Glycine
Glycine USP
Glycine is the simplest amino acid (a single carbon backbone with an amino group) and the second-most abundant amino acid in the human body. It is classified as conditionally essential - the body synthesizes ~3g/day endogenously from serine, but optimal intake (especially for collagen synthesis and glutathione production) likely exceeds endogenous synthesis. Glycine is the most abundant amino acid in collagen (33% of all collagen residues), and collagen turnover represents the largest amino acid demand in the body.
Starting dose. 3g — Pre-bed
Sleep dose: 3g 30-60 minutes before bed (powder dissolved in water has a sweet taste, mixes well). Glutathione/longevity dose: 5-10g daily, often combined with NAC (GlyNAC stack). Can take with food or fasted.
Start here. Every protocol below is ordered lowest-first. Begin at the smallest effective dose, hold about a week to assess tolerance, and step up only if needed.
How it works
Glycine acts as the major inhibitory neurotransmitter in the spinal cord and brainstem via strychnine-sensitive glycine receptors. In the forebrain, glycine acts as an obligatory co-agonist at the NMDA glutamate receptor (binding the glycine-B site), required for NMDA receptor activation. This dual role - inhibitory at one type of receptor, facilitating at another - allows glycine to modulate excitatory balance throughout the CNS.
Pre-sleep glycine is thought to improve sleep quality by reducing core body temperature (peripheral vasodilation) and modulating thermoregulation, which signals sleep onset. It also acts at glycine receptors and NMDA receptors in sleep-regulatory areas (including suprachiasmatic nucleus).
Glycine is one of three substrates for glutathione (GSH) synthesis (with cysteine and glutamate). Cysteine is typically rate-limiting, but in older adults glycine becomes co-rate-limiting due to declining endogenous synthesis. The Baylor GlyNAC studies showed combining glycine + NAC dramatically restored glutathione vs NAC alone in older adults.
Glycine is the dominant amino acid in collagen (33% of residues), making collagen turnover the largest demand on body glycine pools. Joint, tendon, skin, and bone health all depend on adequate glycine availability for collagen synthesis.
Bile acid conjugation: glycine + cholic acid forms glycocholate, the major conjugated bile acid. This affects fat and fat-soluble vitamin absorption.
Glycine is a precursor to creatine (along with arginine and methionine), porphyrin/heme synthesis, purines, and glyoxylate.
What to expect
Nights 1-7: Sleep quality improvements, faster onset.
Evidence
Claims we could not support
No abstract we checked supports these for this molecule at this route. That is not the same as saying they are false — it marks where the evidence is missing.
Dose/route: 3g pre-bed; Oral; 1-3x daily. No checked live PubMed abstract verified this exact displayed dose, route, and frequency for the same molecule/formulation and relevant population.
Mechanism: Glycine acts as the major inhibitory neurotransmitter in the spinal cord and brainstem via strychnine-sensitive glycine receptors. In the forebrain, glycine acts as an obligatory co-agonist at the NMDA glutamate receptor (binding the glycine-B site), required for NMDA receptor activation. This dual role - inhibitory at one type of receptor, facilitating at another - allows glycine to modulate excitatory balance throughout the CNS.. No checked live PubMed abstract provided an exact-molecule/formulation sentence supporting this source-JSON mechanism claim.
Primary safety claim: Loose stools at very high doses (>15g). No checked live PubMed abstract directly verified this source-JSON safety claim at the displayed formulation, route, and regimen.
Interactions & stacking
Two different questions: what is documented about running these together, and what is documented about drawing them into the same syringe. A good pharmacological partner can still have to be pinned separately.
Documented together
Keep separate
Check any specific pair in the Stack & Interaction Checker, which answers both questions separately. Absence of a documented conflict is not evidence of safety.
Pharmacokinetics
Plasma. Rapidly distributed and metabolized.
Oral.
Plasma clearance. Tissue and metabolic effects (collagen, glutathione synthesis) build over days-weeks.
Oral. Glycine is actively transported by amino acid transporters and rapidly absorbed.
Acute sleep/calming effects: 4-6 hours. Chronic glutathione/collagen effects: build over weeks-months of consistent dosing.
Hepatic metabolism via glycine cleavage system, transamination, and conjugation pathways. Some renal excretion.
Storage. Store at room temperature (20-25C) in a cool, dry place. Powder is hygroscopic - keep tightly sealed. Capsules shelf-stable 2+ years.
Regulatory status
Classified as a dietary supplement in the US - no prescription required. Widely available. Used as a food ingredient (sweetener) and in IV fluids in hospital settings. No medical indications approved by FDA but extensive safety record.
Put it to work
Calculate, log & track
Open Glycine straight into OnePin with your vial and dose pre-filled, then let it handle the syringe math and remind you before the vial runs out.
Open Glycine in the app →Go deeper
The guide & community
The complete Glycine walkthrough, real protocol discussion and coaching live inside the BlessUp community on Skool.
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