You can get an upset stomach and a bad taste in your mouth if you have eaten something bad, or if you have a stomach virus or reflux. If it is really bad or persists, it may be something else, so get checked out.
While the list below can be considered as a guide to educate yourself about these conditions, this is not a substitute for a diagnosis from a health care provider. There are many other medical conditions that also can be associated with your symptoms and signs. Here are a number of those from MedicineNet:
Indigestion (dyspepsia) can be caused by diseases or conditions that involve the gastrointestinal (GI) tract, and also by some diseases and conditions that do not involve the GI tract. Indigestion can be a chronic condition in which the symptoms fluctuate in frequency and intensity. Signs and symptoms that accompany indigestion include pain in the chest, upper abdominal pain, belching, nausea, bloating, abdominal distention, feeling full after eating only a small portion of food, and rarely, vomiting.
Gastroenteritis (Stomach Flu)
Stomach flu (gastroenteritis) is a term referred used to describe a variety of gastrointestinal problems. The most common signs and symptoms of gastroenteritis are nausea, vomiting, diarrhea, and abdominal pain. The most common cause of gastroenteritis in the United States is Norovirus. Other causes of gastroenteritis include Rotavirus, Astrovirus, Adenovirus, and Sapovirus. There are bacterial causes of gastroenteritis such as Salmonella, Shigella, Campylobacter Aeromonas, E. coli, Clostridium, Vibrio, Campylobacter, and Yersinia spp. Parasites that cause gastroenteritis include Giardia, Cryptosporidium, Cyclospora, and Entamoeba. Treatment for gastroenteritis is generally home remedies such as keeping hydrated to prevent dehydration. At times, hospitalization may be necessary if dehydration occurs.
Food poisoning is common, but can also be life threatening. The symptoms for food poisoning are fever, abdominal pain, headache, diarrhea, nausea and vomiting. Food poisoning has many causes, for example, chemicals (from toxic fish or plants) and bacteria (Staphylococcus aureus or Salmonella). Treatment of food poisoning depends upon the cause.
Irritable Bowel Syndrome (IBS)
Irritable bowel syndrome (IBS) is a GI (gastrointestinal) disorder with signs and symptoms that include abdominal pain, bloating, increased gas (flatulence), abdominal cramping, diarrhea, constipation, and food intolerance.Two new tests are now available that may help diagnose irritable bowel syndrome with diarrhea and constipation (IBS-M) irritable bowel syndrome with diarrhea (IBS-D), and irritable bowel syndrome with constipation (IBS-C). Treatment for IBS includes diet changes, medications, and other lifestyle changes to manage symptoms.
At MedicineNet, we believe it is important to take charge of your health through measures such as a living healthy lifestyle, practicing preventative medicine, following a nutrition plan, and getting regular exercise. Understanding your symptoms and signs and educating yourself about health conditions are also a part of living your healthiest life. The links above will provide you with more detailed information on these medical conditions to help you inform yourself about the causes and available treatments for these conditions.