The pill is a highly effective and safe form of contraception.

However, as with all types of medication, it does come with some health risks.

The combined contraceptive pill is made up of the female hormones oestrogen and progesterone, which alter the regular hormonal balance in the body. For some users, this may cause side effects.

It is important for those taking the pill to understand the possible impact it can have on their health, so that they recognise any problems if they occur, and get the right medical advice.

Side Effects

Blood Clots

If you are already taking the combined oral contraceptive pill (COCP) or are considering using it, then you should be aware that there is a risk of venous thromboembolism (VTE), more commonly known as a blood clot.

Blood clots can form inside veins when blood slows down or stops moving. Pooling of the blood in one place can cause platelets to knit together, and a solid mass to develop.

When a piece of this mass (blood clot) breaks off and moves, it can travel to the heart or lungs, and cause something called a pulmonary embolism. This can result in a stroke or heart attack.

The Faculty of Sexual and Reproductive Health states that this risk is small and that for most users the benefits of the combined pill outweigh the potential problems.

There are some factors which could leave you more at risk of developing VTE, such as smoking or being overweight. Your GP will take into account any potential contraindications before prescribing the pill as a form of contraception for you.

It is particularly important to make yourself familiar with the symptoms of a blood clot if you are taking the pill. You should watch out for

  •  severe leg pain 
  •  sudden breathlessness
  •  rapid breathing
  •  chest pain
  •  an unexplained cough which may include blood
  •  discomfort in the upper body which may reach the jaw, throat, back or arms
  •  nausea and vomiting
  •  dizziness
  •  difficulty speaking
  •  confusion
  •  loss of or blurred vision
  •  or a severe headache or migraine. 

The increased risk of blood clots is linked to strokes and heart attacks.


There are ongoing studies into the links between the combined hormonal pill and cancer.

There is research to suggest that the pill does pose an ever so slightly higher threat of certain cancers such as breast and cervical cancer. That being said, the pill can also slightly decrease the chances of developing other types of cancer; in particular ovarian and endometrial cancers.

The likelihood of developing ovarian or endometrial cancer decreases when using the combined oral contraceptive. The longer the pill is taken the better the protection from these types of cancer.

For example the FSRH states that the risk of developing ovarian cancer reduces by half after 15 years of COC use.

The NHS offers cervical screening every three years for women over the age of 25 and every five years for those over the age of 50.

It is important to attend your screening appointment so that you can receive treatment as soon as possible if required. If in the meantime you notice any changes then you should arrange an appointment with your GP.

Those with a family history of cancer, in particular cervical or breast cancer, may be advised against the combined hormonal contraceptive.

Contraindications for the combined oral contraceptive:

Due to the potential side effects that the combined pill can cause there are restrictions as to who can take this form of medication. If you fall into any of the below categories or have had a history of any of these conditions then your doctor will probably look to prescribe an alternative contraceptive.


Women who are severely overweight should not use COCP as it can increase the risk of cardiovascular and cerebrovascular problems as well as VTE which can sometimes lead to a stroke or heart attack.


Those who have been diagnosed with hypertension should not use the combined contraceptive pill as it can cause an increase in blood pressure. This could put them at a higher risk of stroke or myocardial infarction.


Migraine symptoms, specifically those combined with aura, can be exacerbated by the female hormones released by the pill. This is because oestrogen and progesterone can act as triggers for migraine symptoms in some women. It can also be an indication of a higher risk of stroke.

Alternative contraceptive options:

If the combined oral contraceptive pill is not suitable for you, there are numerous other contraceptive options available. If any of the above information has given you cause for concern then you should speak to your GP before you make a decision about changing your contraception.

The risks outlined above are small and your GP will take into account your overall health, past medical history and family history when offering a suitable form of contraception.

When used correctly all forms of the pill are highly reliable and safe methods of contraception. The FSRH’s statistics continually rank it as one of the most favoured forms of contraception in the UK.

Page last reviewed:  25/09/2020