HbA1c categories (ADA 2024)
The American Diabetes Association uses three HbA1c ranges to classify blood sugar status. These cutoffs apply to adults who are not pregnant and whose test was performed in an NGSP-certified lab.
| Category | HbA1c (%) | eAG (mg/dL) | eAG (mmol/L) |
|---|---|---|---|
| Normal | Below 5.7 | Below 117 | Below 6.5 |
| Prediabetes | 5.7–6.4 | 117–137 | 6.5–7.6 |
| Diabetes | 6.5–7.9 | 140–171 | 7.8–9.5 |
| Action needed | 8.0 and above | 183 and above | 10.2 and above |
Source: ADA Standards of Medical Care in Diabetes 2024, Table 6.1. eAG values calculated using the ADAG formula (Nathan et al. 2008).
How the ADAG formula works
The ADAG (A1c-Derived Average Glucose) equation was published by Nathan et al. in Diabetes Care (2008) after a study of 507 adults with Type 1 diabetes, Type 2 diabetes, and no diabetes across 10 international sites. The formula is:
eAG (mg/dL) = (28.7 × HbA1c%) − 46.7
eAG (mmol/L) = (1.59 × HbA1c%) − 2.59
Before ADAG, clinicians had to mentally translate between HbA1c percentages and glucose values — two different scales with different units. ADAG bridges the gap so patients can directly compare their lab HbA1c with their home glucometer readings. The ADA and IFCC both endorse the ADAG-derived eAG as the preferred way to communicate long-term glucose control.
HbA1c and diabetes in Pakistan
Pakistan has one of the highest diabetes burdens in the world. The IDF Diabetes Atlas (2021) estimated 33 million adults in Pakistan are living with diabetes — approximately 26% of the adult population — placing Pakistan fourth globally. A significant additional proportion have undiagnosed diabetes or prediabetes.
HbA1c testing is now widely accessible in Pakistan. Accredited laboratories including Chughtai Lab, Agha Khan University Hospital, Shaukat Khanum Memorial, and IDC (Islamabad Diagnostic Centre) all offer NGSP-certified HbA1c assays. Typical cost ranges from Rs. 800 to Rs. 2,000, and the test does not require fasting.
Note that South Asians — including Pakistanis — tend to develop Type 2 diabetes at lower body weights than European populations. This means an HbA1c in the prediabetes range should be taken seriously even in people who appear to be a healthy weight. Dietary intervention and regular physical activity remain the most effective tools for preventing progression from prediabetes to diabetes.
When HbA1c may not be accurate
HbA1c is reliable for most adults, but several conditions can give misleading results. If any of these apply to you, your doctor may prefer fasting glucose or oral glucose tolerance testing instead:
- Haemoglobin variants — HbS (sickle cell), HbC, HbE, and HbD variants are more common in South Asian populations and can interfere with some assay methods, causing falsely low or high readings.
- Anaemia — Iron-deficiency anaemia or B12 deficiency anaemia can cause HbA1c to appear lower than it really is.
- Haemolytic anaemia (e.g. thalassaemia) — Increased red blood cell turnover shortens the averaging window, pushing HbA1c falsely low.
- Recent blood transfusion — Transfused cells have no glycation history, diluting the HbA1c result.
- Pregnancy — HbA1c targets and interpretation differ in pregnancy; separate guidelines apply for gestational diabetes.
If your HbA1c result does not match your home glucometer readings over the same period, raise this with your doctor. They can order an alternative assay method or a fructosamine test that is unaffected by haemoglobin variants.
Frequently asked questions
What is HbA1c?
HbA1c (glycated haemoglobin) measures the percentage of haemoglobin in your blood that has glucose attached. Because red blood cells live about 90 days, HbA1c reflects your average blood sugar over the past 2–3 months — making it the gold-standard test for diagnosing and monitoring diabetes.
What is the ADAG formula used here?
This calculator uses the ADAG (A1c-Derived Average Glucose) equation from Nathan et al. (2008): eAG (mg/dL) = (28.7 × HbA1c%) − 46.7. It was validated across 507 participants and is endorsed by the ADA and IFCC as the best way to translate HbA1c into a glucose value patients can relate to.
What is a normal HbA1c level?
According to ADA 2024 guidelines: below 5.7% is normal, 5.7–6.4% indicates prediabetes, and 6.5% or above on two separate tests confirms diabetes. Most healthy adults without diabetes have HbA1c between 4.5% and 5.6%.
What HbA1c target should I aim for?
The ADA recommends HbA1c below 7.0% for most non-pregnant adults with diabetes. A less stringent target of below 8.0% is acceptable for older adults, those with hypoglycaemia unawareness, or those with limited life expectancy. Your doctor will set a personalised target.
How often should I get an HbA1c test?
If you have well-controlled diabetes, twice a year is standard. If your treatment changes or glucose control is poor, every three months is recommended. People at high risk of diabetes (prediabetes, obesity, family history) should test at least once a year.
Can HbA1c results be inaccurate?
Yes. Conditions that affect red blood cell lifespan — such as iron-deficiency anaemia, haemolytic anaemia, thalassaemia, or recent blood transfusion — can give falsely low or high readings. Haemoglobin variants (HbS, HbC) common in South Asian populations can also interfere with certain assay methods.
Is HbA1c testing available in Pakistan?
Yes. HbA1c tests are widely available at accredited labs across Pakistan including Chughtai Lab, Agha Khan University Hospitals, Shaukat Khanum, and major public hospitals. Costs typically range from Rs. 800 to Rs. 2,000 depending on the city and lab.
What is the difference between HbA1c and fasting blood glucose?
Fasting glucose is a snapshot — it reflects your blood sugar at one moment after an overnight fast. HbA1c is an average over 2–3 months. HbA1c is less affected by daily variation, does not require fasting, and is preferred for monitoring long-term control. Fasting glucose is still used for initial screening.