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compare / Glycine vs Melatonin

Glycine vs Melatonin for sleep: which has better evidence?

Melatonin has the stronger evidence for sleep (Glycine Grade C vs Melatonin Grade B). For sleep, Melatonin has the stronger evidence grade.

Reviewed by Substrate editorial, Independent research collective ·

Platform evidence comparison

These existing platform assessments are separate from the source-reported findings below. They do not represent a direct trial comparing these treatments.

GlycineMelatonin
Gradegrade Cgrade B
Certaintylowmoderate
Effectsmall trials suggest improved subjective sleep quality and reduced next-day fatiguereduces time to fall asleep; best for circadian timing
Studied dose3 g before bed0.5–3 mg
Populationadults—
Safety0 modeled interaction(s)1 modeled interaction(s)
Grade
C
what does the grade mean?
Certainty
low
what does certainty mean?

Grade C / low: hints of benefit in small trials; a well-run RCT could easily push this to B or to null.

Direct comparison evidence

There are no direct RCTs in our corpus comparing Glycine and Melatonin head-to-head for sleep. What we present above is an indirect comparison: each side's own trials, contrasted. This is standard practice for supplement comparisons — dose, population, and outcome-instrument differences between the two evidence bases add uncertainty on top of each side's own grade.

Can you take both?

No modeled interaction between Glycine and Melatonin in our corpus. Absence of a recorded interaction is not proof of additive benefit — combined-effect trials are usually absent for supplement pairs, so treat "stack" claims skeptically.

This filtered view rechecked source-context candidates for current publication and source integrity. Other papers were not evaluated; an empty result does not establish that research is absent. Browse the broader bounded research library.

Source-reported research findings

AI-extracted — pending human review. These findings retain the studied context and are not pooled treatment estimates.

Single study

PMID 38745424: PSQI

  • AI-extracted — pending human review
  • Extraction status: machine extracted. Source status is not human clinical review.
  • Publication status: published. Record review status: not reviewed.
  • Not poolable: one source-reported result, not a pooled treatment estimate.

Authors reported a direction only for sleep quality (PSQI): favours the studied intervention.

Reported p < 0.05.

  • Studied combination: 1.9 mg melatonin + 200 mg elemental magnesium.
  • Studied route/context: unclear.

otherwise healthy individuals with sleep disturbances; double-blinded, randomized, crossover trial. supplement condition versus placebo. sleep quality (PSQI) at 4 week intervention.

Related research with a different studied context; applicability to this question remains limited.

That’s the gist — a fine place to stop. This describes the studied groups, not personal suitability.

Read this finding in study context →Original source · Bring into My Profile

Decision guidance

sources: PMID:22293292 · PMID:23691095 · PMID:15649737

Grade history

No grade changes yet. Initial grade assigned; re-reviewed on every 6 months (Grade C+) — next review by . Methodology v1.

Re-review cadence: every 6 months (Grade C+) · next scheduled by · methodology v1.

Frequently asked

Which has stronger evidence: Glycine or Melatonin for sleep?

Glycine carries Grade C at low certainty; Melatonin carries Grade B at moderate. The stronger evidence points to Melatonin, subject to the caveat that direct head-to-head trials are usually absent for supplement pairings.

Can I take Glycine and Melatonin together?

No modeled interaction between Glycine and Melatonin; combining is not documented to be problematic, but combined-effect trials are also absent, so treat additive benefit claims skeptically.

Have Glycine and Melatonin been compared head-to-head?

Direct RCTs comparing the two for sleep are uncommon. This page contrasts each side's own trial evidence — that is an indirect comparison, which introduces confounds from population and dose differences. See the direct-comparison block above.

What decides between Glycine and Melatonin for me?

Read the decision guidance below — the split usually comes down to population fit, interaction risk with your other medications, and how much certainty you want behind the recommendation.

Related

Cite this page

Citation is encouraged. The proposed reuse license is CC-BY-4.0; status: pending-governance-ratification.

Plain-text citation
Substrate. Glycine vs Melatonin for sleep. https://evidencebased.info/compare/glycine-vs-melatonin-for-sleep. Updated 2026-07-14.
BibTeX
@misc{substrate_evsmelatoninforsleep,
  author = {Substrate editorial},
  title  = {Glycine vs Melatonin for sleep},
  year   = {2026},
  url    = {https://evidencebased.info/compare/glycine-vs-melatonin-for-sleep},
  note   = {evidencebased.info}
}