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Diabetes is a condition where blood glucose levels become too high.

Diabetes is a condition where blood glucose levels become too high.
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Diabetes diagnosis

3-minute read

Diabetes needs to be diagnosed early on so the condition can be controlled and complications avoided.

A blood test is used to diagnose diabetes. Most people with type 1 diabetes and some with type 2 diabetes will develop symptoms such as increased thirst, urination and tiredness. Some people will also find that wounds are slow to heal or that they experience persistent infections. However, many people with type 2 diabetes have no symptoms at all.

During the blood test, blood is taken from a vein and is then sent to a pathology lab for analysis. Tests that might be done include:

  • A fasting sugar (glucose) test: Fasting is required for at least 8 hours, often involving not eating or drinking overnight.
  • A random glucose test, which can be taken at any time during the day.
  • An oral glucose tolerance test (OGTT): The patient, who has already fasted, drinks a sugary drink and then has a blood test done, first one and then 2 hours later. Before the OGTT, the patient needs to eat and drink 150 grams of carbohydrates (found in starchy foods) each day for 3 days. If you need this test, your doctor or the healthcare professional requesting the test can advise on exactly what you need to do.

Another blood test that can be used to diagnose diabetes is the haemoglobin A1c (HbA1c) test, which measures the proportion of haemoglobin protein affected by glucose in circulation in the body.

The HbA1c test provides a particularly useful measurement because it reflects the process of tissue damage that occurs in diabetes.

Video: What is the HbA1c test?

Video provided by Lab Tests Online

Can diabetes be diagnosed with a blood glucose meter or urine test?

A diagnosis of diabetes should not be made using only a blood glucose meter and finger prick, or just a urine glucose test. Although your doctor may take a blood sample with a finger prick during your appointment, you will still need a further blood test to confirm the diagnosis.

How will my doctor know which type of diabetes it is?

Your doctor will ask you about your medical history and the severity of your symptoms, then confirm with further blood tests if they suspect type 1 diabetes. In adults, it is sometimes difficult to distinguish between type 1 and type 2 diabetes.

Several tests, including tests to measure your insulin levels and certain antibodies in the blood, can help your doctor to determine the type of diabetes you might have, but these can take several weeks to confirm.

In the meantime, it is important that you keep in contact with your doctor and monitor your blood glucose levels if instructed to do so. If you are unwell, they may refer you immediately to a hospital or specialist for treatment.

What is pre-diabetes?

Pre-diabetes is a condition in which blood glucose levels are higher than normal, but not high enough to be diagnosed as type 2 diabetes. If your blood test result shows you are in this category, you might have pre-diabetes and your doctor may order a glucose tolerance test.

Pre-diabetes is also referred to as impaired fasting glucose (IFG) or impaired glucose tolerance (IGT) and you may need further blood tests to monitor whether there has been progression onto diabetes at a later date.

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Last reviewed: July 2018

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