There are three blood tests to diagnose Type 2 diabetes. Each one has its pros and cons. For example, one frequently used test is Hemoglobin A1C. While this test is more convenient but it may miss the diagnosis of Type 2 diabetes in its early stages. In fact, it important to diagnose Type 2 diabetes early. Why? Because Type 2 diabetes is a disease of complications. It usually does not cause any symptoms for a long time. But during this period, complications are developing.
As an example, in an excellent study, researchers tested 245 patients for the presence of carotid artery disease and diabetes. A whopping 72% of Type 2 diabetic patients were found to have plaque in their carotid arteries. Surprisingly, these patients had no symptoms from their carotid artery disease. In addition, they did not even know if they had diabetes.1
Blood Tests To Diagnose Type 2 Diabetes
Following are the tests to diagnose diabetes:
1. Fasting Blood Glucose
You go to laboratory after an overnight fast for a blood draw. Usually it is part of a metabolic panel test.
Results of the Fasting Blood Test :
- A Fasting Blood Glucose greater than 125 mg/dl means you have diabetes.
- Fasting Blood Glucose between 100 mg/dl to 125 mg/dl, means you have Prediabetes (Impaired Fasting Glucose.)
Note: You need further testing with an Oral Glucose Tolerance Test if you have Pre-diabetes.
2. HBA1C (Hemoglobin A1c)
Hemoglobin A1c is another blood test for the diagnosis of diabetes. HBA1C (Hemoglobin A1 C) above 6.5% means you have diabetes.
3. Oral Glucose Tolerance Test (OGTT)
Oral Glucose Tolerance Test (OGTT) is the best test for the diagnosis of type 2 diabetes in its early stages. After an overnight fast, a blood test is drawn for glucose. Then, you drink 75 grams of glucose. Subsequently, two more blood tests are drawn: at one hour and at two hours after the drink. You do not eat or drink anything else during this two hour period.
Results of Oral Glucose Tolerance test:
- If Blood Glucose at 2-Hour is greater than 200 mg/dl, you have diabetes.
- 2-Hour Glucose level between 140 mg/dl and 200 mg/dl implies you have Prediabetes (Impaired Glucose Tolerance.)
- A level between 100 mg/dl and 140 mg/dl indicates you have mild Glucose Intolerance, a stage even before Prediabetes.
In normal people, the value should come back to near baseline after 2 hours. For example, if your fasting blood glucose was 95 mg/dl, then two hours after drinking the 75 grams of glucose, it should come back to about 95 mg/dl.
The 2-hour Oral Glucose Tolerance Test (OGTT) has been the international standard for the diagnosis of type 2 diabetes for a long time. Most scientific studies about diabetes utilize it as THE diagnostic test.
Several excellent scientific studies have demonstrated that the Oral Glucose Tolerance Test is a superior test for the diagnosis of type 2 diabetes as compared to the fasting blood glucose test or hemoglobin A1c ( HBA1C). This observation is in line with our clinical experience at the Jamila Diabetes And Endocrine Medical Center.
Which Is The Best Test To Diagnose Diabetes
Oral Glucose Test is the best test to diagnose diabetes, especially in its early stages. On the other hand, HbA1c is a convenient but lazy way to diagnose diabetes. I have found a lot of individuals who have the diagnosis of diabetes based on fasting blood glucose and/or Glucose Tolerance Test, but their HBA1C was still not in the range of diabetes. My findings are consistent with other researchers. For example, researchers from China investigated 1416 subjects for the diagnosis of diabetes. They checked HbA1C in these individuals and also gave them Glucose Tolerance Test. When compared to Glucose Tolerance Test, HbA1C diagnosed diabetes in only 42% of the diabetic patients. In other words, researchers would have missed the diagnosis of Type 2 diabetes in 58% of the cases if they were to rely on HbA1C alone.2
Conversion of Glucose units from mmol/L to mg/dl
Please pay attention to the units in which your blood glucose is reported by the laboratory. In the U.S.A., blood glucose is reported as mg/dl. But in many parts of the world, it is reported as mmol/L.
The conversion factor from mmol/L to mg/dl is 18. For example:
1 mmol/L = 18 mg/dl
7 mmol/L = 126 mg/dl
7.8 mmol/L =140 mg/dl
11.1 mmol/L = 200 mg/dl
For more details about Type 2 diabetes, please refer to my book, “Reverse Your Type 2 Diabetes Scientifically.”