Unintentional weight loss can be caused by depression, cancer, chronic infections and illnesses, drugs and drug abuse, and stress, according to MedlinePlus. It can also be caused by digestive issues such as diarrhea, parasites and infections of the pancreas, eating disorders, undiagnosed diabetes or a malfunctioning thyroid gland.
Unintentional weight loss that is more than 5 percent of total body weight or more than 10 pounds over a 6 to 12 month period is a cause for concern, according MedlinePlus. There are many possible causes of unintentional weight loss, and a health care provider will administer a physical exam that includes questions about diet, hunger, exercise and mood, as well as amount of urination and thirst, incidence of fainting and what medications are being taken.
According to the Mayo Clinic, tests for Addison's disease, celiac disease, diabetes, thyroid function, tuberculosis and HIV may be given to determine the proper course of treatment. Depending on the results of the tests, a health care provider may come up with a diet plan, write a referral to a dietician, prescribe medication or recommend over-the-counter medications. In situations of extreme weight loss, patients may be administered food through a feeding tube, according to Healthline.