A1c of 5.7 to 5.9%: what the result means

An A1c of 5.7% is the first value of the prediabetes range used in the US by the American Diabetes Association (ADA) and the CDC, which runs from 5.7 to 6.4%. A1c 5.8 and 5.9 sit in the same low part of that range. It is not diabetes, which starts at 6.5% confirmed by a second test. It corresponds to an average blood sugar of about 117–123 mg/dL. Canada and the UK start prediabetes at 6.0%, so the same number can be flagged on one report and not on another.

Reference ranges

Category	Reference range
Normal (US, ADA)	below 5.7 (below 39) % (in brackets, mmol/mol)
Prediabetes, low end (US only)	5.7–5.9 (39–41) % (in brackets, mmol/mol)
Prediabetes (US, Canada, UK)	6.0–6.4 (42–47) % (in brackets, mmol/mol)
Diabetes range, if confirmed	6.5 or more (48 or more) % (in brackets, mmol/mol)

Cut-offs depend on the guideline your lab and doctor follow, so check the reference range printed next to your result. A1c is less reliable in anemia, after blood loss or a transfusion, in pregnancy, in kidney or liver disease and with some hemoglobin variants.

A1c 5.7 meaning: what the test shows

A1c (also written HbA1c or hemoglobin A1c) measures how much of the hemoglobin in your red blood cells has glucose attached. Red cells live about three months, so the result reflects your average blood sugar over the past two to three months, not what you ate yesterday. You do not need to fast for it.

At 5.7 to 5.9% your average blood sugar is only slightly above the level considered optimal. This is the lowest-risk part of prediabetes. Most people with this result feel nothing and find out at a routine physical or an employer screening. The CDC estimates that about 115 million US adults have prediabetes, and most of them do not know it.

A1c 5.7, 5.8 and 5.9: average blood sugar

Labs sometimes print an "estimated average glucose" (eAG) next to the A1c. It is calculated from the A1c with a standard formula and includes after-meal peaks, so it usually sits above your fasting glucose:

• 5.7% (39 mmol/mol): about 117 mg/dL (6.5 mmol/L)
• 5.8% (40 mmol/mol): about 120 mg/dL (6.7 mmol/L)
• 5.9% (41 mmol/mol): about 123 mg/dL (6.8 mmol/L)
• 6.5% (48 mmol/mol), the diabetes threshold: about 140 mg/dL (7.8 mmol/L)

Why one report flags 5.8 and another does not

There is no single worldwide cut-off for prediabetes. In the US, the ADA and the CDC count everything from 5.7% up, so most US labs will flag 5.7. Diabetes Canada and UK guidance start prediabetes at 6.0% (42 mmol/mol), so a Canadian or UK report may show 5.8 with no flag at all. Neither lab is wrong: they follow different guidelines.

What all of them agree on is the diabetes threshold: 6.5% or more, confirmed by a repeat test or a second test such as fasting glucose. A result of 5.7 to 5.9 is well below that.

Can the number be off?

A1c depends on red cells living a normal lifespan, so anything that changes that lifespan can move the number without any change in blood sugar. In the 5.7–5.9 range, where a tenth of a point decides the label, this matters:

• iron deficiency and some other anemias can push A1c up; blood loss, a recent transfusion or hemolysis tend to push it down;
• hemoglobin variants such as sickle cell trait can interfere with some lab methods;
• advanced kidney disease, liver disease, pregnancy and some medicines also affect it, and doctors then rely more on glucose tests;
• two tests a few months apart can differ by a tenth or two simply because of the method.

What doctors look at next

One A1c of 5.7% is rarely read alone. Your doctor will usually look at the fasting glucose from the same draw: if it is also 100–125 mg/dL, both point the same way; if it is normal, the 5.7 carries less weight. They also consider age, weight, blood pressure, triglycerides and HDL cholesterol, a family history of diabetes and diabetes during a past pregnancy.

With prediabetes, the ADA suggests repeating the test about once a year, and the CDC says every one to two years; your doctor sets the schedule. A1c changes slowly, so rechecking after a few weeks tells you little. If your result is 6.0 or higher, see the page on HbA1c 6%.

Do I need medication for an A1c of 5.7?

Usually the first conversation is not about medication. US guidance puts lifestyle first in prediabetes: being more active, losing some weight if you carry extra, and cutting back on sugary drinks and highly processed food. The CDC-recognized National Diabetes Prevention Program is built for exactly this range. Whether anything beyond that makes sense for you is a decision for your doctor, based on your overall risk, not on the A1c alone.

When to see a doctor

An A1c of 5.7 to 5.9% is something to discuss at a routine visit with your primary care doctor, not an emergency. Book an earlier appointment if you have strong thirst, pass a lot of urine or lose weight without trying; if you are pregnant or planning a pregnancy; or if your fasting glucose on the same report is 126 mg/dL or more. Call 911 in the US or Canada (999 in the UK) if high blood sugar comes with vomiting, fast deep breathing, confusion or drowsiness.

Sources

Written using public information from:

• American Diabetes Association. 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes—2026. Diabetes Care 2026;49(Suppl 1):S27–S49
• American Diabetes Association: Diagnosis
• CDC: A1C Test for Diabetes and Prediabetes
• CDC: Preventing Type 2 Diabetes
• Diabetes Canada Clinical Practice Guidelines: Screening and diagnosis (prediabetes A1C 6.0–6.4%)
• Diabetes UK: Prediabetes (42–47 mmol/mol)

This material is for general information only. It is not a medical opinion and does not replace a consultation with a doctor. Reference ranges depend on the laboratory and the method — rely on the range printed on your own report. Your doctor makes the final interpretation.