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

Updated on November 21, 2022
 by — reviewed by Jason Williams, PhD (Contributor: George Collins / Editor: Yoko Hill)

In this review, we will look at L-Theanine and how you can add it to your diet. We will also look at how it can benefit sleep, anxiety, and the brain and how it is an amino acid that can help you live a more relaxed and calmer life.

We've all been there – tossing and turning in bed for hours on end, trying desperately to get some shut-eye.

Maybe you've even resorted to taking sleeping pills in hopes of nodding off quickly.

What if we told you that there's a natural nootropic that can help you get the sleep you need, make you feel more relaxed, and improve your focus and concentration?

L-Theanine is an amino acid compound found in green tea that has been shown to have a host of benefits for sleep, anxiety, and the brain.

This article explores the benefits of L-Theanine and looks at the amino acid in more detail while warning you of potential side effects and other relevant information.

From analyzing user experiences, we know it has helped countless people reduce their anxiety levels and make them feel great at work or school.

Let’s learn a little bit more about this mood-boosting supplement and find out if it’s just what your brain needs.

L-Theanine Review Summary

L-Theanine is an amino acid that is commonly found in tea. It is also available in supplement form and is sometimes promoted as a natural treatment for anxiety, stress, ADHD and other conditions. L-Theanine has been shown to promote relaxation without causing drowsiness. It may also help reduce anxiety and improve sleep quality. Additionally, L-Theanine has been shown to enhance cognitive function, relaxation and protect the brain from age-related damage.

Overall, L-Theanine is a safe and effective nootropic with various health benefits for people who use it.


  • Improves mood
  • Reduces anxiety
  • Improves sleep quality
  • Enhances cognitive function


  • It has to be used in combination with caffeine for the best results
  • Can interact with blood pressure medications

What Is L-Theanine?


L-Theanine was originally discovered in 1949 and has been used as a food additive in Japan since the 1950s. It's an amino acid that is found in green tea.

L-Theanine is considered safe for human consumption and is classified as a generally recognized safe (GRAS) substance by the US Food and Drug Administration (FDA).

Theanine without a prefix typically refers to the D-isomer of the compound, which is not found in tea or supplements and does not have the same effects on the body as L-Theanine. However, the L-Theanine form is the only one that has been shown to have any effect on humans.

L-Theanine is structurally similar to the neurotransmitter glutamate and works by inhibiting its activity. L-Theanine has been shown to promote relaxation and mental health in people with stress-related ailments and cognitive impairments [1].

Many animal studies have found that L-Theanine enhances hippocampal activity and exerts anxiolytic effects through its ability to change glutamate and methionine metabolism [2].

An 8-week, randomized, double-blind, placebo-controlled study done in patients with schizophrenia and schizoaffective disorder found that L-Theanine improved symptoms of anxiety and cognitive function [3].

How Does L-Theanine Work In The Brain?

L-Theanine increases levels of neurotransmitters in the brain, including dopamine and serotonin. These neurotransmitters are associated with relaxation and happiness [4].

L-Theanine also increases levels of GABA, a neurotransmitter that inhibits nerve signaling. This inhibitory effect may explain how L-Theanine induces relaxation without causing drowsiness [5].

It also lowers levels of excitatory neurotransmitters, which amplify stress levels. This prevents an excess build-up of glutamate, a chemical related to cognitive disorders and impairment.

In addition, L-Theanine has been shown to improve cognition and increase brain activity during task switching as well as promote alpha wave activity in the brain [6].

What Is L-Theanine Used For?

L-Theanine has been used for centuries in traditional Chinese and Japanese medicine for its calming effects. In recent years, it has gained popularity as a dietary supplement due to its cognitive-enhancing and stress-reducing effects.

L-Theanine is often used as a natural remedy for anxiety, stress, and insomnia. Additionally, it is sometimes included in cognitive-enhancing supplements due to its ability to improve mental clarity and focus.

There is good clinical evidence to support the use of L-Theanine for anxiety and stress relief as well as for improving attention, working memory, and executive functions [7].

L-Theanine is often combined or stacked with caffeine to improve cognitive performance. Caffeine + L-Theanine supplements are popular among students, professionals, and biohackers for their ability to enhance concentration and focus while reducing anxiety levels.

Studies have shown that when combined, these two compounds can lead to increased task accuracy, improved alertness, and reduced reaction times [8].

What Are The Benefits Of L-Theanine For Cognition?

The benefits of L-Theanine for cognition can be attributed to its ability to increase neurotransmitter levels, improve brain activity, and reduce stress levels.

Some of the cognitive benefits of L-Theanine include:

  • Improved task accuracy
  • Increased alertness
  • Reduced reaction times
  • Improved working memory
  • Enhanced executive functions
  • Increased attention span

When combined with caffeine, these benefits are even more pronounced.

Where To Buy L-Theanine Online?

Before buying L-Theanine online, it is important to do your research and ensure you are getting a high-quality supplement. Make sure to look for a supplement that is third-party tested and does not contain any fillers or additives.

