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evidence · mechanism · dose
Supplements/Amino Acid

Glycine

Inhibitory neurotransmitter that improves sleep quality and supports collagen synthesis.

Sleep & RecoverySkin, Hair & NailsHealthy Aging

Overview

Smallest amino acid; inhibitory in brainstem/spinal cord; precursor for collagen, glutathione, and creatine.

Natural sources
  • Bone broth
  • Gelatin
  • Skin/connective tissue of meats
Common forms
  • Glycine powder

Forms & variants of Glycine

Different chemical forms of Glycine behave differently. Browse each form's mechanism, bioavailability, and best-use context.

Collagen stack
Glycine (Collagen Stack)

Free-form glycine paired with collagen for connective tissue synthesis.

Mechanism of action

Activates inhibitory glycine receptors and NMDA glycine site; lowers core body temperature via peripheral vasodilation.

Pathways
  • · Glycine receptor agonism
  • · NMDA co-agonism
Neurotransmitters
  • · Glycine

Effects on the body

Increases
Sleep quality (subjective)
Decreases
Core body temperature
Supports
Collagen synthesis

Organ system effects

Brain & CNS

Promotes deeper sleep via thermoregulation.

Skin

Major constituent of collagen.

Evidence-based benefits

Improves subjective sleep quality

Moderate evidence

Improves daytime alertness after restricted sleep

Moderate evidence

Potential side effects

Common
  • · Mild GI upset at high doses
Rare
    Serious

      Drug interactions

      Clozapine
      May reduce efficacy.
      moderate

      Safety & non-supplemental interactions

      Educational summary — always confirm with your clinician or pharmacist before starting, stopping, or combining with prescription therapy.

      Avoid / monitor with these medications
      • ·Alcohol, benzodiazepines, opioids, sedating antihistamines (additive CNS depression)

      Supplement interactions

      Pairs well with
      • NAC
        Both rate-limiting for glutathione synthesis.
      Avoid combining with

      No specific avoidances listed.

      Dosing & bioavailability

      Typical dose
      3 g before bed
      Study range
      3–5 g
      Timing
      30 min before bed

      Where to buy

      Affiliate-style search links to reputable retailers. We don't endorse specific brands — verify third-party testing (USP, NSF, Informed Sport) before purchase.

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      Wide selection · fast shipping
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      Global delivery · curated brands
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      Thorne
      Practitioner-grade · NSF tested

      Scientific evidence (10)

      RCTSleep Biol Rhythms · 2007

      Glycine ingestion and sleep quality

      Yamadera W, et al.

      Crossover trial of 3 g glycine before bed in insomniacs.

      Key findings

      Improved subjective sleep quality and reduced sleep latency.

      Open study
      RCTSleep Biol Rhythms · 2007

      Glycine ingestion before sleep improves subjective sleep quality

      Yamadera W, et al.

      Crossover trial of 3 g glycine before bed.

      Key findings

      Improved subjective sleep quality and daytime function.

      Open study
      Systematic reviewPubMed (NLM) · 1970

      PubMed: Glycine — Improves subjective sleep quality

      Live PubMed search

      Live results for "Glycine Improves subjective sleep quality" across the PubMed/MEDLINE peer-reviewed index.

      Key findings

      Opens current human and preclinical literature matching Glycine and "Improves subjective sleep quality". Filter by RCT, meta-analysis, or year on the results page.

      Open study
      Systematic reviewPubMed (NLM) · 1970

      PubMed: Glycine — Improves daytime alertness after restricted sleep

      Live PubMed search

      Live results for "Glycine Improves daytime alertness after restricted sleep" across the PubMed/MEDLINE peer-reviewed index.

      Key findings

      Opens current human and preclinical literature matching Glycine and "Improves daytime alertness after restricted sleep". Filter by RCT, meta-analysis, or year on the results page.

      Open study
      Systematic reviewPubMed (NLM) · 1970

      PubMed: Glycine — randomized controlled trial

      Live PubMed search

      Live results for "Glycine randomized controlled trial" across the PubMed/MEDLINE peer-reviewed index.

      Key findings

      Opens current human and preclinical literature matching Glycine and "randomized controlled trial". Filter by RCT, meta-analysis, or year on the results page.

      Open study
      Systematic reviewPubMed (NLM) · 1970

      PubMed: Glycine — meta-analysis

      Live PubMed search

      Live results for "Glycine meta-analysis" across the PubMed/MEDLINE peer-reviewed index.

      Key findings

      Opens current human and preclinical literature matching Glycine and "meta-analysis". Filter by RCT, meta-analysis, or year on the results page.

      Open study
      Systematic reviewPubMed (NLM) · 1970

      PubMed: Glycine — pharmacokinetics

      Live PubMed search

      Live results for "Glycine pharmacokinetics" across the PubMed/MEDLINE peer-reviewed index.

      Key findings

      Opens current human and preclinical literature matching Glycine and "pharmacokinetics". Filter by RCT, meta-analysis, or year on the results page.

      Open study
      Systematic reviewPubMed (NLM) · 1970

      PubMed: Glycine — safety adverse events

      Live PubMed search

      Live results for "Glycine safety adverse events" across the PubMed/MEDLINE peer-reviewed index.

      Key findings

      Opens current human and preclinical literature matching Glycine and "safety adverse events". Filter by RCT, meta-analysis, or year on the results page.

      Open study
      Systematic reviewPubMed (NLM) · 1970

      PubMed: Glycine — dose response

      Live PubMed search

      Live results for "Glycine dose response" across the PubMed/MEDLINE peer-reviewed index.

      Key findings

      Opens current human and preclinical literature matching Glycine and "dose response". Filter by RCT, meta-analysis, or year on the results page.

      Open study
      Systematic reviewGoogle Scholar · 1970

      Google Scholar: Glycine — clinical evidence

      Live Scholar search

      Cross-database citation index for Glycine as it relates to "clinical evidence".

      Key findings

      Includes preprints, theses, and journal articles. Useful for tracking citation counts and follow-on work.

      Open study
      Educational use only. This profile is not medical advice. Consult a qualified healthcare professional before starting any supplement, especially if you take prescription medication or have a chronic condition.