Besides, heartburn or acid indigestion, if untreated, may put you at risk for serious illness, including narrowing of the esophagus, internal bleeding and cancer. The following guide to common symptoms will help you determine whether yours deserve more serious attention.

Acid Reflux. Most people feel heartburn as an uncomfortable sensation of heat, fullness or pressure behind the breastbone or even the back-all caused by the backflow of stomach material, usually containing acid (and sometimes remnants of your last meal) into the swallowing tube, or esophagus. This acid backflow, called gastroesophageal reflux disease (GERD), damages the lining of the esophagus. It doesn’t always cause heartburn, but acid reflux can provoke sore throats, bad breath and a sour taste. It can also irritate the sinuses or gums and cause excessive burping. Stomach contents may trickle into the voice box, causing hoarseness or even an asthma attack.

GERD occurs when the muscular valve, or sphincter, between the stomach and esophagus doesn’t work properly. Normally this valve fits snugly within an opening in the diaphragm where the esophagus joins the stomach. The sphincter opens only to admit food, otherwise staying closed to prevent stomach contents from sloshing into the esophagus.

But increased pressure in the stomach-due to such things as excessive weight, tight clothing, lying down within two hours of eating, carbonated drinks and eating large meals-can overwhelm this valve. Other factors also contribute to reflux problems: consumption of greasy, fatty and fried foods, chocolate, mints, alcohol, coffee (including decaf) and other caffeinated beverages, citrus juices, tomato products, foods prepared with hot pepper, and smoking.

Untreated GERD can lead to thick scars, called strictures, which narrow the esophagus, making swallowing difficult. It can also lead to esophageal ulcers, which may bleed.

Cancer Increase. A more feared complication is esophageal cancer. Since the 1970s there has been a fivefold increase in the esophageal cancer known as adenocarcinoma, which is not clearly associated with alcohol or tobacco.

Among white males, the incidence of this formerly rare tumor has risen more rapidly than any other cancer. Possible factors cited for this rise include reflux caused by an epidemic of obesity, increased dietary fat and the reflux-producing effects of some new medicines. The most common symptoms include the seeming tendency of food to “hang up” painlessly in the chest before reaching the stomach, unexplained weight loss and frequent regurgitation of undigested food.

Chronic damage by acid can also transform the cells lining the esophagus so that they resemble cells normally found in the small intestine. This condition, known as Barrett’s esophagus, leads to adenocarcinoma in 10 percent of patients, making it critically important to identify. Everyone who has chronic reflux, difficulty swallowing or abdominal pain should have an endoscopy, a procedure in which a gastroenterologist inspects the stomach, esophagus and duodenum, and can painlessly sample abnormal tissue. Once identified, doctors can then sample Barrett’s tissue every two years in order to recommend curative surgery if the cells start changing into cancer.

Danger Signs. Certain “alarm symptoms” demand prompt investigation. These include black stools (a sign of serious internal bleeding), difficulty swallowing, unexplained weight loss, inability to eat a complete meal without feeling overly full, or recurrent vomiting. Using endoscopy, doctors can diagnose and treat conditions such as bleeding ulcers and esophageal strictures.

Ulcer pain may be remarkably similar to that of GERD. Usually felt in the upper abdomen, especially between meals and in the wee hours of the morning, when the stomach is most acidic, the discomfort may be gnawing or burning. Severe ulcer disease can lead to massive internal hemorrhage or perforation of the stomach or intestine. As with GERD, ulcer pain is generally assuaged with acid-reducing drugs-but the causes are radically different.

Don’t Blame Stress. A bacteria found the world over causes about 90 percent of ulcers in the duodenum and over 70 percent of gastric ulcers. (Surprisingly, even some doctors don’t know this.) Most people acquire the infection in early childhood by consuming water or food contaminated with this bacteria, Helicobacter pylori.

H. pylori is as common as cavities, but only a minority of those infected ever develop ulcers. A simple blood test detects antibodies to H. pylori, and more than 85 percent of patients can be cured with antibiotics and acid-suppressing medication. However, if you don’t have an ulcer, you might not want to eliminate this microbe, because researchers recently reported that it seemed to protect against a type of esophageal cancer.

Other Culprits. The bulk of the ulcers not related to H. pylori are caused by drugs like aspirin, ibuprofen and naproxen, part of a larger group known as nonsteroidal anti-inflammatory drugs (NSAIDs). Prescribed by the millions and available over the counter, these drugs block the action of an enzyme that the stomach and intestine need for protection against acid. Older people are much more likely to develop ulcers when taking these drugs. (Taking them on a full stomach does nothing to prevent ulcers, despite persistent folklore.)

New Drugs. Two new prescription pain relievers, however, do allow the protective “good” enzymes to form normally. These revolutionary new NSAIDs—celecoxib and rofecoxib—are thus much less likely to create upset stomachs and ulcers. Other new drugs-cimetidine, ranitidine, famotidine and nizatadine-actually reduce acid production. Safe and effective, and available without prescription, they work best in double the amount recommended on the label. Many gastroenterologists now use more powerful acid suppressors known as proton pump inhibitors, or PPIs. For most GERD patients, these medications—omeprazole, lansoprazole, rabeprazole and pantoprazole—are the miracle drugs of the 20th century. Taken once a day, they virtually shut down acid production, eliminating symptoms and healing ulcers, and esophagitis without affecting digestion.

New “Procedures.” Another approach for GERD is to repair the defective valve using laparoscopy-a safe and effective “mini-surgical” technique. Even less invasive techniques aimed at reducing acid reflux are currently being tested.

A simple talk with your doctor can relieve your pain and may save you from major health complications. Why wait?

Dr. Kummer, in private practice of gastroenterology and internal medicine, is also associate chief, Gastroenterology Section, NYU Downtown Hospital, and clinical assistant professor at New York University School of Medicine.