One of the best places to buy L-Theanine online is Pure Nootropics. Not only do they offer high-quality, third-party tested supplements, but they have also been in the game for a long time and have a solid reputation in the nootropics community.

Additionally, they offer free domestic shipping on all orders over $40 and have a very generous return policy.

You can buy L-Theanine online right here:

What Do People Say About L-Theanine On Reddit?

Now that we know what L-Theanine is, what it does, and where to buy it, let’s take a look at what people are saying about it on Reddit.

L-Theanine has been well-received in the nootropics community, with most users reporting positive effects on stress levels, anxiety, and cognitive performance.

Here are some reviews of L-Theanine from Reddit:

“I’ve been taking L-theanine for a few weeks now and I really like it. I was looking for something to help me focus and concentrate better at work, which has definitely helped. I also notice that I am less stressed out and more relaxed in general. Overall, I’m very pleased with this supplement!”


“I started taking L-theanine a few months ago to help with my anxiety and it has definitely helped. I take it every day and I notice that I am less stressed and more able to focus. It has also helped me sleep better at night."

-u/anxious_ One

“L-Theanine has definitely helped me with my anxiety. I notice that I am more relaxed and have an easier time focusing when I take it.”

-u/relieved_ Redditor

As you can see, people are generally very pleased with the effects of L-Theanine on anxiety and stress levels. Additionally, many users report improved cognitive performance, including increased focus and concentration.

If you are looking for a natural way to reduce stress and anxiety levels or improve your cognitive performance, L-Theanine may be worth trying.

How Do You Take L-Theanine For Cognitive Enhancement?

The way you take L-Theanine will depend on your goals. If you are looking to improve cognitive performance, it is best to take L-Theanine with caffeine. This is called 'stacking,' and it is a common practice in the nootropics community.

The rationale behind stacking L-Theanine with caffeine is that the two substances have complementary effects. Caffeine provides a mental boost, while L-Theanine reduces stress levels and improves focus.

L-Theanine alone is best taken on an empty stomach, as food can decrease its absorption. You can take it in the morning or evening, depending on your preference. If you are stacking L-Theanine with caffeine, it is best to take them both in the morning so that the effects of the caffeine do not interfere with your sleep at night.

Some people prefer to cycle L-Theanine on and off, while others take it daily. If you are going to cycle L-Theanine, it is best to take it for 4-6 weeks, then take a break for 2-4 weeks. This will help prevent the body from becoming tolerant to the effects of L-Theanine.

What Is The Recommended Dosage For L-Theanine?

The recommended dosage for L-Theanine is 100-400 mg per day. The dosage will depend on your goals. If you are taking L-Theanine for anxiety relief, a dose of 300-400 mg per day is typically sufficient.

If you are taking L-Theanine for cognitive enhancement, a dose of 200 mg per day may be more effective. It is best to start with a lower dose and increase it gradually until you find the dose that works best for you.

If you stack L-Theanine with Caffeine, you want to aim for a ratio of 1:2 (L-Theanine:caffeine). So, if you take 100 mg of L-Theanine, you would want to take 200 mg of Caffeine.

Higher L-Theanine Dosage For Anxiety & Panic Attacks

If you have severe anxiety or panic attacks, a higher dose of L-theanine may be required for immediate relief. Take a single dose of 600-900 mg L-theanine as soon as you feel your anxiety is out of control. This calms you down within 30-45 minutes of taking it.

What Are The Side Effects Of L-Theanine?

When it comes to side effects, L-Theanine is one of the safest nootropics available. It is non-toxic and well-tolerated by most people. The reason for this is that L-Theanine is an amino acid, which is a building block of protein. It's naturally found in tea leaves and is safe to consume in large quantities.

The most common side effect of L-Theanine is drowsiness. This typically only occurs at high doses (600 mg or more). If you find that L-Theanine makes you drowsy, it is best to reduce the dosage or take it in the evening before bed.

Other potential side effects of L-Theanine may include:

  • Headaches
  • Nausea
  • Diarrhea
  • Fatigue

These side effects are rare and typically only occur at high doses. If you do experience any of these side effects, it is best to reduce the dosage or stop taking L-Theanine altogether.

What Nootropics Are Similar To L-Theanine?

Nootropics that are similar to L-Theanine, according to scientific evidence, are:

Ashwagandha: Ashwagandha is an herb that has been used for centuries in Ayurvedic medicine. It is known for its ability to reduce stress and anxiety levels. Additionally, Ashwagandha has been shown to improve cognitive performance and memory [9].

Rhodiola Rosea: Rhodiola Rosea is an herb that grows in cold, mountainous regions. It has been used traditionally to help cope with stress and fatigue. Rhodiola Rosea has also been shown to improve cognitive performance and memory [10].

Bacopa Monnieri: Bacopa Monnieri is an herb that has been used in traditional Ayurvedic medicine for centuries. It is known for its ability to improve memory and cognitive performance. Additionally, Bacopa Monnieri has been shown to reduce stress and anxiety levels [11].

These three nootropics are all similar to L-Theanine in that they are all effective at reducing stress and anxiety levels. Additionally, they all have cognitive-enhancing properties. However, they each have their own unique mechanisms of action and side effect profiles.

