My Daddy brought me to the vet after he saw me kinda 'gagging' up small pools of clear saliva. Sometimes it would be when I'd wake up and take my first stretch, sometimes it would be when I was eating, and sometimes for no reason. It's not like a "hacking" of a furball, but more like a single "push" and a little spittle would come out. It was only 20 or so times over the course of a few days, but I'm almost 8 and he was concerned.
I went to the vet and was given some antibiotics and had some blood work done. The antibiotics seem to have helped as my gagging has gone away, but the blood results showed an elevated level of the GGT liver enzyme: My GGT level was 20 u/L (normal is 0-6 u/L)
My doctor wasn't too concerned and said other liver enzymes are usually elevated too when there is a problem. She recommended another blood test in 6-8 weeks.
Maybe my kitty buddies have some information to offer? My Daddy loves me VERY much and is always concerned about me!