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Glycine 3g vs L-Theanine — Which Should You Take?

Glycine 3g

amino acids

Typically £8–£25/month

L-Theanine

nootropics

Typically £8–£25/month
Feature
Glycine 3g
L-Theanine
Typical Dosage
3g per day
100-200mg daily
Best Form
Powder
L-Theanine (Suntheanine)
Key Benefits
5 listed
5 listed
Evidence Rating
★★★★
★★★★
Best Time
Evening for sleep support; anytime for general benefits
With caffeine for focus, or evening for relaxation
Upper Limit
10g per day
400mg daily
Side Effects
3 noted
3 noted

Glycine 3g Benefits

Improved sleep quality and sleep onset
Reduced daytime fatigue and hypersomnolence
Cognitive function and mental clarity
Joint and connective tissue support
Nervous system regulation

L-Theanine Benefits

Calm focus without sedation
Reduces caffeine jitters when combined
Promotes alpha brain waves (relaxed alertness)
May improve sleep quality
Anxiety reduction

Glycine 3g Side Effects

Mild gastrointestinal upset at high doses
Sedation or fatigue with evening dosing
Bitter taste in powder form

L-Theanine Side Effects

Very few — one of the safest supplements
Mild drowsiness at high doses
May lower blood pressure slightly

Can You Take Glycine 3g and L-Theanine Together?

In most cases, Glycine 3g and L-Theanine can be taken together safely. However, always check the interactions section of each supplement and consult a healthcare professional if you take medication or have existing health conditions.

Glycine 3g: Minimal interactions; may potentiate sedative medications

Glycine 3g: Generally safe with other supplements and pharmaceuticals

L-Theanine: Caffeine — synergistic (the classic nootropic stack)

L-Theanine: Blood pressure medications — additive hypotensive effect

Which Should You Choose?

Choose Glycine 3g if your primary goal is: improved sleep quality and sleep onset. Choose L-Theanine if your primary goal is: calm focus without sedation.

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Frequently Asked Questions

Is Glycine 3g better than L-Theanine?

It depends on your goals. Glycine 3g and L-Theanine serve different purposes and are often taken together.

Can I take Glycine 3g and L-Theanine together?

In most cases, yes. Glycine 3g and L-Theanine can be taken together safely. However, always check for specific interactions and consult a healthcare professional if you take medication.

What is the best time to take Glycine 3g?

Evening for sleep support; anytime for general benefits

What is the best time to take L-Theanine?

With caffeine for focus, or evening for relaxation

What are the side effects of Glycine 3g?

Mild gastrointestinal upset at high doses. Sedation or fatigue with evening dosing. Bitter taste in powder form.

What are the side effects of L-Theanine?

Very few — one of the safest supplements. Mild drowsiness at high doses. May lower blood pressure slightly.

How We Compare Supplements

This comparison is based on published clinical research, peer-reviewed studies from PubMed, and established nutritional science. We evaluate dosages based on clinically-effective amounts, not manufacturer recommendations. Benefits listed have at least moderate evidence from human studies. When evidence is limited or conflicting, we note this.

Disclaimer: This comparison is for educational purposes only and is not medical advice. Always consult a qualified healthcare professional before starting any supplement, especially if you take medication or have existing health conditions.

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