Hi, thanks for the query to H .C.M. C.
Since you are a diabetic and on insulin
Itchy throat with cough
, it seems you are a patient of allergy
( Asthamatics allergic bronchitis
) , pl don't worry this is not a disease but a mild disorder due to mite ,dust, smoke, pollen.
It is a common feature that in the night when there is decrease in the temp than there is constriction in bronchi ( airways ) and allergic patient feel cough an ditch in the throat, same is with you.
Consult a physician and get an X ray
of chest with blood examination for eiosinophilia and have a treatment according to situation.
Sugar free cough syrup available in market if it combined with bronchodilators than it is good.
Have a good day. Dr. HET