There is no industry-wide threshold. Each carrier sets its own bands in a manual it does not publish, and the trend across several readings carries more weight than any single number.
This is the question we get asked most, and the honest answer is less satisfying than the one most sites give.
Why there is no single number
No carrier publishes its diabetic underwriting bands. What circulates online as “the A1c you need” is broker-reported, not carrier-sourced, and it varies between carriers enough that a single number would be misleading.
What brokers consistently report is that readings under roughly 7.0 to 7.5 produce the most favourable outcomes, that some carriers extend their better classes below 6.5 where there are no complications, and that declines cluster above 9.0. Treat those as practitioner-reported ranges rather than published thresholds.
The trend matters more than the reading
Two years of stable readings is a materially different file from one good reading after three bad ones, even when the latest number is identical. Carriers are pricing control, and control is a pattern rather than a snapshot.
Practically: bring your last three A1c readings with dates, not just the most recent one.
The full treatment of this topic is on Diabetes.