Mini pill: Your guide to the progestogen-only contraceptive pill

The mini pill works slightly differently than the combined pill.
Written by
Tori Crowther
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Last updated on
April 29, 2024
min read
Mini Pill: The Progestogen-Only Contraception Pill | Kin Fertility
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The pill is one of the most commonly used methods of contraception in Australia today — about 27-34% of women take birth control pills [1].

But for something with such a simple name, there sure is a lot to learn when it comes to the oral contraceptive pill. First and foremost, deciding which pill to choose: combination (or combined) pill (progestogen and oestrogen) or the mini pill (progestogen-only). 

Although both have the same primary function as a form of birth control — there are plenty of other reasons, including managing conditions like PCOS and endometriosis — the mini pill works slightly differently than the combined pill and there are pros and cons to both. 

It’s not uncommon to be on a type of pill and not know exactly what it is or how it works. That’s where we come in. We’re breaking down everything you need to know about the progestogen-only pill, whether you’re already on it wanting to learn a little more, or are researching because you’re interested in taking it.

What is the mini pill?

The mini pill — sometimes referred to as POP (progestogen-only pill) — is a type of contraceptive made from progestogen. Progestogen is a synthetically-made version of the hormone progesterone; you'll often see the 2 names used interchangeably.

It is taken at the same time daily without a week of placebo break in the month. It’s continually taken without any “inactive” pills (sometimes called sugar pills). Because of this, you might not get your periods and you may experience breakthrough bleeding if you don’t take your pill during your window. 

It’s a great option for people who can’t, or don't want to, take the combination pill. Breastfeeding parents commonly prefer not to take the combination pill as it can impact milk production [2]. Those over the age of 35, who have thrombosis, heart problems, breast cancer, migraines, or take certain medications may also prefer to avoid the mini pill.

How does the mini pill work?

The progestogen-only pill works in 2 ways. The first is by attempting to stop ovulation, due to the high levels of the hormone, which means there isn’t an egg released by the ovary to be fertilised. This is why it’s important to take the pill as instructed so that your body doesn’t release an egg. 

However,  just to make things a little confusing, not everyone stops ovulating. About 40% of women will still ovulate whilst taking the progestogen-only pill That’s why the second element is so important.

The other way is by thickening the cervical mucus (the opening of the uterus) so that sperm cannot travel to the uterus [3]. This then stops the sperm from reaching and fertilising the egg.

In a nutshell, with the help of a low dose of progestogen, the body works really hard to stop the egg from being fertilised. All from a clever little pill.

Wondering which pill is right for you? Start an online assessment with Kin today.

How effective is the progestogen-only pill?

Now, taking the mini pill with perfect use is 99% effective. But, life happens, and human error exists, so in the real world, it’s about 91% effective.

This is due to the short 3-hour window it needs to be taken each day. In comparison, the combination pill has a window of about 12 hours. So if you're particularly forgetful, you may want to opt for the combination pill instead!

If you miss 1 pill, you should use a backup birth control like condoms for 48 hours. But if you miss 2 or more pills, you’ll need backup for 2 weeks, this is because there’s a chance of ovulation occurring. 

In short: the more you miss pills, the less effective they can be at preventing pregnancy.

Progestogen-only pill vs combined pill

The progestogen-only pill and combined pill both have pros and cons, it’s all down to medical history and personal preference. 

Progestogen-only pill

  • Contains progestogen 
  • Taken every day without a break
  • Must be taken within the same 3-hour window each day
  • Can stop ovulation
  • Can be taken if you smoke
  • Slightly fewer side effects, like headaches and nausea [4] 

Combined pill

  • Contains progestogen and oestrogen 
  • Taken for 3 weeks followed by a week break, or with a week of placebo pills
  • Must be taken in the same 12-hour window each day 
  • Doesn’t stop ovulation 
  • Cannot be taken if you smoke 
  • Slightly more side effects, like breast tenderness and dizziness [4] 

One is not better than the other, it’s all down to your individual circumstances and for what reasons you’re taking the contraceptive pill. 

