The clinical significance of hypoglycemia is important to understand as there are many etiologies and, if not treated, can have devastating consequences, such as coma or even death. Etiologies range from tumors to iatrogenic hypoglycemia, from postprandial hypoglycemia to renal failure. The majority of those who are at risk of getting hypoglycemia are patients treated with insulin or insulin secretion stimulating drugs. However, there are many other causes of hypoglycemia, but the most of them are rare. To diagnose hypoglycemia, Whipple’s triad must be met: symptoms of hypoglycemia, low blood glucose measured at the time of symptoms and relief of symptoms after the blood glucose level is corrected. The cases discussed in this thesis will explore a more common cause of hypoglycemia, sulfonylurea induced (iatrogenic), and a rare cause, insulinoma. In the first case, an elderly patient with renal insufficiency developed hypoglycemia due to the use of glimepiride, a second generation sulfonylurea. By simply taking the medicine out of her regimen the patient did not experience any further hypoglycemic attacks. In the second case, a middle aged woman presented with episodes of lightheadedness and tremors for years with occasional loss of consciousness and weight. These attacks happened at any time, even during fasting, and were relieved by a sweet drink. These signs and symptoms lead to the suspicion of an insulinoma, which was later confirmed with laboratory testing and diagnostic imaging. The tumor was resected, and since, the patient has not had any further hypoglycemic attacks.