Low strengths or "doses" of aspirin are used to make it less likely for your blood to clot. It blocks certain blood cells called platelets and slows down your body’s ability to clot blood. It is used to prevent blood clots forming in blood vessels that lead to your brain and heart muscle. Preventing blood clots in these vessels helps lower your risk of stroke and heart attack.
- Aspirin is especially effective if you have had a heart attack, angina (chest pain), stroke or transient ischemic attack (TIA or mini-strokes). Taking low-dose aspirin reduces the risk of a further event by about 25% over 5 years.
- You may be prescribed aspirin if you have unstable angina or if you have not had a heart attack or stroke but are at high risk of having one – this is checked at a cardiovascular or heart risk assessment. You will also be advised to make lifestyle changes to reduce your risk of having a heart attack or stroke.
Aspirin may not be suitable if you don’t have heart disease and are not considered to be at high risk of developing it. The risk of side effects (particularly the risk of bleeding) outweighs the benefit of preventing blood clots.
The following animation describes how aspirin works in the body (British Heart Foundation).