Can Alzheimer’s Disease Cause Blood in the Stool?

Blood in the stool (also called hematochezia if bright red, or melena if black and tarry) is generally not a direct symptom of Alzheimer’s disease itself. ^[1] Alzheimer’s primarily affects memory, thinking, behavior, and the ability to perform daily activities, while bowel-related changes in Alzheimer’s are more about continence (loss of control) rather than actual bleeding. ^[2] That said, people living with Alzheimer’s do have a higher overall risk of serious gastrointestinal (GI) events including both upper and lower GI bleeding compared to age‑matched peers without Alzheimer’s, so bleeding may occur more often in this group for multiple reasons. ^[3]

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How Alzheimer’s Affects the Bowels (But Not Typically Bleeding)

Alzheimer’s disease commonly leads to problems controlling bowel and bladder movements as the condition progresses. ^[2] These continence problems reflect neurological decline, not injury or ulceration of the GI tract that would cause bleeding. ^[4] Swallowing difficulties and reduced mobility can also contribute to constipation or diarrhea, which may exacerbate hemorrhoids or anal fissures and sometimes result in minor rectal bleeding, but this is indirect rather than a core symptom of Alzheimer’s. ^[4]

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Elevated GI Event Risk in Alzheimer’s

Older adults with Alzheimer’s have been shown to experience more serious GI events such as ulceration, perforation, and bleeding than those without Alzheimer’s. ^[3] In a large cohort of individuals aged 65 and older, rates of upper GI events were higher in those with Alzheimer’s, and lower GI events (including bleeding) were also more frequent. ^[3] This increased risk likely reflects a combination of factors common in Alzheimer’s populations: advanced age, comorbid illnesses, polypharmacy (use of multiple medications), impaired communication of symptoms, and nursing‑home residence. ^[5]

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More Likely Causes of Blood in the Stool

Most cases of blood in the stool in older adults whether or not they have Alzheimer’s arise from conditions unrelated to the dementia itself. ^[5] Common causes include:

• Hemorrhoids or anal fissures (often bright red blood on tissue or bowl). ^[5]
• Diverticular bleeding (sudden, sometimes heavy bleeding). ^[5]
• Colorectal polyps or cancer (blood mixed with stool, changes in bowel habits). ^[5]
• Inflammatory bowel disease or ischemic colitis (abdominal pain with bleeding). ^[5]
• Upper GI sources like ulcers that sometimes present as black, tarry stools (melena). ^[5]

In elderly individuals, a thorough history and timely evaluation (including colonoscopy or imaging) are important, but can be challenging when communication or cognition is impaired. ^[5]

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Medication-Related Bleeding Risks

Medication use is a major contributor to GI bleeding in older adults and is common among those with Alzheimer’s. ^[5] Key medication categories include:

• Nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen or naproxen, which increase ulcer and bleeding risk. ^[5]
• Antiplatelets (e.g., aspirin, clopidogrel) and anticoagulants (e.g., warfarin, DOACs), which raise bleeding risk across the GI tract. ^[5]
• Selective serotonin reuptake inhibitors (SSRIs), bisphosphonates, and steroids, especially when combined with NSAIDs or antithrombotics. ^[6]

Among anti‑dementia drugs, donepezil (an acetylcholinesterase inhibitor) generally shows no increase in peptic ulcer disease or GI bleeding at typical doses of 5–10 mg compared with placebo. ^[7] However, at higher doses (23 mg), there is a small increased incidence of peptic ulcer disease and GI bleeding compared with 10 mg, so caution is reasonable in those with ulcer history or concurrent NSAID use. ^[8]

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Red Flags and When to Seek Care

Blood in the stool should be evaluated, especially if there is:

• Black, tarry stools or persistent bright red bleeding. ^[5]
• Dizziness, fainting, pallor, or signs of anemia. ^[5]
• Abdominal pain, weight loss, or changes in bowel habits. ^[5]

Early colonoscopy and CT imaging can help localize bleeding and allow treatment; if these fail, angiography or surgery may be needed. ^[5] Coordinated care among primary care, gastroenterology, interventional radiology, and surgery is often required to improve outcomes and reduce complications in older adults. ^[5]

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Practical Steps to Reduce Risk

• Review all medications regularly, looking for NSAIDs, antiplatelets, anticoagulants, SSRIs, steroids, and bisphosphonates; discuss safer alternatives where appropriate. ^[5]
• Consider gastroprotection (e.g., proton pump inhibitors) when antithrombotics or NSAIDs are necessary. ^[5]
• Support bowel health with adequate hydration, fiber, and mobility programs to reduce constipation, which can worsen hemorrhoids and fissures. ^[4]
• Monitor for signs of bleeding and anemia in individuals with Alzheimer’s, given the higher baseline risk of serious GI events. ^[3]

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Bottom Line

Alzheimer’s disease itself does not typically cause blood in the stool; bowel issues in Alzheimer’s are more about continence, swallowing, and motility changes. ^[2] Nonetheless, people with Alzheimer’s have a higher risk of serious GI events, including bleeding, largely due to age, comorbidities, and medication use. ^[3] If blood in the stool appears, it is more likely due to common GI conditions (like hemorrhoids, diverticula, or cancer) or medications (NSAIDs, antiplatelets, anticoagulants), rather than Alzheimer’s directly. ^[5] Reviewing medications and obtaining appropriate GI evaluation helps identify the source and guide safe, effective treatment. ^{[5] [6] [8]}