Constant stomach pain is most often caused by a functional gut disorder, meaning your digestive system is sending pain signals even though there’s no visible damage. About 90% of people with chronic abdominal pain fall into this category. The remaining 10% have a structural or inflammatory condition like an ulcer, gallstones, or inflammatory bowel disease. Both types are real, both are treatable, and figuring out which one you’re dealing with starts with paying attention to a few key details.
The Most Common Cause: Your Gut-Brain Connection
Irritable bowel syndrome is the single most common reason for ongoing stomach pain. It’s diagnosed when you’ve had recurring abdominal pain at least one day per week for three months, and the pain is linked to changes in how often you go to the bathroom or what your stool looks like. IBS isn’t dangerous, but it can be genuinely miserable to live with.
Functional dyspepsia is another major one, especially if your pain sits in the upper middle part of your abdomen. You might feel uncomfortably full after eating, bloated, or have a burning sensation. Up to 85% of people who get scoped for these symptoms have completely normal-looking stomachs, which can feel frustrating but is actually an important clue. It means the problem is in how your gut processes and communicates sensations, not in tissue damage.
What ties these conditions together is something called visceral hypersensitivity. Your internal organs have their own network of nerves, and in some people, those nerves develop a lower threshold for pain. Normal things like gas moving through your intestines, food stretching your stomach walls, or fluid shifting around start registering as painful when they shouldn’t. This often develops after a triggering event: a bad stomach infection, a course of antibiotics, a period of intense emotional stress, or even food poisoning. The original problem resolves, but the nerves stay dialed up. Physical pain and emotional stress reinforce each other through shared brain pathways, which is why anxiety and gut symptoms so often travel together. This isn’t “all in your head.” It’s a measurable change in how your nervous system processes signals from your organs.
Where It Hurts Matters
The location of your pain narrows the list of possible causes significantly. Here’s a rough guide to what lives where:
- Upper right side: Gallbladder problems (gallstones, inflammation), liver issues, or sometimes even a lung condition like pneumonia that refers pain downward.
- Upper left side: Gastritis, stomach ulcers, pancreatitis. Rarely, heart-related pain can show up here, particularly if it comes with shortness of breath or chest tightness.
- Upper middle (just below the ribs): Acid reflux, peptic ulcers, gallbladder disease, pancreatitis, or functional dyspepsia.
- Around the belly button: Early appendicitis, small bowel problems, or ulcer-related pain.
- Lower right side: Appendicitis, IBS, inflammatory bowel disease (especially Crohn’s), ovarian cysts, or endometriosis.
- Lower left side: Diverticulitis (more common over age 40), IBS, inflammatory bowel disease, ovarian or uterine conditions.
- Low and central: Bladder infections, IBS, gynecologic conditions including fibroids and endometriosis.
Pain that moves around or doesn’t sit in one reliable spot is more typical of IBS, food intolerances, or stress-related gut dysfunction. Pain that’s always in the same place, especially if it’s getting worse over time, deserves closer investigation.
Food-Related Causes
Lactose intolerance is extremely common worldwide and easy to overlook because symptoms can be mild for years before becoming more noticeable. Fructose intolerance and sensitivity to FODMAPs (a group of fermentable carbohydrates found in wheat, onions, garlic, beans, and many fruits) can also drive constant bloating and pain. These don’t damage your gut, but they pull water into your intestines and feed bacteria that produce gas, creating distension and discomfort.
Celiac disease is less common but frequently missed. It’s an autoimmune reaction to gluten that damages the lining of the small intestine, and its symptoms range from classic diarrhea and weight loss to vague, persistent stomach pain with fatigue and no obvious digestive complaints. The presentation varies so widely that clinical suspicion is often the key to catching it. A simple blood test is the standard first step for screening, and if it’s positive, a biopsy during an upper endoscopy confirms the diagnosis. If you’ve had unexplained stomach pain for months and nobody has checked for celiac disease, it’s worth asking about.
Interestingly, research has found low-grade inflammation in the upper small intestine in over 40% of people with functional dyspepsia. Stress, food sensitivities, smoking, infections, and acid exposure can all change the permeability of the intestinal lining, which may explain why some people develop persistent pain after what seemed like a minor gut issue.
Structural and Inflammatory Conditions
About 1 in 10 people with chronic abdominal pain have something physically identifiable causing it. The most common structural causes include peptic ulcers (sores in the stomach or upper intestine, usually from H. pylori bacteria or long-term use of anti-inflammatory painkillers), gallstones, chronic pancreatitis, and inflammatory bowel diseases like Crohn’s disease or ulcerative colitis.
Endometriosis deserves special mention for anyone with a uterus. It causes tissue similar to the uterine lining to grow in other areas of the pelvis and abdomen, and it frequently presents as chronic lower abdominal pain that may or may not track with menstrual cycles. It’s often misdiagnosed as IBS for years before being identified.
Less commonly, chronic abdominal pain can stem from kidney stones that partially obstruct a ureter, adhesions from previous abdominal surgery, or hernias. Heavy cannabis use can also cause a specific pattern called cannabinoid hyperemesis syndrome, with cycles of nausea, vomiting, and abdominal pain that improve with hot showers and resolve when cannabis use stops.
How Doctors Figure Out the Cause
There’s no single test for chronic stomach pain. Instead, your doctor works through a process of elimination based on your symptoms, pain location, and risk factors. The typical starting point is blood work: a complete blood count to check for anemia or signs of infection, kidney and liver function panels, and often a celiac screening test. A stool test can detect hidden blood, signs of inflammation, or evidence of infections and food intolerances.
If initial tests don’t point to a clear answer, imaging and scoping come next. An upper endoscopy lets a doctor visually examine your esophagus, stomach, and the first part of your small intestine, checking for ulcers, inflammation, or anything unusual. A colonoscopy examines the large intestine and is especially relevant for lower abdominal pain or any changes in bowel habits. A CT scan of the abdomen provides a detailed picture of organs that scopes can’t reach, like the pancreas, kidneys, and deeper portions of the bowel.
For harder-to-reach areas, there are specialized tools. Capsule endoscopy involves swallowing a pill-sized camera that photographs the entire length of your small intestine as it passes through. It’s particularly useful for detecting Crohn’s disease or small bowel bleeding that other tests miss.
If all of these come back normal, that’s not a dead end. It usually points toward a functional disorder like IBS or functional dyspepsia, which are diagnosed based on your symptom pattern rather than a lab result.
Symptoms That Need Urgent Attention
Most chronic stomach pain isn’t an emergency, but certain symptoms alongside it change the picture. Vomiting blood, black or bloody stool, blood in your urine, a swollen and tender abdomen, high fever, persistent vomiting that won’t stop, or pain accompanied by dizziness and shortness of breath all warrant immediate medical evaluation. Unintentional weight loss paired with ongoing abdominal pain is another signal that something beyond a functional disorder may be happening. Pain that started after an accident or injury should also be assessed promptly, even if it seems mild at first.