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Prediabetes

Prediabetes: an early signal, not a destiny

Understand impaired fasting glucose, impaired glucose tolerance, HbA1c-based prediabetes, and why the tests do not always identify the same people.

3 min readEasy read4 sourcesChecked 30 Sept 2026Established

By The Diabetes Guide editorial project · Updated 30 Sept 2026

On this page
In simple words

Prediabetes means blood sugar is higher than usual but not yet in the diabetes range. It is a warning sign and a chance to act.

  1. Step 1: The numbers

    HbA1c 5.7–6.4%, fasting sugar 100–125 mg/dL or a 2-hour test of 140–199 mg/dL are the usual prediabetes ranges.

    For example: Traffic lights: green is below, yellow is prediabetes, red is diabetes range.

  2. Step 2: Why tests disagree

    Each test looks at a different part of how the body handles sugar, so results can differ.

    For example: Three friends describe the same movie: one liked the story, one the music, one the acting.

  3. Step 3: What helps

    Big studies showed lifestyle support and metformin reduced diabetes for high-risk adults. Talk with a clinician about what suits you.

    For example: A team coach helps you choose drills that fit you, not just a poster on the wall.

Remember: Prediabetes can go back to normal, stay the same or move on.

The full story

Want more? Below is the detailed version with the real science words. It is fine to skip it.

The laboratory ranges

These are ADA criteria for nonpregnant people. Pregnancy uses different testing pathways. Organizations differ in some intermediate-risk definitions; for example, WHO's impaired-fasting-glucose lower boundary is higher than the ADA boundary. 2

TestBelow prediabetes rangePrediabetesDiabetes range
HbA1cBelow 5.7%5.7–6.4%6.5% or above
Fasting plasma glucoseBelow 100 mg/dL (5.6 mmol/L)100–125 mg/dL (5.6–6.9)126 mg/dL (7.0) or above
2-hour 75-g OGTTBelow 140 mg/dL (7.8 mmol/L)140–199 mg/dL (7.8–11.0)200 mg/dL (11.1) or above

“Below prediabetes range” does not mean that arbitrarily low glucose is healthy. Diabetes-range results usually need confirmation in the absence of unequivocal hyperglycemia.

What happens inside the body?

Fasting glucose is strongly influenced by liver output and basal regulation. An OGTT challenges the system's handling of a standardized glucose load. HbA1c integrates glucose exposure through glycation of hemoglobin, a protein in red blood cells. These tests sample different aspects of physiology, so agreement is incomplete. Anemia, altered red-cell lifespan and hemoglobin variants can further distort HbA1c. 3

Is progression inevitable?

No. People can move to lower glucose ranges, remain stable or progress. Higher initial glucose, worsening weight or waist trends, family history and other factors influence risk, but they cannot tell an individual how many years remain. Risk is continuous across thresholds rather than changing abruptly at one decimal place. 1

Step by stepA simple model

A conceptual diabetes state machine

↺ This is a loop: the end feeds back to the start.

Below thresholds. Glucose tests are below diagnostic cutoffs; risk still varies.

Read every step in a list
  1. Below thresholds. Glucose tests are below diagnostic cutoffs; risk still varies.
  2. Higher risk. Factors such as family history and previous gestational diabetes inform screening.
  3. Prediabetes. Intermediate glucose ranges; regression, stability and progression are all possible.
  4. Type 2 diabetes. Confirmed diagnostic criteria; care addresses glucose and organ protection.
  5. Possible remission. Glucose below the diabetes threshold without glucose-lowering therapy under the consensus definition.
  6. Monitor / relapse. Ongoing monitoring is needed; relapse may require renewed treatment.
Not an official T2D staging system, prediction model, or inevitable sequence. Prediabetes can return to below-threshold glucose; remission can relapse. Source: Riddle et al.; international consensus group

What intervention evidence actually shows

The Diabetes Prevention Program tested structured lifestyle support and metformin in selected high-risk adults. Both reduced progression compared with placebo; that evidence is stronger than claims based on a particular supplement or a single food. A clinician can help decide whether and how that evidence applies. 4

What to discuss with a clinician

Clarify which test was abnormal, whether confirmation is needed, how other risk factors change interpretation, and which sustainable support is available. Screening intervals depend on risk and guidance. Improving a number is useful, but cardiovascular health, nutrition and quality of life matter too.

Trace the evidence

Sources and further reading

2.Diabetes Tests & Diagnosis (opens in a new tab)

NIH / NIDDK · 2026 · Reference

Established
Who was studied, limits and source check

Limitations: Living patient resource; year denotes access year, not a newly published study.

Source checked 2026-09-30. See the original publication for full methods.

3.The A1C Test & Diabetes (opens in a new tab)

NIH / NIDDK · 2026 · Reference

Established
Who was studied, limits and source check

Limitations: Living reference accessed in 2026; red-cell disorders can make A1c unreliable.

Source checked 2026-09-30. See the original publication for full methods.

4.Diabetes Prevention Program: trial and follow-up (opens in a new tab)

NIH / NIDDK; DPP Research Group · 2002 · Randomized trial

Strong Evidence
Who was studied, limits and source check

Population: US adults at high risk with elevated glucose and overweight

Sample: 3,234 randomized adults

Limitations: Relative risk reductions over about 3 years; not a guarantee for every individual or every prediabetes definition.

Source checked 2026-09-30. See the original publication for full methods.

Source checking is an editorial literature check, not independent medical review. This page is for learning. It cannot diagnose you or make a treatment plan. Evidence labels describe the cited claims, not the whole topic.

What does “Established” mean?

Doctors and scientists agree. This is well known. Like “the sun rises in the east”.

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