This condition is called Ptosis, and occurs when the levator and Muller's muscles fail to function. In some cases this may be due to a palsy of the third cranial nerve, secondary to chronic high glucose levels, but this is by no means the most likely or only possibility. Medications and certain neurological disorders may also be a possibility.
It is a yellow flag and something that should be evaluated in person by your family physician.
What makes you feel this is diabetes related?