L-Theanine dosage


David Tomen
David Tomen
12 minute read
L-Theanine is known for boosting alpha and theta brain waves, anti-anxiety, boosting cognition, improving memory, and better quality sleep

L-Theanine (r-glutamylethylamide) is a non-dietary amino acid found in green tea (camellia sinensis), and the mushroom Xerocomus badius. Structurally, L-Theanine is similar to the neurotransmitters l-glutamate and l-glutamine.

L-Theanine easily crosses the blood-brain barrier. And taken as a supplement or by drinking green tea, reaches your brain within 30-45 minutes.

L-Theanine can lower blood pressure, rejuvenate and relax you, boost your ability to think, improve focus and change your mood. L-Theanine balances brain chemistry and improves cognitive health.

L-Theanine helps:

  • Brain Waves. L-Theanine boosts alpha brain waves (8-12Hz) promoting alert relaxation.[i] And theta brain waves associated with creativity and relief from trauma.
  • Neurotransmitters. L-Theanine increases GABA, serotonin and dopamine levels in your brain. Producing an energizing and calming effect. And improving cognition and memory.
  • Neuroprotection. L-Theanine is an agonist of NMDA receptors and can inhibit synaptic release of glutamate. Protecting your brain from over-stimulation caused by glutamate, and possible glutamate toxicity.


L-Theanine (r-glutamylethylamide) is a non-dietary amino acid found in tea. And especially high levels in green tea (camellia sinensis). L-Theanine was first isolated from green tea in Japan by Sakato in 1949.


As an analogue of glutamate and glutamine, it’s hydrolyzed in your intestine and liver into l-glutamate and ethylamine. And easily crosses your blood-brain barrier.

L-Theanine is one of the very few nootropics known to modulate brain waves. It affects alpha brain waves which are associated with relaxation. Providing an alert calmness, L-Theanine helps in promoting super-learning, flow states and joy.

L-Theanine boosts the neurotransmitters serotonin, dopamine and GABA in your brain. As well as increasing Brain-Derived Neurotrophic Factor (BDNF) and Nerve Growth Factor (NGF).[ii]

L-Theanine is known for helping to relieve stress, improve cognition, boost mood and cognitive function.

L-Theanine boosts brain waves

How does L-Theanine work in the Brain?

L-Theanine boosts brain health and function in several ways. But two in particular stand out.

  1. L-Theanine reduces physical and mental stress. L- Theanine helps increase alpha brain waves which are associated with mental relaxation and concentration.

One study in South Korea worked with 20 healthy male volunteers aged 18 – 30 years.  One group was given L-Theanine tablets, and the other group a placebo daily for 7 days.

Brain waves were measured 40 minutes after administration of the tablets. The researchers analyzed alpha wave power values. And concluded that L-Theanine tablets promoted the release of alpha brain waves related to mental relaxation and concentration.[iii]

In May 2016, researchers at Simon Fraser University in Canada developed a technology to clinically measure brain wave patterns. With this technology, we’re now able to detect cognitive dysfunction before it happens. Imagine the implications of this new technology when applied to the nootropics world.[iv]

  1. L-Theanine increases neurotransmitters. Research shows that L-Theanine increases dopamine, serotonin, and GABA in your brain.[v] And it reduces the excitatory neurotransmitter glutamate which is associated with stress, tension and agitation.[vi]

A study done in Japan worked with 12 people who underwent 4 separate trials. One in which they took L-Theanine at the start of the experiment. One in which they took it half-way through. And two control trials in which they took either a placebo or nothing.

The results showed that L-Theanine resulted in a reduction in heart rate and s-IgA associated with acute stress. The researchers concluded that L-Theanine could cause anti-stress effects via the inhibition of cortical neuron excitation.[vii]


How things go bad:

As we get older, our brain chemistry and energy metabolism changes.

↓ Neurotransmitter levels decline

↑ Glutamate levels increase

↑ Stress levels increase

Long-term memory and mood decline

↓ Quality of sleep declines

All of these changes can happen at any age once we reach adulthood. And are contributing factors to the neurodegenerative diseases of aging, and quality of life.

L-Theanine benefits

L-Theanine energizes without draining, calms without putting you to sleep, and motivates without causing a jagged edge.

L-Theanine is anti-anxiety and calmingTea (as a source of L-Theanine) can have as much caffeine as some coffees. And yet doesn’t exert the same “speedy” effect. And the reason is the ingredient L-Theanine.

