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Medically reviewed by
Dr Daniel Atkinson
GP Clinical Lead
on August 02, 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 progestogen-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 oestrogen as well as progesterone.

The mini pill, sometimes called the progesterone-only pill (POP), can be preferable for certain women who respond adversely to oestrogenic 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 from occurring – but what does the mini pill do in the body to stop pregnancy and how does the progesterone 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 progesterone impact the body in several ways to prevent pregnancy. 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 uterus lining from thickening, which means fertilised eggs would struggle to implant themselves in the uterus.

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 progestogen-only pill whenever you like. But there’s a few thing to know about what day you choose:

If you’re on day one to five of the menstrual cycle, the first five days of your period, the progestogen-only pill will work straight away. If this is the case for you, good news, you’re protected immediately from pregnancy. However, if you have short menstrual cycles, you’ll need to use additional contraception, such as condoms, for two days after you start taking the mini pill.

If you start the progestogen-only pill on day six of your period, or any day following this, you’ll need to use additional contraception until you’ve taken the mini pill for over two days. This is because you won’t be protected immediately.

How to take the mini pill

The mini pill has to be taken daily, at the same time (or within three hours).

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, their periods stop altogether. This is perfectly safe but if you’d like to see a monthly bleed then the progesterone-only pill probably isn’t for you.

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.

Woman with her hands on her head wearing glasses with closed eyes and her hands on her head

Mini pill benefits

There are several benefits of progesterone 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 do not affect breast milk the same way that combined contraceptives do, so you can often start taking the progestogen-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, you can also take the mini pill.

Is the mini pill safe?

For the majority of women, the mini pill is a safe and well-tolerated drug. Because of this, in 2021, it was announced that two progestogen-only pill brands, Hana and Lovima, would be available as pharmacy medications (P) in the UK, meaning women there don’t need a prescription to take them. However, the mini pill is only available through prescription in Australia.

All medications have the ability to cause side effects though, and this is also true of mini pills. The most common side effects associated with progestogen-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 to take. You can’t take progestogen-only pills if you:

  • have cirrhosis or liver tumours,
  • have or have had breast cancer,
  • suffer with liver disease,
  • have arterial disease or heart disease or stroke,
  • have unexplained bleeding in between your periods,
  • take medications which affect the pills effectiveness,
  • think you might be pregnant.

If you take it more than three hours late, get severe diarrohea, vomit within two hours of taking it, or are taking certain medications – the mini pill might not work. If this is the case for you, ask a clinician for advice.

Mini pill effectiveness

Just how effective are progesterone 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 93% effective.

If you do forget to take a pill, but you remember within your three or 12 hour 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 or 12 hours (depending on the type of mini pill you take) – you will no longer be protected from pregnancy. Regardless of how many pills you’ve missed, take one pill as soon as you think to. 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. Refrain from having sex, or use condoms, for 48 hours after you remember to take a pill again.

You may need to seek emergency contraception or take a pregnancy test if you had sex after your forgot to take a pill and before two days have passed since you remembered to take it.

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 progestogen-only pill experience flare-ups with acne, and they’ll likely see their periods return to how they were before taking the mini pill.

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This page was medically reviewed by Dr Daniel Atkinson, GP Clinical Lead on August 02, 2022. Next review due on August 02, 2024.

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