Perhaps not everyone does what I do, nor is it always practical, but like Susan says, when you take both cats to the vet, they won't have a problem with the other when you return home (since they'll smell the same, being in the clinic).
I take my two to the vet together, even if it's just one cat that has an issue. G is a curious, confident cat at home, and Maya is more of the skittish one. However, G gets very anxious and sometimes starts panting in his carrier during car rides to the vet (probably from stress as he had a few issues last year & needed more than a few vet checks) and hisses when he's being checked out, he just hates vet visits. Maya, on the other hand, is just the chillest cat at the vet's, was purring and rolling around on the table, when I pet her, and never makes a big fuss or hardly resists the check ups when she's there, though they may both meow in the car. For this reason, I take them both, as Maya's confidence seems to help G, and the vet tech always realizes one is there for "moral support".
As a side note, I also do try to make their vet visits as least stressful as possible. I use feliway spray in their carrier about 30 minutes prior to leaving, and take it with me to the office so I can use more if needed when they enter the exam room. I also leave their carrier out at all times in my home, put out their favorite goodies inside, leave a soft bed padding, so they can inspect and even take a retreat if they feel like it. They also don't freak out when I move it around the house or put them inside. I also take treats with me to the vet, even if they really aren't in the mood to eat right then, all to form more positive associations. Hopefully your next vet visit will be much better for you and your cats.
Last edited by TabbCatt; 03-08-2015 at 10:44 PM.