NSAID, antiplatelet agentOver the counter and by prescription

Aspirinacetylsalicylic acid (ASA)

Also sold as: ASA, Bayer Aspirin, Entrophen, Aspirin 81

Available without a prescription, but daily low-dose aspirin is a medical decision — not a routine supplement.

Quick answer

What it is
Acetylsalicylic acid — an NSAID at higher doses, and an antiplatelet (blood thinner) at low doses of 75–100 mg.
What it's used for
Occasional pain and fever at regular doses; long-term prevention of further events after a confirmed heart attack or stroke at low doses.
Worth knowing
Low-dose daily aspirin is only appropriate for specific patients under medical guidance — the bleeding risk outweighs the benefit for most healthy adults.
Main safety point
Stomach bleeding is the main risk, and it adds to the risk of any other blood thinner. Never give aspirin to anyone under 18 with a fever or viral illness.

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Drug class

NSAID, antiplatelet agent

Use in Canada

One of the most widely used medications in Canada — primarily OTC for pain relief and low-dose for cardiovascular secondary prevention

DIN (Canada)

00010405, 02261030 +1 more

What is Aspirin?

Aspirin is used for short-term relief of mild to moderate pain (headache, dental pain, muscle aches, menstrual cramps) and to reduce fever. Low-dose aspirin (75–100 mg daily) is used for secondary cardiovascular prevention — reducing the risk of heart attack and stroke in patients who have already had a cardiovascular event. Daily aspirin for primary prevention (no prior event) is no longer broadly recommended in Canadian guidelines due to bleeding risks that outweigh the benefit for most people.

How Aspirin works

Aspirin irreversibly inhibits cyclooxygenase (COX-1 and COX-2) enzymes, which are responsible for producing prostaglandins — molecules involved in pain, inflammation, and fever. This makes aspirin both an analgesic and an anti-inflammatory. Its irreversible effect on COX-1 in platelets also permanently reduces platelet clumping for the life of the platelet (7–10 days), which is the basis for its use in cardiovascular prevention.

Daily aspirin: the guidance has changed

For decades, low-dose aspirin was routinely suggested for adults over a certain age or with cardiovascular risk factors, even without a prior heart attack or stroke — an approach known as primary prevention.

Canadian and international cardiovascular guidelines have since moved away from that recommendation for most people. Large trials found that in adults without established cardiovascular disease, the bleeding risk from daily aspirin — gastrointestinal bleeding in particular — offsets or outweighs the cardiovascular benefit.

If you were told years ago to take a daily aspirin and have not revisited it since, it is worth a conversation. Do not start daily aspirin on your own — and if you are already on it, do not stop on your own either, especially if it was started after a cardiac event.

Where daily aspirin may still be appropriate

  • After a confirmed heart attack or stroke
  • After coronary artery bypass graft (CABG) surgery
  • After placement of a coronary stent
  • Certain cases of atrial fibrillation, as directed by a cardiologist
  • Specific high-risk pregnancy situations, under physician direction

Where daily aspirin is generally not recommended

  • Healthy adults with no cardiovascular disease (primary prevention)
  • Adults over 60 starting aspirin for the first time without a cardiovascular event
  • People with ulcers, a history of GI bleeding, or kidney disease
  • Anyone taking an anticoagulant, unless a physician has specifically directed it
  • Children and teenagers

Forms and strengths

Regular-strength tablets: 325 mg (for pain relief). Low-dose tablets: 80 mg and 81 mg (for cardiovascular prevention, commonly called 'baby aspirin'). Enteric-coated tablets (e.g., Entrophen) are designed to reduce stomach irritation, though evidence that they significantly reduce GI bleeding risk is limited.

How Aspirin is taken

For pain and fever: 325–650 mg every 4–6 hours as needed, maximum 4000 mg/day in healthy adults. For cardiovascular secondary prevention: 75–100 mg once daily, typically under physician direction. Take with food or a full glass of water to reduce stomach irritation. Do not exceed recommended doses. Not for children under 18 years.

This is general information, not a dose for you. Dosing depends on the reason you are taking it, your kidney and liver function, your age, and everything else you take — follow the directions on your own label, and ask us if they differ from what you read here.

If you miss a dose

For daily low-dose aspirin, take it when you remember on the same day, and skip it if the next dose is nearly due — do not take two. If you use aspirin only occasionally for pain, there is no missed dose to make up.

