Low-Dose Aspirin: Who Should Take It and Why

Aspirin myths vs facts

Antiplatelet drug classes compared

Aspirin is one of several drug classes that make platelets less sticky. This table compares the classes factually — which one suits a patient is a medical decision, not a shopping choice.

Primary vs secondary prevention

The distinction decides whether aspirin helps or harms:

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 That advice has been substantially withdrawn. A 2019 systematic review identified 20 randomised controlled trials of aspirin for primary prevention; a pooled analysis of 10 of these trials, involving 144,930 individuals without established cardiovascular disease, found that aspirin reduced the risk of non-fatal heart attack by 21%, but had no statistically significant effect on cardiovascular death and increased the risk of major bleeding by 48%.² This includes the ARRIVE, ASCEND, and ASPREE trials.

A separate pooled analysis of 4 trials involving 20,326 individuals with diabetes found aspirin had no benefit on heart attack or cardiovascular death, yet still increased bleeding by 49%. 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 mechanism behind the bleeding risk is pharmacological. Aspirin irreversibly inhibits COX-1, the enzyme platelets use to make thromboxane A2, a clotting signal. Since platelets have no nucleus, they cannot regenerate COX-1, so the inhibition lasts the full 7–10 day platelet lifespan. The same COX-1 pathway in the stomach lining makes prostaglandins that protect against ulceration, and blocking it there raises the risk of gastric erosion and bleeding, independent of any antiplatelet effect.

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

• Stomach protection: a proton pump inhibitor (such as omeprazole) substantially reduces gastrointestinal bleeding and is recommended for those at higher risk, including older adults and anyone with previous ulcer disease. Ask your doctor whether you should take both.
• Avoid concurrent NSAIDs: ibuprofen and similar drugs multiply the ulcer risk; ibuprofen also interferes with aspirin's antiplatelet effect when taken shortly before it.
• Limit alcohol, which independently raises gastrointestinal bleeding risk.
• Testing and treating Helicobacter pylori in those with ulcer history before long-term therapy.

Aspirin in people with diabetes: the ASCEND trial

People with diabetes have a significantly elevated cardiovascular risk, which makes the primary prevention question particularly pressing for this group. The ASCEND trial, a randomised controlled trial specifically designed to address it, randomly assigned 15,480 adults with diabetes and no prior cardiovascular disease to daily aspirin or placebo, and followed them for an average of 7.4 years.³

Aspirin prevented some serious vascular events but caused a similar number of major bleeds — the benefit and harm were finely balanced, which is why routine aspirin for primary prevention is not recommended even in diabetes. The decision is individual, weighing personal clotting risk against bleeding risk with your doctor.

Around surgery and dental work

Tell your dentist and every doctor that you take daily aspirin. Whether it is paused before a procedure depends on the balance between clotting risk (why you take it) and bleeding risk (what the procedure involves) — plan any pause with your doctor in advance, and never stop on your own.

Warning signs while taking it

Report promptly: black or tarry stools, blood in urine or vomit, unusual or large bruises, nosebleeds that will not stop, or a severe headache unlike any before (a possible sign of bleeding). These can signal significant bleeding even when you feel otherwise well.

Pharmacist's practical notes

Aspirin therapy does not usually require routine blood tests, but it does need vigilance for bleeding. Watch for warning signs such as unusual bruising, nosebleeds that are hard to stop, blood in the urine or stool, black or tarry stools, or vomit that looks like coffee grounds, and report any of these to your doctor promptly. Your doctor may still order periodic blood counts or kidney checks depending on your other medicines and conditions.

Tell your doctor and pharmacist about every other medicine you take, because several common ones raise bleeding risk when combined with aspirin: other blood thinners, antiplatelet medicines, regular NSAID painkillers such as ibuprofen, and some antidepressants. Alcohol also increases the risk of stomach irritation and bleeding. Keep a single updated medicine list and show it at every appointment, including before dental work.

Aspirin protects against clots only while you keep taking it, so a missed dose matters more than with many medicines — but never double up; ask your pharmacist what to do after a missed dose. Store tablets in a cool, dry place; enteric-coated aspirin can break down in moisture, and tablets that smell strongly of vinegar should be replaced. Keep track of refills so therapy is never interrupted without your doctor’s knowledge.

Tell every surgeon, dentist, and proceduralist that you take aspirin well before any planned procedure, because it is often discussed whether to pause it — and that decision belongs to your doctor, balancing clot risk against bleeding risk. Carry a medicine list or card in your wallet, and make sure a family member knows you take it, in case of an emergency.

In India

Aspirin is among the cheapest medicines in India; generic versions are typically inexpensive, though prices vary by brand and city.

It is widely available at pharmacies across India, including the doses used for heart protection. Although it is often sold without a prescription, aspirin for heart protection should only be started, stopped, or paused on a doctor’s advice. Follow your own prescription; never start, stop, or change a dose without your doctor.

Frequently Asked Questions

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.

1. Salicylic Acid (Aspirin). In: StatPearls. Treasure Island (FL): StatPearls Publishing. NCBI Bookshelf NBK519032
2. Christiansen M, Grove EL, Hvas AM. Primary Prevention of Cardiovascular Events with Aspirin: Toward More Harm than Benefit, A Systematic Review and Meta-Analysis. Semin Thromb Hemost. 2019;45(5):478–489. PMID 31096304 · doi:10.1055/s-0039-1687905
3. ASCEND Study Collaborative Group; Bowman L, Mafham M, et al. Effects of Aspirin for Primary Prevention in Persons with Diabetes Mellitus. N Engl J Med. 2018;379(16):1529–1539. PMID 30146931 · doi:10.1056/NEJMoa1804988