Patients with the syndrome have a history of days to weeks of thirst, polyuria and, frequently in the background, a condition such as stroke or renal insufficiency. Weight loss, weakness, visual disturbances and leg cramps are common symptoms. The physical examination demonstrates profound dehydration, poor tissue turgor, soft, sunken eyeballs, cool extremities and, at times, a rapid thready pulse. On presentation, these patients have glucosuria and minimal or no ketonuria or ketonemia. Mild metabolic acidosis with an increased anion gap is present in up to one half of patients with hyperosmolar hyperglycemic syndrome.

Nausea, vomiting and abdominal pain occur less frequently in pataients with hyperosmolar hyperglycemia than in those with diabetic ketoacidosis. Occasionally, patients with the syndrome have constipation and anorexia. Gastric stasis and ileus occur less often than in patients with classic diabetic ketoacidosis.

Abdominal pain or tenderness, nausea and vomiting, lack of bowel sounds and ileus in patients with uncontrolled diabetes may obscure intra-abdominal pathologic processes that require urgent attention. Therefore, historical information and response to therapy are of critical importance. The development of findings secondary to uncontrolled diabetes follows the onset of symptoms rather than precedes it, and the symptoms usually improve markedly following the infusion of fluids and insulin.

Fatty infiltration of the liver, associated with abnormal liver function tests, may be another cause of abdominal pain and tenderness in patients with uncontrolled diabetes. Liver function tests are abnormal in up to one third of patients with uncontrolled diabetes.