Lab result explainedMetabolic panelLast updated November 10, 2026

Estimated average glucose (eAG): the A1C to glucose chart, normal range and what a high eAG means

Estimated average glucose (eAG) · Hemoglobin A1C (eAG is reported alongside the A1C result) · reported in mg/dL (mmol/L outside the US; divide mg/dL by 18)

Estimated average glucose (eAG) is your hemoglobin A1C result translated into the same units as a finger-stick or lab glucose reading, so that a percentage that is hard to picture becomes an average blood sugar in mg/dL. It is calculated, not measured: eAG (mg/dL) = 28.7 × A1C − 46.7, a formula derived from the ADAG study, which compared A1C with months of continuous glucose monitoring in over 500 people. An A1C of 5.7 percent, the top of the normal range, is an eAG of 117 mg/dL; an A1C of 6.5 percent, the diabetes threshold, is 140 mg/dL; and an A1C of 7 percent, the usual treatment goal, is 154 mg/dL.

The number represents your average glucose, day and night, fasting and after meals, over roughly the previous 2 to 3 months, weighted toward the most recent 4 to 6 weeks. That is why it is almost always higher than your fasting glucose: a person with a fasting reading of 100 mg/dL and an eAG of 126 is normal, because meals push glucose up for several hours each day. It is not a prediction of any single reading and it says nothing about how much your glucose swings.

Because eAG is simply A1C in different clothes, everything that makes an A1C misleading applies equally to it: conditions that shorten or lengthen the life of red blood cells (anemia, blood loss, hemolysis, iron deficiency, kidney disease, pregnancy) and some hemoglobin variants shift the result away from your true average glucose. Where there is doubt, a glucose meter, a continuous glucose monitor's glucose management indicator (GMI) or a fructosamine test provides a cross-check.

eAG at a glance

  • What it is: your A1C converted into an average blood glucose over the previous 2–3 months, using eAG (mg/dL) = 28.7 × A1C (%) − 46.7 (or eAG (mmol/L) = 1.59 × A1C − 2.59).
  • Normal: eAG below 117 mg/dL (A1C below 5.7%). Prediabetes: 117–137 mg/dL (A1C 5.7–6.4%). Diabetes: 140 mg/dL or more (A1C 6.5% or more), confirmed on a second test.
  • Treatment goals in diabetes: eAG under 154 mg/dL (A1C under 7%) for most adults; under 183 mg/dL (A1C under 8%) where hypoglycemia is a concern or life expectancy is limited.
  • Quick chart: A1C 5% = 97; 6% = 126; 7% = 154; 8% = 183; 9% = 212; 10% = 240; 11% = 269; 12% = 298 mg/dL.
  • eAG is an average, not a fasting value, and it is normally higher than fasting glucose; it does not show highs and lows.
  • A low eAG (under about 90 mg/dL, A1C under 4.8%) is usually fine but on insulin or sulfonylureas can signal frequent hypoglycemia, and in some people reflects a red-cell problem rather than low sugar.

Have your whole report? Paste it into the free Lab Explainer

Every marker explained in plain language, in context with the others, with questions to bring to your appointment. No account needed.

What eAG measures

Glucose in the blood attaches permanently to the hemoglobin inside red blood cells at a rate proportional to how much glucose is present. Red cells live about 120 days, so the percentage of hemoglobin that is glycated, the A1C, integrates your glucose exposure over that period. The ADAG (A1C-Derived Average Glucose) study, published in 2008, fitted this percentage to the actual mean glucose measured by continuous glucose monitoring and seven-point finger-stick profiles in 507 people with type 1 diabetes, type 2 diabetes and no diabetes over 12 weeks. The resulting straight-line relationship, eAG = 28.7 × A1C − 46.7, is what labs use, and the American Diabetes Association recommends reporting both numbers together.

