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If you have diabetes, it's important to get it diagnosed. So if you have been feeling very hungry or thirsty and losing weight for no reason, see your doctor.

Don't ignore diabetes symptoms. It's important to diagnose diabetes quickly so that you can start treatment and stay as healthy as possible. Mostly, symptoms of type 1 diabetes start in childhood. For more information, see What are the symptoms of type 1 diabetes?

Your doctor will ask you about your symptoms. And he or she will use a blood test to measure how much glucose is in your blood. In the past, doctors always did another test, called an oral glucose tolerance test (OGTT for short), to see if people had diabetes. But now, most people don't need this test.¹

This is a blood test you have first thing in the morning, before you've had breakfast. When you don't eat, it is called fasting. So doctors call this test a fasting plasma glucose test.

The result is called your fasting plasma glucose level. If your level is 126 mg/dL or higher, you could have diabetes. (The mg/dL stands for milligrams per deciliter.) You'll need to have this test a second time to be sure.¹

Your doctor might talk about this level using just the number. For example, your doctor might say, "Your blood glucose is 126."

This is a test of your blood glucose that can be done at any time of the day. The result is called your random blood glucose level. If your level is 200 mg/dL or higher, you could have diabetes. You'll need to have one of the other two tests shown here to be sure.¹

You have this test first thing in the morning, before you eat. First, your doctor measures how much glucose is in your blood (your fasting plasma glucose level). Then you drink a very sugary liquid.

Two hours later, the level of glucose in your blood is measured again. This is called your two-hour plasma glucose level. If your level is at least 200 mg/dL, you could have diabetes. You'll need to have this test a second time to be sure.¹

This information is for educational use only, and is not a substitute for prompt professional medical advice. Readers should always consult a physician or other professional for advice and treatment. ©BMJ Publishing Group Limited 2008. All rights reserved.