Side effects

Common — usually manageable

  • Stomach irritation, nausea, or discomfort — most common with regular or high-dose use
  • Increased tendency to bruise or bleed from cuts and scrapes
  • Heartburn or indigestion
  • Ringing in the ears (tinnitus) at higher doses — a sign of toxicity; reduce dose
  • GI bleeding — can be silent initially; watch for black, tarry stools or blood in stool

Get medical help for these

  • Significant GI bleeding or peptic ulcer — stomach pain, black or bloody stools, vomiting blood — seek emergency care
  • Reye's syndrome (in children with viral illness) — liver and brain damage; always use acetaminophen or ibuprofen in under-18s instead
  • Allergic reaction including bronchospasm — particularly in patients with asthma; difficulty breathing after aspirin requires immediate attention
  • Aspirin poisoning at overdose — ringing in ears, hyperventilation, confusion — emergency

Important warnings

Never give aspirin to anyone under 18 years old for pain or fever — use acetaminophen or ibuprofen instead. Reye's syndrome risk is real, even if rare.

Daily aspirin for primary cardiovascular prevention (no prior heart attack or stroke) is no longer broadly recommended — current Canadian guidelines indicate the bleeding risk outweighs the benefit for most adults without established cardiovascular disease.

Aspirin permanently impairs platelet function for 7–10 days after stopping — tell your surgeon, dentist, or procedure team at least one week in advance.

Combining aspirin with blood thinners (warfarin, apixaban, rivaroxaban) or other antiplatelet drugs (clopidogrel) significantly raises bleeding risk — this combination should be medically supervised, not self-initiated.

Who should take extra care

Children and teenagers
Aspirin is avoided under 18 during fever or viral illness because of Reye's syndrome.
Stomach ulcers or previous GI bleeding
Aspirin significantly raises the risk of another bleed.
People on anticoagulants
Combining aspirin with apixaban, rivaroxaban or warfarin substantially increases bleeding risk and should only be deliberate.
Other NSAIDs
Ibuprofen can block low-dose aspirin's heart protection if taken at the wrong time — ask about spacing.
Pregnancy
Regular-dose aspirin is avoided; low-dose aspirin is sometimes prescribed in pregnancy for specific reasons, which is a different situation.
Asthma with nasal polyps
A minority of people with asthma react badly to aspirin and NSAIDs.

Who should not take it

  • Children and teenagers with viral illness — risk of Reye's syndrome (severe liver and brain damage)
  • Active peptic ulcer or history of significant GI bleeding
  • Aspirin sensitivity or NSAID allergy — particularly in patients with asthma and nasal polyps
  • Third trimester of pregnancy — can affect fetal circulation and increase bleeding risk
  • Bleeding disorders or patients taking anticoagulants (warfarin, apixaban, rivaroxaban) without medical direction
  • Planned surgery or dental procedure within 7–10 days — aspirin permanently reduces platelet function

Drug interactions

Anticoagulants (warfarin, apixaban, rivaroxaban, dabigatran) — significantly increased bleeding risk; any combination should be physician-directed. Clopidogrel — dual antiplatelet therapy used post-stent but increases GI bleeding risk. Ibuprofen and naproxen — combining NSAIDs increases GI bleeding risk substantially; ibuprofen may also blunt the antiplatelet effect of aspirin if taken at the same time. Corticosteroids (prednisone) — increased GI ulcer risk when combined with aspirin. Methotrexate — aspirin can raise methotrexate levels to toxic range. ACE inhibitors and ARBs — high-dose aspirin may reduce their antihypertensive effect. Alcohol — increases GI bleeding risk with aspirin.

Commonly asked about alongside Aspirin: Tylenol, Advil, Aleve, Eliquis.

This is not a complete list. If you take several medications, or buy anything over the counter, a pharmacist medication review is the reliable way to catch interactions that matter.

Coverage in British Columbia

Regular-strength aspirin (325 mg) and low-dose aspirin (81 mg) are available over the counter without a prescription and are not covered under BC PharmaCare as OTC products. If aspirin is prescribed as part of a cardiovascular medication regimen, coverage may apply depending on your PharmaCare plan. Low-dose aspirin is inexpensive and widely available. If you have questions about whether you should be on daily aspirin for cardiovascular reasons, a Pill4Me pharmacist can review your medications and history — call 604-705-3644.

Coverage may depend on indication, PharmaCare plan and Special Authority requirements. Ask Pill4Me Pharmacy to check your coverage, or see BC PharmaCare.

