I did not have an answer for this, but have enjoyed reading the ones you are getting. I wish I knew why it's okay for a diabetic. You would think it's sweet like most over the counter drugs. Thank You for this question!!! It doesn't work for me, but it works for the other three people in my family. Guess you won't know til you try. That stuff worked wonderful for me! I would highly recommend it. It loosens the phlegm in your lungs so that you can cough it up more easily. I keep a bottle on hand at all times. My husband and I are in our 50's, he's diabetic, and we've both had some level of pneumonia, even tho we had pneumonia vaccine. He almost died with it 4 yrs ago. Last year I had a mild form. Dr. prescribed Mucinex, the generic Walgreens brand. The one for nasal AND chest congestion. As soon as we have any type of cold or sinus drainage, I take that so it helps prevent it from accumulating in my chest. He's a severe diabetic and I'm very healthy and it works for both of us. Mucinex is like the other cough syrups/expectorants, like Robitussin, etc.. It has an ingredient that loosens the mucous and makes it easier to cough up. One brand also has a cough suppressant that helps with mild to moderate coughs. There are many generic brands that have the same ingredients, work just as well, and cost a lot less.