Prediabetes and type 2 diabetes: what the guidelines say

Prediabetes and type 2 diabetes both describe blood glucose (blood sugar) running higher than typical, differing by degree. Prediabetes means glucose is elevated above the normal range but not high enough to meet the threshold for diabetes; type 2 diabetes means the body has become resistant to, or does not produce enough of, the insulin that normally keeps blood glucose in range. This page describes what the American Diabetes Association’s current Standards of Care, its annually updated guideline, says about how each is diagnosed and how the guideline frames management.

The diagnostic thresholds the guideline uses

The ADA sets diagnosis using any of three blood tests, and the same three tests define both categories at different cutoffs. Any single one of these results, confirmed on a repeat test in the absence of clear symptoms, is enough to diagnose diabetes; the guideline does not require all three to agree.

Prediabetes, per the guideline, is defined by any of the following:

• A1c (a measure of average blood glucose over roughly three months) of 5.7% to 6.4%
• Fasting plasma glucose (FPG) of 100 to 125 mg/dL, a pattern the guideline calls impaired fasting glucose
• A 2-hour glucose reading of 140 to 199 mg/dL on a 75-gram oral glucose tolerance test (OGTT), a pattern the guideline calls impaired glucose tolerance

Diabetes, per the guideline, is defined by any of the following:

• A1c of 6.5% or higher
• Fasting plasma glucose of 126 mg/dL or higher
• A 2-hour OGTT reading of 200 mg/dL or higher
• A random plasma glucose of 200 mg/dL or higher, but only when accompanied by classic symptoms of high blood glucose or a hyperglycemic crisis

The guideline notes that these three tests do not always agree with each other on the same person: the 2-hour OGTT tends to identify more people with prediabetes or diabetes than A1c or fasting glucose do, because it captures a different aspect of how the body handles a glucose load. That is a real, acknowledged limitation of using any single test in isolation, not an error in the thresholds themselves.

What the guideline says about the categories of options for prediabetes

For prediabetes, the guideline’s primary evidence base is the Diabetes Prevention Program (DPP), a large randomized trial published in 2002. The DPP assigned people with elevated fasting and post-load glucose to one of three groups: placebo, metformin, or a structured lifestyle-intervention program with goals of at least 7% body-weight loss and at least 150 minutes of moderate physical activity per week. Over roughly three years, the intensive lifestyle group had a 58% lower rate of progression to diabetes than the placebo group, and the metformin group had a 31% lower rate than placebo. The lifestyle intervention outperformed metformin in the trial overall, though the ADA’s current guideline notes metformin performed comparably to lifestyle change in certain subgroups, including people with a BMI of 35 or higher and younger adults.

Building on that evidence, the guideline describes two categories of options for prediabetes: structured lifestyle-change programs aimed at the same weight and activity goals the DPP tested, and, for some people, pharmacologic prevention with metformin, described by the guideline as an option worth particular consideration for adults roughly 25 to 59 years old with an elevated-risk profile (for example a BMI of 35 or higher together with a fasting glucose of 110 mg/dL or higher and an A1c of 6.0% or higher), and separately for people with a history of gestational diabetes. This is a description of who the guideline says a metformin conversation may be especially relevant for, not a recommendation that any individual reader take it; that determination depends on a full picture only a clinician has.

What the guideline says about the categories of options for type 2 diabetes

For diagnosed type 2 diabetes, the guideline describes glucose-lowering medication as part of care alongside the same lifestyle categories used in prevention. On medication choice, the guideline has moved toward a person-centered framework rather than a single default first step. It still describes metformin as a commonly used option and notes that it has historically served as the typical starting point when glucose lowering is the only consideration. But the guideline now gives comparable or greater weight to a person’s other conditions: for people with established cardiovascular disease, heart failure, chronic kidney disease, or obesity, it describes classes such as GLP-1 receptor agonists, SGLT2 inhibitors, or dual GIP/GLP-1 receptor agonists as options a clinician may prioritize on the basis of those conditions, independent of the current A1c number. This page names these as categories the guideline describes, not as a recommendation for any individual reader; medication choice and any dose are between a person and their clinician.

The A1c target, and why it is not one-size-fits-all

The guideline states that an A1c goal below 7% is appropriate for many adults with diabetes who are not experiencing hypoglycemia or other quality-of-life effects from treatment. It is explicit, though, that this is a general reference point, not a universal target. The guideline describes lower goals, such as below 6.5%, as potentially appropriate for people in good health with a low burden from treatment, and it describes less stringent goals as potentially appropriate for people with significant cognitive or functional limitations, frailty, serious co-existing illness, or situations where the risks of tighter control, including hypoglycemia, outweigh the benefit. Factors the guideline lists as relevant to where a given person’s target should land include how long they have had diabetes, their life expectancy, the severity of any existing complications, their hypoglycemia risk, and the support systems available to them. Where any individual’s target falls on that range is a clinical judgment, made with a clinician who knows the full picture, not something this page can determine.

Questions to discuss with your clinician

• Which specific test or tests, and what results, were used to place me in the prediabetes or diabetes category?
• Given that different tests can disagree, should more than one test be used to confirm where I stand?
• What would a structured lifestyle program modeled on the DPP look like for someone in my situation, and am I in one of the groups the guideline flags for a metformin conversation?
• What A1c target is appropriate for me specifically, given my health, other conditions, and how long I have had elevated glucose?
• Do I have cardiovascular, kidney, or weight-related factors that would shift which medication class is considered first for me?
• How often should my glucose or A1c be rechecked to see whether the current approach is working?

For related evidence on the lifestyle factors the DPP tested, see physical activity and body weight, or read the companion profiles on high blood pressure and high cholesterol, both of which commonly appear alongside prediabetes and type 2 diabetes.