Chief picked up a lab report in the consultation room and said to the patient opposite him, “Look, this marker is like your ‘report card’ for blood glucose over the past three months — it does not lie.”

Huang Xinwen is an associate chief physician at Lanzhou Ruijing Diabetes Hospital. Every day he faces the question diabetes patients care about most: “Doctor, how well is my blood glucose controlled?” In his consultation room there is always a mirror, and he often tells patients, “This mirror can show how you look now, and glycated hemoglobin is a ‘blood glucose memory mirror’ that can reflect your blood glucose status over the past two to three months.”

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01 A "blood glucose memory mirror" that doesn't lie

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In Director Huang Xinwen's consultation room, glycated hemoglobin is given the image of a "blood glucose memory mirror." He explains that this indicator does not become distorted by a patient's one-day dietary indulgence or mood fluctuation; it is a reliable marker reflecting blood glucose control over the past 2 to 3 months.

The formation of glycated hemoglobin is actually simple: when glucose in the blood remains at high levels for a long time, it "sticks" to hemoglobin, forming glycated hemoglobin. This process is slow and irreversible, like spreading syrup on bread—once it sticks it's hard to separate.

"Each person's red blood cells have an average lifespan of about 120 days, so the detected glycated hemoglobin can tell us about blood glucose status over a past period." Director Huang Xinwen added that it reflects a weighted average over time, with 50% of the value determined by blood glucose concentrations in the most recent month.

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02 What level of glycated hemoglobin is considered controlled?

Regarding target values for glycated hemoglobin, Director Huang Xinwen noted that both the Hong Kong Diabetes Federation and the Mayo Clinic recommend a glycated hemoglobin goal below 7% for most adult patients with diabetes.

However, the latest "Chinese Guidelines for the Prevention and Treatment of Diabetes (2024 edition)" introduces a new concept, emphasizing a shift from disease-centered to patient-centered individualized treatment.

"A one-size-fits-all standard is no longer applicable," Director Huang Xinwen explained, "we need to set individualized targets based on factors such as the patient's age, disease duration, and presence of complications."

For younger patients with a short disease duration, no complications, no cardiovascular disease, and a low risk of hypoglycemia, glycated hemoglobin may be considered to be controlled below 6.5%. For elderly patients, those with multiple complications, high cardiovascular risk, or who are prone to hypoglycemia, glycemic targets can be appropriately relaxed.

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03 Why must it be tested every three months?

The frequency of glycated hemoglobin testing is an important part of diabetes management. Director Huang Xinwen emphasized that this test does not require fasting and can be performed at any time, which provides great convenience for patients.

It is generally recommended to test every 3 months, that is, four times a year. But Director Huang Xinwen noted: "If blood glucose is stably controlled, testing every 6 months is also acceptable."

Why three months? Because the average lifespan of red blood cells is about 120 days, and the measurement of glycated hemoglobin precisely covers this period, allowing a comprehensive reflection of the patient's glycemic control. Regular testing in this way helps doctors and patients promptly assess treatment effectiveness and adjust the treatment regimen when necessary.

In certain special situations, such as pregnancy, severe blood loss, post-transfusion, anemia, or certain hematologic conditions, glycated hemoglobin values may be inaccurate and need to be interpreted in conjunction with other indicators.

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04 Long-term Excess "Invisible Killer" Effect

When glycated hemoglobin remains elevated over a long period, it acts like a silently “invisible killer,” causing systemic damage to the body. Director Huang Xinwen sternly pointed out that chronically high glycated hemoglobin reduces the affinity of red blood cells for oxygen, leading to hypoxia in tissues and cells.

Two landmark studies—the U.S. Diabetes Control and Complications Trial (DCCT) and the U.K. Prospective Diabetes Study (UKPDS)—confirmed the close relationship between glycemic control and complications.

Specific data show that for every 1% reduction in glycated hemoglobin, stroke risk decreases by 12%, myocardial infarction risk decreases by 15%, amputations and peripheral fatal vascular disease decrease by 43%, and microvascular complications decrease by 37%.

Even more striking, for every 1% reduction in glycated hemoglobin, the risk of diabetes-related death decreases by 21%. These data fully illustrate the importance of controlling glycated hemoglobin.

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05 Individualized glucose control is more than just taking medication

Facing the question of how to lower glycated hemoglobin, Director Huang Xinwen emphasized: "Glucose control is not simply taking medicine, but a 'marathon' that requires comprehensive management."

According to the new guideline, treatment decisions should be stratified based on the patient's cardiovascular and renal risk and weight status. For patients with concomitant atherosclerotic cardiovascular disease or at high risk for it, priority should be given to drugs with cardiovascular protective effects.

Director Huang Xinwen noted that if patients with type 2 diabetes can perform self-monitoring of blood glucose, they should undergo at least one structured assessment per year, including self-monitoring skills, testing quality and frequency, and the ability to interpret results.

For newly diagnosed type 2 diabetes patients with severely elevated blood glucose, when HbA1c > 9.0% or fasting glucose > 11.1 mmol/L, accompanied by obvious hyperglycemic symptoms, a short-term intensive insulin therapy lasting 2 weeks to 3 months may be initiated.

“This is like a ‘metabolic reboot’ that can effectively reverse the damage that glucotoxicity has caused to beta cells,” said Director Huang Xinwen by way of analogy.

In front of the clinic mirror, Director Huang Xinwen pointed to the HbA1c test report and told the patient, “This ‘blood sugar memory mirror’ does not lie; it faithfully records your last three months of life. Below 7% is the target, but that is only the beginning.”

He pointed to the follow-up plan in the patient’s file, “We’ll see each other again in three months to see what this mirror will reflect of you.” Outside the window the sun was just right, and in the hospital corridor another patient was holding a newly issued lab slip, scheduling their next “memory mirror” test.