That being said, they are all considered adaptogens, which are substances that help the body adapt to stress.

What Brain Supplements Can L-Theanine Be Stacked With?

L-Theanine is best stacked with other nootropics that have cognitive-enhancing effects. Some of the best nootropics to stack with L-Theanine are:

Caffeine: Caffeine is a stimulant that increases alertness and wakefulness. It also has cognitive-enhancing effects and can improve memory and focus. When stacked with L-Theanine, the two compounds can offset each other’s side effects. For example, L-Theanine can help to reduce the jitteriness associated with caffeine.

Piracetam: Piracetam is a nootropic that has been shown to improve memory and cognitive performance. Additionally, Piracetam can help to protect the brain from age-related damage. When stacked with L-Theanine, the two compounds can enhance each other’s effects.

NooCube: NooCube is a nootropic blend that contains both Bacopa Monnieri and L-Theanine. Additionally, it contains other cognitive-enhancing ingredients such as Huperzine A and Alpha GPC. NooCube is an effective nootropic stack that can help to improve memory, focus, and cognitive performance.

The great thing about NooCube is that you get all the benefits from L-Theanine whilst also getting the benefits from other nootropics that enhance the effects of L-Theanine.

If you're interested in NooCube, you can find this popular nootropic here:

Frequently Asked Questions (FAQ)

Let's take a look at some frequently asked questions about L-Theanine:

How Long Does It Take For L-Theanine To Work?

L-Theanine works quickly. The effects can be felt within 30-40 minutes after ingestion with dosages of 100-200 mg. However, the full effects of L-Theanine may not be realized for several hours.

How Does L-Theanine Make You Feel?

L-Theanine makes you feel relaxed and calm. It does not produce any psychoactive effects and will not make you feel “ high”. People also report feeling more clear-headed and focused after taking L-Theanine.

What's The Half-Life Of L-Theanine?

L-Theanine plasma half-life ranges from 54–78 min, which means that it takes the body around 1 hour to eliminate half of the L-Theanine that has been consumed.

Is It Safe To Use L-Theanine?

L-Theanine is safe for most people. It's a natural compound that's found in tea, and there have been no reports of serious side effects. However, as with any supplement, L-Theanine can cause some slight discomfort in high dosages.


L-Theanine is a powerful nootropic with many benefits for cognitive enhancement. It can be used on its own or stacked with other nootropics such as Caffeine for even greater effects. If you're looking for a safe and effective way to improve your cognitive performance, L-Theanine is a great option.

Its anti-anxiety and stress-reducing effects make it an ideal supplement for those who are looking to improve their mood and well-being. Additionally, its cognitive-enhancing properties can help to improve memory, focus, and attention.


1Hidese, 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
2Ogawa, Shintaro et al. “Effects of L-theanine on anxiety-like behavior, cerebrospinal fluid amino acid profile, and hippocampal activity in Wistar Kyoto rats.” Psychopharmacology vol. 235,1 (2018): 37-45. doi:10.1007/s00213-017-4743-1
3Ritsner, 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
4Dasdelen, M. F., Er, S., Kaplan, B., Celik, S., Beker, M. C., Orhan, C., Tuzcu, M., Sahin, N., Mamedova, H., Sylla, S., Komorowski, J., Ojalvo, S. P., Sahin, K., & Kilic, E. (1AD, January 1). A novel theanine complex, Mg-L-theanine improves sleep quality via regulating brain electrochemical activity. Frontiers. Retrieved July 19, 2022, from https://www.frontiersin.org/articles/10.3389/fnut.2022.874254/full
5Rao, Theertham P et al. “In Search of a Safe Natural Sleep Aid.” Journal of the American College of Nutrition vol. 34,5 (2015): 436-47. doi:10.1080/07315724.2014.926153
6Nobre, 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.
7Baba, 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
8Owen, Gail N et al. “The combined effects of L-theanine and caffeine on cognitive performance and mood.” Nutritional neuroscience vol. 11,4 (2008): 193-8. doi:10.1179/147683008X301513
9Gopukumar, Kumarpillai et al. “Efficacy and Safety of Ashwagandha Root Extract on Cognitive Functions in Healthy, Stressed Adults: A Randomized, Double-Blind, Placebo-Controlled Study.” Evidence-based complementary and alternative medicine : eCAM vol. 2021 8254344. 30 Nov. 2021, doi:10.1155/2021/8254344
10Ma, Gou-Ping et al. “Rhodiola rosea L. Improves Learning and Memory Function: Preclinical Evidence and Possible Mechanisms.” Frontiers in pharmacology vol. 9 1415. 4 Dec. 2018, doi:10.3389/fphar.2018.01415
11Calabrese, Carlo et al. “Effects of a standardized Bacopa monnieri extract on cognitive performance, anxiety, and depression in the elderly: a randomized, double-blind, placebo-controlled trial.” Journal of alternative and complementary medicine (New York, N.Y.) vol. 14,6 (2008): 707-13. doi:10.1089/acm.2008.0018