L-Theanine: Nootropic Benefits, Uses, Dosage, & Side Effects

A review of L-Theanine's nootropic benefits, uses, dosage, and side effects for cognitive enhancement.

In the ever-evolving world of health and wellness, L-theanine supplements emerge as a compelling nootropic for those seeking natural solutions to enhance cognitive function and mental well-being.

This comprehensive article delves into the multifaceted world of L-Theanine, an amino acid structurally similar to glutamine and GABA, found predominantly in green tea and certain mushrooms.

We will unveil its nootropic benefits, recommended dosages, and potential side effects.

Find out everything you need to know about this remarkable, natural nootropic right here!

What is L-Theanine?

L-Theanine (also known as γ–glutamylethylamide and γ-ethylamino-l-glutamic acid, and the brand name Suntheanine), a unique amino acid, is known for its remarkable ability to promote relaxation without drowsiness.(1)

This powerful therapeutic property, unique among amino acids, makes it a sought-after supplement for individuals aiming to balance their mental health and cognitive abilities. It has been shown to play a pivotal role in reducing stress and anxiety, improving sleep quality, and even boosting brain function.

Structurally, L-Theanine is similar to the neurotransmitters glutamate and gamma-aminobutyric acid (GABA), both of which play significant roles in the brain related to mood, cognition, and stress response. Due to its structural similarity, L-Theanine is believed to impact the levels and activity of these neurotransmitters, although the exact mechanisms are still being studied.

One of the most noteworthy characteristics of L-Theanine is its ability to cross the blood-brain barrier, a property that allows it to directly influence brain chemistry. Once in the brain, it is known to promote an increase in alpha brain waves, which are associated with a state of relaxed alertness. This is why many people report feeling a sense of calm focus after consuming black tea.

In addition to its calming effects, L-theanine, often compared to synthetic nootropics for its efficacy, has been studied for potential benefits in specific conditions like ADHD and certain anxiety disorders.

It is a functional food known for improving sleep quality, reducing symptoms of anxiety and stress, enhancing cognitive performance, and potentially boosting the immune system.

L-Theanine, in combination with caffeine, is used as ADHD medications. This combination is believed to enhance cognitive performance – including improved focus, concentration, and alertness – while mitigating some of the jittery side effects commonly associated with caffeine intake.

Due to its safety profile and potential health benefits, L-theanine is also available as a dietary supplement. It is often used for its nootropic (cognitive-enhancing) effects, particularly for improving focus and reducing stress.


  • Boosts cognitive functions such as focus, concentration, and learning capacity
  • Reduces stress and anxiety to promote well-being
  • Crosses the blood-brain barrier to provide potent stimulation of brain activity
  • Promotes brain health and neuroprotection


  • Requires further research to fully understand its mechanism of action
  • This dietary supplement is not approved by the FDA (Food and Drug Administration)

Mechanism of Action

L-Theanine’s mechanism, involving pathways similar to those affected by common neurological medications, is quite fascinating and involves several pathways within the brain:

  1. Modulation of Neurotransmitters: L-theanine has a structure similar to that of glutamate, a key excitatory neurotransmitter in the brain. It is believed to modulate the action of glutamate by either acting as an antagonist at glutamate receptors or by inhibiting glutamate reuptake. This inhibition modulation helps maintain a balance between excitatory and inhibitory neurotransmitters in the brain, which then can reduce anxiety and promote higher information processing speeds.
  2. Increase in Alpha Brain Waves: One of the most significant effects of L-theanine supplementation is its ability to increase alpha brain wave activity. Alpha waves are associated with a state of “wakeful relaxation” – that is, being calm but alert in the mind. This increase in alpha wave activity is thought to be a key factor in the relaxation effect often attributed to tea consumption.
  3. Influence on GABA Levels: GABA (gamma-aminobutyric acid) is an inhibitory neurotransmitter in the brain, playing a crucial role in reducing neuronal excitability throughout the nervous system. L-theanine treatment may increase GABA levels or enhance GABA’s effectiveness, which results in its anxiolytic (anxiety-reducing) and calming effects.
  4. Interaction with Dopamine and Serotonin: L-theanine may also influence the levels of other important neurotransmitters like dopamine and serotonin, both of which play significant roles in mood regulation, cognition, and stress response. By modulating these neurotransmitters, L-theanine can have positive effects on mood, stress levels, and overall brain function.
  5. Synergistic Effect with Caffeine: When consumed as part of tea, L-theanine works synergistically with caffeine. This combination can improve cognitive performance, such as enhanced focus and attention, while L-theanine itself helps mitigate the jitteriness and potential negative effects on sleep quality that can be caused by caffeine.
  6. Neuroprotective Properties:  Research, including significant studies, suggests L-theanine may have neuroprotective effects, potentially beneficial in protecting brain cells against damage and reducing the risk of neurodegenerative diseases.(2) This might be due to its antioxidant properties or its ability to modulate excitotoxicity (cell damage caused by excessive stimulation by neurotransmitters like glutamate).

