reversible contraceptives like an IUD (yeah, that piece of plastic has hormones in it, of course!)
There could be a gap of 7 days before the birth control starts to work and begins effectively preventing pregnancy under certain circumstances.
Understanding exactly how long it takes for birth control pills or other forms of hormonal birth control to become effective is critical because you'll need to use a back-up method of protection until the pill takes effect.
Let's take a look at the different birth control methods, how long each one takes to work, and how they relate to where you are in your menstrual cycle.
Back-up methods in the meantime
If you're not sure what type of birth control pill you have, or you aren't sure what day your period started on, then to be safe, you should use a back-up birth control method, such as a condom, for 7 days after you start taking birth control.
You can begin taking your pill at any time, and after 7 days, it should start to work to prevent pregnancy if you take it correctly.
Note that hormonal birth control methods may cause side effects. That's why talking about your medical history and health habits with your doctor or healthcare provider is important.
Types of barrier methods
Standard and effective barrier methods of birth control include male condoms, the female condom, or a diaphragm.
It's important to remember that birth control pills do not prevent sexually transmitted infections. If there is a chance that you or your partner might have an STI, you should use a barrier method even if your birth control is working to prevent pregnancy.
Diaphragms may not prevent all STIs, so using a condom or female condom is the best choice.
How soon does the pill work for acne or PCOS?
If you're taking birth control for reasons other than contraception, including acne, polycystic ovary syndrome, or endometriosis, it could take 2 or more months to begin taking effect. The exact length of time will depend on your body and the severity of your condition, so it's best to talk to your doctor to understand better how birth control will affect you.
However, when it comes to preventing pregnancy, with a little information about your cycle and the type of birth control you're using, we can narrow down when your birth control starts being effective. Some methods even begin working immediately.
The two types of birth control pills
The time it takes for a birth control pill to work depends on the type of pill and where you are in your menstrual cycle when you first take it.
If your birth control pill is a combination pill that contains both estrogen and progestin, the pill will be effective right away as long as you take it within 5 days of the start of your period.
If you start taking a combination pill during any other part of your menstrual cycle, the pill will begin to work after 7 days. Make sure to use a back-up barrier method during those 7 days.
Combination pills come in various brand names, including:
Check with your doctor if you're not sure if your pill is a combination pill.
Progestin-only pill (mini-pill)
If you take a birth control pill that only contains progestin, it will take effect 48 hours after taking the first pill, no matter where in your cycle you begin taking it.
During those 2 days, you should use a back-up barrier method to prevent pregnancy. Mini-pills are known by different names, including the commonly prescribed Norethindrone™.
Why does it take time for birth control pills to start working
You have to wait to have sex after beginning the pill (or use a condom) because the medication mainly works by preventing ovulation—the ovaries are kept from releasing an egg, so there'll be nothing for sperm to fertilize.
Depending on the type of pill you use, it might also thicken the mucus in your cervix (making it difficult for sperm to swim through and get to the egg).
Birth control pills can also prevent the lining of your uterus from thickening (which is necessary to provide a fertilized egg a place to implant and grow).
How long until birth control hormones take effect
When you have your period, the lining of the uterus and the egg released at the start of that cycle wash away and out of your body, so there's no egg to fertilize, and your uterus isn't ready to accept a fertilized egg even if there was one.
At other points in your cycle, your body has already released an egg, and your uterus prepares for a potentially fertilized egg.
Until the hormones in your birth control pills begin to take effect and create changes in your body, there is a chance you could become pregnant.
Therefore, it's essential to wait for 2 to 7 days, depending on the type of pill you use, or use a backup form of birth control until your pill has time to take effect fully.
Timeframe for emergency contraception pills
Emergency contraception can prevent pregnancy from occurring and might be an option if you have sex too soon after starting birth control pills without using a back-up barrier method.
How soon until the patch, ring, and IUD are effective?
There are several other birth control options available, and they each take effect in different ways.
Birth control patch
The birth control patch releases hormones into your system just like the combination pill, so its delay is similar: it works right away if taken within 5 days of starting your period. Otherwise, wait for 7 days.
The vaginal contraceptive ring works much like the combination pill and the patch, but releases the hormones differently.
Two popular vaginal rings are Annovera™ and Nuvaring™. It has the same delay (although you would generally wait until your period has finished before inserting the ring): Wait or use a barrier method for the first 7 days after beginning the ring.
Birth control shot
You may have heard of the Depo-Provera shot, which is a contraceptive injection that is given every 3 months. When you get the injection, the hormone progestin goes into your body.
Since progestin is the only hormone it contains, the delay is similar to the mini-pill: wait or use a barrier method for 7 days until you have unprotected sex. Check with your doctor to be sure, however.
Intrauterine device (IUD)
An IUD is a small T-shaped device implanted into the uterus. A hormonal IUD, like the popular IUD Mirena™, releases progestin, so its time before it takes effect is the same: wait or use a barrier method for 48 hours.
A copper IUD doesn't use hormones. Instead, it causes an inflammation of the uterus walls that makes pregnancy impossible. It becomes effective immediately, and women have even used it as emergency contraception up to 5 days after unprotected sex.
How long until birth control pills stop working?
One of the benefits of birth control pills is that their effects are reversible. You can stop taking them and get pregnant later in life if you choose to. It might take a few days for your body to resume its usual hormone cycle and release an egg. The exact timing will differ from person to person.
A review of multiple studies in the journal "Contraception and Reproductive Medicine" found a consistent return to fertility for women who had used contraception after they stop taking the pill. Their fertility came back whether they used a combination pill, mini-pill, IUD, or other hormonal methods.
It also didn't matter how long they had used contraception. While the study didn't measure days or weeks, they found consistent successful fertilization rates within 1 year of stopping contraception use.
With so many birth control options available, it can be confusing knowing which one to take and when to take it.
Each type of birth control pill takes some time to become effective. Knowing what type you're using and when your period started can help you understand when your new birth control pills will begin working. To be safe, make sure you use a back-up barrier method of birth control, such as a condom when your birth control pill isn't yet working.
At Favor, our goal is to provide the most up-to-date, objective, and research-based information to help readers make informed decisions. Articles are written by experienced contributors; they are grounded in research and evidence-based practices. All information has been fact-checked and extensively reviewed by our team of experts to ensure content is accurate and on par with current industry standards. Articles contain trusted third-party sources that are either directly linked to in the text or listed at the bottom to take readers directly to the source.