that sort of depends on what you're doing the fasting. If you are fasting occasionally for e.g., blood work, it probably shouldn't have an impact. However, if you fast on a regular basis as a lifestyle choice, it may not be an ideal situation, both in terms of taking Actemra and for your RA in general. When you have a chronic illness, it is important to be as healthy as possible to support your body in getting through each day. One of the ways in which you do this is to make sure you have enough fuel.
I'd recommend that you speak to your rheumatologist about this.
You need to ask your physician. I take Actemra and verify everything with the doctor...and if I am not in a place where I can ask the doctor, I call my local pharmacist, with whom I have a good relationship with.