What is the best time to take melatonin?

Most people take melatonin right before bed.

Ironically, that may be one of the least effective times to take it.

Melatonin is not a sleeping pill. It’s a chronobiotic, a substance that shifts the timing of your internal clock. It doesn’t “knock you out.” Instead, it tells your brain, “It’s dark now.” What it does next depends entirely on when you take it.

This is where the Phase Response Curve (PRC) becomes important.

The PRC shows how melatonin can either shift your circadian rhythm earlier (phase advance) or later (phase delay) depending on timing:

• Phase advance → You feel sleepy earlier and wake up earlier.
• Phase delay → You fall asleep later and wake up later.

Research shows that taking melatonin about 3 hours before your usual bedtime produces the largest phase advance. This is the “sweet spot.” At this point in your biological day, melatonin nudges your internal clock earlier, making it easier to fall asleep sooner and wake up more refreshed.

But taking melatonin at bedtime, which many people do, can actually push your circadian rhythm in the opposite direction. Instead of helping you fall asleep earlier over time, it may cause a phase delay, shifting your internal clock later.

The optimal window sits just before what’s called Dim Light Melatonin Onset (DLMO), the time in the evening when your brain would naturally begin producing melatonin under dim light conditions. For most people, DLMO occurs roughly 2–3 hours before habitual bedtime. That’s why taking melatonin around 3 hours before bed tends to produce the strongest phase-advancing effect.

Another key point:

Melatonin works on biological timing, not sedation. If you take it too late during your biological night, it can send the wrong signal and shift your clock later instead of earlier.

So the takeaway is simple but powerful:

If your goal is to fall asleep earlier, don’t take melatonin at bedtime.

Take it earlier in the evening, around 3 hours before your usual sleep time, so you shift your clock in the right direction.