Does taking contraception increase my risk of blood clots?

Reviewed by our clinical team

The pill is the most popular form of female birth control in the UK – in 2018, it was the most widely used contraceptive method amongst women aged between 15 and 49.

This is starting to change though, the popularity of the pill is starting to wane, as more women turn to long-acting reversible contraception (LARC) such as the implant, injection or coil.

One reason for this may be negative news stories associated with the pill that have cropped up in recent years – and in particular fear-mongering headlines about the risk of blood clots.

While it’s true that taking certain types of the contraceptive pill can increase your risk of blood clots, this risk is still very low. Your risk of getting a blood clot during pregnancy or after a long-haul flight is much higher than getting a blood clot because you are taking the pill. If you’re still concerned, read on for a straightforward guide.

Understanding blood clots

Blood clots are clumps of blood that form in response to injury. This a natural and protective process by the body which helps to stop bleeding – if our blood couldn’t clot, we’d bleed excessively from the tiniest of scratches.

Sometimes, however, blood clots form without an injury and fail to dissolve, causing blockages in the veins or arteries. If these blockages travel to the heart, lungs, or brain they can cause serious issues such as pulmonary embolism, heart attacks and strokes.

The good news is that if you’re young and healthy, your risk of blood clots is really low. It’s also worth bearing in mind that blood clots can be successfully treated if they’re caught in time. Doctors can also prescribe blood thinning medication if they think you might be at risk.

The combined pill and blood clots

When we talk about the pill and blood clots, we’re referring to the combined contraceptive pill. This is the the only type that’s associated with a risk of blood clots.

Combined contraceptives contain synthetic versions of the female hormones oestrogen and progesterone, which in combination are very effective at preventing pregnancy. However, oestrogen has an effect on the blood, making it more “sticky” and therefore slightly more likely to form clots.

Combined hormones are also used in the contraceptive patch and the vaginal ring, which means these types of contraception are also associated with a slightly increased risk of blood clots.

How likely am I to have a blood clot from taking the combined pill?

In 2014, the European Medicines Agency reported that they would expect between five and 12 blood clots to occur among 10,000 women who take combined contraceptives for one year. By comparison, they would expect to see two cases of blood clots among 10,000 women not using these contraceptives.

If you’re thought to be more at risk of blood clots because of your age, weight, medical history, or lifestyle, it’s very unlikely that your GP will prescribe you a combined contraceptive.

As explained in this guide from the NHS, the combined pill is not usually prescribed to women who:

• Smoke (or recently quit smoking) aged 35 or older 
• Are very overweight 
• Are taking certain medications 
• Have had blood clots before 
• Have a family history of blood clots 
• Have certain diseases (e.g. breast cancer, liver disease) 
• Have certain types of migraines 
• Have high blood pressure 

What are the symptoms of a blood clot?

Although it's very unlikely that your combined contraceptive will cause a blood clot, it’s still a good idea to familiarise yourself with the symptoms so you can get medical help if you need it.

Blood clots usually develop in the lower legs, so you may initially notice symptoms there, including: 

• Throbbing, cramping pain or full ache 
• Swelling 
• Redness and warmth

A blood clot that’s travelled to the lungs may cause sudden breathlessness, chest pain, and coughing that brings up blood.

If you experience any of these symptoms you should call 111 immediately for advice.

The benefits of the combined pill

News stories about the combined pill, patch and ring tend to focus on the negatives, but there are plenty of benefits.

Firstly, the combined pill, patch and ring are really good methods of birth control. When taken correctly, it’s 99% effective at preventing pregnancy.

Other benefits to the combined pill, patch and ring include: 

• A reduced risk of ovarian, womb and colon cancer 
• Lighter and less painful periods 
• Less severe PMS symptoms

Combined contraceptives are also thought to offer some protection against, fibroids, ovarian cysts, and non-cancerous breast disease.

The progestogen-only (mini pill) and blood clots

The progesterone-only pill contains just one type of hormone. It does not contain oestrogen. This means that there is no increased risk of blood clots. It can be taken by women who can't take the combined contraceptive for medical reasons.

The progestogen-only pill (POP or “mini” pill) is taken once a day. The main difference is that you have to take it at the same time each day. Certain types of the mini pill can be taken within a 12-hour window; other types must be taken within a three-hour window. There are no varieties of the mini pill that involve a seven-day break.

If you like the ease and convenience of the pill, but you can’t take the combined pill or you don’t want to, the POP is an excellent alternative.

Combined contraceptives and the COVID-19 vaccine

There has been lots of reports in the news around the links between the Oxford AstraZeneca COVID-19 vaccine and rare blood clots. Despite these links, the FSRH still advises that people taking combined contraceptives such as the combined pill, patch or ring, should go for their COVID-19 vaccine when they’re offered it.

People on combined contraceptives shouldn’t stop taking these when they’re called for their vaccine. It won’t help and means you could risk getting pregnant.

If you’re worried about blood clot risk in general with combined contraceptives, you can speak to your GP or send us a message in your Patient Record about switching your contraception.

Other types of contraception

The pill may be the most popular type of contraception among women, but there are many other options if it’s not right for you. If you have trouble remembering to take your pill, or if you simply don’t want to have to think about contraception, consider a long-acting reversible method. 

LARCs available in the UK are: 

• The copper coil (IUD) – lasts five to 10 years
• The intrauterine system or hormonal coil (IUS) – lasts three to five years
• The implant – lasts three years
• The injection – lasts eight to 13 weeks
• The coil, IUS, and implant all have to be fitted and removed by a healthcare professional. Injections should also usually be given by a healthcare professional.

Stock up on routine contraception with Online Doctor

At Online Doctor we stock a range of contraceptive pills, including the traditional combined pill, the low-dose pill, and the mini pill. Visit our contraception clinic to browse pills and learn more about their benefits.

References

https://www.statista.com/statistics/573210/contraceptive-use-among-women-by-type-and-age-in-england/
https://digital.nhs.uk/data-and-information/publications/statistical/sexual-and-reproductive-health-services/2018-19
https://www.mayoclinic.org/symptoms/blood-clots/basics/definition/sym-20050850
https://www.nhs.uk/conditions/blood-clots/
https://thrombosisuk.org/admin/resources/downloads/thrombosisuk-thrombosis-women.pdf
https://www.nhs.uk/conditions/contraception/contraceptive-patch/
https://www.nhs.uk/conditions/contraception/vaginal-ring/
https://www.theguardian.com/society/2021/apr/09/contraception-blood-clot-risk-public-need-better-access-to-advice
https://www.nhs.uk/conditions/contraception/combined-contraceptive-pill/
https://www.nhs.uk/conditions/contraception/the-pill-progestogen-only/
https://www.nhs.uk/conditions/contraception/iud-coil/
https://www.nhs.uk/conditions/contraception/ius-intrauterine-system/
https://www.nhs.uk/conditions/contraception/contraceptive-implant/
https://www.nhs.uk/conditions/contraception/contraceptive-injection/
https://www.fsrh.org/news/fsrh-new-guidance-pill-blood-clots-astrazeneca-april-2021/