Aspirin and Bloody Stool: Side Effect, Risks, and How to Cope

Aspirin can cause gastrointestinal (GI) bleeding, which may show up as black, tarry stools or visible blood in the stool. This is a known safety warning on aspirin labels, and people are advised to seek medical help right away if these symptoms occur. ^[1] Aspirin products consistently list “bloody or black stools,” “vomiting blood,” “feeling faint,” and “stomach pain that does not get better” as signs of stomach bleeding requiring urgent evaluation. ^[2] These warnings apply to regular, low‑dose, and coated formulations of aspirin. ^[3]

How aspirin causes bleeding

• Aspirin reduces platelet function, which helps to prevent clots but also makes bleeding more likely in the stomach or intestines. This can lead to ulcer formation or bleeding that appears as black or bloody stools. ^[4]
• The risk is higher with certain factors: age 60+, prior ulcers or bleeding, use of blood thinners or steroids, taking other NSAIDs, and drinking 3 or more alcoholic drinks daily. Product labels highlight these risk factors clearly. ^{[5] [6]}

When to seek medical care

• Go to urgent care or the emergency department now if you have any of the following while on aspirin: feeling faint, vomiting blood, black or bloody stools, or stomach pain that doesn’t improve. ^[1] Each of these signs can indicate a serious GI bleed. ^[2]

Who is at higher risk

• People older than 60, those with a history of peptic ulcers or GI bleeding, anyone taking anticoagulants (blood thinners) or steroid medicines, and those using other NSAIDs together with aspirin. Alcohol intake (three or more drinks daily) also raises the chance of severe stomach bleeding. ^[4] These risk factors appear across multiple aspirin safety labels. ^[5]

Practical steps to reduce harm

• Use the lowest necessary dose and avoid stacking NSAIDs. Taking ibuprofen or naproxen together with aspirin increases bleeding risk. ^[5]
• Consider stomach protection if you need ongoing aspirin. For people at higher risk of upper GI events, adding a proton pump inhibitor (PPI) can reduce aspirin‑related upper GI ulcers and bleeding and may improve adherence. [PM18] Systematic reviews show PPIs prevent low‑dose aspirin–related GI bleeding better than H2 blockers. [PM22]
• Know the limits of PPIs. PPIs mainly protect the upper GI tract (stomach/duodenum) and do not prevent lower GI bleeding; they may even be associated with small‑bowel injury in some contexts, so protection is not complete. Preventive strategies should address both upper and lower GI risk. [PM20]
• Discuss alternatives and timing with your clinician. In certain high‑risk scenarios (e.g., after a GI bleed), choices like switching antiplatelet strategy or combining aspirin with a PPI are weighed against cardiovascular protection; individualized plans are important because some combinations may affect cardiovascular outcomes. [PM21]
• Avoid alcohol and smoking, and treat H. pylori if present. These measures can lower ulcer risk and bleeding tendency. Labels emphasize alcohol as a modifiable risk factor for stomach bleeding. ^[4]

If bleeding happens while on aspirin

• Stop aspirin and seek urgent medical care immediately. Product guidance instructs users to stop and ask a doctor if signs of stomach bleeding occur. ^[2] Coated or low‑dose forms do not eliminate the risk, so do not wait for symptoms to “pass.” ^[3]
• Expect evaluation. Clinicians may perform blood tests, stool tests, and endoscopy to locate bleeding, and will decide when and how to restart antiplatelet therapy based on your heart/brain risk and bleeding control. Some people will be started on a PPI if aspirin is continued after a bleed. [PM18]

Key takeaways

• Yes aspirin can cause GI bleeding, often showing as black or bloody stools, and this requires urgent medical attention. ^[1]
• Risk is higher with age, prior ulcers/bleeding, alcohol, other NSAIDs, and blood thinners/steroids. ^[5]
• PPIs can meaningfully reduce upper GI complications from aspirin in higher‑risk users, but they do not fully protect the lower GI tract. [PM18] [PM22] [PM20]
• Work with your clinician to balance heart protection with bleeding risk and to choose the safest plan for you. [PM21]