What is aspirin used for?

Aspirin is used to relieve mild to moderate pain, reduce fever, and treat inflammation. In low doses, it is also used to reduce the risk of heart attack and ischemic stroke in selected people.

How does aspirin work?

Aspirin inhibits cyclooxygenase (COX) enzymes, which lowers prostaglandin production to reduce pain, fever, and inflammation. It also reduces platelet aggregation, which helps prevent blood clots.

What is a typical aspirin dose?

Dosing depends on the goal: low-dose regimens are commonly used for antiplatelet effects, while higher doses may be used for pain or fever. Follow a clinician’s advice and product labeling, as total daily dose limits vary by formulation and individual risk.

What are the main risks and side effects of aspirin?

The most important risks are stomach irritation, ulcers, and bleeding, including gastrointestinal bleeding. It can also trigger allergic reactions or worsen asthma in some people.

Who should avoid aspirin or use it only with medical advice?

People with bleeding disorders, active ulcers, aspirin allergy, or those taking anticoagulants should seek medical guidance. Children and teens with viral illnesses should avoid aspirin due to the risk of Reye syndrome.

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Aspirin

Strong study situation·10/10

A higher score indicates better study conditions, but not necessarily effectiveness.

Aspirin is a widely used NSAID for pain relief, fever reduction, and cardiovascular protection, with substantial evidence supporting its use and specific safety considerations.

Anti-inflammatory Cardiovascular Support Cancer-inhibitor

dose range

81–4000 mg

Low-dose (81–325 mg) once daily for cardiovascular protection; higher doses split every 4–6 hours as needed for pain.

Consumption

Take orally with food or a full glass of water to reduce stomach upset.

Not fat-soluble.

Best time

For cardiovascular prevention, take at the same time each day; for pain, use as needed and do not exceed maximum daily dose.

Description

Aspirin (acetylsalicylic acid) is a nonsteroidal anti-inflammatory drug (NSAID) used for over a century to manage pain, fever, and inflammation, and in low doses helps prevent heart attacks and strokes in at-risk individuals.

benefits

Main effects with level of evidence

Strong

Note on evidence

Aspirin’s benefits for pain management and cardiovascular risk reduction are well-supported by meta-analyses and clinical guidelines; evidence for cancer prevention is emerging but less robust.

Pain Relief and Anti-Inflammatory Effects

Strong

Aspirin effectively reduces mild to moderate pain, fever, and inflammation by inhibiting cyclooxygenase (COX) enzymes and reducing prostaglandin synthesis.

Particularly relevant for: General adults · Arthritis and musculoskeletal pain patients

Lancet2016 · The Lancet Cochrane2014 · Cochrane Review: Aspirin for pain

Cardiovascular Protection

Strong

Low-dose aspirin is proven to reduce risk of heart attack and ischemic stroke by inhibiting platelet aggregation, especially in high-risk individuals.

Particularly relevant for: Adults at elevated cardiovascular risk

USPSTF2022 · USPSTF (via NIH)FDAAspirin · FDA Consumer Update: Aspirin

Potential Cancer Prevention

Moderate

Regular aspirin use is associated with reduced incidence of some cancers, particularly colorectal cancer; evidence is promising but not definitive for risk/benefit in the general population.

Particularly relevant for: Adults at increased colorectal cancer risk

JAMAOnc2016 · JAMA Oncology USPSTF2022 · USPSTF (via NIH)

Safety & Information

Important safety information & known risks

For educational purposes only • not medical advice

Aspirin is generally safe when used as directed, but carries risks of gastrointestinal bleeding, ulcers, allergic reactions, and is contraindicated in certain populations.

warning notices

High doses or long-term use increase risk of GI bleeding and ulcers, particularly in older adults and those with prior GI issues.
May cause hypersensitivity or allergic reactions, especially in people with asthma or prior reactions to NSAIDs or salicylates.
Increased risk of bleeding when combined with other anticoagulant or antiplatelet medications.
Contraindicated in children and teenagers with viral infections due to risk of Reye's syndrome.
Avoid use in children or teenagers with viral infections due to risk of Reye's syndrome.
Do not use if you have active peptic ulcers or a known bleeding disorder.
Avoid combination with other NSAIDs or anticoagulants without medical supervision due to increased risk of bleeding.
Use only with clinician supervision if you have a history of gastrointestinal bleeding or allergy to NSAIDs.

Known interactions with medications

Anticoagulants (warfarin, heparin, DOACs)
Other NSAIDs
SSRIs and SNRIs (may increase bleeding risk)

Contraindications / special precautions

Known allergy to aspirin or other salicylates
Active peptic ulcer or gastrointestinal bleeding
Bleeding disorders (e.g., hemophilia)
Children or teenagers with current/recent viral infection

interactions

Important interactions between active ingredient ↔ supplement / medication / food

Aspirin may interact with several drugs and supplements, increasing bleeding risk and affecting efficacy.

Increased bleeding risk with anticoagulants like warfarin.

drug · Warfarin

AvoidStrong

Why

Both drugs inhibit clotting mechanisms, compounding bleeding risk.

recommendation

Do not use aspirin with warfarin except under medical supervision.

FDAAspirin · FDA Consumer Update: Aspirin MayoAspirin · Mayo Clinic: Aspirin

Coadministration with other NSAIDs increases gastrointestinal and renal risks.

drug · Other NSAIDs

AvoidStrong

Why

Combining NSAIDs raises risk of GI bleeding, ulcers, and kidney toxicity.

recommendation

Avoid routine combination or use the lowest effective dose.

NIHODS2022 · NIH Office of Dietary Supplements: Aspirin FDAAspirin · FDA Consumer Update: Aspirin

Aspirin may reduce vitamin C levels.

nutrient · Vitamin C

CautionLimitedVitamin C

Why

Aspirin can increase renal clearance of vitamin C.

recommendation

Monitor vitamin C status if using high-dose aspirin chronically.

ExamineAspirin · Examine.com Aspirin

mechanisms of action

Brief explanations of how it works

COX Enzyme Inhibition

Aspirin irreversibly inhibits cyclooxygenase enzymes (COX-1 and COX-2), blocking prostaglandin and thromboxane production and leading to reduced inflammation, pain, fever, and platelet aggregation.

Lancet2016 · The Lancet Cochrane2014 · Cochrane Review: Aspirin for pain

Inhibition of Platelet Aggregation

Aspirin acetylates COX-1 in platelets, irreversibly inhibiting thromboxane A2 formation and reducing the ability of platelets to clump together, which helps prevent blood clots.

USPSTF2022 · USPSTF (via NIH)FDAAspirin · FDA Consumer Update: Aspirin

Potential anti-tumor effects

Aspirin’s anti-inflammatory actions and effects on cell signaling may inhibit cancer cell growth and promote apoptosis, particularly in colorectal tissue.

JAMAOnc2016 · JAMA Oncology

Sources & References

Primary literature and reviews on which these statements are based

8 sources

Lancet2016

The Lancet

USPSTF2022

USPSTF (via NIH)

JAMAOnc2016

JAMA Oncology

NIHODS2022

NIH Office of Dietary Supplements: Aspirin