The conversion is a population average, and the confidence interval around it is wide. In ADAG, an A1C of 7 percent corresponded to a mean glucose of 154 mg/dL, but the 95 percent range for individuals was about 123 to 185 mg/dL. People differ in how fast their red cells turn over and in how readily glucose crosses the red-cell membrane (sometimes called the glycation gap), so two people with the same true average glucose can have A1C values half a percentage point apart. Average A1C for a given glucose is also slightly higher, by about 0.3 to 0.4 percentage points, in Black adults than in white adults, for reasons that are not fully understood.

The glucose management indicator (GMI) from a continuous glucose monitor is the mirror image: it takes the measured mean glucose from at least 14 days of CGM data and estimates what the A1C would be (GMI = 3.31 + 0.02392 × mean glucose in mg/dL). A gap of more than about 0.5 percentage points between GMI and lab A1C suggests that something is distorting the A1C, usually a red-cell issue, and that the CGM average is the more trustworthy guide for that person. Fructosamine, which reflects the previous 2 to 3 weeks, is the usual alternative when A1C cannot be relied on.

Normal range for eAG

Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.

GroupTypical range (mg/dL (mmol/L outside the US; divide mg/dL by 18))Notes
NormalBelow 117 mg/dL (A1C below 5.7%)An A1C of 5.0% is an eAG of 97 mg/dL; 5.5% is 111 mg/dL. Labs apply the same formula; the A1C assay itself can vary slightly between labs.
Prediabetes117–137 mg/dL (A1C 5.7–6.4%)A1C 6.0% is 126 mg/dL. Risk of progression to diabetes is highest toward the upper end.
Diabetes (diagnostic threshold)140 mg/dL or more (A1C 6.5% or more)Diagnosis requires a second confirmatory test (repeat A1C, fasting glucose of 126 or more, or an oral glucose tolerance test) unless symptoms are clear.
General treatment goal in diabetesBelow 154 mg/dL (A1C below 7%)ADA goal for most non-pregnant adults; some people aim for under 140 (A1C under 6.5%) if achievable without hypoglycemia.
Relaxed goalBelow 183 mg/dL (A1C below 8%)For older adults, limited life expectancy, frequent hypoglycemia or multiple other conditions.
Poorly controlled212–298 mg/dL (A1C 9–12%)A1C 9% = 212, 10% = 240, 11% = 269, 12% = 298 mg/dL. Risk of complications and of symptoms such as thirst and weight loss is high; treatment is intensified.
Very highAbove 300 mg/dL (A1C above 12%)A1C 13% = 326, 14% = 355 mg/dL. Often newly diagnosed diabetes or missed treatment; checked for ketones and dehydration.
PregnancyA1C is not used to diagnose gestational diabetesFaster red-cell turnover lowers A1C in pregnancy, so eAG underestimates true glucose; oral glucose tolerance testing is used instead.
Full ADAG conversioneAG = 28.7 × A1C − 46.7 (mg/dL); eAG = 1.59 × A1C − 2.59 (mmol/L)95% confidence range for an individual is roughly ±20 percent; an A1C of 7% maps to an average of 154 (123–185) mg/dL.

High estimated average glucose

A high eAG means your average blood glucose over the previous 2 to 3 months has been above normal, and it carries exactly the same meaning as the A1C it was calculated from. An eAG of 117 to 137 mg/dL (A1C 5.7 to 6.4 percent) is the prediabetes range, where the body is beginning to resist insulin or produce less of it; roughly 5 to 10 percent of people in this band develop diabetes each year, and about a third of US adults are in it, most without knowing. An eAG of 140 mg/dL or more (A1C 6.5 percent or more), confirmed by a second test, is diabetes.

In someone who already has diabetes, the eAG shows how well treatment is working, and the gap between the result and the target tells you how far there is to go. Each 1 percentage point of A1C corresponds to about 29 mg/dL of average glucose, so moving from an eAG of 212 (A1C 9 percent) to 154 (A1C 7 percent) means lowering your round-the-clock average by about 58 mg/dL. The UKPDS and DCCT trials showed that each 1 point fall in A1C reduces the risk of eye, kidney and nerve complications by roughly 25 to 35 percent and heart attacks by around 14 percent over the following years.

