Indigestion happens when your stomach struggles to process food comfortably, leading to pain, bloating, burning, or fullness in your upper abdomen. It affects roughly 10% of the global population at any given time, and most cases trace back to a handful of causes: what you eat, medications you take, stress, or how your stomach moves and senses food. Sometimes there’s an identifiable problem like an infection or ulcer. More often, everything looks structurally normal but your digestive system is simply more reactive than average.
What’s Happening Inside Your Stomach
Your stomach is designed to expand when food arrives, churn it with acid, then push it into your small intestine. Indigestion can result from a breakdown at any point in that process. Some people have delayed gastric emptying, meaning food sits in the stomach longer than it should. Others have impaired accommodation, where the stomach doesn’t relax and expand properly after a meal, creating a sensation of uncomfortable fullness even after eating a small amount.
A third mechanism involves heightened sensitivity. Your stomach wall contains nerve endings that signal fullness and pressure to your brain. In some people, these nerves overreact to normal levels of stretching, producing pain, bloating, or nausea at volumes that wouldn’t bother someone else. This visceral hypersensitivity is one of the main drivers of chronic indigestion that has no visible cause on imaging or endoscopy.
Foods and Drinks That Trigger Symptoms
Fatty foods are one of the most common culprits. Fat relaxes the muscular valve between your esophagus and stomach, allowing acid to splash upward. It also slows digestion, so food lingers in your stomach longer. This combination creates the heavy, burning discomfort you feel after a greasy meal.
Alcohol does something similar, relaxing that same valve and giving stomach acid a clear path into your esophagus. Caffeine can trigger symptoms too, especially when you’re consuming it multiple times throughout the day from coffee, tea, chocolate, or energy drinks. Spicy foods, citrus, and carbonated beverages are other frequent offenders, though triggers vary widely from person to person. Paying attention to which foods consistently precede your symptoms is more useful than memorizing a generic list.
Medications That Irritate the Stomach
Over-the-counter pain relievers like ibuprofen, naproxen, and aspirin are a major and underrecognized cause of indigestion. These drugs, collectively called NSAIDs, interfere with the mucus layer that protects your stomach lining from its own acid. They also reduce blood flow to the gut, making the tissue more vulnerable to damage. If you take NSAIDs regularly, even at standard doses, they can cause persistent upper abdominal pain, burning, and nausea.
Antibiotics, iron supplements, and certain blood pressure medications can also irritate the stomach lining. If your indigestion started around the time you began a new medication, that connection is worth exploring.
How Stress Affects Your Digestion
Your brain and gut are in constant two-way communication. Stress, anxiety, and depression don’t just make you more aware of stomach discomfort. They physically change how your digestive system works. Psychological stress can alter the speed of contractions in your gastrointestinal tract, increase acid secretion, and heighten the sensitivity of nerve endings in your stomach wall. Even the thought of eating can trigger your stomach to start producing acid before food arrives.
This is why indigestion often flares during high-pressure periods at work, relationship conflicts, or major life transitions. It’s not “all in your head,” but your head is genuinely part of the equation. People who experience chronic indigestion with no structural cause often see meaningful improvement when they address underlying stress or anxiety.
When an Infection Is the Cause
A bacterium called H. pylori lives in the stomach lining and is one of the most common infections worldwide. It can cause chronic inflammation, ulcers, and persistent indigestion. In studies of people with dyspepsia symptoms, roughly 60 to 73% tested positive for H. pylori across all age groups, compared to about 51% of people without symptoms. The infection is typically diagnosed with a breath test or stool test and treated with a course of antibiotics.
H. pylori doesn’t always cause symptoms. Many people carry it without knowing. But if you have ongoing indigestion that doesn’t respond to dietary changes, testing for this infection is a standard and worthwhile step.
Functional Dyspepsia: When Tests Come Back Normal
If your indigestion has persisted for at least six months, with active symptoms for the past three months, and no structural problem is found on endoscopy or imaging, you may have what’s called functional dyspepsia. The formal criteria require at least one of four symptoms: uncomfortable fullness after meals, feeling full too quickly while eating, upper abdominal pain, or upper abdominal burning.
Functional dyspepsia is not a diagnosis of exclusion that means “we don’t know.” It reflects a real set of problems involving how your stomach moves, senses, and communicates with your brain. Vagal nerve dysfunction, where the nerve that controls stomach relaxation and motility doesn’t work optimally, is one proposed mechanism. Treatment typically involves a combination of dietary adjustments, acid-reducing medications, and sometimes low-dose medications that target nerve sensitivity or gut motility.
Over-the-Counter Treatments Compared
Three main categories of medication address indigestion, and they work differently. Standard antacids neutralize acid that’s already in your stomach. They work within minutes but wear off quickly. They’re best for occasional, mild symptoms.
H2 blockers reduce acid production by blocking histamine signals in the stomach. They start working within one to three hours and last about eight hours. These are a good middle-ground option for people who get indigestion predictably, like after dinner.
Proton pump inhibitors (PPIs) block the acid-producing pumps in your stomach lining directly. They’re the most powerful option, reducing acid output for 15 to 21 hours per day, but they take up to four days to reach full effect. PPIs work best for frequent or severe symptoms but aren’t ideal for quick, occasional relief. Long-term PPI use carries its own considerations, so they’re generally better suited for a defined treatment course rather than indefinite daily use.
Symptoms That Need Prompt Attention
Most indigestion is uncomfortable but not dangerous. Certain symptoms alongside indigestion, however, warrant prompt evaluation with an endoscopy. These include unintentional weight loss of more than 5% of your body weight over 6 to 12 months, difficulty swallowing, pain when swallowing, vomiting that won’t stop, vomiting blood or passing black stools, unexplained iron deficiency anemia, or a family history of upper gastrointestinal cancer. Anyone 60 or older with new or worsening indigestion should also be evaluated with endoscopy, even without these additional warning signs.
If your indigestion is mild, intermittent, and clearly tied to meals or stress, you can reasonably start with dietary changes and over-the-counter treatments. If it’s persistent, worsening, or accompanied by any of those red flags, earlier investigation is the right call.