Diagnostic criteria for diabetes, significance of glycated hemoglobin, and intervention for prediabetes.

15. How is diabetes diagnosed?

If you are diagnosed with diabetes, you should go to the hospital to have your blood sugar tested. It is best to test both fasting blood sugar and postprandial blood sugar.

Normal blood glucose levels: fasting blood glucose <6.1 mmol/L; 2-hour postprandial blood glucose <7.8 mmol/L.

Blood glucose levels for diabetes: fasting blood glucose ≥7.0 mmol/L, 2-hour postprandial blood glucose ≥11.1 mmol/L. If either of these values ​​is exceeded, diabetes can be diagnosed. For accuracy, the test can be repeated on another day.

"7" and "11" are two important numbers that are key to diagnosing or monitoring diabetes.

**16. Why is glycated hemoglobin considered the "gold standard" for diagnosing diabetes?**

In recent years, many hospitals have added glycated hemoglobin (HbA₁c) to their blood glucose testing programs.

This is because glucose in the blood can irreversibly bind with hemoglobin in red blood cells to form glycated hemoglobin.

Blood sugar levels fluctuate throughout the day, while glycated hemoglobin levels fluctuate very little.

Red blood cells have a lifespan of 120 days, so measuring glycated hemoglobin levels can accurately reflect a patient's blood sugar levels over the past 2 to 3 months.

The normal range of glycated hemoglobin is 4% to 6%, while it is elevated in diabetic patients.

The general target for glycated hemoglobin is set at <6.5%, but this standard can easily lead to hypoglycemia in the elderly. Therefore, it is recommended that those over 60 years of age adjust the target to <7%.

Although this inspection has advantages, due to limitations in our country, it will take time before this standard can be widely promoted.

**17** What is prediabetes?

Before the onset of type 2 diabetes, when blood sugar levels are already higher than normal but do not yet meet the diagnostic criteria for diabetes, this stage is called prediabetes.

To facilitate the distinction between prediabetes and diabetes in terms of blood glucose levels, two concepts have been proposed: impaired fasting glucose and impaired glucose tolerance.

If fasting blood glucose is between 6.1 and 6.9 mmol/L, it indicates impaired fasting glucose; if postprandial blood glucose is between 7.8 and 11.0 mmol/L, it indicates impaired glucose tolerance.

Impaired fasting glucose and/or impaired glucose tolerance are both prediabetes, which is only one step away from diabetes and is progressing towards the diabetes stage.

There are three possible outcomes for prediabetes: one is that it develops into true diabetes; another is that it remains unchanged; and the third is that it returns to normal.

If left untreated, 30% of people with prediabetes will develop diabetes each year.

If this group of people takes measures such as controlling their diet, increasing exercise, and losing weight, about half of them can return to normal blood sugar levels.

Some people find it difficult to stick to strict diet control, and the effects may not be obvious. In addition to improving unhealthy lifestyle habits, medication can be used to prevent the progression to diabetes. Commonly used medications include acarbose (Glucobay) and metformin.

**Reference range for blood glucose (mmol/L)**

Blood glucose test items: Fasting blood glucose, Normal: 3.9-6.1, Prediabetes: 6.1-7.1, Diabetes: 7.1 or higher.

Blood glucose test results: 2-hour postprandial blood glucose. Normal: 4.4–7.8 mmol/L; Prediabetes: 7.8–11.1 mmol/L; Diabetes: 11.1 mmol/L or higher.

**18. Can a blood glucose meter diagnose diabetes?**

The diagnostic criteria for diabetes must be based on the results measured by a hospital laboratory. Blood glucose levels measured by a glucometer can be used to monitor the condition of diabetes, that is, to understand how well blood glucose is controlled, but cannot be used to diagnose diabetes.

This is because when hospital laboratories test blood sugar, they use plasma with red blood cells and other formed elements removed, while blood glucose meters measure whole blood from capillaries.

Because red blood cells contain less glucose, the results obtained by the two methods will differ to some extent, with blood glucose meter readings generally being about 15% lower.

In addition, blood glucose meters are less accurate than hospital measurements due to the influence of instrument performance, test strip quality, and measurement technology.

Therefore, if you are diagnosed with diabetes, you should go to the hospital for a blood glucose test.

For blood glucose monitoring in diabetic patients, a blood glucose meter is perfectly adequate.