Glycine vs Melatonin
Both are used for sleep better. Here's how they compare on human evidence, mechanism, safety and availability — in plain English.
| Glycine | Melatonin | |
|---|---|---|
| Human evidence | ★★★☆☆ | ★★★★★ |
| Legal status | OTC Supplement | OTC Supplement, Prescription |
| How it works | Smallest amino acid; inhibitory neurotransmitter at spinal/brainstem glycine receptors (GLRA1), lowers core body temperature (a sleep-onset trigger) via peripheral vasodilation, and supplies one-third of collagen's amino acids. Mimics some… | Pineal hormone binding MT1/MT2 receptors (MTNR1A/MTNR1B) in the suprachiasmatic nucleus — shifts the circadian clock rather than sedating. Most people massively overdose it. |
| In plain English | An amino acid that gently cools you down and quiets the nervous system for sleep, and is the main brick in collagen. Dirt cheap, very safe. | The "it's night" hormone. It re-times your body clock, so it's best for jet lag and late sleep phase, not as a sledgehammer sedative. 0.5 mg works as well as 10 mg with less morning fog. |
| Bottom line | One of the most undervalued supplements — sleep + connective tissue + longevity. | Overused at 10–20× the effective dose. Start at 0.5 mg. |
| Availability | Available over the counter | Prescription only |
Which is better for sleep better?
Melatonin has the stronger human-evidence rating (★★★★★ vs ★★★☆☆), but the right choice still depends on your goal, tolerance and budget.
Common questions
Is Glycine or Melatonin better for sleep better?
Melatonin has the stronger human-evidence rating (★★★★★ vs ★★★☆☆), but the right choice still depends on your goal, tolerance and budget.
What's the difference between Glycine and Melatonin?
Glycine: One of the most undervalued supplements — sleep + connective tissue + longevity. — Melatonin: Overused at 10–20× the effective dose. Start at 0.5 mg.