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Birth Control Pill: Known Side Effects and Risks

What are the side effects of birth control pills?

Most women who take the pill do not develop any side effects. However, a small number of women may feel nausea, have headaches, or soreness in their breasts.

For better understanding, we recommend checking out our previous article on the Birth Control Pill: The Basics first, if you haven’t already.

These symptoms usually go away within days or weeks of starting the pill. If they persist, they should consult a doctor who can recommend a brand of birth control pills that may be better suited for them.

Some women experience breakthrough bleeding after starting on the birth control pill. This is usually nothing to worry about, and tends to settle after 2-3 months of use. However, if it is persistent, or if you are concerned, you should tell your doctor and switch to a brand or formulation that offers better cycle control.

Other less common side effects include tiredness, change in sex drive, skin changes, and mood changes. These are unusual and you should tell the doctor if you have any lasting symptoms.

Many women believe that taking the pill makes you put on weight; however, this has inconsistent evidence in terms of it being a direct association. If you are however suspicious of weight gain after being on the pill, you may wish to discuss it with the doctor.

The pill sometimes causes a rise in blood pressure, so those taking it should have their blood pressure checked every six months, and stop taking the pill if their blood pressure becomes too high.

Effect of birth control pills on fertility

Many women are concerned about whether the birth control pill has any effects in terms of fertility and if there is a delay in its return. They can be assured that the evidence has not suggested any significant delay in return to fertility, and that is regardless of its duration of use. There is also nothing to suggest that fertility can be adversely affected by the use of the birth control pill.

What are the risks associated with pill use?

The pill is a safe choice of contraception for most women who have no particular health related issues. However, there are some adverse effects and risks that are associated with its use. It is important to be aware of these risks as well as discuss them with our doctor before using the birth control pill.

Venous thromboembolism (VTE) Venous thromboembolism or VTE is a term referring to blood clots in the veins and it is a serious condition which requires urgent treatment. There is a known small increase in risk of venous thromboembolism associated with the use of the combined birth control pills. The risk increases with the dose of estrogen in the formulation or brand and also varies depending on the type of progestogen in the pill. However, the number of cases of VTE in women using the pill remains very small. Also, the risk of this condition is lower whilst taking the pill as compared to during pregnancy and the post-natal period. For most women, it is safe to take the pill from a VTE perspective, however each person’s risk is assessed individually by the doctor to ensure its safety of use.

Heart attack and stroke

There is a very small increase in the risk of a heart attack and stroke associated with the use of the combined birth control pill. This is further increased in women with multiple risk factors for these conditions. The risk appears to be greater in those taking pills with higher doses of estrogen in them. However, in healthy users, the incidence of these conditions is very uncommon. Women with cardiovascular disease are advised to be cautious and discuss their risk with the doctor who can recommend other methods of contraception that may be better suited.


Birth control pills are know to reduce the risk of cancers like endometrial cancer and ovarian cancer. However, these are known to have a small increase in the risk of breast cancer and cervical cancer.

Breast cancer: There is a small increased risk of breast cancer which has been found to be associated with use of the combined hormonal contraceptive pill.

This risk reduces with time after stopping it's use. However, women with a current history of breast cancer and those with known gene mutations (BRCA1) should not be taking the combined birth control pill. It can be noted that there are other ways of reducing your risk of developing breast cancer such as a healthy lifestyle, avoiding smoking, and limiting your alcohol intake. Cervical cancer: There is also a small increased risk of cervical cancer that is associated with using the combined hormonal contraceptive pill for over 5 years, and it increases with further duration of use. The risk however reduces over time after stopping the pill and is no longer increased after about 10 years after its been stopped. Women should be up to date with their cervical smear tests according to the national screening programs (usually done every 5 years between the ages of 25-65 years).

Things to take note of

Whilst taking the pill, if you experience any of the following symptoms or signs, it is important to get urgent medical attention:

  • sudden chest pain

  • coughing up of blood

  • find it hard to breathe

  • have pain or swelling in the lower leg

  • have a very bad headache

  • sudden weakness or numbness of an arm, leg, or one side of the face

  • speech disturbance

  • dizziness or feeling faint

Who cannot use the birth control pill?

The conditions and situations that are likely to cause risks and adverse effects, and may mean that you will not be able to take the pill include:

  • If you are over 50 years old

  • If your BMI is 35 kg/m2 or more

  • If you smoke and are aged 35 years or older (Also, if you are aged over 35 years and have smoked within the previous year)

  • If you have migraine with aura

  • If you have had a baby up to six weeks ago and are breast-feeding

  • If you are not breast feeding but had a baby up to 3 weeks ago (this is because there is an increased risk of having VTE during this period)

  • If you have more than one risk factor for heart disease (such as smoking, high blood pressure, obesity, diabetes, older age)

  • If you have a history of heart disease, high blood pressure, stroke or problems with your heart valves

  • If you have a current or past history of venous thromboembolism (VTE)

  • If you have a family history of VTE in a first-degree relative (father/mother/sister/brother) under the age of 45 years

  • If your mobility is reduced due to major surgery or disability (this increases your risk of developing a VTE)

  • If you have diabetes that has affected your kidneys, eyes, nerves or blood vessels

  • If you have breast cancer

  • If you have liver or gall bladder disease

  • If you have systemic lupus erythematosus (SLE) with positive anti-phospholipid antibodies

  • If you are known to have mutations that make your blood more likely to clot, such as factor V Leiden deficiency

  • If you are taking certain medications - this may not be a contraindication but it can affect the effectiveness of the pill.

Not all of these conditions mean you definitely should not take the pill. Our doctors will be able to advise whether it is safe for you use birth control pills once they have reviewed your health profile.

There are many forms of birth control and within the category of the combined birth control pill, there are many brands and formulations. All the combined birth control pills share the same mechanism of action, however they can vary in terms of their adverse effects. It is therefore important to have a detailed consultation with the doctor before initiating, and make an informed choice about which type of contraception would be best for you.

Once you have made your decision to use the pill, it is also important to know when and how to take it and what to do in circumstances such as when pills have been missed. There is also another article which details information about missed pills and emergency contraception.



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Girum T, Wasie A. Return of fertility after discontinuation of contraception: a systematic review and meta-analysis. Contracept Reprod Med. 2018;3:9. Published 2018 Jul 23. doi:10.1186/s40834-018-0064-y


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