A high eAG does not say when the glucose is high. Two people with the same eAG of 170 can have very different patterns: one with a fasting glucose of 160 and modest meal spikes, the other with a fasting glucose of 110 and large spikes after meals. Finger-stick profiles or a continuous glucose monitor reveal the pattern and guide which change, whether to food, timing, activity or a particular medication, will help most. A high eAG with normal glucose readings, or vice versa, should raise the question of a red-cell condition distorting the A1C.

Common causes

  1. Type 2 diabetes and prediabetes

    Insulin resistance in muscle, liver and fat, with a gradual decline in insulin secretion, raises glucose first after meals and then while fasting. This is the cause behind the overwhelming majority of high eAG results, and weight, waist size and family history are the main risk factors.

  2. Type 1 diabetes and other insulin-deficient states

    Autoimmune loss of insulin-producing cells (type 1, including adult-onset LADA), pancreatitis, pancreatic surgery and cystic fibrosis all cause high and often widely swinging glucose; eAG is raised and ketones may be present.

  3. Medications

    Corticosteroids (prednisone, dexamethasone) are the commonest drug cause and can push eAG up by 30 to 60 mg/dL within weeks; antipsychotics, thiazides, some HIV drugs, tacrolimus, cyclosporine and high-dose niacin also raise glucose.

  4. Weight gain, inactivity and dietary pattern

    Rising body weight, especially abdominal fat, and low physical activity worsen insulin resistance; diets high in refined carbohydrate and sugary drinks raise post-meal glucose and, over months, the eAG. In people with diabetes, a lapse in medication adherence shows up the same way.

  5. Hormonal conditions

    Cushing's syndrome, acromegaly, hyperthyroidism, pheochromocytoma and polycystic ovary syndrome each raise glucose by increasing insulin resistance or counter-regulatory hormones; PCOS is a common and under-recognized cause of prediabetes in younger women.

  6. Iron deficiency and iron-deficiency anemia

    A shortage of iron prolongs the life of red cells, giving glucose longer to attach, and raises A1C by up to about 0.5 to 1 percentage point (14 to 29 mg/dL of eAG) without any change in actual glucose. Treating the iron deficiency lowers the A1C.

  7. Other conditions that slow red-cell turnover

    Vitamin B12 or folate deficiency, splenectomy and aplastic anemia leave older red cells in circulation and falsely raise A1C and eAG. Severe hypertriglyceridemia, high bilirubin and chronic alcohol use can also interfere with some assays.

  8. Hemoglobin variants

    Hemoglobin S, C, E and D traits and others can interfere with certain A1C assay methods, producing falsely high (or low) results. Labs can use a variant-tolerant method, or glucose readings and fructosamine are used instead.

  9. Acute illness and stress

    Infection, surgery, heart attack and severe stress raise glucose through cortisol and adrenaline; if sustained for weeks, the eAG rises. A single stressful day does not change it, since the result averages months.

Symptoms that can go with it

  • Often none in the prediabetes range and in early type 2 diabetes
  • Increased thirst and frequent urination, especially at night, once average glucose exceeds about 180–200 mg/dL
  • Unexplained weight loss, fatigue and blurred vision
  • Slow-healing cuts, recurrent skin, urine or yeast infections
  • Tingling, burning or numbness in the feet from nerve damage after years of high glucose
  • Increased hunger, particularly after meals, with large glucose swings
  • Nausea, abdominal pain, rapid breathing and confusion with very high glucose and ketones, which is an emergency

Low estimated average glucose

A low eAG, roughly under 90 mg/dL (A1C under about 4.8 percent), is uncommon and in a person not taking glucose-lowering medication it is usually a healthy result or a laboratory artefact rather than a problem. Many lean, active people, particularly young women, have an A1C of 4.5 to 5.0 percent with entirely normal glucose readings. The one group in whom it matters clinically is people with diabetes treated with insulin or sulfonylureas, where a low or sharply falling eAG can mean frequent hypoglycemia is being averaged in with high readings; the ADA cautions that a low A1C in this setting should prompt a review of glucose data for lows.

