Fasting blood sugar test

A blood sample is taken after the fasting interval specified by your clinician or laboratory. Water may be allowed, but food, sweet drinks and some medicines can affect preparation, so follow the instructions you receive. The result is interpreted with your symptoms, medical history and sometimes another test rather than in isolation. An unexpected result may lead to repeat testing or assessment for Prediabetes or Type 2 Diabetes. The test does not show every aspect of glucose control, and a Continuous Glucose Monitor serves a different purpose.

Confirm when to stop eating and which drinks are permitted. Tell the testing team about diabetes medicines, insulin, pregnancy, illness and any difficulty completing the fast. Do not skip or double a prescribed medicine unless the clinician has given a clear plan. Bring a list of medicines and note symptoms such as unusual thirst, frequent urination, blurred vision, shakiness or sweating. Eat normally before the instructed cut-off unless your clinician advises otherwise.

Contact a clinician promptly if fasting causes severe shakiness, sweating, confusion, fainting or inability to stay awake, especially if you use glucose-lowering treatment. Seek urgent care for severe confusion, loss of consciousness, difficulty breathing or repeated vomiting. A result outside the expected range is not an emergency by itself, but it should be followed up so the next step is clear. Diabetes Screening can provide broader assessment and education.

How long should I fast, and may I drink water? Should I change any medicine before the test? What follow-up test will clarify an unexpected result? Would Diabetes Medication Management or a Diabetes Education Programme help me understand the plan?