Based on NIH | Can heart failure or its treatments cause blood in stool, and when should I seek urgent medical care?

Blood in the stool is not a typical symptom of heart failure itself, but it can occur due to common treatments and co‑existing conditions, and it can sometimes be an emergency. Certain heart medicines (especially blood thinners, antiplatelets, and NSAIDs) significantly raise the risk of gastrointestinal (GI) bleeding, which may show up as bright red blood, maroon stool, or black, tarry stool. ^{[1] [2]} Immediate evaluation is recommended if you see blood in your stool, have black/tarry stools, or vomit blood, because GI bleeding can be serious and sometimes life‑threatening. ^{[3] [4]}

How heart failure and its treatments can lead to blood in stool

• Antiplatelet drugs (e.g., aspirin, clopidogrel) and anticoagulants (“blood thinners”) are widely used in people with heart disease and heart failure and are well‑known causes of GI bleeding. ^[1] Dual antiplatelet therapy (two antiplatelet drugs together) increases bleeding risk several‑fold compared with one agent. ^[5]
• NSAIDs (e.g., ibuprofen, naproxen) for pain can cause ulcers and bleeding anywhere in the stomach or intestines at any time during treatment, and the risk is higher in older adults and those with poor overall health. ^[6] NSAIDs can also worsen heart failure, so they should be avoided or used only with medical guidance. This dual risk worsening HF and causing GI bleeding makes NSAIDs particularly concerning in HF. ^{[7] [2]}
• Some heart medications have rare bleeding side effects. For example, digoxin has rare reports of black, tarry stools or blood in stool; such symptoms warrant prompt medical attention if they occur while taking it. ^[8]
• After a heart attack or in heart failure, multiple factors raise bleeding risk, including older age, kidney dysfunction, combination therapy (e.g., anticoagulant plus antiplatelet), and diabetes. When GI bleeding occurs in this setting, it is linked with a higher risk of death, underscoring the need for rapid care. ^[5]

What blood in stool can look like

• Black, tarry stools (melena) suggest bleeding from higher up in the digestive tract (stomach or small intestine). This is an urgent warning sign. ^{[9] [10]}
• Bright red blood on or mixed with stool (hematochezia) usually signals bleeding from the lower colon or rectum, though brisk upper GI bleeding can sometimes appear this way. ^[10]
• Dark maroon stools can indicate bleeding from the small intestine or right colon. ^[10]

When to seek urgent or emergency care

• Call emergency services or go to the emergency department now if you have blood in your stool and any signs of shock or heavy bleeding, such as dizziness, fainting, rapid heartbeat, rapid breathing, pale/clammy skin, confusion, low urine output, or a drop in blood pressure. ^{[11] [12]}
• Seek immediate medical attention the same day if you notice black, tarry stools; see visible blood in stool; or vomit blood or “coffee‑ground” material. These are all urgent warning signs and should not wait. ^{[3] [4]}
• Contact your clinician promptly if you notice any new change in stool color (black or red) even without other symptoms, as evaluation is still recommended. ^{[9] [13]}

Common causes to consider in people with heart disease

• Medication‑related bleeding from antiplatelets, anticoagulants, and NSAIDs is common and often preventable with careful medication review and stomach protection when appropriate. ^{[1] [5]}
• Peptic ulcers or gastritis can be triggered or worsened by NSAIDs and blood thinners, leading to black or bloody stools. ^{[2] [6]}
• Colonic sources (e.g., diverticulosis, angiodysplasia, hemorrhoids) are frequent in older adults and can cause bright red or maroon bleeding; blood thinners can make these bleeds more obvious or heavier. ^[10]
• Less common drug effects (e.g., rare GI bleeding signs with digoxin) should be considered if symptoms start after a new medicine or dose change. ^[8]

What to expect during medical evaluation

• Initial assessment focuses on stability: vital signs, blood counts, and whether IV fluids or a blood transfusion are needed. ^[4]
• Endoscopy: Upper GI endoscopy (EGD) can locate and treat bleeding ulcers; colonoscopy evaluates lower sources. Early endoscopy helps find and stop bleeding and is often feasible even when on “blood thinners,” after careful risk balancing and, if needed, partial reversal. ^[1]
• Medication management may include temporarily holding or reversing anticoagulation in significant bleeding, balanced against the risk of clotting events; specific approaches vary by drug and kidney function. ^{[14] [1]}
• Prevention after a bleed often includes a proton‑pump inhibitor (PPI) for acid‑related disease and testing/treating H. pylori to reduce rebleeding risk, especially if antiplatelet therapy must continue. ^[1]

How to lower your risk going forward

• Review your medication list with your clinician or pharmacist, especially if you take aspirin, clopidogrel, anticoagulants, or NSAIDs. Avoid over‑the‑counter NSAIDs unless your clinician agrees, because they increase both GI bleeding and heart failure risks. ^{[7] [6]}
• Ask whether you need stomach protection (e.g., a PPI) if you must remain on antiplatelet or anticoagulant therapy and have risk factors for ulcers. ^[1]
• Limit alcohol and stop smoking to reduce ulcer and bleeding risks; follow dosing exactly and avoid combining multiple medicines that raise bleeding risk (e.g., NSAIDs plus aspirin). ^[15]
• Monitor for warning signs: black stools, bright red blood, dizziness, or fainting; seek immediate care if they appear. ^{[3] [11]}

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Quick reference: When to act

Situation	What to do
Black, tarry stool or visible blood in stool	Seek immediate medical care today. [3] [9]
Vomiting blood or “coffee‑grounds” material	Seek immediate medical care or call emergency services. [3] [4]
Bleeding with dizziness, fainting, fast breathing/heart rate, pale/clammy skin, confusion, low urine	Call emergency services now (possible shock). [11] [12]
Mild streaks of blood without other symptoms	Contact your clinician promptly for guidance and evaluation. [13]

Recognizing these signs early is important because GI bleeding can escalate quickly, and people taking blood thinners or antiplatelets are at higher risk for significant blood loss. ^{[5] [4]}