Primary vs Secondary Prevention

Type	Meaning	Aspirin Recommended?
Primary prevention	No previous heart attack or stroke	Generally NO (bleeding risk outweighs benefit)
Secondary prevention	Previous heart attack, stroke, or stent	YES: strongly recommended
Peripheral artery disease	Known narrowing of leg arteries	YES
High-risk surgery patients	Discuss with surgeon	Sometimes

Important Shift in GuidelinesGuidelines changed after 2018. Aspirin for PRIMARY prevention (no prior event) is no longer routinely recommended for most people. The bleeding risk (stomach bleeds, brain bleeds) was found to outweigh the modest benefit in people who haven't already had a heart attack.

How to Take Aspirin Safely

Take with food or milk to reduce stomach irritation
Enteric-coated (EC) tablets are gentler on the stomach
Never take aspirin with ibuprofen: ibuprofen blocks aspirin's antiplatelet effect
Tell your dentist and all doctors you take daily aspirin

Stomach ProtectionIf you take daily aspirin, adding a PPI (such as omeprazole 20 mg) reduces bleeding risk by 80%. Ask your doctor whether you should take both.

Can I stop aspirin if I don't want to take it?

If you're on aspirin for secondary prevention (after a heart attack or stroke), stopping it significantly increases your risk of another event. Never stop without discussing with your doctor.

Does aspirin prevent cancer?

There is evidence aspirin reduces colorectal cancer risk with long-term use, but cancer prevention is not currently a standard indication: the bleeding risk must be balanced.

Which aspirin dose is best?

75–100 mg daily is the standard antiplatelet dose. Higher doses do not provide more benefit but cause more bleeding. In the US, 81 mg (baby aspirin) is most commonly used.

Why the advice on primary prevention changed

For decades low-dose aspirin was widely recommended to healthy adults to prevent a first heart attack. That advice has been substantially withdrawn. Large trials published from 2018 onwards found that in people without established cardiovascular disease, the reduction in cardiovascular events was small and closely matched by an increase in serious bleeding, including gastrointestinal and intracranial haemorrhage. Several guidelines now advise against routine aspirin for primary prevention, particularly over the age of 70, and recommend an individual discussion where risk is high and bleeding risk is low.

The picture is quite different in secondary prevention. In people who have already had a heart attack, ischaemic stroke, or who have known coronary or peripheral arterial disease, the benefit clearly exceeds the bleeding risk and aspirin remains standard long-term therapy. If you are taking aspirin and are not sure which category applies to you, that is a worthwhile question to raise, because the answer determines whether continuing is appropriate.

Reducing the bleeding risk

A proton pump inhibitor substantially reduces gastrointestinal bleeding and is recommended for those at higher risk, including older adults and anyone with previous ulcer disease.
Avoiding concurrent NSAIDs, which multiply the ulcer risk; ibuprofen also interferes with aspirin's antiplatelet effect when taken shortly before it.
Limiting alcohol, which independently raises gastrointestinal bleeding risk.
Testing and treating Helicobacter pylori in those with ulcer history before long-term therapy.

Around surgery and dental work

Aspirin is frequently continued through minor procedures, including most dental extractions, cataract surgery and skin procedures, because the risk of stopping in someone with established cardiovascular disease can exceed the bleeding risk of continuing. Stopping is sometimes required for surgery with a high bleeding risk or where bleeding into a closed space would be serious. Because aspirin irreversibly inhibits platelets for their lifespan, an interruption of around seven days is needed for full recovery of platelet function. This decision belongs with the team performing the procedure together with your prescriber, and should not be taken unilaterally.

Warning signs while taking it

Black tarry stools, vomiting blood or material resembling coffee grounds, unexplained bruising, prolonged nosebleeds, or new severe headache all warrant prompt medical attention. Unexplained iron deficiency anaemia in someone taking long-term aspirin should prompt investigation for occult gastrointestinal bleeding rather than iron replacement alone.

References

The clinical information on this page is drawn from peer-reviewed sources indexed by the US National Library of Medicine. Links go to the source so you can read it yourself.

Salicylic Acid (Aspirin). In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK519032

Low-Dose Aspirin: Who Should Take It and Why