I've done it before when I had a bad cough, needless to say the nurses were not so pleased with me...but obviously I survived.
I would speak to the doctor before you cancel...you don't want to exacerbate your disease if you don't have to.
My nurse always asks if I have an active infection before she starts the drug.
Talk to your doctor, get his opinion.
I have had 3 Remicade infusions and for two of them, when I went in, I had a low-grade fever. The first time the nurse called my doctor and spoke to the pharmacist and they decided to move ahead with the infusion. The second time I had a fever, my GI was out and the pharmacist said to go ahead anyhow so they did.
I am with the others on here--I would rather have the Remicade while not feeling too great then pay the consequences of waiting for the infusion.