The other common explanation is a shortened red-cell lifespan. Anything that replaces red cells faster than normal, including recent blood loss or transfusion, hemolytic anemia, treated iron deficiency (reticulocytosis), pregnancy, advanced kidney disease on erythropoietin, chronic liver disease and some hemoglobin variants, gives glucose less time to attach, so the A1C and eAG underestimate the true average glucose. In these situations a normal eAG can hide diabetes, and fructosamine or direct glucose testing is used instead.

Common causes

  1. Healthy glucose regulation

    Normal insulin sensitivity, a normal weight and regular activity keep the round-the-clock average in the 80s to 100s; an A1C of 4.5 to 5.2 percent (eAG 82 to 102 mg/dL) is common in such people and needs no action.

  2. Over-treatment of diabetes

    Insulin or sulfonylureas dosed above requirements produce recurrent hypoglycemia that drags the average down; an eAG well below target in someone on these drugs is reviewed with meter or CGM data, and doses are usually reduced.

  3. Hemolysis, blood loss and transfusion

    Hemolytic anemias, bleeding, recent transfusion and recovery from iron deficiency all put young red cells into the circulation, which have had less time to pick up glucose; A1C can fall by 1 to 2 percentage points below what the glucose would predict.

  4. Pregnancy and chronic kidney disease

    Red-cell turnover speeds up in pregnancy, and erythropoietin treatment in kidney disease has the same effect; both lower A1C relative to glucose, which is why neither relies on A1C for diagnosis.

  5. Hemoglobin variants and assay interference

    Some variants and high-dose vitamin C or E, and some drugs (dapsone, ribavirin, antiretrovirals), lower A1C on certain assays. The lab can switch methods or fructosamine can be used.

  6. Insulinoma and other causes of true low glucose

    Rarely, a tumor producing insulin, adrenal insufficiency, severe liver disease or advanced malnutrition keep glucose genuinely low; these present with symptoms of hypoglycemia rather than through the eAG.

Symptoms that can go with it

  • None in most people with a low eAG
  • On insulin or sulfonylureas: shakiness, sweating, hunger, palpitations, confusion or night sweats and headaches on waking, which point to hypoglycemia
  • Fatigue, pallor, breathlessness or jaundice when a red-cell disorder is lowering the A1C

Read it alongside

  • Hemoglobin A1C — eAG is calculated from it; the two are the same test in different units and should always be read together.
  • Fasting glucose — a fasting value of 100–125 mg/dL is prediabetes and 126 or more is diabetes; eAG is normally 20–40 mg/dL higher than fasting glucose because it includes post-meal readings.
  • Hemoglobin, MCV and reticulocyte count — anemia or a high red-cell turnover means the eAG may not reflect true glucose.
  • Ferritin and iron saturation — iron deficiency falsely raises A1C and eAG by up to about 0.5 to 1 percentage point of A1C.
  • Fructosamine — reflects the previous 2 to 3 weeks and is the alternative when A1C is unreliable; roughly, fructosamine 300 µmol/L corresponds to an A1C of about 6.5 percent.
  • Fasting insulin and HOMA-IR, or C-peptide — show whether a high eAG comes from insulin resistance (high insulin) or insulin deficiency (low C-peptide), which guides treatment.
  • Continuous glucose monitor GMI and time in range — the measured counterpart of eAG; a gap of more than 0.5 A1C points between GMI and lab A1C suggests the A1C is distorted.
  • Lipids, creatinine, urine albumin-creatinine ratio — a high eAG is assessed alongside the other components of cardiovascular and kidney risk.

