Diabetes, type 2 - Diagnosis 

Diagnosing type 2 diabetes 

It is important for diabetes to be diagnosed early so treatment can be started as soon as possible.

If you experience the symptoms of diabetes, visit your GP as soon as possible. They will ask about your symptoms and may request urine and blood tests.

Urine and blood tests

Your urine sample will be tested for glucose. Urine doesn't usually contain glucose, but if you have diabetes, glucose can overflow through the kidneys and into your urine.

If your urine contains glucose, a specialised blood test called a glucose tolerance test (see below) can be used to determine whether you have diabetes.

Glucose tolerance test

A glucose tolerance test (GTT), also sometimes known as an oral glucose tolerance test (OGTT), can show whether your body is having problems processing glucose.

Prior to having the test, you will be asked not to eat or drink certain fluids for 8-12 hours. You may also need to avoid taking certain medications before the test because they may affect the results. You will be advised about this.

Before the test, a blood sample is taken so your blood glucose can be measured. You will then be given a sweet glucose drink.

After drinking the glucose drink, your blood glucose will be measured again after two hours. As you'll have a long time to wait between blood tests, it's a good idea to take something to read or listen to.

Test results

After your glucose tolerance test is complete it should be possible to determine whether you have impaired glucose tolerance (IGT) or diabetes, based on the amount of glucose in your blood both before and after drinking the glucose drink.

Blood glucose is measured in millimoles per litre, often written as mmol/l.

For someone without diabetes, the amount of glucose in their blood should be:

  • less than 6 mmol/l before the test
  • less than 7.8 mmol/l two hours after the test

If you have IGT, the amount of glucose in your blood will be:

  • 6-7 mmol/l before the test
  • 7.9-11 mmol/l two hours after the test

If you have diabetes, the amount of glucose in your blood will be:

  • more than 7 mmol/l before the test
  • more than 11 mmol/l two hours after the test

If your test results indicate you have IGT, you may be advised to make lifestyle changes. Medication to lower your blood glucose level may also be recommended.

If your results indicate you have diabetes, medication will probably be prescribed to lower your blood glucose level and help keep it under control.

Read more about treating type 2 diabetes.

Page last reviewed: 24/07/2012

Next review due: 24/07/2014


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The 3 comments posted are personal views. Any information they give has not been checked and may not be accurate.

HowtoTestforDiabetes said on 15 February 2013

Make sure you really avoid drinks/food before the test as it will skew the results. The sweet drink was awful by the way..ugh! Thanks ted - http://HowtotestforDiabetes.com

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TigerPaw2011 said on 22 March 2011

I'm stumped. My test came back clear, yet I have pretty much all of the symptoms listed above. Is it back to square one, or could I still have diabetes but it just didn't show in the results on that day? It was a non-fasting test, by the way.

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Rainbow6 said on 07 March 2011

It would be helpful to explain how Diabetes is actually diagnosed. There is obviously confusion as some patients comments have referred to full-blown type 2 as opposed to borderline results. What are the result levels for normal, impaired results and actual Diabetes? Are these different for NHS than other countries? Have these changed in recent years and why? I am unclear if there is a link in the progress of this condition. There seems to be very little information on this metabolic condition with the same old links to obesity, age, and lifestyle.

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