L-Theanine
A 2026 meta-analysis of 31 RCTs (n=1,168) found a single 200mg dose taken 30–60 minutes before testing improved choice reaction time; its acute stress effect was modest and driven by high-risk-of-bias studies, and anxiety effects were inconsistent. With caffeine, an 11-study meta-analysis (Camfield 2014) found moderate effects versus placebo on alertness and attention-switching accuracy; Kahathuduwa 2016 found additive effects with no interaction, and Foxe 2012 found no added benefit over either compound alone. The one alpha-wave (MEG) trial found higher alpha activity at 2 hours, and only in people with higher trait anxiety.
Evidence reviewed:
Mechanism of action
L-theanine is a non-protein amino acid found primarily in green tea. It crosses the blood-brain barrier and has been linked to increased alpha brain wave activity. It also modulates GABA, serotonin, and dopamine levels. Combined with caffeine, it improved attention measures versus placebo in several trials, though Foxe 2012 found no added benefit over either compound alone.
Clinical evidence summary
A 2026 meta-analysis of 31 RCTs (n=1,168) found a single 200mg dose taken 30–60 minutes before testing improved choice reaction time; its acute stress effect was modest and driven by high-risk-of-bias studies, and anxiety effects were inconsistent. With caffeine, an 11-study meta-analysis (Camfield 2014) found moderate effects versus placebo on alertness and attention-switching accuracy; Kahathuduwa 2016 found additive effects with no interaction, and Foxe 2012 found no added benefit over either compound alone. The one alpha-wave (MEG) trial found higher alpha activity at 2 hours, and only in people with higher trait anxiety.
Human effect matrix
Based on human clinical trials only. Animal and in-vitro data excluded.
| Effect | Evidence | Magnitude | Studies |
|---|---|---|---|
| Calm Focus (Alpha Waves) | preliminary | Small | 1 |
| Anxiety & Stress | mixed | Small | 2 |
| Sleep Quality | moderate | Small | 1 |
| With Caffeine | moderate | Moderate | 4 |
Evidence key: Strong = multiple consistent RCTs · Moderate = smaller/fewer RCTs · Preliminary = early trials or small n · Mixed = conflicting results
Documented benefits
- Faster reaction time after a single 200mg dose
- Better attention with caffeine than with placebo in several trials
- Small improvements in subjective sleep quality
Side effects & cautions
- Extremely well tolerated — no serious adverse events across a 31-RCT meta-analysis
- Possible mild sedation at high doses
- Generally considered very safe
How to take
Stacking recommendations
Ingredients that pair well with L-Theanine and why.
The trials we cite used 50–250mg theanine with 40–250mg caffeine. Versus placebo, the combination improved attention measures in several trials, though Foxe 2012 found no added benefit over either compound alone; in a controlled trial (Rogers 2008) theanine did not significantly reduce caffeine jitteriness.
Both have anxiolytic properties working via different mechanisms. L-Theanine provides immediate calm; Bacopa builds sustained stress tolerance over weeks. A gentle, non-sedating anxiety-reduction combination.
Both target stress through distinct pathways (GABA modulation for theanine; HPA axis for ashwagandha). Good daytime anxiety stack without sedation.
Frequently asked questions
What is the ideal ratio of L-Theanine to caffeine?
No trial has established an ideal ratio. The positive combination trials used 97–250mg theanine with 40–160mg caffeine — for example 100mg theanine with 50mg caffeine (Owen 2008), 250mg with 150mg (Haskell 2007) and 200mg with 160mg (Kahathuduwa 2016). A meta-analysis found the caffeine dose drove the effect more than the theanine dose.
Does L-Theanine work without caffeine?
Partly. On its own, a single 200mg dose improved choice reaction time in a 2026 meta-analysis of 31 RCTs, but anxiety effects were inconsistent and the one alpha-wave trial found an effect only in people with higher trait anxiety. It's not stimulating on its own.
Is it safe to take L-Theanine every day?
Yes. Green tea contains theanine and has been consumed daily for millennia without toxicity concerns. No tolerance develops. Chronic daily use is both safe and effective. No cycling required.
Why take a supplement when I can just drink green tea?
A standard cup of green tea contains ~25–50mg of L-Theanine — well below the 100–200mg therapeutic dose. You would need 4–8 cups of green tea to match a single supplement dose, along with a significant caffeine load. Supplements allow precise dosing without unwanted caffeine.
Can L-Theanine help with sleep if taken at night?
Modestly. A 2025 meta-analysis (18 studies, n=897) found small improvements in subjective sleep onset latency, daytime dysfunction and overall sleep quality. It doesn't cause sedation. Combinations with magnesium are popular but have not been tested in a trial.