Frequently asked questions

Is aspirin better than ibuprofen for pain?
Not necessarily. Both are NSAIDs that reduce pain and inflammation. Ibuprofen tends to be better tolerated at standard OTC doses for most acute pain situations — headache, muscle aches, dental pain. Aspirin is effective but has largely been replaced by ibuprofen and acetaminophen for everyday pain relief. Where aspirin is unique is in its antiplatelet effect — it permanently reduces platelet clumping, which is why it's used for cardiovascular secondary prevention rather than routine pain relief. Your Pill4Me pharmacist can help you choose the right option for your situation.
Can I take aspirin every day?
That depends on why you'd be taking it. Daily low-dose aspirin (75–100 mg) is recommended for secondary cardiovascular prevention — meaning people who have already had a heart attack, stroke, or established coronary artery disease. For primary prevention (no prior cardiovascular event), current Canadian guidelines recommend against routine daily aspirin for most adults because the bleeding risk outweighs the benefit. If you're unsure whether you should be on daily aspirin, speak with your physician or pharmacist rather than starting it on your own.
What is low-dose aspirin used for?
Low-dose aspirin (75–100 mg, sometimes called 'baby aspirin') is primarily used for secondary cardiovascular prevention — reducing the risk of a second heart attack or stroke in people who have already had one. It works by permanently reducing the ability of platelets to clump together and form clots. It is also sometimes prescribed by a physician in specific high-risk pregnancy situations (e.g., preeclampsia prevention). It is not an effective pain reliever at this dose.
Why is aspirin not recommended for children?
Aspirin carries a rare but serious risk of Reye's syndrome in children and teenagers — especially when taken during a viral illness like influenza or chickenpox. Reye's syndrome causes swelling of the liver and brain and can be life-threatening. This is why acetaminophen and ibuprofen have largely replaced aspirin for fever and pain in anyone under 18. Never give aspirin to a child without explicit direction from a physician.
Can aspirin cause bleeding?
Yes — this is one of aspirin's most important clinical effects and risks. Because aspirin permanently impairs platelet function for 7–10 days, cuts and scrapes take longer to stop bleeding, bruises appear more easily, and there is an increased risk of stomach (GI) bleeding with regular use. GI bleeding can be silent initially — watch for black, tarry stools. If you are taking aspirin and scheduled for surgery or a dental procedure, tell the provider at least one week in advance.
Is it safe to take aspirin with blood thinners?
Not without medical supervision. Combining aspirin with anticoagulants (warfarin, apixaban, rivaroxaban) or other antiplatelet drugs (clopidogrel) significantly raises the risk of serious bleeding — including GI bleeding and brain bleeds. This combination is sometimes used intentionally in certain cardiovascular conditions under close monitoring, but should never be self-initiated. Always tell your pharmacist if you're prescribed a new blood thinner while already on aspirin, or vice versa.
What is the difference between regular aspirin and low-dose aspirin?
Regular aspirin (325 mg) is used for pain relief and fever. Low-dose aspirin (75–100 mg, often sold as '81 mg' in Canada) is used for its antiplatelet effect in cardiovascular prevention — it is not an effective pain reliever at this dose. The clinical uses and risk profiles are different. Taking regular-strength aspirin daily for cardiovascular prevention would significantly increase your bleeding risk without proportional benefit.
Can I take aspirin if I'm pregnant?
Regular or high-dose aspirin is not recommended during most of pregnancy — especially in the third trimester, where it can affect fetal circulation and increase bleeding risk. Low-dose aspirin (81 mg) is sometimes prescribed by a physician for specific high-risk situations, such as preeclampsia prevention. This is a medical decision, not an OTC self-care one. If you're pregnant and considering aspirin for any reason, speak to your physician or pharmacist first.

Related reading

Related medications

Tylenol (acetaminophen)Advil (ibuprofen)Aleve (naproxen sodium)Eliquis (apixaban)

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Pill4Me Pharmacy is at 5625 Promontory Rd Unit 101, Chilliwack, BC. We deliver free to Chilliwack, Sardis, Promontory, Vedder and Yarrow, and you can reach a pharmacist directly at 604-705-3644.

Reviewed by a Pill4Me pharmacist · Last reviewed August 17, 2026

Medical disclaimer: This page is general educational information about Aspirin and is not individualized medical advice, a diagnosis, or a treatment recommendation. Talk to your pharmacist or prescriber before starting, stopping, or changing any medication. BC PharmaCare coverage criteria change over time — confirm current coverage with us.