When I originally asked my pulmo about 3 vs 7 he said the same thing but he would have prescribed it if i had asked for it! I cannot remember if he told me later on to try 7% or if I just did it on my own (ordered from Amazon)? But when I switched to 7% I had less exacerbations. It did help more than the 3% for sure. So I would not listen to that instruction and see how you tolerate the 7%. At first you might adjust to it. Now I have a prescription for Pulmosal 7% but I still use the Amazon brand also since I nebulize 1.5 vials in the morning session. I use one of Pulmosal and 1/2 of the Amazon brand afterwards just to extend my treatment time.