When it comes to preventing pregnancy, there’s an abundance of birth control methods out there. Whether you’re interested in the pill, or you want to learn more about other forms of contraception (such as the implant, IUD or patch), there will never be a one-size-fits-all approach to choosing the birth control method that’s “right” for your body. 

The birth control pill is still the most widely used prescription contraceptive method in the United States, according to a CDC’s NCHS analysis.

Birth control pills (oral contraceptives) are “pills that you take every day to prevent a pregnancy,” says Dr. Lonna Gordon, MD the chief of Adolescent Medicine at Nemours Children’s Hospital in Orlando, Florida.

Wondering what to expect before going on the pill? In conversation with USA TODAY, an expert weighs in to answer your FAQs.

How to use the birth control pill

There are two different types of birth control pills: combination oral contraceptive pills and progestin-only pills, Gordon says. 

Combination pills come in a variety of dosing packets, and they contain a mixture of “active” pills containing hormones, and “inactive” (hormone-free) pills that are taken daily, per Cleveland Clinic. Conventionally, birth control pill packs come in 21-day, 24-day and 28-day cycles. For the most part, the naming “has to do with how many days have active hormones in them, and then how many days have placebo [pills],” Gordon says. 

Progestin-only pills mostly come in 28-day packs, Gordon says. When taking this pill, timing and precision are key. There is only a very small forgiveness window with this type of pill, and it must be taken at the exact time daily to maintain the pill’s effectiveness in preventing pregnancy, she says.

How long does it take to adjust to the pill?

The body makes its own hormones, so when you begin taking an oral contraceptive, the amount of hormones your body makes will adjust “based on what it's receiving from the birth control pill.” So, “I usually recommend giving the body two to three cycles” to adjust to the pill, Gordon says. 

Once the pill takes full effect, it doesn’t just help prevent pregnancy — for people who struggle with hormonal acne, it can clear up your skin. If you experience intense period cramps, the pill can lighten your period, helping to alleviate menstrual pain, Gordon says. Taking the pill may lower the risk of developing uterine and ovarian cancers. It can also be prescribed to treat endometriosis, per Cleveland Clinic.

How long does it take for the pill to work?

Once you begin taking the pill, you'll “need a week to prevent pregnancy,” Gordon says. 

There are, of course, nuances at play. How long it takes for the pill to reach its full effectiveness will depend on the type of pill you take (combination or progestin-only), and where you are in your menstrual cycle.

When it comes to combination pills, if you begin taking the pill within five days of when your period begins, you are protected from the start. However, if you begin taking the pill at any other point during the menstrual cycle, you won’t be protected from pregnancy until seven days after starting the pill, according to Planned Parenthood. 

The progestin-only pill becomes effective in preventing pregnancy after two days of usage, according to Mount Sinai.

How effective is the pill?

“When we talk about effectiveness, we always like to talk about what's perfect use and what's typical use,” says Gordon. 

When it comes to perfect use, if the combined pill and the progestin-only are taken consistently, they are both 99% effective at preventing pregnancy from occurring, per Mayo Clinic. The typical use failure rate for both pills is 7%, according to the CDC.

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