Over the past decade, several laboratory tests have been introduced to veterinary medicine that allow the minimally invasive assessment of diseases of the gastrointestinal tract, liver, and pancreas. Although some of those tests have limited clinical use in a practice setting and have more use as research tools, other tests, such as serum cobalamin and folate concentrations, find wide application in everyday veterinary practice. In some cases, definitive diagnosis requires invasive or expensive procedures, but these new laboratory tests have greatly aided veterinarians in diagnosing gastrointestinal diseases. This discussion provides an overview of new diagnostic tests that will allow the minimally invasive assessment of gastrointestinal function.