You can actually see L-Theanine’s effect in your brain using an EEG. Brain waves are smoothed out rather than flattened out.[viii] So your body is relaxed, your mind is calmed, but you don’t get sleepy. And L-Theanine, once it crosses the blood-brain barrier, raises levels of serotonin and dopamine.[ix]

L-Theanine even improves your quality of sleep. Researchers in Japan gave volunteers 200 mg of L-Theanine daily and recorded their sleep patterns. Sleep quality, recovery from exhaustion, and feeling refreshed were all enhanced by L-Theanine.[x]

And L-Theanine puts you in a better mood. Once it crosses your blood-brain barrier, L-Theanine changes levels of amino acids affecting serotonin, dopamine, and GABA. Having a modulating effect on mood.[xi]

How does L-Theanine feel?

Your unique neurochemistry including neurotransmitters, brain waves, brain structure and even regional brain activity will influence your response to L-Theanine.L-Theanine improves mood

Most neurohackers report a calming effect within 30 – 45 minutes of taking L-Theanine. Cognition gets a boost, and energy levels rise without the jitteriness caused by stimulants like caffeine.

Some report L-Theanine has stopped their anxiety and panic attacks. Just don’t combine it with anti-anxiety meds like Xanax.

Most report an overall improvement in the sense of well-being and quality of life. And nearly all remark on better quality sleep.

L-Theanine Clinical Research

Green Tea reduces incidence of stroke

Research has found that if L-Theanine is present in the body at the time stroke occurs, brain damage will be significantly reduced.

In this monster study done in China, researchers selected 14,212 subjects from 12 provinces. Ages ranged from 35 – 60 years old. The study looked at tea drinking status, dose and type of teas.

This study concluded there was a 40% decreased risk of stroke in those who drank green, black or jasmine teas.[xii]

L-Theanine improves memory

In this double-blind, placebo-controlled study, the effect of L-Theanine on memory and attention was investigated.

91 subjects with mild cognitive impairment were enrolled in this study. One group received 1,680 mg of L-Theanine daily for 16 weeks. And the control group received a placebo.

The study concluded that L-Theanine increased brain Theta waves associated with cognitive alertness and creativity. And there were improvements in memory. The results of this study suggested that L-Theanine has potential as an intervention for cognitive improvement.[xiii]

And that is an understatement by any stretch. People spend years meditating. With the goal of reaching consistent access to brain wave states like Theta. In this trial, they did it with a dose of L-Theanine. The same type of dose you could get with a few cups of quality green tea.

L-Theanine reduces stress

Considerable research has been dedicated to L-Theanine and its benefits to stress reduction in both animal and human studies. And we have ample documentation that corticosterone and stress exert negative effects on memory.[xiv]

Corticosteroids which are secreted after stress, have a profound impact on long-term potentiation and memory formation.[xv]

In this animal study, rats were fed water containing L-Theanine for 3 weeks and put through some stress inducing exercise. The researchers found that corticosterone levels were lower in the rats who used L-Theanine compared to those who had none.

In fact, stress had no effect on the animals who were fed L-Theanine. Memory was not affected. The researchers concluded that L-Theanine modified corticosterone secretion. And L-Theanine is a strong preventive measure in preventing memory loss otherwise induced by stress.[xvi]

L-Theanine Recommended Dosage

Recommended dosage of L-Theanine is 100 – 400 mg once or twice per day. With a maximum of 1,200 mg per day according to the Cleveland Clinic.[xvii]

L-Theanine is water soluble so you can take it with water.L-Theanine dosage

Labels on quality green tea often only display the amount of green tea leaf available in each bag in milligrams (mg). But not its L-Theanine content. Green tea that’s steeped correctly will offer 1-2% L-Theanine per cup. So 1,500 mg of green tea leaf would be about 30 mg. of L-Theanine (at 2%).

We often say that YMMV, and this is especially applicable to L-Theanine. Find out what works best for you. Start at a lower dose like 100 mg. And work your way up until you achieve the effects you’re looking for.

L-Theanine Side Effects

L-Theanine is a naturally occurring amino acid found in plants like tea or one species of mushroom. So it’s considered non-toxic and very safe.

Theanine seems to decrease blood pressure. So if you’re on meds for high blood pressure, use L-Theanine with caution. Your blood pressure could go too low.

Type of L-Theanine to Buy

L-Theanine is available in green, black and white teas. Green tea contains the most L-Theanine.

