HbA1c (Glycated Hemoglobin): Values, Meaning, and Targets for Diabetes
HbA1c — glycated hemoglobin — is the reference parameter for assessing glycemic control over the past 2–3 months. A single blood glucose measurement tells you what happened at that moment; HbA1c tells the story of the last 90 days.
What is Glycated Hemoglobin
Glycated hemoglobin (HbA1c or A1C) is the percentage of hemoglobin — the protein in red blood cells that carries oxygen — that has become "glycated," meaning it has bound to glucose in the blood. This binding is proportional to the amount of glucose present in the blood over the lifespan of the red blood cell (approximately 90–120 days).
The higher the average blood glucose in the last 3 months, the higher the HbA1c will be. It's like a "long-exposure photograph" of blood sugar.
HbA1c Values: Reference Table 2026
| HbA1c (%) | HbA1c (mmol/mol) | Classification | Estimated Average Glucose (mg/dL) |
|---|---|---|---|
| < 5.7% | < 39 | Normal | < 117 |
| 5.7–6.4% | 39–46 | Pre-diabetes | 117–137 |
| ≥ 6.5% | ≥ 48 | Diabetes Mellitus | ≥ 140 |
Therapeutic targets for diabetics
| Patient Category | HbA1c Target | Rationale |
|---|---|---|
| Healthy adult with type 2 diabetes | < 7.0% | General standard |
| Motivated young type 1 diabetic | < 6.5% | Maximum complication reduction |
| Patient with frequent hypoglycemic episodes | < 8.0% | Safety first |
| Frail elderly (>70 years, comorbidities) | < 8.0–8.5% | Avoid dangerous hypoglycemia |
| Pregnancy with diabetes | < 6.0% | Reduced risk of fetal complications |
| Gestational diabetes | < 6.5% | SIGO 2024 |
Source: ADA Standards of Care 2025; AMD-SID Italian Standards 2024.
HbA1c vs. Daily Blood Glucose: Which to Use
They are complementary, not interchangeable:
| Blood Glucose (glucometer) | HbA1c | |
|---|---|---|
| What it measures | Glucose at this moment | Average glucose over the last 90 days |
| When it's useful | Daily management, therapy adjustment, hypoglycemia | Periodic assessment of control, diagnosis |
| Frequency | Daily or multiple times a day | Every 3–6 months |
| Where it's done | At home with a glucometer | In the laboratory or with point-of-care devices |
| Requires fasting | Depends on the type of measurement | No |
The home glucometer (like the G1 Pro) is the tool for daily management. HbA1c is the tool for quarterly evaluation with the diabetologist.
HbA1c — Average Blood Glucose Conversion Table
| HbA1c (%) | Estimated Average Glucose (mg/dL) | Average Glucose (mmol/L) |
|---|---|---|
| 6.0% | 126 | 7.0 |
| 6.5% | 140 | 7.8 |
| 7.0% | 154 | 8.6 |
| 7.5% | 169 | 9.4 |
| 8.0% | 183 | 10.2 |
| 8.5% | 197 | 10.9 |
| 9.0% | 212 | 11.8 |
| 10.0% | 240 | 13.4 |
How to Lower HbA1c
Every percentage point reduction in HbA1c reduces the risk of microvascular complications (retinopathy, nephropathy, neuropathy) by 35–40% (UK Prospective Diabetes Study). Strategies include:
- More frequent blood glucose monitoring: patients who measure their blood glucose multiple times a day have HbA1c values that are, on average, 0.5–1% lower
- Low glycemic index diet: reduces HbA1c by 0.3–0.5%
- Regular physical activity: 150 min/week of aerobic exercise reduces HbA1c by 0.5–0.7%
- Weight loss: every 1% of weight lost reduces HbA1c by approximately 0.1%
- Adherence to pharmacological therapy: unauthorized discontinuation of metformin increases HbA1c by an average of 1–1.5% in 3 months
Limitations of HbA1c: When it's Unreliable
In some conditions, HbA1c does not accurately reflect average blood glucose:
- Hemolytic anemia (accelerated red blood cell destruction): falsely low HbA1c
- Hemoglobinopathies (thalassemia, sickle cell anemia): unreliable results
- Iron deficiency anemia: HbA1c can be falsely high
- Pregnancy: red blood cells regenerate more quickly — HbA1c only reflects the last 4–6 weeks
- Recent transfusion: changes hemoglobin composition
In these cases, the doctor may resort to alternative tests such as fructosamine or CGM monitoring to assess glycemic control.
Frequently Asked Questions
HbA1c 6.8%: Am I diabetic?
Yes — an HbA1c ≥ 6.5% is diagnostic for diabetes mellitus according to ADA 2025 guidelines. However, diagnosis requires confirmation with a second test (another HbA1c blood draw or a fasting blood glucose) in the absence of obvious hyperglycemic symptoms.
How often should HbA1c be tested?
For diabetics under treatment: every 3 months if control is not optimal or therapy has been changed; every 6 months if control is stable and at target. For people with pre-diabetes: every 6–12 months.
Can I calculate HbA1c from glucometer values?
Yes, approximately. The VitaeChek G1 Pro app automatically calculates the average blood glucose for the last 14, 30, and 90 days — which you can convert to estimated HbA1c using the table above. It does not replace a laboratory blood test, but it gives you an idea of the trend between visits.
