Hemoglobin A1C 5.7 to 6.4 %

The Standards call this range "a group of individuals at high risk for diabetes and cardiovascular outcomes" and say people in it "should be informed of their increased risk for diabetes and cardiovascular disease and counseled about effective strategies to lower their risks." The risk inside the range is not flat. The Standards describe it as "continuous and curvilinear," rising disproportionately as A1C climbs, and for an A1C above 6.0 percent they say "Aggressive interventions and vigilant follow-up should be pursued."

Monitoring. Recommendation 3.1: "monitor for the development of diabetes at least annually." Table 2.5 says the same, yearly testing for anyone with an A1C of 5.7 or higher.

The program the ADA refers you to. Recommendation 3.3, grade A, refers adults with overweight or obesity at high risk to a diabetes prevention program, with a target of at least 5 to 7 percent of starting body weight lost through a reduced-calorie eating pattern plus at least 150 minutes a week of moderate-intensity physical activity. The evidence behind that referral is the Diabetes Prevention Program trial, which the Standards report "could reduce the risk of incident type 2 diabetes by 58% over 3 years." Weight loss did most of the work: every kilogram lost cut progression risk by 16 percent over 3.2 years, and 150 minutes of weekly activity cut it by 44 percent even without hitting the weight goal. Certified programs delivered by phone, app or telehealth count (Recommendation 3.6). The CDC's National DPP admits adults 18 and older with a BMI of 25 or higher (23 for Asian Americans) who have not been diagnosed with type 1 or type 2 diabetes and are not pregnant, and who have had an A1C between 5.7 and 6.4 percent within the past year, a prior gestational diabetes diagnosis, or a high-risk score on its risk test.

Metformin. Recommendation 3.7 says metformin "should be considered" for adults at high risk, and names the groups it means: people aged 25 to 59 with a BMI of 35 or higher, a fasting glucose of 110 mg/dL or higher, an A1C of 6.0 percent or higher, and anyone with prior gestational diabetes. In the DPP it was less effective than lifestyle change overall, and as effective in people with a BMI of 35 or higher and in participants aged 25 to 44. The Standards say no other drug has long-term data for prevention alone, and Recommendation 3.10 says to consider periodic vitamin B12 assessment in people on long-term metformin, especially with anemia or peripheral neuropathy.

The heart. Recommendation 3.11: prediabetes carries heightened cardiovascular risk, so this result should prompt screening for and treatment of blood pressure, lipids and the other modifiable risk factors. The Standards are candid about one limit: the prevention trials mostly enrolled people with impaired glucose tolerance on an OGTT, not people identified by A1C alone.