Prediabetes HbA1c: what your results mean

Your lab report shows an HbA1c of 41 mmol/mol (5.9 percent) or a fasting glucose of 108 mg/dL. Is that prediabetes? It depends on whose cut-off you use: the ADA, the WHO and NICE in the UK draw the line in different places. You can keep your reports in a folder or in Sam's Health Vault, which, with your consent, reads HbA1c and glucose from each report so you can check them and compare your last two reports.

This article covers the numbers on the sheet, where guidelines differ and what to take to your next check. What usually comes next after a result in the risk range is in Prediabetes: what to do next after your result. Whether you have prediabetes is your doctor's call. If a later test points to type 2 diabetes, the type 2 diabetes page shows what Sam keeps there.

Which HbA1c and fasting glucose numbers count as prediabetes?

Three tests can show it: HbA1c (also called A1C), fasting plasma glucose and the oral glucose tolerance test (OGTT). In the UK you may also hear "borderline diabetes", according to Diabetes UK. Germany's national guideline speaks of an increased diabetes risk rather than prediabetes.

HbA1c reflects your average blood sugar over roughly the past two to three months. The German Diabetes Association (DDG) notes that it does not depend on fasting or the time of day. Fasting glucose is a venous blood draw after 8 to 12 hours without food. The DDG names 8 to 9 am as the time for it, because levels vary over the day.

US sources such as the NIDDK give HbA1c in percent, UK sources such as Diabetes UK in mmol/mol. Both describe the same result: 5.7 percent is 39 mmol/mol, 6.0 percent is 42 mmol/mol and 6.5 percent is 48 mmol/mol.

Why don't the guidelines agree?

Fasting glucose has two cut-offs. US guidance from the NIDDK starts the prediabetes range at 100 mg/dL, and Germany's national guideline uses the same number. The WHO starts at 110 mg/dL. Germany's family-medicine society DEGAM backs that higher limit. So do the drug commission of the German Medical Association and two other societies. NICE in the UK starts its high-risk band at 5.5 mmol/L, about 99 mg/dL, close to the US limit.

HbA1c has two cut-offs too. The ADA starts at 5.7 percent. NICE starts its high-risk band at 42 mmol/mol, which is 6.0 percent. Diabetes UK uses the same 42 to 47 mmol/mol band.

The glucose tolerance test is disputed as well. The DDG and the German Society of Internal Medicine see a reason for it when HbA1c and fasting glucose disagree or fall in the risk range. DEGAM and the drug commission see no role for it in general practice.

Here is how one report reads under each set of rules. Say it shows an HbA1c of 41 mmol/mol (5.9 percent) and a fasting glucose of 108 mg/dL.

• By the US cut-offs, both results are in the prediabetes range.
• By the WHO limit, the fasting glucose is below the range.
• By NICE rules, the HbA1c is below the range, because NICE starts at 42 mmol/mol. The fasting glucose of 108 mg/dL is 6.0 mmol/L, though, and NICE starts its high-risk band at 5.5 mmol/L, so it falls inside.

Same blood, three readings. A result just below a cut-off is not an all-clear: it can sit within the measurement error. Germany's national guideline also says a diabetes diagnosis based on results near a cut-off should be rechecked over time. Which reading applies to you is a conversation with your doctor.

What does the range printed on your report mean?

Next to each result your lab prints a range. MedlinePlus, the health site of the US National Library of Medicine, explains where it comes from. Reference ranges are built from the results of large groups of healthy people. Labs often use different ranges, so you compare a result only with the range on your own report. A result inside the range is not always a guarantee of good health.

HbA1c adds age to the mix: it rises over the years even in people without diabetes. Germany's national guideline shows reference ranges from two large German studies. For people aged 40 to 59 they reach 6.2 percent. A result of 5.9 percent can therefore sit inside your lab's range and still fall in the prediabetes range.

The same applies in Sam. For each value Sam reads from a report, the app shows whether it sits inside the range your lab printed. That is your lab's range, not a statement about whether you have prediabetes. If a report prints no range, Sam shows nothing for that value.

Why can HbA1c and fasting glucose disagree?

The two tests measure different things: HbA1c reflects weeks, fasting glucose one morning. Without symptoms, the NIDDK says, a result in either range should be repeated on a different day. For a diabetes diagnosis, German guidance asks for at least two lab results in the diabetes range. If the results disagree or fall in the risk range, the national guideline recommends a third lab value, possibly an OGTT.

