Glycine vs L-Arginine
Sleep vs Amino Acid · evidence-backed comparison
- • Glycine has the stronger evidence base (moderate (some rcts)).
- • Glycine has the broader effect profile across the 9 effect categories.
- • Glycine is cheaper per serving ($0.10 vs $0.35).
- • Glycine has a slightly cleaner safety profile.
- • Glycine has higher bioavailability (better absorption).
Side-by-side traits
| Trait | Glycine | L-Arginine |
|---|---|---|
Category | Sleep | Amino Acid |
Active compound | Glycine | L-arginine |
Form available | Powder, Capsule | Powder, Capsule |
Source | synthetic | microbial |
Typical dose | 3 g before bed | 3–6 g daily (acute) |
Dose range | 3–5 g | 3–6 g |
Loading protocol | — | — |
Best taken with | water, 30 min before bed | empty stomach |
Best time of day | evening | pre-workout |
Bioavailability How efficiently the body absorbs and utilizes the compound. | Very High (5/5) | Low (2/5) |
Onset time | Acute: 30–60 min | Acute: 60 min |
Half-life | ~1 hour | ~1 hour |
Evidence level Quality and quantity of human research. | Moderate (some RCTs) | Limited (small studies) |
Overall effect Subjective effect magnitude. | Low (2/5) | Low (2/5) |
Muscle / strength | Low (2/5) | Low (2/5) |
Physical energy | Very Low (1/5) | Moderate (3/5) |
Focus / cognition | Low (2/5) | Very Low (1/5) |
Mood / stress | Moderate (3/5) | Very Low (1/5) |
Sleep quality | High (4/5) | Very Low (1/5) |
Immunity | Very Low (1/5) | Low (2/5) |
Recovery Post-exercise recovery support. | Low (2/5) | Low (2/5) |
Longevity / healthspan | Moderate (3/5) | Low (2/5) |
Safety rating 5 = exceptionally well-tolerated; 1 = significant risk profile. | Very High (5/5) | High (4/5) |
Price per serving Approximate USD per typical daily dose. | $0.10 | $0.35 |
Vegan friendly | Yes | Yes |
Gluten free | Yes | Yes |
3rd-party tested | Yes | Yes |
About Glycine
Sweet-tasting amino that lowers core body temperature for deeper sleep. Cheap, well-tolerated, and especially useful with magnesium glycinate.
About L-Arginine
Nitric oxide precursor — but most arginine is broken down in the gut. L-citrulline raises blood arginine more reliably for pumps.
Vetted brands, third-party testing, ships worldwide.
Vetted brands, third-party testing, ships worldwide.
Glycine safety
Common side effects:
- • Generally none
Avoid if:
- • Clozapine therapy
Drug interactions:
- • Clozapine
L-Arginine safety
Common side effects:
- • GI upset
- • Diarrhea (high doses)
Avoid if:
- • Recent heart attack
- • Herpes flare-ups
Drug interactions:
- • Sildenafil, blood pressure meds
Common uses
- • Deep sleep
- • Sleep quality
- • Collagen synthesis
Stacks well with: Magnesium Glycinate, Melatonin
Common uses
- • Pump
- • Erectile function
- • Blood flow
Stacks well with: L-Citrulline
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Medical disclaimer
SupplementDuel is for educational purposes only and is not medical advice. Consult a physician before starting, stopping, or combining supplements — especially if you are pregnant, breastfeeding, take prescription medication, or have a chronic condition.