Thank you for asking me to respond.
There could be two main reasons for your note being able to lift your arms beyond shoulder level.
One is Frozen shoulder, and this is common in diabetics. The shoulder becomes stiff gradually over a period of time. It is often self limiting and over 18 months it resolves.
The other is rotator cuff tear. This can happen gradually following inflammation of the cuff. The inflammation usually results due to impingement or pinching of the cuff between the AC joint and the shoulder joint.
You need to get an MRI done in order to determine which of these two conditions are affecting your shoulder. Treatment will vary accordingly. In the meantime you can take pain meds to relieve the pain.
Note: I cannot prescribe meds as it is prohibited by Practo.