Blood Sugar

What does a high HbA1c mean?

The short answer

HbA1c (glycated haemoglobin) measures how much of the haemoglobin in your red blood cells has glucose attached, which reflects your average blood sugar over roughly the last 2 to 3 months. Below 5.7% is normal. A high result means blood sugar has been running above normal: 5.7% to 6.4% is prediabetes and 6.5% or above is in the diabetes range.

Also called: haemoglobin A1c, glycated haemoglobin, A1C, glycosylated haemoglobin · Updated 3 November 2026 · Sources listed below

What HbA1c measures

Glucose in your blood attaches to haemoglobin, the oxygen-carrying protein in red blood cells. HbA1c measures the share of haemoglobin with glucose attached: the more glucose in your blood over time, the higher the result.

Red blood cells live about three months, so HbA1c shows your average blood sugar over the past two to three months (MedlinePlus), with the most recent 30 days counting most (NIDDK). You do not need to fast for it (NIDDK). Fasting glucose and fasting insulin are separate tests a doctor can add.

HbA1c ranges

These cut-offs come from the American Diabetes Association (ADA) and are used by the CDC, NIDDK and MedlinePlus.

ResultRange
NormalBelow 5.7%
Prediabetes5.7% to 6.4%
Diabetes rangeWithout symptoms, a repeat test on a different day is needed to confirm6.5% or above

These cut-offs are for diagnosis. HbA1c is not used to diagnose type 1 diabetes or gestational diabetes (NIDDK), and people already living with diabetes have individual targets set by their doctor. Reference ranges vary between laboratories, and the range printed on your own report takes priority. Ranges vary between laboratories, and the range printed on your own report takes priority.

What a high HbA1c result means

A high HbA1c means your blood sugar has been running above normal for months. In the prediabetes range, 5.7% to 6.4%, it signals a higher risk of type 2 diabetes, but NIDDK says prediabetes can be reversed: in the US Diabetes Prevention Program, people at high risk who lost 5% to 7% of their starting weight reduced their chance of developing the disease.

A result of 6.5% or above is in the diabetes range, but one result is not a diagnosis. Without symptoms, a repeat test on a different day is needed to confirm it (NIDDK), and your doctor will check that nothing is distorting the reading.

Common causes

What a low HbA1c result means

For most people without diabetes, a result at the low end of normal is simply good news. An unusually low HbA1c can be a false reading: increased red blood cell turnover and some haemoglobin variants usually make it read lower (ADA), because younger red cells have had less time to collect glucose. If you take medicines that lower blood sugar, your doctor sets your target.

Common causes

What moves HbA1c

Nutrition

NIDDK's prediabetes advice centres on healthy eating and weight management. In the US Diabetes Prevention Program, losing 5% to 7% of starting weight reduced the chance of type 2 diabetes in people at high risk (NIDDK).

Training

Getting more physically active is a core step in CDC and NIDDK advice for reversing prediabetes. Working muscles take up glucose from the blood, so regular activity across the week supports a lower average.

Sleep and stress

NIDDK includes enough sleep in its prediabetes advice and links sleep apnoea to insulin resistance; the CDC's lifestyle change programme teaches stress management.

Habits

Smoking, including e-cigarettes and second-hand smoke, is a risk factor for insulin resistance and prediabetes (NIDDK). HbA1c rewards changes kept up for months, not a strict week before a test.

How fast HbA1c can change

Red blood cells live about three months, so HbA1c is a rolling average of roughly the last 2 to 3 months, weighted towards the most recent 30 days (NIDDK). A Day 90 re-test is the first point at which it covers a full cycle of change, though some earlier weeks still feed in. It can show whether your average blood sugar has moved, and in which direction. It cannot show daily spikes or lows (NIDDK), the last few days, or a diagnosis on its own. A change in iron status or recent blood loss between tests can also move the number for reasons unrelated to glucose.

Before your test

When to speak to your doctor

Speak to your doctor about any result of 5.7% or above, so they can confirm it and plan re-testing. A result of 6.5% or above needs prompt follow-up and a confirmatory test. Get same-day medical advice if a high result comes with strong thirst, passing much more urine, unexplained weight loss, blurred vision or extreme tiredness. Vomiting, confusion, fast breathing or drowsiness with high blood sugar is an emergency: call emergency services.

On the Wolfburgh panel

HbA1c is one of the 17 markers on the Wolfburgh blood panel. Your sample is collected at home with RedDrop One, an FDA-cleared collection device, and a licensed physician reviews every panel before your care team sees it.

The Nutritionist and Trainer work on diet, weight and activity and the Behaviour Specialist on sleep, stress, smoking and consistency, while the Partner Physician reads HbA1c with triglycerides and HDL, part of the same metabolic picture, and ferritin, since low iron can push HbA1c up. Members re-test at Day 90, backed by the 90-Day Results Guarantee.

Common questions about HbA1c

What is a normal HbA1c level?

By American Diabetes Association criteria, also used by the CDC, an HbA1c below 5.7% is normal, 5.7% to 6.4% is prediabetes and 6.5% or above is in the diabetes range. A diabetes-range result without symptoms needs a repeat test to confirm it. People with diabetes have individual targets, and the range printed on your own lab report takes priority.

How can I lower my HbA1c?

Sustained changes to weight, food and activity are the main levers. In the US Diabetes Prevention Program, losing 5% to 7% of starting weight cut the chance of type 2 diabetes in people at high risk. The CDC adds healthy eating and more physical activity, and NIDDK adds enough sleep and stopping smoking. Because HbA1c averages about 3 months, judge changes at a re-test around then.

Can an HbA1c result be wrong?

Yes, sometimes. Iron deficiency can make it read falsely high, conditions that shorten red blood cell life, such as recent blood loss, can make it read low, and some haemoglobin variants can push it either way. Pregnancy, kidney failure, liver disease, HIV and some medicines also affect it, and the ADA recommends glucose-based tests for diagnosis in several of these situations.

How often should HbA1c be retested?

For tracking change, retesting much sooner than about 3 months shows little, because HbA1c averages blood sugar over that period. NIDDK says people with diabetes should have an A1C test at least twice a year, and a first diabetes-range result without symptoms should be repeated on a different day to confirm it. For prediabetes, your doctor sets the schedule.

Sources

  1. MedlinePlus (NIH). Hemoglobin A1C (HbA1c) Test
  2. NIDDK (NIH). The A1C Test & Diabetes
  3. NIDDK (NIH). Insulin Resistance & Prediabetes
  4. American Diabetes Association (Diabetes Care). 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes 2026
  5. CDC. Diabetes Testing
  6. CDC. Preventing Type 2 Diabetes

This page is general information, not medical advice, and it does not replace a consultation with your own doctor. Never start, stop or change a medicine or supplement because of something you read here.

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