A great side benefit for neurohackers is green tea also contains caffeine. A cup of good quality green tea has less caffeine than a cup of coffee. About 10 mg less.

L-Theanine + Caffeine stack

One study done at Unilever in the UK looked at the combined effects of L-Theanine and caffeine on cognitive performance and mood. They compared 50 mg of caffeine with and without 100 mg of L-Theanine.

The research team had 27 volunteers participate. And based measurements on word recognition, rapid visual information processing, critical flicker fusion threshold, attentions switching and mood.

Performance was measured at the beginning, and again 60 minutes and 90 minutes after consumption. Separated by a 7-day washout period.

Caffeine improved alertness at 60 mins. And accuracy on attention-switching at 90 mins. The L-Theanine and caffeine combination improved both speed and accuracy, and reduced susceptibility to distracting information on the memory task.

The research team concluded that, “L-Theanine and caffeine in combination are beneficial for improving performance on cognitively demanding tasks”.[xviii]

And for an added bonus, L-Theanine takes the jittery-edge off of caffeine consumption.

The best pre-formulated caffeine + L-Theanine stack I’ve tried, and use is the new Performance Lab® Caffeine+. It contains Natural Caffeine (from Coffea Robusta seeds) 50 mg, L-Theanine (Suntheanine®) 100 mg, Ajipure® L-Tyrosine 250 mg, with a balanced NutriGenesis® B-Complex. For alert clean energy without the jitters.

L-Theanine from green tea

Extracting the optimal amount of L-Theanine from green tea is both art and science.

Researchers at the University of Newcastle in Australia set out to determine optimal conditions for water extraction of L-Theanine from green tea. They examined 4 different extraction methods. And learned that temperature, extraction time, ratio of water-to-tea and tea particle size had significant impacts on extraction yield of L-Theanine from green tea.

They concluded, “The optimal conditions for extracting theanine from green tea using water were found to be extraction at 80 °C for 30 min with a water-to-tea ratio of 20:1 mL/g and a tea particle size of 0.5-1 mm.” [xix]

So to get the most nootropic value when using green tea as your L-Theanine source – follow the directions. Just sayin’…

L-Theanine Supplements

L-Theanine is available in capsule or tablet form from several supplement manufacturers. Japanese company Taiyo is the oldest and most established company in the green tea supplement industry. Taiyo developed and patented a method for L-Theanine extraction from green tea called ‘Suntheanine®’.

Suntheanine can be found in some of higher quality pre-formulated nootropic stacks. For example, Mind Lab Pro® contains 11 brain enhancing nootropic compounds including Suntheanine.

Research has shown that some supplement makers using their own extraction method for L-Theanine, contain more than just the “L” form of Theanine. Turns out if it’s not done exactly right, you end up with a “D” form of Theanine.

D-Theanine may have a very different action in your body than L-Theanine. We’re not saying it’s dangerous. You just may not get all the benefit of pure L-Theanine.

So read the labels and reviews by people who have tried the product. 

I recommend Mind Lab Pro because it uses Suntheanine. And addresses all aspects of anxiety resistance, memory and cognitive enhancement, stabilizes mood, brain repair, and maintenance.

This premium nootropic stack is designed to affect neurotransmitters, cognitive energy, brain waves, neuroprotection, and regeneration. See my Mind Lab Pro review for a detailed report.

You will also find Suntheanine® in the new Performance Lab® Caffeine+. It contains Natural Caffeine (from Coffea Robusta seeds) 50 mg, L-Theanine (Suntheanine®) 100 mg, Ajipure® L-Tyrosine 250 mg, with a balanced NutriGenesis® B-Complex.

Nootropics Expert Recommendation

L-Theanine 100 – 500 mg per day

Nootropics Expert Tested and ApprovedI recommend using L-Theanine as a nootropic supplement.

Your body cannot make L-Theanine on its own. It’s a non-dietary amino acid only available from tea (and one little-known mushroom).

L-Theanine affects Alpha and Theta brain waves. This alone will help calm your mind, reduce stress, and help you stay alert.  You’ll get even more cognitive benefit by stacking L-Theanine with caffeine.

L-Theanine helps boosts the neurotransmitters dopamine, serotonin, and GABA. Improving alertness and attention. And boosting cognition and memory.

And it reduces the excitatory neurotransmitter glutamate which is associated with stress, tension and agitation.

L-Theanine helps to prevent strokes, and even reduces the damaging effects if you’ve had a stroke.

