Melatonin might be the most misunderstood supplement on the shelf. Patients often describe it as a sedative — something that "knocks you out" the way a sleeping pill might. That's not really what it does, and the mismatch between expectation and effect is where most of the disappointment comes from.
Melatonin is a timing signal, not a sedative. Your body produces it naturally as evening falls, and it helps tell your circadian clock that night has arrived. Taken as a supplement, it works best as a way to nudge the timing of your sleep window — useful for jet lag, shift work, or a circadian rhythm that's drifted later than you'd like — rather than as something that forces sleep on demand.
Dose matters more than people assume, and higher isn't better. Many over-the-counter products are sold in doses well above what the evidence supports for a timing effect (some in the 5-10mg range), when much lower doses — often in the 0.5-1mg range — are what's typically studied for shifting circadian timing. Taking too much can blunt the very signal you're trying to reinforce.
Timing also matters as much as dose: melatonin taken too close to your desired bedtime does little, since the useful window is generally a few hours before sleep, not right at lights-out. If you're using it for jet lag or a delayed schedule, that timing needs to shift along with your goal — which is exactly the kind of thing worth discussing with a sleep specialist rather than guessing.