You do not have to wait for your period to start birth control. Most hormonal birth control methods can be started at any point in the menstrual cycle, as long as pregnancy can reasonably be ruled out. Starting right away does not reduce how well birth control works when it is used correctly.
Research comparing “quick start” methods with waiting until the next period shows similar pregnancy rates, side effects, and continuation over time. Studies have found no meaningful difference in safety or effectiveness between starting during a period and starting on another day of the cycle. For many people, starting immediately helps avoid delays and lowers the chance of unintended pregnancy.
Timing can affect whether backup protection is needed at first. When birth control is started during the first few days of a period, it usually works right away. If it is started later in the cycle, using condoms or avoiding sex for a short time may be advised until the method becomes fully effective.
Birth control should be started with guidance from a healthcare professional to be sure the method is appropriate and pregnancy has been ruled out. Do not start or switch birth control on your own without medical advice.