What usually happens next

  1. A first eAG of 140 mg/dL or more (A1C 6.5% or more) without classic symptoms is confirmed with a second test, either a repeat A1C or a fasting glucose, before diabetes is diagnosed.
  2. An eAG in the prediabetes range (117–137 mg/dL) is usually rechecked in 6 to 12 months, with a structured lifestyle program in between; the Diabetes Prevention Program showed this cuts progression to diabetes by 58 percent over 3 years.
  3. If the eAG and your meter or CGM readings disagree by more than about 20 to 30 mg/dL, ask about anemia, iron studies, kidney function, pregnancy or a hemoglobin variant, and whether fructosamine or a different A1C method would be more reliable.
  4. In established diabetes, A1C and eAG are checked every 3 months until the goal is reached and then every 6 months; expect your clinician to set an individual target (eAG under 154 for most adults) rather than a single universal number.
  5. A rising eAG on stable treatment prompts a review of adherence, weight, new medications (particularly steroids), and whether a second agent is needed; a falling eAG below target on insulin or sulfonylureas prompts a check for hypoglycemia.
  6. Use the chart or formula to translate your own target into glucose terms: if your goal is an A1C of 7 percent, your meter readings should average around 154 mg/dL across the day, with fasting values of roughly 80–130 and post-meal peaks under 180.

Diet, lifestyle and natural levers with evidence

What can move eAG once the cause is known. Nothing here replaces finding the cause.

Weight loss when overweight

Strong evidence

In the DiRECT trial, a structured low-calorie program producing an average loss of 10 kg put type 2 diabetes into remission (A1C under 6.5 percent off medication) in 46 percent of people at one year, rising to 86 percent of those who lost 15 kg or more. In the Look AHEAD trial, intensive lifestyle intervention lowered A1C by about 0.6 percentage points (around 17 mg/dL of eAG) more than usual care at one year. For prediabetes, losing 5 to 7 percent of body weight reduced progression to diabetes by 58 percent over 3 years in the Diabetes Prevention Program.

Structured exercise, both aerobic and resistance

Strong evidence

A meta-analysis of 47 randomised trials (8,538 people with type 2 diabetes) found structured exercise training lowered A1C by 0.67 percentage points on average, about 19 mg/dL of eAG, with the largest effect (0.9 points) when aerobic and resistance training were combined and when total exercise exceeded 150 minutes a week. Advice to exercise without a structured program achieved less (about 0.4 points). Each session improves insulin sensitivity for 24 to 72 hours, so spreading activity across the week matters more than a single long session.

Carbohydrate quality and quantity

Moderate evidence

Meta-analyses of dietary trials in type 2 diabetes show that low-carbohydrate (under 26 percent of calories), Mediterranean and low-glycaemic-index patterns each lower A1C by roughly 0.3 to 0.5 percentage points (about 10 to 15 mg/dL of eAG) more than control diets at 3 to 12 months, with the low-carbohydrate advantage fading after a year as adherence falls. A 2020 meta-analysis found that increasing fiber intake by about 15 g a day, toward 35 g, lowered A1C by about 0.6 points. Removing sugar-sweetened drinks is the single change with the largest effect per effort.

Sleep and shift-work pattern

Moderate evidence

Short sleep (under 6 hours) and untreated obstructive sleep apnea each raise insulin resistance; in people with diabetes, sleep apnea is associated with A1C about 0.5 to 1 point higher, and meta-analyses of CPAP trials show a small A1C reduction (about 0.2 to 0.3 points) with regular use. Extending sleep by about an hour in short sleepers improved insulin sensitivity in short trials. Rotating night shifts are associated with higher A1C and diabetes risk, and keeping meal times regular partly offsets this.

Berberine

Moderate evidence

In randomised trials in type 2 diabetes, berberine at 0.5 g two to three times a day for 3 months lowered A1C by about 0.7 to 0.9 percentage points (20 to 26 mg/dL of eAG) and fasting glucose by about 20 to 25 mg/dL, an effect similar to metformin in the pilot trial by Yin and colleagues and confirmed in a 2015 meta-analysis of 27 trials. It activates AMPK and improves insulin sensitivity. Trials are short, mostly Chinese, and add-on rather than replacement therapy.

Berberine inhibits CYP3A4 and CYP2D6 and can raise levels of many drugs; combined with insulin or sulfonylureas it can contribute to hypoglycemia; it is avoided in pregnancy, breastfeeding and newborns, and causes constipation or stomach upset in some people.

Cinnamon

Preliminary evidence

A 2013 meta-analysis of 10 randomised trials (543 people with type 2 diabetes) found cinnamon at 120 mg to 6 g a day for 4 to 18 weeks lowered fasting glucose by about 25 mg/dL but did not significantly change A1C; later meta-analyses have reported A1C reductions of 0.1 to 0.3 points at best, with wide variation between trials. At most, it is a minor adjunct.

