When to stop Test Prop before Dr. test

Newb here. 45yo male. Been lifting 3 years. In my 4th week of TRT (tested a little low ttl test=240). Getting the standard 100mg test cyp once a week. My last (4th) visit I was tested (blood work) again and I'll be tested a 3rd time in 4 more weeks. Then no more blood work for 3 months.

Finally found a way to supplement that (friend recommended GD), so I have some Test Prop & Test E on the way. After the 3rd blood work, I'm going to start the Test E weekly, in combo with the Dr's test cyp. But in the meantime, I'd like to do the Test Prop for a couple of weeks.

I'm guessing if I go a week without the Test Prop, just before my 3rd blood work, that should be enough to get my levels back to where they'd be with just the Dr.s TRT. Is that a correct assumption? Or should I give it longer or should I just not touch it until after the 3rd blood work?

TL;DR - How long before Test Prop is out of my system for blood work?

Thanks