Get Your Dog Care Questions Answered by Experts
Hello and thank you for using this site to help you.
Blood in the urine can mean bladder stones or a urinary tract infection and either would need antibiotics, and if there are stones then maybe a change in diet.
At this point, because we are not sure of the cause for urgency, it is important that he have enough fresh water to drink to continue to flush out the system.
At age 14 though, you can't rule out other issues that may be a bit more serious, such as what is listed in the link below or bladder cancer.
since you are going to the Vet tomorrow I would suggest you not give anything because if your vet want to prescribe a pain medication it may have to wait until something like aspirin leaves the body. As well aspirin thins the blood which could make bleeding worse. I would just make sure he has enough fresh water. Also if they need to do blood work you don't want meds in the system