It's important to diagnose diabetes as early as possible, so that treatment can be started.

If you experience the symptoms of diabetes, you should visit your GP as soon as possible. They'll ask about your symptoms and may request a urine and blood test.

Urine and blood tests

Your urine sample will be tested to see whether it contains glucose. Urine doesn't usually contain glucose, but if you have diabetes, some glucose can overflow through the kidneys and into the urine. Your urine may also be tested for ketones (chemicals) that indicate type 1 diabetes.

If your urine contains glucose, a blood test can be used to confirm the diagnosis of diabetes. A sample of your blood will be taken in the morning, before you've had anything to eat, and it will be tested to measure your blood glucose levels.

If your blood glucose levels aren't high enough for your GP to diagnose diabetes, you may need to have an oral glucose tolerance test (OGTT), which is also sometimes referred to as a glucose tolerance test (GTT).

After drinking a glucose drink, samples of your blood will be taken every half an hour, for two hours. The samples will be tested to find out how your body is dealing with the glucose.

Glycated haemoglobin (HbA1c)

The glycated haemoglobin (HbA1c) test is another blood test that can be used to diagnose diabetes.

In people who've already been diagnosed with diabetes, the HbA1c test is often used to show how well their diabetes is being controlled.

The HbA1c test gives your average blood glucose level over the previous two to three months. The results can indicate whether the measures you're taking to control your diabetes are working.

Antibody tests

There are blood tests for specific antibodies that can identify type 1 diabetes.

If you've been diagnosed with diabetes, it's recommended that you have your HbA1c measured at least twice a year. However, you may need to have your HbA1c measured more frequently if:

• you've recently been diagnosed with diabetes
• your blood glucose remains too high
• your treatment plan has been changed

Unlike other tests, such as the GTT, the HbA1c test can be carried out at any time of day and doesn't require any special preparation, such as fasting. However, it's less reliable in certain situations, such as during pregnancy.

The advantages associated with the HbA1c test make it the preferred method of assessing how well blood glucose levels are being controlled in a person with diabetes.

HbA1c is also increasingly being used as a diagnostic test for type 2 diabetes, and as a screening test for people at high risk of diabetes.