Can aspirin cause blood in urine?

Yes, aspirin can be linked to blood in the urine (hematuria) because it affects platelet function and increases bleeding risk. Guidance for blood in urine lists antiplatelet drugs such as aspirin among medicines tied to urinary bleeding. ^[1] Blood in the urine is also listed among possible adverse effects for certain aspirin-containing products. ^[2]

How aspirin can lead to hematuria

• Aspirin reduces platelets’ ability to clump, which can make bleeding more likely in various organs, including the urinary tract. ^[1]
• Consumer and professional drug information for aspirin products includes bloody or cloudy urine among side effects that warrant medical attention. ^[2]
• While not everyone will experience this, visible blood in urine should be evaluated, because it can have both harmless and serious causes. ^{[3] [4]}

Important context and variability

• Some older observational studies did not find a strong association between routine aspirin use and dipstick hematuria in certain populations, suggesting risk may depend on individual factors. [PM20]
• The overall bleeding profile of aspirin is clearer for the stomach and brain; urinary bleeding can still occur, especially with other risk factors (age, concurrent blood thinners, kidney disease, recent procedures). ^{[5] [1]}

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When to seek medical care

• Any urine that looks pink, red, or cola-colored should be checked by a clinician, because it’s hard to tell if color changes are true blood without testing. ^{[3] [4]}
• If you notice bloody or cloudy urine after starting or while taking aspirin, contact a healthcare professional promptly for guidance. ^[2]
• Seek urgent care if bleeding is heavy, you pass clots, feel faint, or have pain with fever, because more serious conditions may need immediate treatment. ^[3]

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What to do right now

• Do not stop prescribed aspirin on your own if it was recommended for heart or stroke prevention; instead, call your prescriber to discuss next steps. Adjustments often depend on your cardiovascular risk and bleeding severity. ^[5]
• List all medicines and supplements you take, especially other NSAIDs (like ibuprofen or naproxen) or anticoagulants (like warfarin), because combining these can raise bleeding risk. ^{[6] [7]}
• Hydrate and avoid strenuous, contact-heavy exercise until evaluated, since hard exercise can sometimes trigger transient hematuria. ^[1]

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How clinicians typically evaluate hematuria

• Urinalysis and urine microscopy to confirm blood and look for infection. ^[4]
• Review of medications, including aspirin dose and other blood-thinning agents. ^[1]
• Depending on findings and risk factors, you may need kidney/bladder imaging or cystoscopy to rule out stones, tumors, or structural causes. ^[4]

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Coping and prevention tips

• Use the lowest effective aspirin dose and take it exactly as directed to reduce bleeding risk. ^[5]
• Avoid stacking NSAIDs; do not add over-the-counter ibuprofen or naproxen unless your clinician says it’s safe. This increases bleeding risk. ^{[6] [7]}
• Limit alcohol, which can worsen bleeding when combined with NSAIDs. ^[6]
• Monitor for other bleeding signs: nosebleeds, black stools, unusual bruising; report them to your clinician. ^[8]
• If aspirin is necessary for your heart, your clinician may discuss alternative strategies (dose changes, different antiplatelet therapy, gastroprotection if GI risk is high) tailored to your situation. ^[5]

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Key takeaways

• Aspirin can be associated with blood in urine for some people, due to its antiplatelet effect. ^[1]
• Visible hematuria should always be evaluated, regardless of aspirin use, to find and treat the cause. ^{[3] [4]}
• Do not stop prescribed aspirin without medical advice; contact your clinician to balance bleeding risks with heart protection. ^[5]

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