What's the matter with high blood sugar and normal glycated hemoglobin?

Some patients have high blood sugar levels but normal glycosylated hemoglobin. From a medical point of view, this data is mismatched. One possibility is that there is an error in the blood sugar measurement, and another possibility is that the glycated hemoglobin and blood sugar do not match.

(1) Blood glucose measurement and its error

①Due to reasons such as instrument aging, maintenance and measurement methods, the blood sugar results measured by the blood glucose meter may not be accurate. Once the data measured by the blood glucose meter is inaccurate, the results of glycated hemoglobin will naturally not match the results of blood glucose.

② In order to detect whether there is a problem with your blood glucose meter, you often use your own blood glucose meter and other blood glucose meters to measure your blood glucose respectively, and then compare the measured blood glucose values.

③The best way to determine whether there is a problem with the blood glucose meter is to draw blood and send it to the laboratory for testing using a large biochemical analyzer while measuring blood sugar with the blood glucose meter. But it is worth noting that blood sugar testing with a biochemical analyzer must be done in a timely manner, otherwise the blood sugar value obtained will be low due to the effect of glycolysis.

④ Since the blood glucose meter measures the blood glucose level in capillary blood and the biochemical analyzer measures the blood glucose level in venous blood, the error between the two is small when fasting, but the error is slightly larger after a meal.

⑤ It is generally believed that as long as the error between the blood sugar value measured by the blood sugar meter and the blood sugar value measured by the biochemical analyzer does not exceed 15%, the blood sugar value measured by the blood sugar meter is considered accurate.

⑥ Some blood glucose meters are equipped with standard solution. The range of glucose in the standard solution is marked on the bottle label, which is convenient for verifying whether the measured value of the blood glucose meter is correct.

(2) Mismatch between glycosylated hemoglobin and blood sugar

① Glycated hemoglobin reflects the average blood sugar level over the past 2 to 3 consecutive months. When blood sugar fluctuations only occur in fasting blood sugar in the morning, and blood sugar control is ideal at other time periods, glycated hemoglobin may be normal. The two are not contradictory.

②The blood sugar value measured by the blood sugar meter only reflects the blood sugar value at a certain point in the day (such as before meals, after meals or before going to bed). A high blood sugar value detected once or in one day is only a part of 2 to 3 months. If the blood sugar level in the remaining period is normal or low, the average blood sugar level may still be normal.

In other words, unless you monitor your blood sugar continuously for 24 hours a day, you can't truly know the changes in your blood sugar during the day. Otherwise, even if blood sugar is monitored most of the day, there may be many periods of high blood sugar or prolonged hypoglycemia (without the patient's awareness) that go undetected, resulting in the average blood sugar (i.e., glycated hemoglobin) not matching the blood sugar value measured at a certain time or time.

③If both hypoglycemia and hyperglycemia occur frequently, it is entirely possible that glycosylated hemoglobin is maintained within the normal range. In this case, glycated hemoglobin cannot reflect the true blood sugar changes.