Stomach pain has dozens of possible causes, ranging from trapped gas and indigestion to infections, inflammation, and conditions that need emergency care. The location, timing, and quality of the pain all offer clues about what’s going on. Most episodes are short-lived and linked to something you ate, a virus, or stress, but persistent or severe pain signals something that deserves medical attention.
Why Location Matters
Your abdomen contains organs from multiple body systems packed into a relatively small space, so where you feel pain narrows the list of likely causes considerably. Pain in the upper right side is most commonly linked to the gallbladder (gallstones or inflammation), the liver, or sometimes a kidney stone. Upper left pain points more toward the stomach itself, the pancreas, or the spleen. It can also, in rarer cases, come from the heart.
Lower abdominal pain follows a similar pattern. Pain on the lower right is the classic location for appendicitis, though it can also stem from inflammatory bowel disease, irritable bowel syndrome, or gynecologic conditions like ovarian cysts or ectopic pregnancy. Lower left pain shares many of the same causes but is particularly associated with diverticulitis, a condition where small pouches in the colon wall become inflamed. Pain that sits right in the center of your abdomen, around the belly button, often originates from the intestines or stomach and tends to be vaguer and harder to pinpoint.
Common Everyday Causes
The vast majority of stomach pain episodes come from a handful of familiar culprits. Gas and bloating cause crampy, shifting pain that moves around the abdomen and typically resolves on its own within hours. Eating too quickly, swallowing air, or consuming foods that ferment in the gut (beans, cruciferous vegetables, carbonated drinks) all increase gas production.
Indigestion, also called dyspepsia, produces a burning or gnawing discomfort in the upper abdomen, often after meals. You might feel uncomfortably full before finishing a normal-sized meal, or nauseated afterward. This can be a one-off reaction to rich or spicy food, but when it keeps happening, it sometimes reflects gastritis, which is inflammation of the stomach lining. The most common triggers for gastritis are a bacterial infection called H. pylori and long-term use of over-the-counter painkillers like ibuprofen or aspirin. Alcohol and bile flowing backward from the small intestine can also irritate the lining over time.
Constipation is another frequent cause that people often overlook. When stool builds up in the colon, it creates pressure and cramping that can be felt across the lower abdomen or even higher up. Viral gastroenteritis, the so-called “stomach bug,” causes pain along with nausea, vomiting, and diarrhea that usually clears within one to three days. Food poisoning follows a similar pattern but tends to come on faster, often within hours of eating contaminated food.
IBS vs. Inflammatory Bowel Disease
These two conditions sound alike but work very differently inside the body. Irritable bowel syndrome (IBS) is a functional disorder, meaning the gut looks normal under a scope but doesn’t behave normally. Pain in IBS comes largely from visceral hypersensitivity: the nerves in your gut overreact to stretching, gas, or normal contractions. There’s little or no measurable inflammation, yet the symptoms (cramping, bloating, diarrhea or constipation) can be severe.
Inflammatory bowel disease (IBD), which includes Crohn’s disease and ulcerative colitis, involves ongoing, measurable inflammation that damages the intestinal lining. A stool test measuring a protein called calprotectin can help distinguish the two. Levels below 40 micrograms per gram generally rule out significant inflammation, while levels above 100 suggest IBD. The gray zone between 40 and 100 is harder to interpret and may require further testing. One important nuance: people with IBD in remission can develop IBS-like symptoms driven by nerve sensitivity rather than active inflammation, which means the two conditions sometimes overlap in the same person.
Pain That Comes From Outside the Abdomen
Not all stomach pain starts in the stomach. Your body’s nerve wiring can route pain signals from distant organs into the abdomen, a phenomenon called referred pain. A heart attack, particularly in women, can present as upper abdominal discomfort rather than classic chest pain. Pneumonia in the lower lobes of the lungs sometimes causes upper abdominal pain that feels like a stomach problem. Kidney stones typically produce flank pain that radiates into the lower abdomen and groin.
