Blood Sugar Question?

I have a question regarding my fasting blood sugars and I would love for someone to answer it for me!

As many of you know I work bartending 4 nights a week, and on these nights I am at my job from 8pm until 3am.

Sometimes I use this time as my (8 hour) fast, and take my reading around 3:30am.

On nights that I don’t work I usually eat my last meal around midnight, stay up for a few hours more, and then take my reading when I wake up around 10am or so.

I feel like I am eating as consistently as possible, however I find that my blood sugars at 3:30am (after my shift) are right on the money, usually ranging from 85 – 100, but my morning blood sugars (after eating at midnight, then sleeping and waking around 10am) are higher ranging from 120-150.

Can anyone tell me why this is?

The only big difference that I can think of is while I am at work I am fairly active, and when I sleep during my fast I am not.

Could this make such a drastic difference in my numbers?

Any explanation would be very helpful!