When does the progestogen-only pill start to be effective?

You can start the POP or mini pill at any point during your cycle. But when you start it will depend on when it is effective at preventing pregnancy. If you start the pill as soon as day 1 of your cycle, it will be effective and prevent pregnancy, immediately.

If you start the pill from day 5 onwards, you’ll need to use a backup contraceptive, or avoid penetrative sex, for the first 2 pills you take. 

This is because it takes 2 days for the progestogen to thicken the cervical mucus.

What stops the progestogen-only pill from working?

The pill does its job very well but there are a few things that might stop it from working effectively.

Not taking it during your 3-hour window

It’s important not to delay taking it as there’s a chance of ovulation occurring. 

If you’re vomiting or have diarrhoea

Sickness through vomiting or diarrhoea can impact the effectiveness of the pill. If you are unwell, you’ll need a backup contraceptive during this time and depending on how long you’re sick for, you might experience breakthrough bleeding. 

Certain medicines

We’d be here all day if we listed out all of the medications that can cause drug interactions, so this is one best left for your doctor. Some medications, although may interact, can be used together but be sure to check this with your doctor on a case-by-case basis.

Do you get your period on the mini pill?

In short: it depends. There’s no one answer as some people’s periods will stop and others will have a regular cycle.

One of the most common side effects of the progestogen-only pill is an irregular period, for some that means lighter, lesser periods with just some spotting, whereas others have their periods as normal. 

This is why women who take the pill to manage heavy periods, often choose the progestogen-only pill to suppress their bleeding [5].

What are the side effects of the mini pill?

Although the progestogen-only pill is completely safe to use, as with all medications, it comes with a few side effects. With the help of your trusted medical professional, it’s up to you to decide whether the side effects are manageable. 

Changes in bleeding

It’s common to experience changes in your menstrual cycle, especially during the first 3 months after taking the pill whilst your body adjusts.

Typically with the progestogen-only pill people experience lighter bleeds but they may also see breakthrough bleeding, spotting and general irregular bleeding. Some people find that their periods stop altogether, which can be a big positive of the progesterone-only pill. 

Breakthrough bleeding

This one is closely related to the above point but deserves its own point. This is because up to 70% of people can experience a breakthrough bleed or spotting at some point whilst on the progestogen-only pill.

This is nothing to worry about (although, if you have concerns, always visit your GP), but some people find it to be a nuisance and is one of the main reasons people stop using the mini pill [4]. 


Unfortunately, headaches are a common side effect. However, it’s the preferred contraceptive pill over the combined for those suffering from migraines [6]. 

Skin changes

Although some people find their skin clears up, there’s a chance the progestogen-only pill can worsen conditions like acne

Changes in libido

For some the pill can increase sex drive, for others, it can be decreased. This is due to the change in hormones and the body adjusting. 

Ovarian cysts

This sounds alarming, but it’s usually nothing to worry about. The progestogen-only pill can increase the likelihood of small cysts on the ovaries. Often these don’t need any treatments but sometimes they require removal. Speak to your doctor if this is a particular concern. 

Mood changes

Something to keep a close eye on is changes in your mood, which can range from low mood to irritability and depression [5]. 

If you feel this is impacting daily life, it isn't something you "should just put up with" as there may be other birth control options out there to prevent pregnancy without this side effect.

Weight gain

The topic of weight gain on the progestogen-only pill and other birth control pills isn't super clear-cut. Since there are many factors that contribute to changes in weight or weight gain, it's difficult to say for certain whether it's a side effect.

Some people do find that it causes weight fluctuations, but this 2013 study suggested there wasn't a strong link [7].

Impacts breast milk production

If you're breastfeeding, you may opt for the POP because studies suggest it can impact milk production [2].

Human error

Now, this isn’t really a side effect necessarily, but inconsistent use can impact other side effects, as well as the pill’s effectiveness.  

Generally, side effects lessen after a few months of the body adjusting to the change in hormones, however, if you have any concerns, always contact a medical professional. 

Photo credit: Getty Images

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