Thanks for asking this question.
You have not mentioned the names of any over the counter medicines which you are likely to use for hot flashes. There are hundreds of them available in the market. Of them, some may influence blood sugar levels which can go against your diabetes. So, it is wise to talk with your doctor, before going for a self treatment. He can advise you with this and can suggest some better medication than OTC drugs. The one which your doctor prescribes will surely suit your personal needs. Sometimes a blood test may also be needed to diagnose the exact problem with you.
Good luck.