This belongs in a buying guide rather than a mechanism page because it is the local reason people conclude they bought a bad vial when they did not.
A 5mg vial reconstituted in 2.5mL of bacteriostatic water gives 50 units, which is 200mcg on a U-100 syringe. The protocol is to inject 30 to 60 minutes before sleep on an empty stomach. Manila late-night eating culture is the main reason people here see weak results: the Jollibee run, the lugaw stop, the midnight milk tea. If you ate at 11pm, your 11:30pm shot is essentially wasted, because insulin blunts the growth hormone pulse the peptide is meant to trigger.
Price that out. A wasted nightly dose on a ₱2,000 vial that holds twenty-five doses is roughly ₱80 a night thrown away, plus a cycle that reads as a failure and gets blamed on the supplier. Fixing the eating window costs nothing. See the injection timing note for the general version of this.