Nausea can have countless causes.

Food poisoning, viral infections, medications, pregnancy, migraine, reflux, anxiety, and many gastrointestinal conditions can all produce nausea.

Stomach cancer can also cause nausea in some people, particularly when the tumor affects normal stomach function or causes obstruction.

That does not mean that recurring nausea automatically indicates cancer.

However, persistent nausea without an obvious explanation—especially when accompanied by vomiting, weight loss, abdominal pain, or difficulty eating—should be evaluated.

6. Vomiting

Vomiting can occur for many reasons, most of which are unrelated to cancer.

But persistent or recurrent vomiting is a symptom that should receive medical attention.

In some cases of stomach cancer, a tumor can interfere with the movement of food through the digestive tract.

If vomiting becomes frequent or makes it difficult to keep food or fluids down, medical evaluation is particularly important.

Vomiting blood is even more concerning and requires prompt medical attention.

Blood in vomit may appear bright red or resemble dark coffee grounds.

7. Abdominal Pain or Discomfort

Pain in the upper abdomen can have many causes.

It may be related to:

• gastritis,
• ulcers,
• reflux,
• gallbladder problems,
• pancreatic disorders,
• infections,
• or other gastrointestinal conditions.

Stomach cancer can also cause abdominal discomfort or pain.

The characteristics of the pain matter.

Pain that is persistent, progressively worsening, repeatedly returns without an obvious explanation, or occurs together with other warning signs should be discussed with a doctor.

Severe or sudden abdominal pain requires prompt medical evaluation regardless of the suspected cause.

8. Difficulty Swallowing

Difficulty swallowing is known medically as dysphagia.

Although it is not a symptom of every stomach cancer, it can occur when cancer develops near the upper part of the stomach or the area where the esophagus meets the stomach.

A person may feel as though food is getting stuck or having difficulty moving downward.

Difficulty swallowing can also be caused by many other conditions, including esophageal disorders, reflux-related narrowing, neurological conditions, and other structural problems.

Nevertheless, new or progressive difficulty swallowing should not be ignored.

9. Black or Tarry Stools

Bleeding somewhere in the upper digestive tract can sometimes cause stools to become black and tar-like, a condition known as melena.

Stomach cancer can cause gastrointestinal bleeding, although many other conditions can do the same.

Ulcers are a common example.

Certain foods, supplements, and medications can also alter stool color.

But genuinely black, tarry, sticky stools—particularly when accompanied by weakness, dizziness, abdominal pain, or vomiting blood—require prompt medical evaluation.

Significant gastrointestinal bleeding can become an emergency.

10. Anemia and Unusual Fatigue

Stomach bleeding may sometimes occur slowly and remain unnoticed.

Over time, chronic blood loss can contribute to iron-deficiency anemia.

Anemia can cause symptoms such as:

• unusual tiredness,
• weakness,
• shortness of breath with activity,
• dizziness,
• headaches,
• or reduced exercise tolerance.

Iron-deficiency anemia has many possible causes.

For example, dietary deficiency, menstrual blood loss, ulcers, intestinal disorders, and other bleeding sources can all contribute.

In some adults, unexplained iron-deficiency anemia warrants investigation for gastrointestinal blood loss.

It should not automatically be attributed to stomach cancer—but it should not be ignored either.

11. Bloating or a Feeling of Pressure

Persistent bloating may be another symptom.

Some people describe a sensation of pressure, fullness, or swelling after meals.

Bloating is extremely common and can be caused by dietary factors, constipation, food intolerances, irritable bowel syndrome, reflux, and many other conditions.