Nootropic Benefits of L-Theanine

L-theanine’s nootropic benefits stem from its ability to modulate neurotransmitters, increase alpha brain waves, and its synergistic effects with caffeine. These actions contribute to improved cognitive function, mood regulation, and stress reduction.

Overall, this amino acid promotes a unique state of relaxed alertness, beneficial for both mental performance and emotional well-being.

Here’s a closer look at the nootropic benefits of L-theanine in your daily wellness regimen. 

1. Improved Focus and Attention

L-theanine helps in sharpening focus and improving attention, particularly when combined with caffeine. This makes it useful for tasks that require sustained concentration.(3)

2. Enhanced Cognitive Performance

During studies, researchers found that L-theanine improved overall cognitive performance in healthy adult participants, including better mental clarity and quicker reaction times.(4)

3. Reduction in Stress and Anxiety

By increasing GABA levels and modulating other neurotransmitters like serotonin and dopamine, L-theanine can help in reducing psychological stress and anxiety.

This is potentially beneficial for patients looking for a natural treatment for schizoaffective disorder or schizophrenia.(5)

4. Improved Sleep Quality

While not a sedative, L-theanine improves sleep quality due to its relaxation-inducing effects, which leads to a more restful state.

5. Increased Relaxation Without Drowsiness

L-theanine uniquely promotes relaxation without causing drowsiness, making it beneficial for those seeking calmness while remaining alert and productive.(6)

6. Enhanced Mood

Through its impact on neurotransmitters like dopamine and serotonin, L-theanine can have a positive effect on mood, contributing to feelings of well-being and reducing symptoms of depression in some individuals.

7. Boost in Alpha Brain Wave Activity

The increase in alpha brain waves associated with L-theanine intake is linked to enhanced creativity, improved problem-solving abilities, and a state of calm alertness.(7)

8. Neuroprotection

L-theanine has neuroprotective effects that reduce the risk of cognitive decline and support brain health over time.(8)

9. Synergistic Effects with Caffeine

When taken with caffeine, L-theanine enhances the positive cognitive effects of caffeine (like increased alertness and attention) while reducing its negative side effects (such as jitteriness).(9)

This nootropic stack is a helpful companion in the treatment of ADHD (attention deficit hyperactivity disorder).(10)

10. Reduction in the Impact of Stress on Cognitive Function

By mitigating the body’s stress response, L-theanine can help maintain cognitive function during stressful situations.

Uses of L-Theanine

L-Theanine has gained popularity due to its various beneficial uses in promoting mental and physical health, such as the following:

  • Stress and Anxiety Reduction: L-theanine is known to reduce symptoms of stress and anxiety, particularly effective in conditions like generalized anxiety disorder and panic attacks.
  • Improvement in Sleep Quality: Though not a sedative, L-theanine can help improve the quality of sleep by promoting relaxation.
  • Enhancement of Cognitive Functions: It’s used to boost cognitive functions such as focus, attention, and memory, especially in combination with caffeine.
  • Mood Regulation: L-theanine may positively influence mood by modulating neurotransmitters like serotonin and dopamine.
  • Increased Relaxation: It promotes a state of relaxed alertness, beneficial for meditation, yoga, or any activities that require a calm but alert state.
  • Neuroprotective Potential: There’s ongoing research into L-theanine’s potential as a neuroprotective agent, which might be beneficial in preventing cognitive decline.
  • Mitigation of Negative Effects of Caffeine: When paired with caffeine, L-theanine helps reduce jitteriness and other negative side effects of caffeine.
  • Support in Cardiovascular Health: Some studies suggest L-theanine may have a role in supporting heart health, though more research is needed in this area.
  • Enhancing Immune Function: Early research indicates a potential role for L-theanine in supporting the immune system.
  • Alleviation of Premenstrual Syndrome (PMS) Symptoms: Some users report relief from PMS symptoms when taking L-theanine supplements.