Cassia cinnamon contains coumarin, which can harm the liver at sustained doses above about 0.1 mg/kg a day (roughly 1 teaspoon of cassia powder daily for an adult); Ceylon cinnamon contains very little. Can add to the effect of glucose-lowering drugs.

When to see a clinician promptly

  • Very high glucose symptoms with an eAG above about 300 mg/dL (A1C above 12%): intense thirst, frequent urination, vomiting, abdominal pain, rapid breathing, drowsiness or confusion can mean diabetic ketoacidosis or hyperosmolar state and need emergency care.
  • Any finger-stick or lab glucose above 300 mg/dL that persists, or above 250 with ketones in the urine or blood, regardless of the eAG.
  • A first eAG of 140 mg/dL or more (A1C 6.5% or more), to arrange a confirmatory test and start a plan, and sooner if you have thirst, weight loss or blurred vision.
  • A low or falling eAG while taking insulin or a sulfonylurea, particularly with episodes of shakiness, sweating, confusion or waking with headaches, which suggests hypoglycemia and a need to adjust doses.
  • An eAG that disagrees sharply with your meter or CGM readings, or an eAG result during pregnancy, since the A1C may not be reliable and a different test is needed.
  • An eAG in the prediabetes range with a family history of diabetes, a larger waist, PCOS or a history of gestational diabetes, to be enrolled in a prevention program and have lipids and blood pressure checked.

Frequently asked questions

What is eAG on a blood test?

eAG stands for estimated average glucose. It is your hemoglobin A1C result converted into the mg/dL units used by glucose meters, using the formula eAG = 28.7 × A1C − 46.7, so that you can compare your 2 to 3 month average with your daily readings. It is not a separate measurement, and it carries exactly the same information as the A1C. An eAG of 126 mg/dL, for example, is an A1C of 6.0 percent.

What is a normal estimated average glucose?

Below 117 mg/dL, which corresponds to an A1C under 5.7 percent. Between 117 and 137 mg/dL (A1C 5.7 to 6.4 percent) is prediabetes, and 140 mg/dL or more (A1C 6.5 percent or more) on two tests is diabetes. For people already diagnosed with diabetes, the usual treatment goal is an eAG under 154 mg/dL (A1C under 7 percent), relaxed to under 183 (A1C under 8 percent) for some older adults or those at risk of hypoglycemia.

How do I convert A1C to average glucose?

Multiply the A1C by 28.7 and subtract 46.7 to get mg/dL (or multiply by 1.59 and subtract 2.59 for mmol/L). A1C 5% = 97 mg/dL; 5.5% = 111; 5.7% = 117; 6% = 126; 6.5% = 140; 7% = 154; 7.5% = 169; 8% = 183; 8.5% = 197; 9% = 212; 9.5% = 226; 10% = 240; 11% = 269; 12% = 298. Each 1 percentage point of A1C equals about 29 mg/dL of average glucose. To go the other way, add 46.7 to the eAG and divide by 28.7.

Why is my eAG higher than my fasting glucose?

Because eAG is an average of every moment of the day, including the hours after meals when glucose rises, while a fasting reading is taken at the daily low point. A fasting glucose of 95 with an eAG of 120 is a normal pattern. A large gap, say fasting readings around 100 with an eAG of 160, suggests big post-meal spikes that a meter only catches if you test 1 to 2 hours after eating; a continuous glucose monitor shows the full pattern.

Is an eAG of 126 bad?

An eAG of 126 mg/dL is an A1C of 6.0 percent, which is in the prediabetes range (117 to 137). It is not diabetes, but it means your average glucose has been above normal for the past 2 to 3 months and that your risk of developing type 2 diabetes is raised, roughly 5 to 10 percent per year without changes. Losing 5 to 7 percent of body weight if overweight, 150 minutes of weekly activity and cutting sugary drinks reduce that risk by more than half; the test is usually repeated in 6 to 12 months.

