The easiest way I know with the U40s is to make a sample syringe where the .25 increase would be (start with more -colored water- and let out a tiny bit until you are where the original dose plus the increase would be. Mark the syringe with tape or permanent amrker and set it out for comparison when you shoot the new dose.)
I can't remember why you don't want to do the U100s. If it is a vet issue, I don't think you need a prescription if you order from ADW. (Someone will correct me if I am wrong)
Definitely think an increase is a good idea, if you monitor.