Aspirin
Aspirin has been shown to lower the risk of getting some cancers, including bowel cancer.
But the drug may also cause side effects, such as indigestion or bleeding, and we don’t know how safe it is to take regularly.
Doctors do not usually recommend taking aspirin regularly for bowel cancer prevention unless you have a condition called Lynch Syndrome, or you’re taking part in a clinical trial. If you’re thinking of taking aspirin, speak to your GP or cancer specialist first. They can advise you on the safety of aspirin and whether it might benefit you.
Who should take aspirin?
Research shows that aspirin reduces the risk of bowel cancer in people who have a genetic condition called Lynch syndrome. Aspirin has also been shown to reduce the risk of other cancers related to Lynch syndrome such as womb (endometrial) cancer.
The National Institute for Health and Care Excellence (NICE) recommend that everyone with Lynch syndrome should take aspirin daily. Research shows that taking aspirin daily can reduce the risk of bowel cancer in people with Lynch syndrome by 63%.
The results of these studies were based on participants taking a 600mg daily dose of aspirin.
However, new research suggests that a lower dose of 75-100mg is just as effective at reducing the risk of bowel cancer in people with Lynch syndrome. This matters because high doses of aspirin can increase the risk of some side effects.
Doctors do not usually recommend taking aspirin regularly for bowel cancer prevention unless you have Lynch syndrome, or you’re taking part in a clinical trial. If you’re thinking of taking aspirin, speak to your GP or cancer specialist first. They can tell you about the safety of aspirin and whether it might benefit you. Aspirin may also cause side effects, such as indigestion or bleeding, and we don’t know how safe it is to take regularly.
The Lynch choices website has more information about aspirin and bowel cancer risk in people with Lynch syndrome.
Side effects of aspirin
The most common side effects of aspirin are indigestion and bleeding. Up to 1 in 10 people (10%) may get more nose bleeds, bleed for longer or bruise more easily. In rare cases, aspirin can cause more serious side effects, like bleeding or ulcers in the stomach.
You may not be able to take aspirin if you have had other medical problems like asthma, stomach ulcers or problems with your liver, kidneys or heart. Your GP may check if you have bacteria called Helicobacter pylori in your stomach, which can cause stomach ulcers. Getting rid of these bacteria can reduce the risk of stomach ulcers when you are taking aspirin.
Speak to your specialist
If you have Lynch syndrome, taking aspirin daily could help reduce your risk of bowel cancer. But it’s really important not to start aspirin on your own. Talk to your GP or specialist first.
They can explain the benefits and risks for you personally, discuss ways to protect your stomach (for example, by testing for Helicobacter pylori or prescribing a proton pump inhibitor like omeprazole) and check whether aspirin is safe alongside any other medication you take.
Questions to ask your doctor:
- Should I take aspirin to help lower my cancer risk?
- What dose would you recommend for me?
- What side effects should I look out for?
- Can I do anything to protect my stomach?
- Will aspirin affect my other medications or health conditions?
- Can I get aspirin on prescription, or do I need to buy it myself?
You may also find these pages helpful:
- The Lynch Choices website provides information to help people with Lynch syndrome make decisions, such as taking aspirin and having surgery
- Lynch syndrome UK provide information and support for people with Lynch syndrome. They also have an online support group with almost 4000 other people with Lynch syndrome
Updated November 2025
We're accredited as a Trusted Information Creator by the Patient Information Forum. This means the way we write our resources has been independently assessed as health information you can trust.
