Is blood in stool a common symptom of stomach cancer?

Blood in the stool can occur with stomach cancer, but it is more commonly seen when the disease is advanced rather than early. ^[1] Stomach cancer symptoms can be subtle at first; later stages may cause black, tarry stools (melena) or visible blood in the stool due to bleeding within the stomach. ^[2] In people undergoing evaluation for suspected stomach cancer, blood in the stool is one of the possible signs along with anemia and fatigue. ^[3]

How stomach cancer leads to blood in stool

• Tumor bleeding: Cancers in the stomach can ulcerate or erode into blood vessels, causing slow or sometimes brisk bleeding that passes through the intestines and appears as black or bloody stools. ^[1] Slow, chronic bleeding may not be obvious and can be detected with stool tests or lead to low red blood cells (anemia). ^[4]
• Advanced disease signs: Vomiting blood and black stools are recognized features when the cancer is more advanced. ^[1] Feeling full quickly, weight loss, and fatigue can accompany bleeding-related anemia. ^[2]

Key point: Black, tarry stool suggests upper digestive tract bleeding, which includes the stomach. ^[5] Bright red blood often points to lower tract sources, but heavy upper bleeding can occasionally present with fresh red blood. ^[6]

Other causes to consider

While stomach cancer can cause bleeding, many other conditions are more common causes:

• Peptic ulcers or gastritis (inflammation/sores in the stomach). ^[7]
• Esophagitis or esophageal varices (vein bleeding in the esophagus). ^[8]
• Lower GI sources like hemorrhoids or colon polyps/cancers for bright red blood. ^[8]

Because causes vary, distinguishing upper versus lower GI bleeding by stool appearance helps guide the next tests. ^[5]

Red‑flag symptoms that need prompt care

• Black, tarry stools or vomiting blood. ^[5]
• Dizziness, weakness, or signs of anemia from ongoing blood loss. ^[4]
• Unexplained weight loss and fatigue in the context of possible stomach cancer. ^[3]

GI bleeding can be urgent, and severe cases may require immediate treatment. ^[9]

How doctors evaluate bleeding when stomach cancer is suspected

• Blood tests: Checking for anemia (low red blood cells) that can result from chronic stomach bleeding. ^[4]
• Stool tests: Fecal occult blood tests can detect hidden blood due to small amounts of bleeding. ^[10]
• Upper endoscopy (EGD): A camera-guided test to directly see the stomach lining, identify bleeding sources, and take biopsies to confirm cancer. ^[11]
• Additional GI bleeding work‑up: Endoscopy is the most used test to localize and treat bleeding in the digestive tract. ^[12] Nasogastric lavage and stool analyses may assist in determining the source. ^[13]

Upper endoscopy with biopsy is the standard to diagnose stomach cancer and locate bleeding sites for potential treatment. ^[11]

Management of blood in stool from stomach cancer

• Stabilization in acute bleeding: Intravenous fluids, blood transfusions, and urgent endoscopy to control bleeding. ^[9]
• Endoscopic hemostasis: Techniques like clipping, cautery, or injection to stop bleeding from a tumor or ulcer. ^[13]
• Treating the cancer: Oncologic treatments (surgery, chemotherapy, radiation) are tailored to stage and can reduce tumor‑related bleeding. ^[4]
• Ongoing care: Monitoring for anemia and repeating endoscopy if bleeding recurs; interventional radiology (embolization) or surgery may be used when endoscopic control is not sufficient. ^[14]

Many bleeding sources can be treated once found, and managing the underlying cancer is central to long‑term control. ^[13]

What you can watch for

• Stool color changes: Black, sticky stools are a warning sign of upper GI bleeding. ^[5]
• Vomiting blood or “coffee‑ground” material. ^[5]
• Fatigue and shortness of breath from anemia due to chronic bleeding. ^[4]

If you notice any of these signs, seeking medical care promptly helps reduce risks and speeds diagnosis and treatment. ^{[9] [13]}

Summary

Blood in the stool can happen with stomach cancer, particularly in advanced stages, and may appear as black, tarry stools due to upper GI bleeding. ^[1] Slow, ongoing bleeding may lead to anemia, often detected with blood or stool tests, while upper endoscopy is the key test to confirm the diagnosis and control bleeding. ^{[4] [11]} Management ranges from urgent stabilization and endoscopic hemostasis to definitive cancer treatments, with many effective options once the bleeding site is identified. ^{[13] [9]}