If you're going on the pill to prevent pregnancy, it's important to know how long it'll take for your birth control to become effective. Until you're in the clear, you'll need to use a backup method of contraception, such as condoms.
The exact time frame varies depending on the type of pill and where you were in your cycle when you began taking it. "Progestin-only pills contain the hormone progestin, which thickens cervical mucus, making the sperm's ability to reach an egg nearly impossible. Progestin-only pills can also prevent ovulation," Savita Ginde, MD, vice president of medical affairs at Stride Community Health Center and former chief medical officer of Planned Parenthood of the Rocky Mountains, told POPSUGAR. If you take a progestin-only pill within the first five days of starting your period, it will offer immediate protection. Anything beyond five days will take 48 hours.
Combination pills require a bit more consideration because they contain two hormones that prevent ovulation: progestin and estrogen. Like progestin-only pills, you'll be immediately protected if you start taking a combination pill within five days of starting your period. Dr. Ginde explained. But if you begin taking a combination pill at any other time in your cycle, it will take a full seven days of use before becoming fully effective.
Just remember that every body is different, so there are exceptions. "Pills are synthetic hormones that interact with our natural hormones to manipulate the body's ability to become pregnant," Dr. Ginde said. These rules are based on starting at a specific time in a typical 28-day menstrual cycle — but not all women have consistent cycles. If your periods are irregular, you'll want to take extra precautions: "For example, women taking the progestin-only pill with cycles shorter than 23 days should never assume the pill will take immediate effect and should wait a full 48 hours," she said. This all sounds a bit complicated, but it boils down to this: to be safe, Dr. Ginde recommends using a backup method for the first 48 hours when taking progestin-only pills and for a full week with combination pills.
Finally, even if you have a typical 28-day menstrual cycle, certain medical conditions can impact how long it takes for birth control to become effective — particularly digestive disorders like Crohn's disease and irritable bowel syndrome. "With serious diarrhea or vomiting, our body's ability to absorb any oral medication correctly is limited, including the pill," Dr. Ginde said. If you're dealing with a any chronic medical condition, ask your health care provider if you should use another form of birth control in order to ensure that you're as protected as possible.