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Amino acids & derivatives

Glycine

Glycine (2-aminoacetic acid)

Glycine is a simple amino acid sold mostly as powder or capsules. Small, short human sleep studies most commonly used 3 g shortly before bedtime and reported modest subjective sleep or next-day-fatigue signals; that is not strong evidence for broad focus or energy effects. Compare products by grams per serving, price per gram, capsule count, added ingredients, and batch-quality information.

Sleep SupportEndogenous CompoundFood DerivedClinical ResearchMixed EvidenceLow Risk ProfileGi Side Effects
Updated August 2026/4 min read/4 citations
Reviewed by the NootropicsIndex editorial team.Method: prioritize cited human research and official safety or regulatory sources; compare retailer-listed prices without endorsing products.Affiliate disclosure
01

What is it?

What glycine is

1

Glycine is a non-essential amino acid and the smallest standard amino acid. Supplement listings commonly present free-form glycine as powders or capsules; it is distinct from collagen products, which are mixed proteins.

What the human evidence supports2
The useful consumer evidence is narrow: short trials suggest modest sleep-quality or next-day-fatigue signals. It does not support broad focus, memory, productivity, stress, or energy promises.
02

Names, aliases and forms

Common Namesglycine; aminoacetic acid; glycocoll
Chemical Name2-aminoacetic acid
Molecular FormulaC2H5NO2
03

Mechanisms of action

Receptor roles do not prove a nootropic effect

2

Glycine participates in inhibitory glycine-receptor signaling and acts as a co-agonist at NMDA receptors. These roles explain research interest, but mechanistic relevance alone does not establish a felt benefit for healthy shoppers.

04

Potential effects and evidence map

Human supplementation evidence is limited. A 2024 systematic review found small, heterogeneous adult studies across several outcomes and emphasized bias and sample-size limitations. The clearest consumer-facing signal is modest, short-term sleep-quality or next-day-fatigue findings in small trials; it does not support broad nootropic claims.

Effect domainMagnitudeGrade
Sleep quality2
AcuteConfidence: Medium

A 2024 review found modest short-term subjective sleep-quality or next-day-fatigue signals in small adult glycine studies.

Note Small samples, heterogeneous methods, and bias concerns keep this evidence cautious.

2/5
C
Focus / attention2
UnknownConfidence: Medium

There is no established direct focus or productivity benefit in healthy supplement users.

Note Do not extrapolate receptor mechanisms or restricted-rest findings into broad nootropic effects.

0/5
E
05

Typical dosages and timing

small human studies23 g

The cited short sleep-study literature commonly used 3 g shortly before bedtime. This is a research context, not a personalized dosing recommendation, and it should not be confused with much larger clinical research protocols.

06

Timing & effect horizon

Effect horizonAcute
Acute
Observed on a short horizon2

The cited sleep-study literature used short 2-4 day protocols with same-night or next-day assessments. These data do not establish a lasting cognitive effect or a standard long-term cycle.

07

Safety, side effects and risk profile

Keep the evidence boundary visible2
Amino-acid identity does not substitute for long-term supplementation evidence. Do not use small short-term sleep studies to justify higher-dose or extended self-experimentation.
GI discomfort2
Confidence: Low

The small adult literature does not define a clear common adverse-effect pattern at studied consumer doses; gastrointestinal tolerance can still differ with gram-level powder servings.

Note The Norwegian assessment found no adverse-health signal for its lower 20-650 mg/day supplement scope, while evidence for higher retail doses remains limited.

1/5
C
Interaction risk2
Confidence: Low

The small human evidence base does not define a reliable medication-interaction profile.

Note Absence of interaction findings is not proof that none exist.

1/5
E
Pregnancy / lactation caution2
Confidence: Low

This adult evidence base does not establish supplementation safety in pregnancy or lactation at retail-dose levels.

Note The systematic review evaluated adult studies, not a pregnancy or lactation safety program.

1/5
E
Evidence uncertainty2
Confidence: High

Small and heterogeneous studies limit confidence in consumer claims outside narrow sleep contexts.

Note This is an evidence-limit signal, not an intrinsic high-risk finding for typical healthy-adult use.

2/5
C
healthy-adult evidence4

Short adult studies and the available safety assessment do not identify a strong common adverse-effect pattern at the doses they assessed. Evidence is less informative for higher retail amounts, long-term use, and special populations.

08

Interactions and cautions

Medication-interaction evidence is sparse2

The available adult studies are too small and narrow to establish a reliable medication-interaction profile. A lack of reported interactions is not proof that none exist.

09

How it compares

powder and capsules1

For powders, compare price per gram, serving scoop size, added flavoring, and available batch-quality information. For capsules, compare total grams per bottle and the capsule count needed to reach a gram-level serving.

10

Practical buying and quality notes

  • Compare like-for-like forms and units. Powder is usually simplest to normalize by price per gram; capsules may be more convenient but can obscure the total grams per bottle. Check added ingredients and whether a seller provides current batch-quality information.1
11

FAQ

Is glycine a nootropic?

2

Not in the strong direct-focus sense. The available human supplement evidence is more relevant to narrow, short-term sleep contexts than to standalone focus, memory, or productivity benefits.

What amount has been studied for sleep?

3

The cited short sleep trial used 3 g close to bedtime. This trial context is not a universal dose or a substitute for assessing the rest of a product label.

Is a long-term glycine cycle established?

2

No. The consumer-relevant studies are short and do not establish a standard long-term supplementation cycle or durable cognitive outcome.

12

References

  1. PubChem Compound Summary for Glycine. National Center for Biotechnology Information.
  2. Soh J, Raventhiran S, Lee JH, Lim ZX, et al. The effect of glycine administration on the characteristics of physiological systems in human adults: A systematic review. GeroScience. 2024.
  3. Bannai M, Kawai N, Ono K, Nakahara K, Murakami N. The effects of glycine on subjective daytime performance in partially sleep-restricted healthy volunteers. Frontiers in Neurology. 2012.
  4. Tell GS, Froyland L, Haugen M, et al. Risk Assessment of Other Substances: Glycine. Norwegian Scientific Committee for Food Safety. 2018.
Note

This page is informational and summarizes available evidence. It is not medical advice, a recommendation, or a substitute for guidance from a qualified clinician.