When to measure IGF-1 post HGH injection?

Will start to take HGH next month

Just got the lab results from my IGF-1 blood work

42y male
127,0 ng/mL

When I start using and get up to lets say 4ui daily, which is the best time to go do the blood work to see how much it raised?

In the morning, 60 min after the injection, straight to the lab to collect?