Can Parkinson’s Disease or Its Medications Cause Blood in the Stool?

Blood in the stool (hematochezia or melena) is not a typical symptom caused directly by Parkinson’s disease (PD) itself, but certain PD medications, especially levodopa/carbidopa combinations, have been associated with gastrointestinal (GI) bleeding and duodenal ulcers, which can present as blood in the stool. ^[1] Package inserts for multiple carbidopa‑levodopa formulations list “gastrointestinal bleeding” and “development of duodenal ulcer” as reported adverse reactions, indicating a plausible medication-related cause. ^[2] This signal is consistent across different extended‑release and immediate‑release formulations of carbidopa‑levodopa. ^{[3] [4] [5] [6]}

---

How Parkinson’s Itself Affects the Gut

PD commonly affects the autonomic nervous system and the GI tract, leading to constipation, slow stomach emptying, swallowing difficulties, and anorectal dysfunction rather than bleeding. ^[7] These GI symptoms are frequent and often correlate more with disease severity than with the use of dopaminergic drugs. ^[8] While constipation is very common in PD, it does not inherently cause bleeding unless complications such as hemorrhoids or anal fissures develop. ^[9]

---

Medication-Related GI Bleeding: What We Know

• Levodopa/carbidopa: GI bleeding and duodenal ulcer formation are listed among adverse effects for various carbidopa‑levodopa products, suggesting a potential risk. ^[2] Similar listings appear across extended‑release tablets, reinforcing the signal. ^[1] These reactions are uncommon but recognized. ^{[5] [6]}

• Other dopaminergic adjuncts (COMT inhibitors): Entacapone and tolcapone mainly cause diarrhea and dopaminergic side effects, with tolcapone requiring liver monitoring; GI bleeding is not highlighted as a typical adverse effect in reviews. ^[10] Overall, entacapone is generally well tolerated, with diarrhea being the most prominent GI issue. ^{[11] [12] [13]}

• Clinical trials of carbidopa/levodopa ER vs IR: Report abnormal labs such as blood in urine but not a signal for frequent stool bleeding; constipation is noted as a symptom. ^[14]

Bottom line: If blood in the stool appears while taking levodopa/carbidopa, a medication-related GI bleed or ulcer is one of several possibilities to consider, alongside common non‑PD causes. ^[2] This warrants medical evaluation to confirm the source and severity. ^[1]

---

Other Common Causes of Blood in Stool in People With PD

• Hemorrhoids or anal fissures: Constipation and straining are common in PD and can lead to bright red blood on the stool or toilet paper. ^[9] This is a frequent, benign cause but still needs assessment if bleeding persists or is heavy. ^[9]

• Peptic ulcers or gastritis: Can cause black, tarry stools (melena) or, less commonly, red blood; risk rises with NSAIDs (like ibuprofen/naproxen), steroids, or anticoagulants. ^[15] Older age and alcohol use further increase GI bleed risk from NSAIDs. ^{[16] [17]}

• Antiplatelet/anticoagulant therapy: Aspirin, clopidogrel, warfarin, and DOACs increase the risk of gross GI bleeding, especially in those with prior ulcers or when combined therapies are used. ^[18] Proton pump inhibitors (PPIs) and treating Helicobacter pylori reduce upper GI bleeding risk in at‑risk patients. ^{[18] [19]}

---

Red Flags That Need Urgent Care

• Black, tarry stools (melena) or maroon stools suggesting upper GI bleeding.
• Persistent or heavy bright red bleeding, dizziness, fainting, or signs of anemia (fatigue, pale skin).
• New abdominal pain with bleeding, or vomiting blood.

These can indicate a significant GI bleed and should be evaluated promptly, often with labs and endoscopy. ^[18] Early endoscopy helps identify and treat bleeding sources, even when low‑intensity anticoagulation is present. ^[18]

---

Practical Steps if You Notice Blood in the Stool

• Do not stop PD medications abruptly, as this can worsen symptoms; instead, contact your clinician to review the regimen, especially levodopa/carbidopa. ^[2] They may adjust dosing or add protective strategies if an ulcer is suspected. ^[1]

• Review all non‑PD drugs you take:

  • NSAIDs, steroids, antiplatelets, and anticoagulants raise GI bleeding risk; your clinician may consider gastroprotection (PPIs) or alternatives. ^{[15] [16] [17] [18] [19]}

• Manage constipation gently:

  • Hydration, fiber, stool softeners, and osmotic laxatives can reduce straining and bleeding from hemorrhoids/fissures. ^[20] Constipation is common in PD, and prevention helps minimize bleeding risk. ^{[9] [20]}

• Testing and follow‑up:

  • Stool testing and endoscopy may be recommended to identify the source. ^[18] If an ulcer is found, PPIs and H. pylori treatment lower rebleeding risk, even if antiplatelets must continue. ^[18]

---

Summary Table: PD, Medications, and GI Bleeding

Factor	Typical GI Effects	Link to Blood in Stool	Notes
Parkinson’s disease	Constipation, anorectal dysfunction, gastroparesis	Indirect (via hemorrhoids/fissures)	GI symptoms correlate with disease severity more than drugs. [8] [7] [9]
Levodopa/carbidopa	Nausea, dyspepsia; reported GI bleeding and duodenal ulcer	Possible	GI bleeding/duodenal ulcer listed in official labeling. [2] [1] [5] [6]
Entacapone/tolcapone (COMT inhibitors)	Diarrhea, dopaminergic effects; tolcapone hepatotoxicity monitoring	Uncommon	Bleeding not a typical adverse effect; diarrhea prominent. [10] [11] [12] [13]
NSAIDs/steroids	Gastritis/ulcers	Strong	Risk increases with age, alcohol, anticoagulants; use lowest effective dose and consider PPI in high‑risk patients. [15] [16] [17]
Antiplatelets/anticoagulants	Mucosal bleeding risk	Strong	Prior ulcer, combination therapy, high intensity anticoagulation raise risk; PPIs and H. pylori eradication reduce upper GI bleeding. [18] [19]

---

Key Takeaways

• Blood in the stool is not a typical direct symptom of PD, but levodopa/carbidopa has documented associations with GI bleeding and duodenal ulcers in product labeling. ^[2] Other PD adjuncts mainly cause diarrhea and are not commonly linked to bleeding. ^{[10] [11]}
• Common non‑PD contributors NSAIDs, antiplatelets, anticoagulants, and constipation‑related hemorrhoids are often responsible and should be reviewed. ^{[15] [18] [9]}
• Seek medical evaluation for any new or significant bleeding, and do not abruptly stop PD medications; instead, coordinate with your clinician for safe adjustments and protective measures such as PPIs when appropriate. ^{[18] [19]}