Tests to diagnose diabetes

image_3_240x240sep03Out of the estimated 24 million people with diabetes, one third, or eight million, don’t know they have the disease. According to Martin J. Abrahamson, M.D., Medical Director and Senior Vice President at Joslin Diabetes Center, this is because people with type 2 diabetes often have no symptoms. However, a simple blood test is all you need to find out if you are one the millions with untreated diabetes.

Who should be tested?
The American Diabetes Association (ADA) recommends that everyone aged 45 and over should be tested for diabetes, and if the results are normal, re-tested every three years. Testing should be conducted at earlier ages and carried out more frequently in individuals who have any of the following diabetes risk factors:

  • You have a parent or sibling with diabetes
  • You are overweight (BMI higher than 25)
  • You are a member of a high-risk ethnic population (African American, Hispanic American, Native American, Asian American or Pacific Islander)
  • You had gestational diabetes or a baby weighing over 9 pounds
  • Your HDL cholesterol levels are 35 mg/dl or less, and/or your triglyceride level is 250 mg/dl or above
  • You have high blood pressure
  • You have polycystic ovarian syndrome
  • On previous testing, had impaired glucose tolerance or impaired fasting tolerance

What tests are used for diagnosis?

  • Fasting Plasma Glucose: This blood test is taken in the morning, on an empty stomach. A level of 126 mg/dl or above, on more than one occasion, indicates diabetes.
  • Casual or Random Glucose: This blood test can be taken anytime during the day, without fasting. A glucose level of 200 mg/dl and above may suggest diabetes.

If any of these test results show signs of diabetes, testing should be repeated on a different day to confirm the diagnosis. If a casual plasma glucose equal to 200 mg/dl or above is detected, the confirming test used should be a fasting plasma glucose or an oral glucose tolerance test.

Diagnosing Diabetes and Learning About Prediabetes
There are several ways to diagnose diabetes. Each way usually needs to be repeated on a second day to diagnose diabetes.

Testing should be carried out in a health care setting (such as your doctor’s office or a lab). If your doctor determines that your blood glucose level is very high, or if you have classic symptoms of high blood glucose in addition to one positive test, your doctor may not require a second test to diagnose diabetes.

diabetes 1

A1C
The A1C test measures your average blood glucose for the past 2 to 3 months. The advantages of being diagnosed this way are that you don’t have to fast or drink anything.

Diabetes is diagnosed at an A1C of greater than or equal to 6.5%

Result A1C
Normal less than 5.7%
Prediabetes 5.7% to 6.4%
 Diabetes 6.5% or higher

 

Fasting Plasma Glucose (FPG)
This test checks your fasting blood glucose levels. Fasting means after not having anything to eat or drink (except water) for at least 8 hours before the test. This test is usually done first thing in the morning, before breakfast.

Diabetes is diagnosed at fasting blood glucose of greater than or equal to 126 mg/dl

Result Fasting Plasma Glucose (FPG)
Normal less than 100 mg/dl
Prediabetes 100 mg/dl to 125 mg/dl
Diabetes 126 mg/dl or higher

 

Oral Glucose Tolerance Test (also called the OGTT)
The OGTT is a two-hour test that checks your blood glucose levels before and 2 hours after you drink a special sweet drink. It tells the doctor how your body processes glucose.

Diabetes is diagnosed at 2 hour blood glucose of greater than or equal to 200 mg/dl

Result  Oral Glucose Tolerance Test (OGTT)
Normal  less than 140 mg/dl
Prediabetes  140 mg/dl to 199 mg/dl
Diabetes  200 mg/dl or higher

Random (also called Casual) Plasma Glucose Test
This test is a blood check at any time of the day when you have severe diabetes symptoms.
Diabetes is diagnosed at blood glucose of greater than or equal to 200 mg/dl

What is Prediabetes?
Before people develop type 2 diabetes, they almost always have “prediabetes” — blood glucose levels that are higher than normal but not yet high enough to be diagnosed as diabetes.

Doctors sometimes refer to prediabetes as impaired glucose tolerance (IGT) or impaired fasting glucose (IFG), depending on what test was used when it was detected. This condition puts you at a higher risk for developing type 2 diabetes and cardiovascular disease.

If you have prediabetes, you should be checked for type 2 diabetes every one to two years.

Results indicating prediabetes are:

  • An A1C of 5.7% – 6.4%
  • Fasting blood glucose of 100 – 125 mg/dl
  • An OGTT 2 hour blood glucose of 140 mg/dl – 199 mg/dl

Preventing Type 2 Diabetes
You will not develop type 2 diabetes automatically if you have prediabetes. For some people with prediabetes, early treatment can actually return blood glucose levels to the normal range.

Research shows that you can lower your risk for type 2 diabetes by 58% by:

  • Losing 7% of your body weight (or 15 pounds if you weigh 200 pounds)
  • Exercising moderately (such as brisk walking) 30 minutes a day, five days a week

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Dr. Rajiv Kovil
Consultant Diabetologist, Dr. Kovil’s Diabetes Care Centre

Dr. Rajiv Kovil is a Consultant Diabetologist at Dr. Kovil’s Diabetes Care Centre, the first Preventive Diabetes Centre & Diabetic Foot Clinic in Mumbai, KLS Memorial Hospital and Holy Spirit Hospital among others. He is a founder member of United Diabetes Forum, a forum of practising diabetologists in India. He has also written various articles on diabetes for medical journals such as Asian Journal of Diabetology and Medical Image. His Preventive Diabetes Centre & Diabetic Foot Clinic is an initiative to provide preventive diabetic measures as well as to function as a specialized Foot Clinic for diabetic patients not only in terms of equipment but more importantly in terms of expertise.

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