Do you know the “gold standard” for blood sugar monitoring?

Author: Hou Jiayi, Deputy Chief Technician, Shanxi Provincial Hospital of Traditional Chinese Medicine

Reviewer: Li Ning, deputy chief physician, Shanxi Provincial People's Hospital

Diabetic patients need to control their blood sugar. Long-term stable blood sugar can avoid chronic complications of diabetes. Glycated hemoglobin is the "gold standard" for long-term blood sugar stability. This is a very useful indicator for "diabetics". So what is glycated hemoglobin? How to use glycated hemoglobin? Let's introduce it from 5 aspects.

1. What is glycosylated hemoglobin?

We know that the red blood cells in human blood contain hemoglobin, which is commonly known as hemoglobin. When glucose in the blood comes into contact with hemoglobin, the two will cross-link together to form glycated hemoglobin, also known as glycosylated hemoglobin. When the concentration of glucose in the blood is high, the content of glycated hemoglobin formed by the human body is relatively high. This glycation reaction is slow, continuous and irreversible. The level of glycated hemoglobin depends on the blood sugar concentration and the time that blood sugar comes into contact with hemoglobin, but it has nothing to do with factors such as when the blood is drawn, whether the patient is fasting, and whether insulin is used.

Figure 1 Glycated hemoglobin blood collection tube

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2. Why is glycated hemoglobin an indicator of good blood sugar control?

Glycated hemoglobin reflects the average blood sugar level of diabetic patients in the past 2 to 3 months. The average lifespan of human red blood cells is 120 days. Before the death of human red blood cells, the content of glycated hemoglobin in the blood will remain relatively unchanged. Therefore, the content of glycated hemoglobin in the blood changes every 120 days. Any situation that shortens the lifespan of red blood cells can reduce the measured value of glycated hemoglobin. Due to different physiological conditions of different people, there are some differences in the lifespan of red blood cells, which is not exactly 120 days. Therefore, glycated hemoglobin reflects the average blood sugar level of diabetic patients in the past 2 to 3 months.

3. Is it true that the lower the glycated hemoglobin, the better?

The results of glycosylated hemoglobin test are expressed as a percentage. The glycosylated hemoglobin level of non-diabetic patients is 4% to 6%. However, the lower the glycosylated hemoglobin, the better. This perception is inaccurate. Diabetes treatment emphasizes the principle of individualization, and the control standard of glycosylated hemoglobin varies from person to person. Sometimes, for those with severe conditions, blindly pursuing a low glycosylated hemoglobin value is not worth the loss.

4. Glycated hemoglobin and blood glucose monitoring, is it enough to measure only one?

In general, the changing trends of blood sugar and glycosylated hemoglobin are consistent, but sometimes the changes between the two are inconsistent. For example, in the case of fulminant type 1 diabetes, glycosylated hemoglobin may not keep up with the speed of acute blood sugar changes, and therefore cannot reflect the true average blood sugar level. Glycated hemoglobin and self-blood sugar monitoring are not mutually exclusive, but complementary. Both have their own advantages and disadvantages for blood sugar management in diabetic patients. Compared with random blood sugar, the test value of glycosylated hemoglobin is not affected by temporary accidental factors and has nothing to do with whether the patient is fasting when blood is collected, so it is more stable. Blood sugar can reflect the immediate situation.

5. How often should glycosylated hemoglobin be measured?

If the blood sugar control of diabetic patients has reached the standard and the blood sugar control state is relatively stable, they should undergo glycosylated hemoglobin testing at least twice a year, and they can do blood sugar monitoring at home on weekdays; for those diabetic patients who need to change their treatment plan or whose blood sugar control state is unstable, they should undergo glycosylated hemoglobin testing once every 3 months. In order to obtain accurate results and the frequency of annual testing is not high, it is recommended that "diabetics" go to the hospital for glycosylated hemoglobin testing.

Figure 2 Instruments used in hospitals to detect glycosylated hemoglobin

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