Stomach aches have dozens of possible causes, ranging from something as simple as eating too fast to conditions that need medical attention. Most episodes are short-lived and tied to food, stress, or a mild infection. But when pain is persistent, severe, or accompanied by other symptoms, the location and quality of the pain can reveal a lot about what’s going on. Roughly 8 to 10 percent of adults worldwide deal with recurring upper abdominal discomfort that has no clear structural explanation, a condition called functional dyspepsia, which gives you a sense of just how common stomach pain is.
Acid Reflux and Stomach Irritation
The most frequent causes of pain in the upper stomach area, around and above the belly button, involve acid. Your stomach produces acid to digest food, and a ring of muscle at the top of the stomach (the lower esophageal sphincter) normally keeps that acid contained. When this muscle weakens or relaxes too often, acid escapes upward into the esophagus, causing the burning and aching of acid reflux. Occasional reflux is normal. When it becomes chronic, it’s called GERD.
Several things can weaken that muscle over time. Smoking relaxes it directly and also triggers coughing that forces it open repeatedly. Obesity and pregnancy both increase pressure inside the abdomen, pushing stomach contents upward. A hiatal hernia, where the top of the stomach slides up through the diaphragm, traps acid and pulls the sphincter out of position. Even certain foods relax the muscle in higher doses: chocolate, coffee, alcohol, mint, garlic, onions, and fatty foods are common culprits. Fatty foods also take longer to digest, giving acid more time to splash back up.
When the stomach lining itself becomes inflamed (gastritis) or develops an open sore (a peptic ulcer), pain tends to sit in the upper middle abdomen and can feel like a burning ache. These conditions are often caused by overuse of anti-inflammatory painkillers like ibuprofen or by a bacterial infection called H. pylori, which spreads through contaminated food, water, or contact with an infected person’s bodily fluids. A hallmark clue: H. pylori pain typically feels worse on an empty stomach.
Food Intolerances and Dietary Triggers
If your stomach ache reliably shows up after eating certain foods, an intolerance is a likely explanation. Lactose intolerance (from dairy) and fructose intolerance (from fruit sugars and many processed foods) are among the most common. The mechanism is straightforward: your body lacks the enzyme to break down that particular sugar in the small intestine, so it passes undigested into the colon. Bacteria there ferment it, producing gas. The undigested sugar also draws water into the colon through osmosis. The combination of excess gas and fluid causes bloating, cramping, pain, and often diarrhea.
These reactions can be hard to pin down because they’re dose-dependent. You might tolerate a small amount of milk but feel miserable after a large glass. Keeping a food diary for a few weeks, noting what you ate and when symptoms appeared, is one of the most practical ways to identify a pattern before pursuing formal testing.
Infections That Target the Gut
Viral gastroenteritis, often called a “stomach bug,” is one of the most common acute causes of stomach pain. Norovirus is the usual suspect in adults, spreading rapidly through contaminated surfaces, food, and close contact. The pain comes on suddenly and is typically accompanied by nausea, vomiting, and diarrhea. Most cases resolve on their own within one to three days, though dehydration is the main risk, especially in children and older adults.
Bacterial infections from contaminated food (Salmonella, E. coli, Campylobacter) follow a similar pattern but may produce more severe symptoms, including bloody diarrhea and higher fevers. Food poisoning from bacterial toxins tends to hit faster, sometimes within hours of eating, while infections that require bacteria to multiply in your gut may take a day or two to develop.
IBS and Inflammatory Bowel Disease
Irritable bowel syndrome (IBS) is a chronic condition defined by recurring abdominal pain that’s linked to changes in bowel habits. The diagnostic threshold is at least 12 weeks of abdominal discomfort over a 12-month period, along with at least two of the following: pain that improves after a bowel movement, a change in how often you go, or a change in the consistency of your stool. Symptoms often flare after large meals or during periods of stress. Crucially, IBS doesn’t cause visible damage to the intestines. Scopes and imaging come back normal.
Inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis, is fundamentally different. IBD involves destructive inflammation that can be seen on imaging and during colonoscopy, and it can permanently damage the intestines. If your abdominal pain comes with bleeding, unintentional weight loss, anemia, or fevers, those are hallmarks of IBD rather than IBS.
How Stress Causes Real Stomach Pain
Stress-related stomach aches aren’t imaginary. Your gut and brain are in constant two-way communication through a network of nerves, hormones, and immune signals. When you’re under chronic stress, your body releases cortisol and other stress hormones that directly alter how your digestive system works. Stress changes how fast (or slow) food moves through your gut, makes the intestinal lining more permeable, and, perhaps most importantly, amplifies how your nervous system interprets sensations from your digestive tract.
That last point matters a lot. Pain-sensing nerve endings run through every layer of your gut wall, and they respond to stretching, acidity, and chemicals released by immune cells. Under chronic stress, these nerves become hypersensitive, a phenomenon called visceral hypersensitivity. Normal amounts of gas or digestive movement that you’d never notice in a calm state can register as pain. This is a major driver of symptoms in people with IBS and functional dyspepsia, and it explains why managing stress often improves gut symptoms even when nothing about the gut itself has changed.
Where It Hurts Can Tell You Why
The location of abdominal pain is one of the most useful clues to its cause, because different organs send pain signals to predictable areas.
- Upper middle (epigastric): Acid reflux, gastritis, peptic ulcers, and pancreatitis. Pancreatic pain often radiates to the back. A heart attack can also present as upper abdominal pain, especially in women and older adults.
- Upper right: Gallbladder problems are the most common cause, including gallstones and gallbladder inflammation. Liver conditions can also produce pain here.
- Upper left: Less common, but can involve the spleen or the tail of the pancreas.
- Lower right: Appendicitis is the classic concern. The pain often starts vaguely around the belly button and then migrates to the lower right over several hours.
- Lower left: Diverticulitis, an inflammation of small pouches in the colon wall, is the most common cause of acute lower-left abdominal pain in adults over 50.
- Lower abdomen generally: Urinary tract infections, kidney stones, and in women, ovarian cysts or other reproductive conditions.
Pain that’s hard to pinpoint or that seems to move around is more typical of functional conditions like IBS, gas, or viral infections affecting the whole gut.
Causes That Aren’t Digestive at All
Some stomach aches originate entirely outside the digestive system. The heart and gut share overlapping nerve pathways, which is why a heart attack can present as nausea, vomiting, and upper abdominal pain rather than chest pain. This is more common in women, people with diabetes, and older adults. Heart failure can also cause right upper quadrant pain by backing up fluid into the liver.
Kidney infections and kidney stones frequently cause abdominal pain, usually on one side and often radiating to the back or groin. Urinary tract infections can produce lower abdominal cramping. In women, ectopic pregnancy and ovarian torsion are serious causes of sudden lower abdominal pain that require emergency treatment. In men, testicular torsion can refer pain to the lower abdomen.
Signs That Stomach Pain Needs Urgent Attention
Most stomach aches pass on their own or respond to simple measures like avoiding trigger foods, staying hydrated, and resting. But certain patterns signal something more serious. Sudden, severe pain that doesn’t let up is different from a dull ache that comes and goes. Pain that worsens with movement or when you press on your abdomen and release (rebound tenderness) can indicate inflammation of the abdominal lining. A rigid, board-like abdomen is an emergency sign.
Other warning signals include vomiting blood or material that looks like coffee grounds, black or tarry stools (which indicate bleeding higher in the digestive tract), high fever alongside abdominal pain, significant unintentional weight loss, and pain accompanied by an inability to keep any fluids down. Abdominal pain with chest pressure, jaw pain, or shortness of breath warrants immediate evaluation for a cardiac cause, regardless of your age.