Glycine is a non-essential amino acid found in many protein-rich foods and made by the body. It also acts as a neurotransmitter and supports multiple cellular processes.

How does glycine help with sleep?

Taken before bedtime, glycine may improve subjective sleep quality and help with sleep onset in some people. It is commonly used to reduce next-day fatigue related to poor sleep.

What is a typical glycine dosage?

A common supplemental range is 3–5 g per day, often taken in the evening for sleep support. Individual needs vary based on goals and tolerance.

Can glycine support blood sugar control?

Glycine may support glucose metabolism and insulin function in some contexts, particularly in people with impaired glucose regulation. It should not replace prescribed diabetes care.

Is glycine safe and are there side effects?

Glycine is generally well tolerated at typical supplemental doses, but some people may experience mild gastrointestinal discomfort. If you are pregnant, breastfeeding, or taking medications, consult a clinician before use.

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Glycine

Moderate study situation·7/10

A higher score indicates better study conditions, but not necessarily effectiveness.

Glycine is a non-essential amino acid supplement commonly used to support sleep, metabolic health, and neurological function.

Sleep Improvement Cognitive Enhancement Glucose Metabolism Neuroprotective

dose range

3–5 g

Single dose before sleep, or split into smaller doses for other indications.

Consumption

Dissolve in water or take as capsules/tablets, ideally before bedtime for sleep improvement.

Not fat-soluble.

Best time

Most evidence supports pre-sleep ingestion for sleep quality; timing for metabolic uses may be flexible or with meals.

Description

Glycine is a naturally occurring amino acid found in protein-rich foods and as a supplement. It serves as a neurotransmitter, aids in cellular processes, and may support sleep, glucose regulation, and cognitive health.

benefits

Main effects with level of evidence

Moderate

Note on evidence

Clinical trials support benefits for sleep quality and metabolic health, with moderate evidence for neuroprotective roles. Glycine is well-studied for safety at typical supplemental doses.

Improves sleep quality and onset

Moderate

Clinical studies show glycine supplementation before bedtime can enhance subjective sleep quality and reduce daytime fatigue without affecting sleep architecture.

Particularly relevant for: Adults with sleep complaints · Shift workers · General adult population

2 · Yamadera, W., et al. (2007) – Glycine ingestion improves subjective sleep quality in human volunteers, a randomized, double-blind, crossover study.6 · Examine.com – Glycine 8 · Cochrane Review – Amino acid interventions for sleep

Supports glucose metabolism and insulin sensitivity

Limited

Supplementing with glycine may improve insulin secretion and reduce oxidative stress, potentially aiding blood sugar control in people with impaired glucose tolerance or type 2 diabetes.

Particularly relevant for: People with metabolic syndrome · Individuals with impaired glucose tolerance

3 · Cruz, B. L. D., et al. (2008) – Oral glycine administration improves insulin response to glucose load in healthy, elderly adults 5 · NIH Office of Dietary Supplements – Glycine

Potential neuroprotective effects in psychiatric and neurological conditions

Limited

As a neurotransmitter, glycine modulates NMDA receptors and adjunct therapy may reduce negative symptoms in schizophrenia, though more research is needed in other neurologic contexts.

Particularly relevant for: People with schizophrenia or other psychiatric disorders

4 · Popova, N. K., et al. (2014) – Glycine encephalopathies and Schizophrenia: from Molecular Biology to Clinical Applications 6 · Examine.com – Glycine

Safety & Information

Important safety information & known risks

For educational purposes only • not medical advice

Glycine is generally well tolerated but high doses may cause mild GI upset and should be avoided with kidney or liver problems.

warning notices

May cause loose stools or mild GI symptoms at high doses (>10 g/day).
Avoid supplemental glycine in people with significant liver or renal impairment.
Pregnant or breastfeeding women should use only with clinical supervision.
Avoid high doses if you have kidney or liver disease.
Do not use large doses without clinical supervision if pregnant or breastfeeding.
Monitor for drug interactions if taking clozapine or other antipsychotics.

Known interactions with medications