How accurate is estimated average glucose?

As a population formula it is good, but for an individual it is approximate. In the study that derived it, an A1C of 7 percent corresponded to an average glucose of 154 mg/dL, but the 95 percent range for individuals was about 123 to 185 mg/dL, because people differ in red-cell lifespan and in how readily glucose attaches to hemoglobin. Conditions such as anemia, iron deficiency, kidney disease, pregnancy and hemoglobin variants shift the result further. If your meter or CGM average and your eAG disagree by more than 20 to 30 mg/dL, the discrepancy itself is worth discussing.

Can eAG be high without diabetes?

Yes, in two ways. First, the prediabetes range (117 to 137 mg/dL) is above normal but below the diabetes threshold. Second, a falsely high result can occur when red cells live longer than usual, most often from iron deficiency, which can raise A1C by up to about 0.5 to 1 percentage point, and with vitamin B12 or folate deficiency, after splenectomy, and with some hemoglobin variants on certain assays. A single test is never diagnostic on its own; a repeat A1C or a fasting glucose is used to confirm.

What is the difference between eAG and GMI?

They are mirror images. eAG starts from a lab A1C and estimates what your average glucose has probably been over 2 to 3 months. GMI (glucose management indicator) starts from your actual measured average glucose on a continuous glucose monitor, over at least 14 days, and estimates what the A1C would be (GMI = 3.31 + 0.02392 × mean glucose). When they agree, both can be trusted; when they differ by more than about 0.5 A1C points, the CGM average is usually the better guide to your true glucose, and the reason for the gap (often a red-cell condition) is worth checking.

References

  1. Nathan DM, Kuenen J, Borg R, Zheng H, Schoenfeld D, Heine RJ; A1c-Derived Average Glucose Study Group. Translating the A1C assay into estimated average glucose values. Diabetes Care (2008)
  2. American Diabetes Association Professional Practice Committee. Standards of Care in Diabetes—2025: 2. Diagnosis and classification of diabetes; 6. Glycemic goals and hypoglycemia. Diabetes Care (2025)
  3. Hemoglobin A1C (HbA1c) test. MedlinePlus, US National Library of Medicine (2023)View source
  4. The A1C test and diabetes. National Institute of Diabetes and Digestive and Kidney Diseases (2018)View source
  5. A1C test. Mayo Clinic (2023)View source
  6. Bergenstal RM, Beck RW, Close KL, et al.. Glucose management indicator (GMI): a new term for estimating A1C from continuous glucose monitoring. Diabetes Care (2018)
  7. Sacks DB, Arnold M, Bakris GL, et al.. Guidelines and recommendations for laboratory analysis in the diagnosis and management of diabetes mellitus. Diabetes Care (2023)
  8. Umpierre D, Ribeiro PA, Kramer CK, et al.. Physical activity advice only or structured exercise training and association with HbA1c levels in type 2 diabetes: a systematic review and meta-analysis. JAMA (2011)
  9. Lean ME, Leslie WS, Barnes AC, et al.. Primary care-led weight management for remission of type 2 diabetes (DiRECT): an open-label, cluster-randomised trial. The Lancet (2018)
  10. Reynolds AN, Akerman AP, Mann J. Dietary fibre and whole grains in diabetes management: systematic review and meta-analyses. PLoS Medicine (2020)
  11. Yin J, Xing H, Ye J. Efficacy of berberine in patients with type 2 diabetes mellitus. Metabolism (2008)
  12. Allen RW, Schwartzman E, Baker WL, Coleman CI, Phung OJ. Cinnamon use in type 2 diabetes: an updated systematic review and meta-analysis. Annals of Family Medicine (2013)

Related markers

Related conditions

Evidence guides

Worried about your number?

Ask AskMN what your eAG result could mean in the context of your other results, symptoms and medications. Free, unlimited, no account needed.

Ask about my eAG

This page is educational and is not medical advice or a diagnosis. Lab results have to be interpreted together with your history, symptoms and other results by a clinician who knows you. Do not start or stop a supplement to change a lab value before the cause is known.