Where to Buy L-Theanine

The safety of L-theanine also depends on the quality of the supplement. It’s important to choose high-quality products from reputable manufacturers.

Luckily, we have done deep diving through multiple retailers to find the best online supplier for L-theanine, SuperSmart.com.

This reputable online nootropics company has a comprehensive library, third-party testing, and affordable prices, with worldwide shipping since 1992.

Their customer reviews are full of satisfied users, and we are one of them!

L-Theanine Dosage

Determining the appropriate dosage of L-theanine is important for maximizing its benefits while minimizing potential side effects.

The optimal dosage can vary depending on the individual’s age, health status, and the specific benefits they are seeking. 

However, here are some general guidelines based on existing research and common usage:

  • Typical Dosage Range: For most people, a typical daily dosage of L-theanine ranges from 100 to 400 mg. This range is often considered effective for achieving the desired nootropic and calming effects.
  • Dosage in Combination with Caffeine: When L-theanine is taken in combination with caffeine (as often found in green tea), a common ratio is approximately 2:1 or 1:1, L-theanine to caffeine. For example, 200 mg of L-theanine may be paired with 100 mg of caffeine.
  • Dosage for Stress and Anxiety: For reducing stress and anxiety, dosages towards the higher end of the typical range (e.g., 200-400 mg) are often used.
  • Dosage for Cognitive Enhancement: For enhancing focus and cognitive performance, lower doses (100-200 mg) are commonly used, particularly when combined with caffeine.

L-Theanine is available in various forms, including capsules, and tablets, and as a constituent in teas, particularly green tea. The form influences absorption and effectiveness.

L-Theanine Side Effects & Safety

For the majority of users, L-Theanine is well-tolerated, and side effects are rare.

When they do occur, they are typically mild and can include:

  • Headache
  • Dizziness
  • Gastrointestinal issues

Some safety considerations include:

  • Pregnancy and Breastfeeding: There is limited research on the safety of L-theanine during pregnancy and breastfeeding. Therefore, it is generally advised to avoid use during these periods.
  • Interaction with Medications: L-theanine may interact with medications like blood pressure drugs, stimulants, and sedatives. It can also affect the efficacy of drugs for ADHD and certain psychiatric medications.
  • Pre-existing Health Conditions: Individuals with pre-existing health conditions, particularly those related to the liver or kidneys, should consult with a healthcare provider before taking L-theanine supplements.
  • Allergic Reactions: While rare, allergic reactions to L-theanine can occur. Anyone with a known allergy to tea leaves should avoid L-theanine supplements.
  • Overuse or High Doses: Consuming very high doses of L-Theanine may increase the risk of side effects. For example, although L-theanine is known for promoting relaxation without drowsiness, some people might experience sedative effects, particularly at higher doses.

Overall, L-Theanine has been consumed for centuries by people drinking tea with few reported side effects, suggesting a good safety and efficacy profile for long-term use in moderate amounts.


In conclusion, L-Theanine stands out as a remarkable and versatile amino acid, offering a multitude of benefits for both the mind and body.

From its ability to enhance cognitive functions and mood to its calming effects on stress and anxiety, L-Theanine is a testament to the power of natural compounds in supporting overall health and well-being.

Whether you’re a student looking for a focus boost, a professional seeking stress relief, or simply someone interested in maintaining good mental health, L-Theanine presents a compelling, natural option. Its unique ability to induce relaxation without drowsiness and to work synergistically with caffeine makes it a standout choice in the world of nootropics.

As we continue to navigate the complexities of our fast-paced world, the calming and cognitive-enhancing properties of L-Theanine might just be the natural ally we need.

So, next time you sip on a cup of green tea, take a moment to appreciate the subtle yet powerful effects of L-Theanine, nature’s little secret for a more relaxed and focused mind. 

Remember, a calm mind is not only a healthy mind but also a powerful tool for achieving overall wellness and success.


How long does L-Theanine take to work?

The effects of L-Theanine can often be felt within 30 minutes to 2 hours, and it can be used either as needed or regularly. 

