Progesterone only pill (Minipill)

What is the minipill? This is an oral form of contraception which contains only progestogen i.e there is no oestrogen contained in it. How does it work? It acts mostly by making the cervical mucus thick and sticky, thereby preventing sperm from reaching the egg to fertilise it. In very few patients it prevents ovulation.There are currently 2 types of progestogen only pills on the market, Noriday and Cerazette. Each is discussed in further detail below:

Noriday (Traditional Mini Pill)

How effective is it?

When used properly it can be approximately 95% effective. However because it does not stop ovulation in the majority of women the failure rate is higher than that of the combined pill.

Who is suitable to take it?

The minipill is suited to women over 35 years of age, in particular smokers or breastfeeding women. It is also suitable for women who cannot take oestrogen for example women with a personal or family history of blood clots, women with high blood pressure, obesity or diabetes.

Are there any side effects?

Most women will report some minor side effects when starting the minipill, almost all of which will resolve quickly. These include breast tenderness, mood swings, bloating and headaches. Irregular bleeding while on the minipill can persist for some months after starting it.

How do I take it?

The minipill is usually started on day 1 of a period. Breast feeding women can start it at any time. If you start it on day 1 you are covered for contraception immediately. If you are staring it any other time in the cycle you can rely on it as contraception after 7 tablets.

The pack of pills consists of 28 tablets, one of which is taken every day without a break. The pill must be taken at the same time every day; taking the minipill more than three hours late can reduce its efficacy. Your periods will continue to occur naturally on the minipill.

How do you get pregnant while on the minipill?

This may occur if you are not consistent in your pill taking. You must take your minipill within the same three hour time period each day or the efficacy as a contraceptive will be decreased. You should use extra precautions such as condoms for the following 7 days and consider taking the morning after pill if you have had sex since missing the pill. Taking certain medications such as antibiotics and vomiting/diarrhoea can also interfere with the minipill.

How do I start the minipill?

You need to be checked by a doctor before starting the minipill. This includes a blood pressure measurement and a brief medical history. An initial prescription for three months is issued, and subsequently a maximum of six monthly scripts are issued by the doctor.


What is it?

Cerazette is another form of progesteron only contraceptive pill, more commonly known as the minipill. However it is different from the previously discussed from of minipill in several ways.

How does it work?

It acts by suppressing ovulation and therefore is a more reliable form of contraception than the previoulsy mentioned minipill. It also acts by thickening the cervial mucus, making it difficult for sperm to move upwards.

How effective is it?

When used properly for one year less than 1 woman in 1,000 will get pregnant using Cerazette. This is similar to the contraceptive cover provided by the combined oral contraceptives.

Who is suitable to use it?

Cerazette is suitable for most healthy women. It is particularly useful for young women who need a very reliable form of contraception but who may struggle to remember to take a daily tablet. It is also useful for women for whom oestrogen-containing contraception is unsafe e.g. those suffering from epilepsy, a history of thrombosis or blood clots and certain form of migraine.

What are the side effects?

These include irregular vaginal bleeding, nausea, acne, mood changes, breast tenderness and headache.

How do I take it?

Cerazette is taken daily as a tablet. The tablets are packaged in 28’s and there is no break to be taken between packets. It should be taken at the same time every day, but your contraceptive cover is still in place unless you are more than 12 hours late taking your pill.

How do you get pregnant while taking it?

You have 12 hours to remember to take your pill which allows flexibility. The commonest mistakes made are taking antibiotics at the same time as cerazette, being more than 12 hours late taking your pill, and vomiting and diarrhoea within 4 hours of taking your pill. If you take extra precautions as described in the information leaflet of your contraceptive pill then you should be safe. These include either using condoms or continuing your pills without taking a break, depending on when the above scenarios occur in your pack.

How do I start?

If you are changing from another from of contraception such as the combined pill or nuvaring your doctor should be able to advise you on how to do this safely without losing contraceptive cover. If you are starting Cerazette without previously using contracpetion you should aim to start it on Day 1 of a new cycle. You can then rely on it for contraception from the first pill onwards. If you start it any time from Day 5 onwards you must use another form of contraception for the first 7 days of your pack.