For some reason the volume on my portable phone (kx-t7885) is very low even though it is adjusted to the highest setting...(the problem just started one day). Removing the battery did not cure the issue nor did lowering and then raising the volume setting.

Any suggestions on how to fix... the phone is almost unusable in its current state

It could be the port to which it is connected. Try moving it to a different port. Reset the base and the handset.

We've never had the 7885 have high enough volume for anyone

Thanks for the suggestion...tried it... did not improve

that is true...but in this case there was a very noticeable drop in output volume that just happened one day

I'd say Panasonic repair is your next stop! John C.