Gastroesophageal Reflux Disease (GERD): This is a common condition characterized by stomach acid frequently flowing back into the tube connecting the mouth and stomach (esophagus). The symptoms of GERD, such as epigastric pain and nausea, match the patient's presentation and are prevalent in the general population.

Peptic Ulcer Disease: This condition, which includes gastric and duodenal ulcers, can cause epigastric pain and nausea. The pain is often described as burning and may improve or worsen with eating.
Gastritis: Inflammation of the stomach lining can lead to epigastric pain, nausea, and vomiting. It can be caused by infection, alcohol, or nonsteroidal anti-inflammatory drugs (NSAIDs).
Functional Dyspepsia: Also known as non-ulcer dyspepsia or indigestion, this condition is characterized by recurring signs and symptoms of indigestion that have no obvious cause.

Myocardial Infarction: Although less common, myocardial infarction (heart attack) can present with epigastric pain and nausea, especially in women. It is crucial to consider this diagnosis due to its high mortality rate if missed.
Pancreatitis: Inflammation of the pancreas can cause severe epigastric pain that radiates to the back, nausea, and vomiting. It requires immediate medical attention.
Cholecystitis: Inflammation of the gallbladder, often due to gallstones, can cause right upper quadrant or epigastric pain, nausea, and vomiting.

Zollinger-Ellison Syndrome: A rare disorder characterized by excessive gastric acid production due to a gastrin-secreting tumor, leading to severe peptic ulcers and diarrhea.
Gastric Cancer: Although rare, especially in younger populations, gastric cancer can present with epigastric pain, nausea, and weight loss. It is more common in certain geographic areas and with specific risk factors.
Infectious Causes: Certain infections like Helicobacter pylori can cause gastritis and peptic ulcers, but other less common pathogens might also be considered based on travel history, immune status, and exposure risks.