Doctors diagnose hypoglycemia using a medical history, physical examination, and tests to check the blood sugar level.

Generally, you are diagnosed with hypoglycemia if you have a low blood sugar level and symptoms that go away after you have taken glucose to restore your blood sugar level.¹

Medical history

Your doctor will ask questions about:

• What symptoms you experience-how long they last, when they occur, how often they occur, and what happens to your symptoms when you eat something.
• Past medical treatments, any current medical conditions, and whether you are taking medicines (bring all medicines-both prescription and nonprescription-to your appointment for review) or receiving other treatment.
• Diet and nutrition, such as what and when you eat, and whether you have had recent changes in your eating or bowel habits.
• Whether you have gained or lost weight recently.

Because an episode of hypoglycemia can impair mental functioning, your doctor may also want to talk to friends or relatives who have seen your symptoms.

Physical examination

Your doctor also will look for conditions that may cause hypoglycemia, including signs of:

• Liver disease, such as an enlarged liver.
• Kidney disease, such as swelling (edema), and too much urea in the blood.
• Malnutrition, such as extreme weight loss.
• Adrenal gland disease, such as too much pigment (color) in the skin and/or low blood pressure.

Primary laboratory tests

Often hypoglycemia is a complication of diabetes treatment. If you are not being treated for diabetes or another obvious cause of low blood sugar, you will have laboratory tests to confirm hypoglycemia. Ideally, your doctor would like to do these tests when you are experiencing symptoms. But because this is usually not possible, you probably will have tests that attempt to reproduce symptoms. These tests are usually done in a clinic or a hospital.

In some cases, home glucose monitors, which are often used by people who have diabetes, may be used to evaluate possible hypoglycemia. But a low blood sugar reading needs to be confirmed by these formal laboratory tests:

• Overnight fast. You will be asked not to eat overnight, and you will have your blood sugar and insulin levels checked the following morning. In many cases, this test will tell your doctor if you have fasting hypoglycemia.
• Prolonged supervised fast. The primary test for hypoglycemia is a prolonged (48- to 72-hour) supervised fast. You will be asked to fast until the symptoms of moderate low blood sugar develop, or until blood glucose levels drop below 45 mg/dL. If at the end of 72 hours you do not have low blood sugar, you may be asked to exercise for 30 minutes. This test also can help determine why confirmed hypoglycemia is occurring.

During the prolonged supervised fast test, your blood is drawn at regular intervals to monitor how well your body controls blood sugar levels. Various laboratory tests measure substances in the blood, such as glucose, insulin, and C-peptide.

Other tests