The Pill

The Pill

What is the pill?

Medications taken by mouth that act as contraceptives are collectively known as 'the pill'. There are two types of oral contraceptive pill (OCP), namely the combined oral contraceptive pill (COC) and the minipill or progestogen-only pill (POP). Combined pills are more widely used and contain a combination of two hormones, oestrogen and a progestogen. The mini-pill contains one hormone, a progestogen.

What is the combined pill?

All combined pills available in Ireland at present contain a low dose of oestrogen. The main difference is in the second component, the progestogen. Pills containing the older or second generation progestogen appear to be less likely to cause blood clots while pills containing the newer or third generation progestogen are less likely to cause side effects such as irregular bleeding and breast tenderness. Your doctor will discuss the choice of pill that best suits you.

Which are the more commonly used combined pills?

Yasmin is one of the most commonly prescribed birth control pills in Ireland.

Microlite and Ovranette are also combined pills available in Ireland with second generation progestogen.

Cilest, Femodene, Mercilon, Marviol and Minulet are available with third generation progestogen.

All these pills are monophasic. This means that each of the 21 pills in the packet contains the same dose of both hormones. There are also triphasic preparations. This means that the pills contain differing doses of both hormones at different stages throughout the packet. These may be useful for women with persistent PMS or irregular bleeding on the pill. Your doctor will advise you if they might be useful for you.

Triphasic pills available in Ireland include Logynon, Tri-Minulet, Trinordiol and Triodene.

How does it work?

Combined pills increase the levels of oestrogen and progesterone in the body. This in turn affects the production of FSH (follicle stimulating hormone) and LH (luteinizing hormone). These hormones are produced in the pituitary gland (a regulator gland located at the base of the brain, behind the eyes). FSH and LH are involved in the release of the egg or ovum from the ovary. If ovulation is interrupted, the ovary does not release an egg and pregnancy cannot occur.

Combined pills are taken for 21 days with a seven-day break before starting again. They are packaged with the days of the week clearly marked for convenience.

The first course of pills is generally started on the first day of a period (Day 1) or the fifth day after bleeding starts (Day 5). Contraceptive protection is immediate with a Day 1 start. Additional contraceptive precautions are required for seven days after a Day 5 start.

Subsequent packets are started on the eighth day after finishing the previous packet. During the seven days off the pill a woman usually gets a period. Periods on the pill are generally lighter, less painful and more regular than a woman’s own period.

How effective is the combined pill?

Taken correctly, the combined pill is a very reliable contraceptive with a failure rate of less than one pregnancy per 100 woman-years. This means that less than one pregnancy will occur among 100 women using this method for a year. However, this presumes that the pill is taken correctly. If the pill is forgotten then the woman is not adequately protected and could become pregnant. In actual use, the failure rate is likely to be between two and three pregnancies per 100 woman-years.

When might the combined pill fail?

The commonest reasons for failed contraception are:

For maximum effectiveness, the combined pill should be taken at approximately the same time each day. If one or more is forgotten then one is not adequately protected.

If a woman vomits within three hours of taking the pill, she should consider it likely that the pill has been lost. Severe diarrhoea may also result in the pill being lost. In these cases the 'seven day rule' should be applied (see below).

A number of medications, including many commonly used antibiotics and anticonvulsant drugs may interfere with the action of the pill. Antibiotics interfere with the absorption of the pill from the gut therefore less drug is available within the body for chemical effect. Anti-convulsants accelerate the rate of drug breakdown in the liver so that insufficient amounts of the hormones reach the pituitary to prevent the production of FSH and LH.

It is very important to tell your doctor if you are on other medications when being prescribed the pill or if you are on the pill when being prescribed antibiotics.

What to do if I forget a pill?

If a pill is forgotten but remembered within 12 hours of the usual time, it may be taken at that time. No additional precautions are needed.

Where the pill is more than 12 hours late, the woman has vomited within three hours of taking the pill or she has started on medications that interfere with the pill, the 'seven day rule' should be invoked.

The seven-day rule means that a woman should take the last forgotten pill as soon as she remembers it, even if this means taking two pills at the same time. The remaining pills in the packet should be taken at the correct time.

However, the woman should regard herself as not being adequately protected for the next seven days. She should take the additional precaution of also using condoms or not have sex at all. It is important that seven consecutive pills are taken after a forgotten pill. If there are less than seven left in the packet, a new packet should be started without taking a break. This will usually postpone the period until the end of the next packet. This is perfectly safe and does no harm.

Are there other benefits of taking the combined pill?

It is an excellent treatment for irregular, heavy or painful periods. It is referred to as a cycle regulator when used for this purpose.

The pill is often successfully used for treatment of PMS (pre-menstrual syndrome).

It is also an effective treatment for acne.

It protects against cancer of the womb (uterus) and ovary. Women who take the pill halve their risk of developing cancer of the ovary in later years. This benefit is sustained for many years after stopping the pill.

What are the main drawbacks of taking the combined pill?


It needs to be taken daily to ensure contraceptive protection. It is medically unsuitable for some women, for example those with hypertension (high blood pressure) or those who have had a blood clot in the past. If you have any medical problems, you should discuss them with your doctor before commencing the combined pill.

Side effects may occur. While these may be a nuisance, they are rarely of medical significance and tend to settle down over the first few months of use. The commonest side effects would be irregular bleeding, nausea, headaches and breast tenderness.

There is much debate about whether the pill causes weight gain. It may be a contributory factor in some women although the majority of women taking the pill notice no change in their weight.

Women taking the pill are at an increased risk of developing blood clots. This potentially serious side effect is not common and is more associated with pills containing higher levels of oestrogen. There is also a small increase in the risk of developing breast cancer. This small risk may be outweighed by the reduced risk of other cancers, particularly of the womb or ovaries.

Despite popular mythology, the pill does not prevent sexually transmitted disease.

The pill has been extensively studied since its discovery more than fifty years ago and it is a safe and reliable contraceptive. However, there is a clear association between cigarette smoking and increased risk of side effects while on the pill.

It is important to see your doctor for a check up every six months while you are taking the pill.

What is the minipill?


The minipill is also known as the progestogen-only pill. The only minipill available in Ireland is Noriday. The minipill works mainly by changing the chemical composition of the mucus in the cervix (neck of the womb) making it impenetrable to sperm. In some women it may prevent ovulation but this effect is variable.

The minipill is taken continuously for 28 days without a break. There are no pill free days with the minipill. Once a packet is finished, a new packet must be started the very next day to maintain contraceptive protection.

The minipill is usually started either on the first day of a period (Day 1) or the fifth day after bleeding starts (Day 5). Contraceptive protection is immediate with a Day 1 start. Additional contraceptive precautions are required for seven days after a Day 5 start.

The minipill needs to be taken within three hours of the same time each day. If a minipill is forgotten the seven-day rule should be invoked (see above).

How effective is the minipill?


The minipill is slightly less effective than the combined pill. In ideal use, it has a failure rate of less than two pregnancies per 100 woman-years. This means that fewer than two pregnancies will occur among 100 women using this method for a year.

However, this presumes that the pill is taken correctly. It is easy to forget to take the pill or take it too late in the day. In actual use the failure rate is likely to be between two and a half and four pregnancies per hundred woman-years.

Women with medical conditions that prevent combined pill use may take the minipill. Breastfeeding women may take it.

Irregular periods are common with the minipill and it is not recommended as a cycle regulator.

Back to top of page