Mini pills

What is the progestin only birth control pill?

Mini pills (or “progestin-only birth control pills” if you’re into the lingo) are a little different to what you might know as “The Pill”. Generally “The Pill” refers to combined birth control pills that contain two hormones, progestin and oestrogen. Progestin-only tablets have just one hormone in them (a type of progesterone).

They’re more suitable than the conventional combined pill for some women, because they don’t contain oestrogen. But there’s virtually no difference in how effective they are as long as you take them correctly.

You’ll take the progestin only pill without a break, every day of the month. The difference being that in combined pills, you’ll get 21 in a pack (or 21 with seven inactive pills), or occasionally 24 (or 24 + 4 inactive pills). With mini pills, you get 28 in a pack (and they’re all active).

Because it’s taken every day without a break, a lot of women who take the mini pill find that their periods become either much, much lighter or (more likely) stop altogether. Some women see this as a big advantage to using it over the combined pill, with which you’ll still often get a withdrawal bleed.

How does the progestin-only mini pill work?

The progestin-only pill works by thickening the mucus in the cervix. Yep, we know. Mucus isn’t everyone’s favourite word. But what this does is make it harder for sperm to travel through, and to fertilise an egg.

There are different types of progestin in mini pills, such as desogestrel and norethisterone, and the effects can be slightly different. As well as working some mucus magic, a desogestrel pill can stop ovulation too.

For the progestin-only mini pill to work properly, it has to be taken at the same time every day. If you are late taking the pill, it counts as missing it. The missed pill window is shorter with some mini pills (3 hours) than it is with the combined pill (24 hours), so be sure to read the leaflet before you start.

There is however, a mini-pill with a 24 hour missed pill window, called Slynd. It contains drospirenone and works just like any other mini pill. The main difference is the extra flexibility you get from the extended missed pill window.

What are the advantages of progestin-only pills?

One of the biggest advantages of the mini pill is that it is safer to use for some women than the combined pill, because it doesn’t contain any oestrogen. You’re more likely to take the mini pill if you get migraines, if you’re breastfeeding, or if you are at a higher risk of blood clots due to high blood pressure or being overweight.

The main disadvantage is that most progesterone pills have a shorter missed pill window at three hours (compared to 12 hours for most combined pills). However, this shouldn’t be a problem with Slynd as it has a 24-hours missed pill window.

How effective is the progestin-only pill?

Very effective, when it’s used correctly. There are two methods used to measure effectiveness: perfect use and typical use.

Perfect use is taking the mini pill exactly as stated in the instructions, without making any mistakes. Effectiveness associated with this method is over 99%, meaning that in 100 women taking the pill over a year, less than one will get pregnant.^[1]

Typical use is taking the pill correctly for the most part, but making occasional mistakes (missing a pill, or taking it late). Effectiveness for this method is thought to be around 91%, meaning that around nine in 100 women using the progestin only pill will get pregnant over one year.

When to start taking the progestin-only pill

If you’re not already taking the pill or using another form of hormonal contraception, you can start taking the progestin-only pill at any point during your cycle. Or you can wait until you have your period.

When you’re ready to start using progestin-only birth control, pick a convenient time to take it because you’ll have to take it at this time every day.

If you wait for your period, and you start taking the mini pill in the first day your period, you’ll be protected from becoming pregnant right away. So you don’t need to worry about using a diaphragm or condoms.

You won’t be protected against pregnancy right away if you start taking it at any other point during your cycle. So if you’re not on your period and start taking the progestin-only pill, make sure you use extra protection like a condom for the first seven days that you take it.

Starting when switching from another pill

When you switch from the combined pill or another type of progestin-only pill, you can take your first one the day after you finish the last pill in your previous pack.

If you’re changing from the skin patch or the vaginal ring, start on the day after your patch or ring is removed. If you do this, you won’t need to use extra protection.