Melatonin
The sleep/circadian hormone your pineal gland makes when it gets dark. Signals "night" to the body. Most people take it orally; this is an injectable form, for sleep timing and as an antioxidant.
Standard
Units at 2 mg/mL. Low doses (0.5–1 mg) often work better and cause less morning grogginess than high doses.
Cycle & timing
Cycle: As needed; can be used nightly or for jet-lag/shift-work resets.
Timing: 30–60 min before desired sleep; for jet lag, time to the destination night.
Where: SubQ, abdomen. (Oral/sublingual is the more common route.)
What to expect
Faster sleep onset and circadian shifting. Not a sedative, it signals timing, so a dark, low-stimulation environment matters.
How much to buy
For weeks of nightly low-dose use:
Men & women
Unisex, dose by protocol, not sex; start low. Discuss with a prescriber in pregnancy / breastfeeding.