Stomach pain is one of the most common health complaints, and the causes range from a meal that didn’t sit well to conditions that need medical attention. In 2018, abdominal pain was the single most frequent reason adults visited an emergency department in the United States, accounting for over 6 million treat-and-release visits. Most of the time, though, the cause is far less dramatic than what sends people to the ER.
Where It Hurts Narrows Down the Cause
Your abdomen holds dozens of organs packed into a relatively small space, and pain in different areas points to different problems. Upper right pain often involves the liver, gallbladder, or the upper portion of the pancreas. Upper left pain is more likely tied to the stomach itself, the spleen, or the main body of the pancreas. Lower right pain raises concern for the appendix, while lower left pain commonly involves the lower colon.
Pain that’s hard to pinpoint, or that seems to be everywhere at once, is more typical of gas, bloating, a stomach virus, or stress-related discomfort. The more precisely you can locate the pain, the easier it is to identify what’s going on.
Food Poisoning and Stomach Viruses
Infections are among the most common reasons your stomach hurts suddenly. The two big categories, food poisoning and viral gastroenteritis (stomach flu), feel similar but behave differently.
Food poisoning hits fast. Bacteria that grew in undercooked or improperly stored food typically cause symptoms within two to six hours of eating. You’ll feel nauseous, may vomit or have diarrhea, and the whole episode tends to be relatively brief, often resolving within a day.
A stomach virus, on the other hand, takes longer to show up. The incubation period runs about 24 to 48 hours after exposure, and symptoms generally last around two days, sometimes longer. You catch it the same way you catch a cold: through close contact with other people, not from food. Both can cause intense stomach cramps, but the timeline and source are the key differences.
Food Intolerances and Dietary Triggers
If your stomach hurts repeatedly after eating, a food intolerance is worth considering. Lactose intolerance is the most well-known example. People who don’t produce enough of the enzyme needed to break down lactose, the sugar in milk and dairy, end up with belly pain, gas, bloating, and diarrhea after consuming dairy products.
Histamine sensitivity is another common trigger. Histamines occur naturally in cheese, avocados, bananas, pineapples, chocolate, and red wine. For people who are sensitive to them, these foods can cause abdominal pain and digestive upset that’s easy to mistake for other conditions. Gluten, artificial sweeteners, and certain fermentable carbohydrates (often grouped under the term FODMAPs) are other frequent culprits. Keeping a food diary for a few weeks can help you spot patterns between what you eat and when pain flares up.
Stress and the Gut-Brain Connection
Stress doesn’t just make your stomach feel bad psychologically. It changes how your gut physically works. Your brain and digestive system are in constant two-way communication. When you’re anxious, angry, or under sustained pressure, your brain sends signals that alter the movement and contractions of your intestines. This can speed things up (causing diarrhea) or slow things down (causing constipation and cramping).
There’s also a pain amplification effect. People under chronic stress often perceive gut pain more intensely because their brains become more responsive to pain signals from the digestive tract. The pain is real, not imagined, but it’s being generated or worsened by the nervous system rather than by structural damage to the organs. This is one reason stomach pain sometimes defies easy diagnosis: imaging and lab work come back normal, yet the discomfort persists.
Ulcers and Stomach Lining Damage
Peptic ulcers are open sores that develop on the inner lining of the stomach or the upper part of the small intestine. They cause a burning or gnawing pain in the upper abdomen that often worsens between meals or at night, when the stomach is empty.
Two things cause most ulcers. The first is a bacterium called H. pylori, which survives in stomach acid by producing an enzyme that neutralizes the acid around it. This allows it to burrow into the stomach lining and trigger persistent inflammation. The second is regular use of common pain relievers like ibuprofen and aspirin. These medications suppress a protective mechanism in the stomach lining, leaving it vulnerable to damage from its own acid. If you take over-the-counter anti-inflammatory painkillers frequently and notice a persistent burning in your upper stomach, that connection is worth investigating.
IBS: When Pain Becomes Chronic
Irritable bowel syndrome affects a large portion of the population and is one of the most common reasons for ongoing stomach pain. It’s classified as a syndrome, meaning it’s defined by a pattern of symptoms rather than visible damage to the intestines. Colonoscopies and imaging in people with IBS look normal.
The core issue appears to be a disrupted communication loop between the brain and gut. Nerve endings in the bowel lining become unusually sensitive, and the muscles that move food through the intestines don’t contract in a normal rhythm. Spasms can push stool through too quickly (causing diarrhea) or too slowly (causing constipation as too much water is absorbed). The hallmark of IBS is chronic abdominal pain along with alternating constipation and diarrhea, bloating, gas, and sometimes mucus in the stool.
IBS is different from inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis. IBD causes visible, destructive inflammation in the intestines and can lead to bleeding, anemia, weight loss, and fever. IBS does not cause inflammation, does not increase the risk of colon cancer, and rarely requires hospitalization. The distinction matters because the treatments are very different.
Pancreatitis and Gallbladder Problems
Pain in the upper abdomen that gets worse after eating, especially fatty meals, may point to the gallbladder or pancreas. Gallstones can block the duct that drains the gallbladder, causing sudden, intense pain in the upper right abdomen that can radiate to the back or right shoulder blade. Episodes often last several hours and tend to strike after large or greasy meals.
Acute pancreatitis causes upper abdominal pain that may start mild and escalate to severe and constant. Nausea, fever, and a rapid pulse often accompany it. The pain frequently worsens after eating and can radiate to the back. Both conditions require medical evaluation.
When Stomach Pain Signals an Emergency
Appendicitis follows a recognizable pattern in about half of cases: pain starts near the belly button, then migrates to the lower right abdomen over several hours. The pain worsens with movement, coughing, or deep breathing. Loss of appetite and nausea typically follow. In roughly 80% of adults with appendicitis, symptoms develop and escalate within 48 hours.
Several other situations call for urgent care. Severe pain paired with vomiting so intense you can’t keep liquids down is one. Complete inability to have a bowel movement, especially combined with bloating and a history of abdominal surgery, may indicate a bowel obstruction. Pain that resembles a previous episode but is notably more severe or different in character is another signal to take seriously. Fever, bloody stool, or pain that steadily worsens over hours rather than coming and going all warrant prompt evaluation.