Is Diarrhea a Symptom of Stomach Cancer? Causes and Management

Diarrhea is not among the most common early symptoms of stomach (gastric) cancer; early signs are more often vague stomach upset, indigestion, or discomfort, which can overlap with many benign conditions. ^[1] Still, diarrhea can occur in people with cancer due to multiple reasons, including cancer treatments, infections, or, less commonly, the cancer itself. ^{[2] [3]}

How Stomach Cancer Usually Presents

• Early-stage stomach cancer often has nonspecific symptoms such as upset stomach and general abdominal discomfort, making early diagnosis difficult because these symptoms are common in non-cancer conditions. ^[1]
• Because early symptoms are vague, persistent or worsening digestive issues warrant medical evaluation, even if they seem minor. ^[1]

Can Cancer Cause Diarrhea?

• Certain cancers can directly cause diarrhea; these include neuroendocrine tumors, colon cancer, lymphoma, medullary thyroid cancer, and pancreatic cancer. ^[3]
• While stomach cancer is not typically listed among the leading cancers that directly cause diarrhea, people with stomach cancer can still experience diarrhea from other cancer-related factors, especially treatments or infections. ^{[3] [2]}

Common Causes of Diarrhea in People With Cancer

• Cancer treatments such as chemotherapy, radiation, immunotherapy, targeted therapies, and some stem cell/bone marrow transplants can cause diarrhea. ^{[2] [4]}
• Infections are more likely during or after treatment and can trigger diarrhea; antibiotics used to treat infections may also cause diarrhea. ^[4]
• Surgery involving parts of the gastrointestinal tract can lead to diarrhea, particularly if sections of the intestine are removed. ^[4]

When to Seek Medical Care Urgently

• Contact a healthcare professional right away for any of the following: six or more loose stools per day for over two days, blood in the stool or rectal area, weight loss due to diarrhea, fever ≥38°C (100.5°F), loss of bowel control, cramps or diarrhea lasting more than a day, or diarrhea with dizziness on standing. ^{[5] [6] [7] [8]}
• Even milder diarrhea that starts to interfere with daily activities should prompt a call to your care team. ^[6]

Evidence-Based Self-Care and Management Tips

• Hydration first: At the start of diarrhea, switch to clear liquids such as water, clear broths, apple juice, or ice pops; avoid milk products initially. Aim for roughly 2–3 liters (8–12 cups) of fluid daily unless your clinician advises otherwise. ^[9]
• Gentle diet progression: As symptoms improve, add low-fiber foods like bananas, rice, applesauce, and toast (often called the “BRAT” approach) and other easy-to-digest, low-residue options. ^[9]
• Monitor dehydration signs: Thirst, dry mouth/skin, reduced urine, darker urine, fatigue, cramps, and lightheadedness are warning signs to increase fluids and seek help if persistent. ^[10]
• Follow your oncology team’s plan: Many cancer centers use stepwise algorithms for treatment-induced diarrhea (for example, starting with dietary measures and loperamide, and escalating care if symptoms persist or are severe). ^[11]
• Patient handouts from cancer programs provide practical do’s and don’ts (foods to limit, fluid/electrolyte strategies, and when to call) that are periodically updated. ^{[12] [13]}

Clinical Management in Treatment-Induced Diarrhea

• Oncology teams often apply standardized algorithms to grade severity and guide therapy; these may include anti-diarrheal medicines (such as loperamide), fluid and electrolyte replacement, temporary diet modification, and evaluation for infection. ^[11]
• Some drugs (for example, irinotecan) have specific management pathways because they can cause early or late-onset diarrhea; clinicians may add agents like atropine (for early cholinergic symptoms) or high-dose loperamide protocols for late diarrhea. ^{[14] [15]}

Practical Do’s and Don’ts

• Do: Maintain hydration with clear fluids and oral rehydration/electrolyte solutions as advised. ^{[9] [10]}
• Do: Eat small, frequent meals of low-fiber foods as symptoms improve. ^[9]
• Do: Keep a symptom diary (stool frequency, appearance, triggers) and share with your care team; early reporting helps prevent complications. ^[6]
• Don’t: Ignore red flags like blood in stool, fever, severe or persistent diarrhea, or dizziness; seek prompt medical care. ^{[5] [6] [7] [8]}
• Don’t: Assume all diarrhea is from treatment; infections and other causes need evaluation. ^[4]

Bottom Line

• Diarrhea is not a classic early symptom of stomach cancer, which more commonly presents with nonspecific stomach upset or discomfort. ^[1]
• In people with cancer, diarrhea often stems from treatments, infections, or other conditions, and it requires careful monitoring and timely communication with the care team. ^{[2] [4]}
• Use hydration, dietary adjustments, and clinician-directed medications to manage symptoms, and follow clear thresholds for seeking urgent help. ^{[9] [11] [5] [6] [7] [8] [10] [13]}