About starting azathioprine:

I have been on azathioprine for 16 months or so. It has been effective for my
joint swelling from autoimmune arthritis.

Before my rheumatologist doc started me on it, she ordered some kind of blood work to test for a genetic marker connected to in/tolerance of azathioprine. I was ok to take it.

Also, she tested my liver function frequently at the start of the medication. At month one and then month 3, if I recall correctly. Now I am back to routine testing.

Also, she started me on it slowly. I think it was one pill a day for the first month, then the blood test, then 2 pills a day and the blood test.

My doc is very, very cautious-- belt-and-suspenders kind of person. Maybe not all doctors follow this protocol.