Top stacks containing L-Theanine
L-Theanine in Australia
Theanine -- marketed on this site as L-theanine, the naturally occurring isomer -- is a permitted active ingredient in the TGA's Permissible Ingredients Determination, entered under the single name 'Theanine' at Schedule 1 item 4911. The Determination requires the route of administration to be oral and caps the maximum recommended daily dose of the medicine at 450 mg of theanine. It also mandates two label warning statements: that the product is not recommended for pregnant or lactating women, and that it is for adults only. The theanine entry carries no sponsor-exclusivity clause of the kind attached to citicoline's entry in the same Determination.
Dose cap and label warnings the Determination sets for theanine
Item 4911 of Schedule 1 lists 'THEANINE' with purpose code A (active ingredient) and three specific requirements: oral administration only, a maximum recommended daily dose of the medicine that must not exceed 450 mg of theanine, and two mandatory label warning statements -- 'Not recommended for use by pregnant and lactating women' and 'Adults only'. The Determination does not use the name 'L-theanine'; the entry covers theanine generally, and there is no separate 'L-theanine' entry, so an AUST L-listed medicine containing the amino acid is assessed against this theanine entry and its three requirements.
Products in Australia
- Mind Lab Pro7.5/10Personal Importation SchemeLocal price: ≈ $89/month
- NooCube7/10Personal Importation SchemeLocal price: ≈ $84.99/month
- Performance Lab Caffeine 26.3/10Personal Importation SchemeLocal price: ≈ $59/month
- Pre Lab Pro5.7/10Personal Importation SchemeLocal price: $79 · Servings per container: 20
TGA (AUST L)
Is L-theanine specifically named in the TGA's permissible ingredients list?
No -- the Determination lists it simply as 'Theanine' at Schedule 1 item 4911, not 'L-theanine'. Any listed medicine using the L-theanine form must still meet the requirements set for theanine generally: oral route, a 450 mg daily dose cap, and the pregnancy/lactation and adults-only warning statements on the label.
What's the maximum theanine dose permitted in an AUST L medicine?
'The maximum recommended daily dose of a medicine must not exceed 450 mg of theanine,' per Schedule 1 item 4911 of the Determination. Reviewed AU products on this site naming L-Theanine as a hero ingredient (mind-lab-pro-review, hunter-focus-review, noocube-review, performance-lab-caffeine-2-review, pre-lab-pro-review) carry no AUST L number in this site’s Australian catalogue.
State & territory guides
Sources: Therapeutic Goods (Permissible Ingredients) Determination (No. 2) 2026 (F2026L00707), as compiled 17 September 2026 (Compilation No. 1, F2026C00940) -- Schedule 1, item 4911 (Theanine) · Therapeutic Goods (Permissible Ingredients) Determination (No. 2) 2026 (F2026L00707), as compiled 17 September 2026 (Compilation No. 1, F2026C00940) -- Schedule 1, item 4911 (Theanine) · TGA -- Permissible ingredients determination (overview) · Therapeutic Goods (Permissible Ingredients) Determination (No. 2) 2026 (F2026L00707), as compiled 17 September 2026 (Compilation No. 1, F2026C00940) — Schedule 1, item 1428, citicoline entry (sponsor clause, for comparison)
Regulatory note
Therapeutic goods available in Australia are regulated by the Therapeutic Goods Administration (TGA). AUST L–listed products carry pre-approved permitted indications; AUST R–registered products are higher-evidence. Imported products without TGA listing are not assessed by Australian regulators. This page is editorial, not promotional, and does not constitute medical advice. Always read the label and follow directions for use. Consult a qualified healthcare professional before starting any supplement.
Sources (11)expand
- PMID 42410082Cognitive and affective effects of L-Theanine: a systematic review and meta-analysis of 31 randomized trials (2026)
- PMID 24946991Acute effects of tea constituents L-theanine, caffeine, and epigallocatechin gallate on cognitive function and mood: a systematic review and meta-analysis (2014)
- PMID 18006208The effects of L-theanine, caffeine and their combination on cognition and mood (2007)
- PMID 26869148Acute effects of theanine, caffeine and theanine-caffeine combination on attention (2016)
- PMID 26797633Anti-Stress, Behavioural and Magnetoencephalography Effects of an L-Theanine-Based Nutrient Drink: A Randomised, Double-Blind, Placebo-Controlled, Crossover Trial (2016)
- PMID 40056718The effects of L-theanine consumption on sleep outcomes: A systematic review and meta-analysis (2025)
- PMID 17891480Time for tea: mood, blood pressure and cognitive performance effects of caffeine and theanine administered alone and together. (2008)
- PMID 18681988The combined effects of L-theanine and caffeine on cognitive performance and mood. (2008)
- PMID 21040626The combination of L-theanine and caffeine improves cognitive performance and increases subjective alertness. (2010)
- PMID 22326943Assessing the effects of caffeine and theanine on the maintenance of vigilance during a sustained attention task. (2012)
- PMID 25761837A double-blind, placebo-controlled study evaluating the effects of caffeine and L-theanine both alone and in combination on cerebral blood flow, cognition and mood. (2015)