What is the elimination half-life of L-Theanine?

For L-Theanine, the elimination half-life is relatively short. Studies suggest that L-Theanine’s half-life is around 2.5 to 5 hours in humans. This means that it is metabolized and excreted from the body relatively quickly, which is why some people choose to take L-theanine in divided doses throughout the day to maintain its effects.

Should you cycle L-Theanine?

No, there is no strong evidence suggesting the need to cycle L-Theanine. It does not tend to cause tolerance or dependency, and its effects do not appear to diminish significantly over time with continuous use.

Can I stack L-Theanine with other nootropics?

L-Theanine is known for its synergistic effects, especially when combined with caffeine. Additionally, L-Theanine can be stacked with other nootropics such as racetams or cholinergic supplements for cognitive enhancement, or with other mood-supporting supplements for stress relief, and is effective. 

How should I store L-Theanine?

Excessive heat and moisture can degrade L-Theanine. A cupboard away from heat sources is ideal.

Sources, Studies, and Scientific Research
  1. Saeed, Muhammad et al. “L-theanine: an astounding sui generis amino acid in poultry nutrition.” Poultry science vol. 99,11 (2020): 5625-5636. doi:10.1016/j.psj.2020.07.016
  2. Kakuda, Takami. “Neuroprotective effects of theanine and its preventive effects on cognitive dysfunction.” Pharmacological research vol. 64,2 (2011): 162-8. doi:10.1016/j.phrs.2011.03.010
  3. Nobre, Anna C et al. “L-theanine, a natural constituent in tea, and its effect on mental state.” Asia Pacific journal of clinical nutrition vol. 17 Suppl 1 (2008): 167-8.
  4. Hidese, Shinsuke et al. “Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial.” Nutrients vol. 11,10 2362. 3 Oct. 2019, doi:10.3390/nu11102362
  5. Ritsner, Michael S et al. “L-theanine relieves positive, activation, and anxiety symptoms in patients with schizophrenia and schizoaffective disorder: an 8-week, randomized, double-blind, placebo-controlled, 2-center study.” The Journal of clinical psychiatry vol. 72,1 (2011): 34-42. doi:10.4088/JCP.09m05324gre
  6. Evans, Malkanthi et al. “A Randomized, Triple-Blind, Placebo-Controlled, Crossover Study to Investigate the Efficacy of a Single Dose of AlphaWave® L-Theanine on Stress in a Healthy Adult Population.” Neurology and therapy vol. 10,2 (2021): 1061-1078. doi:10.1007/s40120-021-00284-x
  7. Baba, Yoshitake et al. “Effects of l-Theanine on Cognitive Function in Middle-Aged and Older Subjects: A Randomized Placebo-Controlled Study.” Journal of medicinal food vol. 24,4 (2021): 333-341. doi:10.1089/jmf.2020.4803
  8. De Felice, Marta et al. “l-Theanine Prevents Long-Term Affective and Cognitive Side Effects of Adolescent Δ-9-Tetrahydrocannabinol Exposure and Blocks Associated Molecular and Neuronal Abnormalities in the Mesocorticolimbic Circuitry.” The Journal of neuroscience : the official journal of the Society for Neuroscience vol. 41,4 (2021): 739-750. doi:10.1523/JNEUROSCI.1050-20.2020
  9. Anas Sohail, Anas et al. “The Cognitive-Enhancing Outcomes of Caffeine and L-theanine: A Systematic Review.” Cureus vol. 13,12 e20828. 30 Dec. 2021, doi:10.7759/cureus.20828
  10. Kahathuduwa, Chanaka N et al. “Effects of L-theanine-caffeine combination on sustained attention and inhibitory control among children with ADHD: a proof-of-concept neuroimaging RCT.” Scientific reports vol. 10,1 13072. 4 Aug. 2020, doi:10.1038/s41598-020-70037-7

Jacob Kovacs is a cognitive neuroscientist and author at WholisticResearch, specializing in nootropics and neuroactive peptides. His expertise in neuroscience and psychopharmacology bridges cognitive science with drug development. Kovacs’ work focuses on enhancing cognitive functions and brain health through innovative, efficient neuroactive compounds that overcome traditional pharmacokinetic challenges. His contributions are pivotal in advancing the understanding and treatment of neurological diseases.