Even the diaphragm, the muscle separating your chest from your abdomen, can create confusing signals. When the underside of the diaphragm is irritated (by blood, infection, or air after surgery), the pain can show up in the shoulder or collarbone area rather than the belly. This wiring quirk exists because the nerve supplying the diaphragm originates from the same spinal level as the nerves that supply the shoulder skin.
How the Pain Feels Offers Clues
The character of abdominal pain tells you something about which tissues are involved. Deep, dull, hard-to-locate pain that makes you restless and unable to sit still usually comes from the organs themselves. This is called visceral pain, and it tends to sit in the midline of the abdomen because the organs’ nerve supply runs to both sides of the spinal cord equally. Gallbladder colic, early appendicitis, and intestinal cramping all start this way.
Sharp, well-localized pain that gets worse with movement, coughing, or being jostled is a different signal. It means the lining of the abdominal cavity (the peritoneum) is irritated, and it’s typically lateralized to one side. People with this type of pain instinctively lie still, often curled up with knees drawn toward the chest. If someone in this position experiences a spike in pain when a car hits a bump or when the bed is shifted, that’s a hallmark of peritonitis, inflammation of the abdominal lining that usually requires urgent care.
Causes That Need Emergency Attention
Certain patterns of abdominal pain require same-day evaluation or a trip to the emergency room. Appendicitis classically begins as vague pain around the belly button, then migrates to the lower right within 12 to 24 hours, becoming sharp and constant. Gallbladder inflammation (acute cholecystitis) produces severe right upper quadrant pain lasting more than four to six hours, often with fever. Diverticulitis causes left lower quadrant pain with localized tenderness and sometimes fever.
More dangerous conditions include a perforated organ, where stomach acid or intestinal contents leak into the abdominal cavity, and mesenteric ischemia, where blood flow to the intestines is cut off. Both produce severe pain that’s often out of proportion to what a physical exam reveals.
Red flags that suggest a serious cause include:
- Rigid abdomen that feels board-like and is painful to touch
- Blood in vomit or stool, including dark, tarry stools
- Fever with localized pain, especially in the upper right or lower quadrants
- Pain that worsens with any movement, including coughing or being bumped
- Fainting, rapid heartbeat, or signs of shock
- Jaundice (yellowing of the skin or eyes) alongside abdominal pain
What Happens During Evaluation
When abdominal pain is persistent or severe enough to warrant medical evaluation, the process is fairly standard. A physical exam follows a specific sequence: visual inspection first (looking for distension, discoloration, or visible bulges), then listening to the abdomen with a stethoscope before any pressing. Listening comes before pressing because pushing on the belly can alter bowel sounds and muddy the findings. Normal bowel sounds occur five to 35 times per minute. Absent sounds raise concern for serious conditions like blocked or dying bowel.
Imaging often follows the physical exam. Ultrasound and CT scans are the two main tools. For suspected appendicitis, CT is significantly more sensitive than ultrasound (94% vs. 76%), making it the preferred choice in adults. For gallbladder inflammation, both perform equally well at about 73% sensitivity, so ultrasound is often tried first since it’s faster, cheaper, and doesn’t involve radiation. For conditions like diverticulitis, CT again outperforms ultrasound (81% vs. 61%).
Chronic vs. Acute Pain
Pain that comes and goes or persists for three months or longer meets the clinical definition of chronic abdominal pain. The causes shift away from emergencies and toward conditions like IBS, food intolerances (lactose and fructose being the most common), chronic gastritis, endometriosis, and functional abdominal pain, where the nervous system amplifies pain signals without any visible damage to the organs.
Acute pain, by contrast, develops over hours to days and is more likely to have a specific structural cause: an inflamed appendix, a gallstone blocking a duct, a bowel obstruction, or an infection. The distinction matters because the workup and urgency are very different. Chronic pain generally calls for methodical testing and dietary or lifestyle changes, while acute pain may need imaging and intervention the same day.