Glycine
The simplest amino acid. Used most often for sleep and skin.
Glycine is the smallest amino acid and the most abundant one in collagen, which is why it turns up in both bedtime formulas and skin and joint stacks. Three grams taken shortly before bed has been studied for shortening the time it takes to fall asleep and for improving morning alertness, working through a different pathway than magnesium or melatonin. It is also a building block for glutathione, the body's central antioxidant, and for creatine synthesis. Free-form glycine and glycine powder are the same compound at the same dose, so form choice is about taste (mildly sweet) and format rather than absorption.
Reference values
Daily reference values from official nutrition authorities. These are population reference figures, not personal recommendations.
| RDA | Upper limit | Source |
|---|---|---|
| 3000 mg | 9000 mg | UK |
Forms and bioavailability
Not all forms are absorbed equally. The form on your supplement label affects how much your body can actually use.
| Form | Absorption | With food | Timing | Evidence |
|---|---|---|---|---|
| glycine (free form) | Typical | Either | Evening | Likely |
| glycine powder | Typical | Either | Evening | Likely |
How it pairs with other supplements
Works well with
Both promote sleep quality through distinct mechanisms (glycine: NMDA-mediated thermoregulation; magnesium: GABA modulation).
Stack Almanac tracks your glycine dose and timing, and surfaces the glycine and magnesium pairing when you're taking both for sleep, so the two are visible as a stack rather than stumbled onto by accident.
Track your Glycine in Stack Almanac
Last reviewed: 2026-07-22. Reference values are adult-general RDAs from UK. Individual needs may vary. This page is for informational purposes only and is not a substitute for professional medical advice.