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Blood glucose monitoring is an important part of day-to-day management for patients with diabetes. Among the many indicators, glycated hemoglobin is regarded as the "gold standard" for glucose control.

It can reflect the patient's average blood glucose level over the past 2–3 months and is not affected by immediate factors such as the time of blood draw, fasting status, or medication use. Nonetheless, many patients still have considerable misunderstandings about this key indicator.

01 Confusion about the standard

4%～5.9%

Many patients believe that the closer the glycated hemoglobin value is to the normal range (usually 4%–5.9%), the better. This view overlooks the core principle of diabetes care—individualization.

Glycemic targets need to be formulated comprehensively based on factors such as patient age, disease duration, presence of complications, and risk of hypoglycemia. For example, for elderly patients with long disease duration, severe cardiovascular disease, or frequent hypoglycemia.

Pursuing overly strict low values may instead greatly increase the risk of severe hypoglycemia, which is counterproductive. Individualized control targets should be determined under the guidance of a professional physician.

02 Differences in monitoring

Some patients believe that since there is the "stable" metric of glycated hemoglobin, frequent daily fingertip blood glucose monitoring is less important. This is a common misconception.

The relationship between glycated hemoglobin and blood glucose monitoring is similar to that between a "semester final grade" and "daily quizzes." The former reflects long-term, average control but cannot reveal the detailed day-to-day fluctuations in blood glucose.

The latter can immediately reflect blood glucose changes before and after meals and before and after exercise, helping to identify the specific effects of food, medication, and activity on blood glucose. The two are complementary, not mutually substitutive.

Only by using them together can you both grasp overall trends and finely manage daily fluctuations, achieving comprehensive, stable glycemic control.

03 Limits of stability

Although HbA1c is renowned for its stability, it is not absolutely reliable. In certain special circumstances it may be “distorted” and fail to accurately reflect the true average blood glucose level.

The most typical situation is when blood glucose changes dramatically over a short period, for example in “fulminant type 1 diabetes,” where glucose spikes sharply while red blood cell lifespan is about 120 days.

The rate of change of HbA1c is far too slow to keep up with acute changes in blood glucose, so its value will be relatively low and cannot truly represent extremely high glucose states.

In addition, a variety of disease states can also interfere with test results. Iron deficiency anemia, alcohol abuse, and hypertriglyceridemia may cause falsely elevated results. Hemolytic anemia, mid-to-late pregnancy (increased blood volume), chronic renal failure, blood loss, or hemoglobinopathies may cause falsely lowered results.

04 Convenience of Testing

A common misconception is that testing for glycated hemoglobin requires fasting in the same way as measuring fasting blood glucose. In fact, because it measures the proportion of hemoglobin in red blood cells that is bound to glucose,

this binding process is slow and irreversible, so the test result is not affected by short-term diet. Patients can have blood drawn for testing at any time, whether fasting or postprandial, which is very convenient.

However, as mentioned in the third misconception, if a patient is known to have any of the above anemias or hemoglobin abnormalities that can affect test results, they should proactively inform their physician.

In such cases, it is usually recommended to comprehensively assess glycemic control by combining blood glucose with glycated serum albumin (reflecting blood glucose levels over the past 2–3 weeks) and other indicators.

05 Frequency Rules

As the "gold standard," should it be tested frequently to closely monitor changes? The answer is no. Excessively frequent testing not only increases economic burden but is also unnecessary.

Because its value reflects long-term trends, it will not undergo large short-term fluctuations. Chinese and international mainstream guidelines recommend: for patients with stable and controlled glycemia, testing twice a year is sufficient.

For patients who undergo major adjustments to therapy, or whose glycemic control is not at target, testing once every 3 months (i.e., quarterly) is a reasonable frequency, which helps assess the effect of the new treatment plan.

A baseline test is essential for patients newly diagnosed with diabetes.

That seemingly ordinary percentage on the lab report contains all the information about the patient’s diet, exercise, medication use, and even lifestyle over the past two to three months. It is not a simple number; it reflects every moment the patient restrained their diet, every day they persisted with exercise, and every time they took medication as prescribed.

Only by understanding it scientifically and avoiding common misconceptions can this “golden ruler” be used effectively.