This -- I believe this is the latest advice.
Early-on, doctors advocated HGH right before bed. Suppossedly that aligned with your own natural HGH production.
But most of the thinking now (I believe breaks toward doing it first thing in the morning and laying off carbs (I was told an hour).
Here are a couple of other largely-accepted HGH beliefs:
1) Always use HGH with low blood sugar. HGH in the presence of high blood sugar can damage tissues.
2) The maximum dose you can effectively process is around 2.0-2.4 units. Shooting much more than 2.4 is best done by splitting the dose and separating the shots by several hours (or more).
3) The HGH molecule is very frail (27k+ daltons -- a huge and wobbly molecule). Don't shake vials. But also, be careful about even the smallest stray bubble when you inject. That bubble can act like a foaming agent and tear-up some of your dose. It doesn't keep well after reconstitution even in the refrigerator either (think days, not weeks).
It'll type more if I remember it. The best advice I ever got was from the Anti-Aging Group (a legal physician clinic) down in Florida.