howtosupplement
Sleep/Cognition

Glycine

A simple amino acid that may improve sleep quality and next-day alertness in adults with occasional poor sleep.

Glycine

Glycine

52
score
C
evidence
Safe
risk

Proven Benefits

01Improves sleep quality
02May improve next-day alertness
03May shorten sleep onset
04May improve sleep efficiency

Chemical Forms

Recommended
  • L-glycine
  • Free-form glycine powder
  • Free-form glycine capsules
Avoid
    Expert Note

    Glycine is a simple amino acid, and there is no meaningful human evidence that specialty forms outperform plain free-form glycine. Powder is usually the cheapest way to reach the studied bedtime dose, while capsules are fine if you prefer convenience.

    Protocol

    Amount
    3 g
    Frequency
    Once nightly
    When
    30-60 minutes before bed, mixed in water; consistency matters more than exact timing.

    Condition-Based Dosing

    Occasional sleep dissatisfaction
    3 g 30-60 minutes before bed
    Sensitive stomach or first-time use
    Start with 1-2 g nightly for 3-4 nights, then increase to 3 g if tolerated

    Safety & Limits

    Upper Safe Limit
    No official UL established (no IOM UL); short-term studies have used up to 0.8 g/kg/day with acceptable tolerability.
    Cycling
    Safe for continuous use

    Contraindications

    Pregnancy or breastfeeding — limited supplemental safety data beyond normal dietary intake
    Severe kidney disease — concentrated amino acid supplements should be used only with clinician guidance
    Schizophrenia or antipsychotic treatment — high-dose glycine has been studied therapeutically and should not be self-prescribed

    Synergies

    Melatonin

    Melatonin helps with circadian timing, while glycine may complement sleep onset and sleep quality through thermoregulation and inhibitory signaling.

    L-theanine

    L-theanine may reduce pre-sleep mental activation, while glycine appears to work more through temperature regulation and sleep architecture.

    Avoid Combining With

    • ✕Caffeine within 6-8 hours of bed (can overpower the sleep benefit)
    • ✕Alcohol near bedtime (disrupts sleep architecture and can mask benefit)
    Updated Invalid Date