How long do you have to wait for your background check?

Hi!! I just got my c.n.a license and I applied at a rehabilitation center last week. I got an interview. They told me I got the job. Went and took my drug test and pass. Now im just waiting on my background check. It's been a week and no call yet. So im just seeing how long did you have to wait? Is it normal to take this long? I know I have nothing in my background check that would flag me so its kinda making me anxious that I havent heard anything back. Also I use to work in a health care setting when I was younger as a dietary aid and I remember it only took 3 days to come back. So I don't know its because I didn't need a certificate for that position and now that I have one for a c.n.a its takes them longer to verify it.