HbA1c is measured on hemoglobin in red blood cells, so it can be skewed. The NIDDK and the DDG list:

• Higher than it should be, for example with anemia from low iron.
• Lower than it should be, for example while anemia from low iron is being corrected.
• Unreliable with kidney failure or liver disease.
• Off in either direction with some hemoglobin variants.
• Not suitable during pregnancy and up to about two months after giving birth, according to the DDG.
• Not suitable either after a transfusion, a blood donation or heavy bleeding, or in the first two months of some medicines that raise blood sugar.

To make such effects visible, the DDG recommends a current hemoglobin value from a blood count.

Near a cut-off, measurement error matters too. Germany's national guideline asks doctors to consider the "minimum difference". It is how far a result must be from a cut-off to differ from it with confidence. The lab should state it.

Home glucose meters are not approved for making a diagnosis, says the DDG. That takes venous blood and quality-assured lab methods.

How often should prediabetes be retested?

There is no single answer:

• ADA (US): At least once a year, with the frequency adjusted to your individual risk.
• NIDDK (US): A test for type 2 diabetes every year.
• NICE (UK): For people with a high risk score and results in its high-risk band, a blood test at least once a year, ideally the same type of test.
• German guideline groups: For results in the risk range, the DDG and the German Society of Internal Medicine suggest a first recheck after three months, then every six months. DEGAM considers the fasting glucose at the health check every three years enough when nothing else points to diabetes.

Your doctor decides what interval applies to you.

Some symptoms are a reason not to wait for your next scheduled test: strong thirst, peeing more than usual, feeling very tired, losing weight without trying, stomach pain or new vision problems such as blurred vision. The NHS symptoms page advises seeing a GP. Germany's national guideline is stricter: it says glucose should then be measured without delay, because these symptoms can point to an emergency. So contact your doctor's office straight away and ask for a blood sugar check. Don't wait for your next scheduled test, and don't wait for it to pass. If the office is closed, use your local out-of-hours doctor service (NHS 111 in the UK). More on these signs in Prediabetes Symptoms: Why You Usually Feel Nothing.

Call your local emergency number (112 in the EU, 999 in the UK, 911 in the US) if you have symptoms of high blood sugar, for example thirst or peeing more, and any of these come with them:

• Feeling or being sick.
• Stomach pain.
• Breathing more deeply or quickly than usual.
• A faster heartbeat than usual.
• Fruity-smelling breath.
• Feeling very drowsy or confused.

The NHS gives these as reasons to call 999. They can be signs of diabetic ketoacidosis, which can be life threatening, even if you have never been diagnosed with diabetes. Also call if you suddenly cannot see from one or both eyes or have sudden severe eye pain. Don't drive yourself: ask someone to drive you or call an ambulance.

What should you bring to the appointment?

The NHS suggests writing down your two or three most important questions. List all your medicines, including vitamins and supplements, and ask what your results mean. For a lab-results visit, that comes to:

• All your lab reports, including older ones, with the full blood count.
• A list of everything you take. Some medicines affect blood sugar and HbA1c.
• Anything that can skew HbA1c: pregnancy, a recent blood donation, heavy bleeding, known anemia.
• Whether you had fasted before the blood draw.

Questions that fit the numbers:

• Which fasting glucose cut-off do you use, 100 or 110 mg/dL?
• Do I need another test or a glucose tolerance test?
• When is my next check, and with which test?
• Is the change since my last report bigger than the measurement error?

For the medicines, see what to include on a medication list. For the visit in general, there is a doctor appointment checklist for a chronic condition.

In Sam, your reports sit in the Health Vault and you can show your medication list in the app. You create the monthly report yourself, from the 1st for the month before, as a PDF. For that, allow notifications and Apple Health access and tell the app whether you have a chronic condition. From your second report on, you also need to have recorded how you felt on at least 15 of the last 30 days. The report covers activity, sleep and stress. For lab reports it shows numbers, such as how many reports you added that month, not the lab values. It is not a doctor report. In Ask Sam you can ask, for example, how your HbA1c changed since your last report, as long as both reports use the same unit for HbA1c. The answers are based on your data and are not medical advice.

What can Apple Health add, and what can't it?

