Yes. Most carriers allow a reconsideration request after a documented period of improved control. It is never automatic — you have to ask, with current labs.
A rating assigned during a bad stretch is not a life sentence, and a surprising number of people never find this out.
How reconsideration works
You request it, with current records. The carrier re-reviews the file against its present guidance. A rating assigned for a controllable condition is often reduced or removed when the numbers support it.
The waiting period is set by the carrier rather than by any industry standard, so ask yours what it requires.
Nobody does this for you
There is no annual review and no letter in the mail. If your A1c has come down meaningfully since you were rated, that is worth a phone call to whoever wrote the policy.
The alternative
If reconsideration is refused, shopping the policy against the current market is the other move. Carrier appetite shifts, and a file that was expensive three years ago may be priced differently now.
The full treatment of this topic is on Diabetes.