Glycine vs Melatonin

for sleep

Stronger evidence: Melatonin

Stronger effect: Melatonin

Safety: Melatonin carries a uncertain interaction; Glycine has none recorded.

For sleep, Melatonin has the stronger evidence grade.

grade C low certainty

small trials suggest improved subjective sleep quality and reduced next-day fatigue

3 g before bed, adults

grade B moderate certainty

reduces time to fall asleep; best for circadian timing

0.5–3 mg

sources: PMID:10000002 · PMID:00000006