As of October 2026, no Apple Watch measures blood sugar. In 2024 the US FDA stated that it had not authorized any smartwatch or smart ring to measure or estimate glucose on its own. More on that in Can Apple Watch measure blood sugar?.

Apart from your lab reports, glucose readings appear in Sam only when a meter or sensor saves them to Apple Health. You then switch on the Blood Pressure & Glucose group. For the question of prediabetes, the lab results from venous blood are what counts.

What Sam reads from Apple Health are everyday measures such as steps, exercise minutes and sleep. You see them as trends over 7 days, 30 days or 6 months, in the same app as your lab reports. They are numbers to bring along, not a lifestyle measure. Sam has no influence on your lab values. Both the ADA's 2026 Standards and Germany's national guideline recommend lifestyle measures for results in this range; what that means for you is a conversation with your doctor. The prediabetes overview lists what Sam keeps.

Keep your lab reports in Sam and bring the changes to your visit

You walk into the appointment with your reports and what changed between them, instead of hunting for loose sheets.

• Instead of a folder: you add each report as a photo or PDF. With your consent, Sam reads HbA1c, glucose and your blood count from the report, and you check the values before saving. Sam shows the range your lab printed next to each value.
• Instead of comparing sheets yourself: Sam compares your last two reports and shows up to three of the biggest changes, as long as the units match.
• Instead of guessing in the consulting room: steps, exercise minutes and sleep from Apple Health are in the same app as trends over weeks.

Sam does not measure blood sugar and can't tell you whether you have prediabetes. More on the prediabetes page.

Try Sam for free

Sam is a wellness companion, not a medical device. It does not diagnose, treat, cure or prevent any disease or health condition. Always consult a qualified professional for medical decisions.

Related reading

• Can Apple Watch measure blood sugar?
• Medication list for your doctor: what to include
• Doctor appointment checklist for a chronic condition
• Living with type 2 diabetes: movement and sleep
• Prediabetes: what to do next after your result
• Prediabetes Symptoms: Why You Usually Feel Nothing

Sources

Updated: October 2026

• American Diabetes Association: 2. Diagnosis and Classification of Diabetes: Standards of Care in Diabetes 2026, Diabetes Care 2026; 49 (Suppl 1) (Table 2.2)
• American Diabetes Association: 3. Prevention or Delay of Diabetes and Associated Comorbidities: Standards of Care in Diabetes 2026, Diabetes Care 2026; 49 (Suppl 1): S50-S60 (Recommendations 3.1, 3.3 and 3.4)
• NIDDK: Insulin Resistance & Prediabetes (last reviewed March 2025) and The A1C Test & Diabetes (last reviewed April 2018)
• National Institute for Health and Care Excellence: Type 2 diabetes: prevention in people at high risk (PH38) (published 2012, last updated 15 September 2017; recommendations 1.4.1 and 1.6.5)
• Diabetes UK: Prediabetes (reviewed 27 January 2026)
• German Medical Association, KBV, AWMF: National Disease Management Guideline Type 2 Diabetes, version 3.0 (2023), chapter 3 (table 8, recommendation 3-2, differing society positions on recheck intervals; in German)
• German Medical Association, KBV, AWMF: National Disease Management Guideline Type 2 Diabetes, version 3.0 (2023), chapter 4 (tables 10, 14 and 15, recommendations 4-3, 4-4, 4-5 and 4-7, minimum difference; in German)
• German Diabetes Association (DDG): Landgraf R et al., Definition, classification, diagnosis and differential diagnosis of diabetes mellitus: Update 2025 (PDF), Diabetologie und Stoffwechsel 2025; 20: S127-S143, doi 10.1055/a-2566-7533 (figure 1, tables 5 and 6; in German)
• MedlinePlus (US National Library of Medicine): How to Understand Your Lab Results (updated 4 September 2025)
• NHS: Type 2 diabetes: symptoms (reviewed 10 February 2025), High blood sugar (hyperglycaemia) (reviewed 17 March 2026), Diabetic ketoacidosis (reviewed 8 June 2023), Vision loss (reviewed 28 August 2025) and What to ask your doctor (reviewed 12 January 2023)
• U.S. Food and Drug Administration: Do Not Use Smartwatches or Smart Rings to Measure Blood Glucose Levels (21 February 2024)