Birth control pills are a safe and effective method of preventing unintended pregnancy. For some people, the pill can also help reduce symptoms caused by their periods, such as heavy bleeding and irregular cycles.
In this article, we examine whether a person can start their birth control pills midcycle, and the benefits, risks, and side effects of doing so.
Can you start the pill midcycle?
It can take several days for the pill to start preventing pregnancy.
To understand how the pill works, it is important to know what happens during a typical menstrual cycle.
The average cycle takes place over the course of 28 days:
- Days 1–7: This is the beginning of a period when bleeding usually occurs for around 4 to 8 days. During this time, a person's hormone levels, especially estrogen, are low and growths called follicles develop on the ovaries. These follicles contain an egg, or ovum.
- Day 8: A person has usually stopped bleeding, and one of the follicles will start releasing estrogen and grow larger. This estrogen causes the uterine lining to become thicker.
- Days 11–13: Estrogen levels reach their peak, and there is an increase in luteinizing hormone (LH). This hormone will eventually cause the follicle to burst and release an egg.
- Day 14: This is typically the day of ovulation when the follicle releases an egg. This egg usually lives for around 12 to 24 hours. If sperm is present during this time, it may fertilize the egg. Sperm can live for 3 to 5 days inside the body.
- Days 15–24: The egg, regardless of whether fertilization has taken place, will travel down the fallopian tube toward the uterus. The ruptured follicle will now begin producing the hormone progesterone, which makes the uterine lining even thicker, creating an ideal environment for a fertilized egg to implant.
- Days 24–28: If the egg is unfertilized, it will break down during this time. Estrogen and progesterone levels start to decrease, which leads to the uterus shedding its lining and the start of a person's next period.
Most people can start taking birth control pills at any point during their menstrual cycle. However, it can take several days for the pill to establish a consistent hormone cycle that prevents pregnancy.
By starting the pill midcycle, around the point of ovulation, a person is at risk of pregnancy and should use a backup contraceptive method until they have taken the pill for at least 7 consecutive days. To be extra cautious, use another form of birth control, such as condoms and foam, during the first month.
How and when to start the pill?
No hard-and-fast rule exists as to when to start the pill. The recommendations on when to start also depend upon what type of pill a woman is taking. There are two main types of birth control pill:
- The combination pill, which contains synthetic versions of the hormones estrogen and progesterone. These hormones prevent ovulation from occurring as well as reducing the likelihood of fertilization and implantation.
- The minipill, which contains a synthetic version of progesterone only. It is also known as the progestin-only pill. The minipill primarily prevents pregnancy by causing the cervical mucus to thicken and the womb lining to thin. This reduces the chances of fertilization and implantation of an egg.
Doctors often recommend starting the combined pill either on the first day of a person's period or the first Sunday after starting their period.
Starting on the first Sunday serves two purposes: it provides a consistent day for starting pills and may affect the menstrual timing so that the person will not likely be on their period over a weekend. This may or may not be a benefit to some people.
However, not everyone has a regular menstrual cycle. A person may start their period and then have it again 2 weeks later. In this instance, some people may find it difficult to time their pills according to "starting a cycle."
For a person with irregular periods, the best time to start taking the pill may be whenever they are ready to begin regulating their periods.
A person can usually start the minipill at any time during their cycle. The minipill typically protects against pregnancy within 48 hours of starting it.
However, people who do not start taking the minipill during their period should use another form of contraception for at least the first 2 days. It might be wise to use other contraceptive measures for a full cycle.
For maximum effectiveness, it is crucial to take the minipill during the same 3-hour window each day. A person should choose a time of day that is convenient and easy to remember.
Many people set up a daily reminder to ensure they take their pill at the same time each day.
Benefits and risks of starting midcycle
Results of one study suggest that taking birth control pills when pregnant may not cause any harm.
While there are no clear health benefits to starting midcycle, some people may find it convenient to begin taking their birth control pills as soon as they get them.
However, starting the pill midcycle means that a person will not be protected from pregnancy immediately.
Anyone who chooses to start the pill outside the first 5 days of their menstrual cycle should use a backup method of contraception, such as condoms, for at least:
- 7 days if using the combined pill
- 2 days if using the minipill
Another potential risk of starting the pill midcycle is that a woman may already be pregnant. However, a large Danish study suggests that taking birth control pills during early pregnancy will not harm the fetus.
When starting midcycle, it can also take longer for a person's body to adjust to the new hormone cycle. In some people, this may cause spotting or irregular bleeding. It may take a few months after starting the pill midcycle for more regular periods to return.
Side effects of starting the pill midcycle
The possible side effects of birth control pills are the same regardless of when the person starts taking them and include:
- breast tenderness
- irregular menstrual bleeding
- mood changes
Typically, these symptoms will subside within 3 months of taking the pill. However, if a person continues to experience bothersome side effects after this time, they may wish to talk to their doctor about switching to another type of birth control pill.
Deciding when to start taking birth control pills is largely down to personal preference and the type of pill. A person who starts the pill during the first 5 days of the start of their period should have immediate protection against pregnancy.
Anyone who chooses to start the pill midcycle should use backup contraception for at least 7 days if using the combined pill and at least 2 days if using the minipill.
To be extra careful, a person may wish to consider using another form of birth control during the first month of taking either type of birth control pill.