Skipping meals, frequent vomiting, or showing discomfort after eating might seem like minor stomach issues. But in some cases, these subtle changes can point to something much more serious—stomach cancer. The most common forms, such as gastric adenocarcinoma and lymphoma, are aggressive diseases. Recognizing the signs early gives your dog the best chance at treatment success and a better quality of life.
Stomach cancer occurs when abnormal cells in the lining of the stomach grow uncontrollably and form tumors. These growths may cause internal bleeding, block digestion, and sometimes spread to organs like the liver or lymph nodes. Though relatively rare, it is a life-threatening condition most often diagnosed in middle-aged or senior dogs.
Because the early symptoms mimic routine digestive upsets, it’s important for owners to watch for patterns that persist. Below are ten warning signs that should not be overlooked:
If your dog refuses food for several days in a row—even favorite meals or treats—it could indicate more than just fussiness. Stomach cancer–related appetite loss usually doesn’t improve with changes in food or feeding schedule.
A rapid drop in body weight of 10% or more is a red flag. You may notice more prominent ribs or hips and reduced muscle mass around the back legs.
Throwing up multiple times a week, especially long after meals, is concerning. Vomit that contains blood (bright red or coffee-ground–like) signals internal bleeding and requires urgent care.
Dogs may take on a “prayer position,” move stiffly, or avoid being touched on the stomach if in pain. These behaviors may start mild but usually worsen over time.
Dark, sticky stools with a metallic smell are often caused by bleeding in the upper digestive system. Taking a photo can help your veterinarian assess the severity.
If food comes back up shortly after eating or your dog repeatedly adjusts their neck to swallow, a tumor may be blocking the passageway between the esophagus and stomach.
Excessive sleep, avoiding walks, or tiring quickly are signs that your dog is not feeling well. Compare current activity levels to your pet’s usual routine to spot changes.