Renee -
It is an over the counter supplement, so you could take it without letting the doctor know.
My personal policy is to always let my docs know when I add or delete a med or a supplement, so they have a full picture of what is going on.
That said, my pulmonologist was indifferent to whether I took it, but the pain doc was a fan because it has anti-inflammatory properties. Her attitude is the same about Mucinex, but I know it works. However, she was not my doc when I had sticky, thick mucus causing sinus infections and ear infections many times a year.
Sue