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Medically reviewed by
Dr Daniel Atkinson
GP Clinical lead
on September 28, 2022.
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What is the mini pill?

The mini pill is a hormonal method of contraceptive pill that prevents pregnancy. It differs from combined contraception because it only contains one hormone, always a version of progesterone.

The progestin-only pill is over 99% effective when you use it perfectly. Your cover is still 91% effective when it’s used on a more ‘typical’ basis. This makes it just as effective as combined methods of contraception, which contain synthetic estrogen as well as progestin.

The mini pill, sometimes called the progestin-only pill (POP), can be preferable for certain women who respond adversely to estrogenic side effects (those associated more with combined pills). The mini pill is taken daily. Unlike combined pills, there are no “pill free” breaks or placebo pills — you take active mini pills continuously.

How does the mini pill work?

The mini pill, not to be confused with ‘the pill” (the combined pill), prevents pregnancy. But what does the mini pill do in the body to stop pregnancy, and how does the progestin-only pill work?

During the menstrual cycle, progesterone is naturally released in rising and falling quantities; this affects how the body prepares for pregnancy. Mini pills contain synthetic progesterone, and this is at a lower level than the progesterone found in combined contraceptive pills.

When you take the mini pill, the additional levels of progestin impact the body in several ways to provide contraception. For example, the mini pill can suppress ovulation, which means eggs may not be released. It also thickens vaginal mucus, which can block sperm. Lastly, the mini pill prevents the uterine lining from thickening, which means fertilized eggs would struggle to implant themselves and grow.

How long does the mini pill take to work?

If you’re thinking about taking mini pills, you’ve probably wondered how long it takes progestin birth control to work. Firstly, you can start taking the progestin-only pill whenever you like. But there’s a few things to know about what day you choose:

If you’re on the first five days of your period, the progestin-only pill will work straight away and you’re protected immediately from pregnancy. However, if you have short menstrual cycles, you’ll need to use additional contraception like condoms for 2 days after you start taking the mini pill.

If you decide to start the progestin-only pill after the fifth day of your period, you’ll need to use additional contraception until you’ve taken the pill for over two days. You won’t be protected immediately.

How to take the mini pill

There are two different types of mini pill which are taken in slightly different ways.

The traditional mini pill has to be taken within three hours of the same time daily. Some countries have a second type of mini pill which uses desogestrel as the progestin, and those have a longer efficacy window of 12 hours. Unfortunately, desogestrel mini pills aren’t yet available in the US, though you can find desogestrel alongside estrogen in several combined pills.

When you receive your mini pill, take care to read over the specific instructions on how to take it. Each pill packet contains 28 pills which are to be taken daily. If you miss taking a pill or pills it will reduce the overall effectiveness of the mini pill. It’s best to get into the habit of taking it each day at the same time.

Does the mini pill stop periods?

A big question for many when choosing a contraceptive is about periods. So, do you get a period on the mini pill? This can depend on how your body responds to the introduction of new hormones. Your periods may change — they usually get lighter and less frequent and, for many women, may stop altogether. This is perfectly safe, but if having your period every month is a welcome physical sign that you’re not pregnant, mini pills may not be the best choice.

You might not be able to take the mini pill if you want your periods to stay the same or if you experience unexplained vaginal bleeding between periods.

Mini pill benefits

There are several benefits of progestin-only pills, some of which might make them more preferable to certain women over the combined pills.

One benefit of the mini pill is that, like the combined pill, it doesn’t interfere with the process of sex. It can also cause menstrual bleeding to stop altogether (though it doesn’t always).

Mini pills don’t affect breast milk the same way that combined contraceptives do, so you can often start taking the progestin-only pill shortly after giving birth, even if you intend to breastfeed.

The mini pill doesn’t provide you with permanent protection from pregnancy, meaning if you decide to stop taking it in the future, your ability to get pregnant won’t be impacted.

Women can take the mini pill up to the age of 55, which is typically around the age of menopause. If you’re over the age of 35 and smoke, it’s safe for you to take the mini pill.

Is the mini pill safe?

For the majority of women, the mini pill is a safe and well-tolerated medication. However, all medications have the ability to cause side effects and this is also true of mini pills. The most common side effects associated with progestin-only pills include, but aren’t limited to, nausea, headache, low libido, tender breasts, depression and fatigue. 

The mini pill isn’t always safe for everyone. You can’t take progestin-only pills if: 

  • You have cirrhosis or liver tumours 
  • Have or had breast cancer 
  • Have liver disease,
  • Have arterial disease or heart disease or stroke 
  • Have unexplained bleeding in between your periods 
  • Take medications which affect the pill’s effectiveness 
  • Think you might be pregnant.  

If you take the mini pill and you throw up or have diarrhea within two hours, you may not have properly absorbed it. Take another pill afterwards to ensure contraceptive protection is not affected.

Mini pill effectiveness

Just how effective are progestin-only pills? Well, mini pills are highly effective, even when not taken perfectly. “Perfect use” describes remembering to take them every day, at the right time, and never missing a single pill. If you use the mini pill perfectly, you’ll have over 99% protection from pregnancy.

With “typical use,” which takes into account the average use of the mini pill including missed pills and incorrect timings, it still remains around 91% effective.

If you do forget to take a pill, but you remember within your three hour efficacy window, take it as soon as you remember and then take your next pill at the regular time. This should not impact your protection.

If you forget to take a pill and it’s been longer than three hours, you will no longer be protected from pregnancy. Regardless of how many pills you’ve missed, take one pill as soon as you remember you missed a dose. Take the next pill at the usual time; this might mean taking two pills in a single day. Then resume taking your daily pills at the same time each day. Use condoms when having sex for the next two days as your protection builds back up.

You may need emergency contraception if you had sex after missing a pill. Emergency contraception like the “morning-after pill” needs to be taken within a specific window of time, so be sure to read the directions and speak to your doctor if you have questions.

Coming off the mini pill

You can stop taking the mini pill at any time; it’s safe to stop taking it whenever you like and your ability to become pregnant will not be affected.

However, just as starting the pill can cause a number of noticeable changes in the body, coming off the pill can do the same. Some women who stop taking the progestin-only pill experience flare-ups with acne, and they’ll likely see their periods return to normal.

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This page was medically reviewed by Dr Daniel Atkinson, GP Clinical lead on September 28, 2022. Next review due on September 28, 2024.

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