Diabetes Diagnosis
Testing For Diabetes

Diabetes Diagnostic Criteria


How Is Diabetes Diagnosed?


How Is Diabetes Diagnosed?
What Is The Criteria For Diagnosis?
What Is The A1C Test?

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This article covers the diagnosis of type 1 and 2 diabetes. The diagnosis of gestational diabetes is dealt with separately.

How Is Diabetes Diagnosed?

Initially your doctor may perform a urine analysis to check for signs of high blood sugar. To do this, you will need to provide a urine sample, into which the doctor will stick a specially coated strip or dipstick. The dipstick changes color according to the level of blood sugar present. The results are instantaneous. However, this test alone is not enough to make a diabetes diagnosis. For a clinical diagnosis, one or more of the following tests must be carried out:

Fasting Plasma Glucose (FPG) Test: This is a blood test which measures your blood glucose levels after you have fasted for at least 8 hours. It is used to detect diabetes and pre-diabetes. Results will show:
Healthy blood glucose: FPG under 100
Prediabetes: FPG 100 - 125
Diabetes: FPG more than 125

Random Plasma Glucose Test: This is a blood test taken randomly whether or not you have eaten. It is normally recommended if the FPG test is positive (to double-check). A blood glucose level of 200 mg/DL or higher, plus the presence of the following signs of diabetes - increased urination, unexplained weight loss and increased thirst - can mean the patient has diabetes.

Oral Glucose Tolerance Test (OGTT): Yet another blood test that measures glucose levels - but with this one first you need to fast for 8 hours, then drink a glucose beverage and wait for a further 2 hours before being tested. This test might be performed if the fasting or random test is not conclusive.
Healthy blood glucose: Under 139 mg/dL
Prediabetes: 140-199 mg/dL
Diabetes: 200 mg/dL and above.

What Is The Criteria For Diagnosis?

The standard definition of diabetes is too much, or excessive glucose in a blood sample. But over the years doctors and authorities have disagreed about what is considered 'excessive'. In 1997 they lowered the blood-glucose levels necessary to be diagnosed with diabetes because too many people were suffering diabetic complications, even though there were not diagnosed with the disease under the then-current standards. In 2003 the threshold was lowered again. Subsequently the World Health Organization (WHO) and the American Diabetes Association have agreed the following standard criteria:

Diabetes will be diagnosed if the person has:

• FPG more than 125 mg/dl (7 mmol/l)*
• 2-h PG** 200 mg/dl or more (11.1 mmol/l)

* In the United States measurements are given as mg/dl (millimoles per liter), but in the UK and most of Europe they are stated as mmol/l. To translate a mmol/l measurement into mg/dl, simply multiply it by 18.
**This refers to plasma glucose (PG) levels which are tested 2 hours after drinking a glucose drink (the OGTT test).

The WHO recommends that if a patient's blood glucose levels appear high on a first test, but they are not displaying symptoms of diabetes, then they should not be diagnosed on one test alone. Most patients will start with an FPG test, and then progress to either the oral or random plasma test.

What Is The A1C Test?

This is a newer test to the market, which only requires a pin-prick of blood to test for signs of diabetes (and no fasting is required). Also called the hemoglobin A1c test and HbA1 test, it can check a person's average blood sugar levels over the previous 3 months. Although some doctors still prefer to use the traditional tests outlined above, since 2009, a panel of international experts agreed that the A1C test is accurate enough to help diagnose both type 1 diabetes and type 2 diabetes (but not gestational diabetes). It is hoped that the convenience of the test will help more people check for prediabetes. Additionally the American Diabetes Association recommends that people who are receiving diabetes treatment should have an A1C test twice a year to check that they are managing their blood glucose levels correctly (see diabetes tests). Tests are sold for this purpose over the counter in pharmacies; brand names include A1C Now Self-Check by Bayer which costs around $30.

See also our article on the causes of diabetes and a
re there any home tests for diabetes?

  Related Articles on Diabetes

For more related conditions, see the following:

Blood Glucose Monitoring
Diabetes Facts: Learn about the statistics
Diabetes Resources - Check out our list of websites and resources.

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