And L-Theanine has been shown to improve sleep quality.

I suggest starting with a dose of 100 – 250 mg of L-Theanine daily for nootropic use. Using either a quality supplement, or high quality green tea.

As a supplement, Suntheanine® is your best and safest choice for getting the kind of L-Theanine your brain can use. I recommend my favorite pre-formulated nootropic stack Mind Lab Pro® which includes Suntheanine.

Mind Lab Pro contains a synergistic blend of 11 brain enhancing nootropics covering all aspects of cognition and brain health. See my full Mind Lab Pro review for more.

Or for a smooth energy boost I recommend the new Performance Lab® Caffeine+. For alert clean energy without the jitters.

As an Amazon Associate I earn from qualifying purchases. This post may also contain other affiliate links and I will be compensated if you make a purchase after clicking on my links.


[i] Mason R. “200 mg of Zen” Alternative and Complementary Therapies. July 2004, 7(2): 91-95. (source)

[ii] Yamada T., Terashima T., Wada K., Ueda S., Ito M., Okubo T., Juneja L.R., Yokogoshi H. “Theanine, r-glutamylethylamide, increases neurotransmission concentrations and neurotrophin mRNA levels in the brain during lactation.” Life Sciences. 2007 Sep 29;81(16):1247-55. (source)

[iii] Song C.H., Jung J.H., Oh J.S., Kim K.S. “Effects of Theanine on the Release of Brain Alpha Wave in Adult Males.” Korean Journal of Nutrition 2003 Nov;36(9):918-923. (source)

[iv] Hajira S. G. et. Et. “Developing Brain Vital Signs: Initial Framework for Monitoring Brain Function Changes Over Time.” Frontiers in Neuroscience. 2016 May 12;10:211 (source)

[v] Nathan P.J., Lu K., Gray M., Oliver C. “The neuropharmacology of L-theanine(N-ethyl-L-glutamine): a possible neuroprotective and cognitive enhancing agent.” Journal of Herbal Pharmacotherapy. 2006;6(2):21-30. (source)

[vi] Lu M., Gray, Oliver C. “The Neuropharmacology of L-Theanine(N-Ethyl-L-Glutamine)” Journal of Herbal Pharmacotherapy Volume 6, Issue 2, 2006 (source)

[vii] Kimura K., Ozeki M., Juneja L.R., Ohira H. “L-Theanine reduces psychological and physiological stress responses.” Biological Psychology. 2007 Jan;74(1):39-45. (source)

[viii] Kakuda T., Nozawa A., Unno T., Okamura N., Okai O. “Inhibiting effects of theanine on caffeine stimulation evaluated by EEG in the rat.”Biosci Biotechnol Biochem. 2000 Feb;64(2):287-93. (source)

[ix] Yokogoshi H., Kobayashi M., Mochizuki M., Terashima T. “Effect of theanine, r-glutamylethylamide, on brain monoamines and striatal dopamine release in conscious rats.” Neurochemistry Research. 1998 May;23(5):667-73. (source)

[x] Kobayashi K., Nagato Y., Nobuyuki, Sugimoto S. “Effects of L-Theanine on the Release of .ALPHA.-Brain Waves in Human Volunteers.”  Nippon Nogeikagaku Kaishi 72(2):153-157 · December 1997 (source)

[xi] US Patent Application 20040171624; Japanese Patent Application 2001-253740 (source)

[xii] Chen Z., Li Y., Zhao L.C., Zhou B.F., Yang J., Wang Z.W., Guo M., Wu Y.F. “[A study on the association between tea consumption and stroke]. -in Chinese Zhonghua Liu Xing Bing Xue Za Zhi. 2004 Aug;25(8):666-70. (source)

[xiii] Park S.K., Jung I.C., Lee W.K., Lee Y.S., Park H.K., Go H.J., Kim K., Lim N.K., Hong J.T., Ly S.Y., Rho S.S. “A combination of green tea extract and l-theanine improves memory and attention in subjects with mild cognitive impairment: a double-blind placebo-controlled study.”Journal of Medicinal Food. 2011 Apr;14(4):334-43. (source)

[xiv] Garcia R. “Stress, hippocampal plasticity, and spatial learning.”Synapse. 2001 Jun 1;40(3):180-3. (source)

[xv] Joëls M., Karst H., DeRijk R., de Kloet E.R. “The coming out of the brain mineralocorticoid receptor.” Trends in Neuroscience. 2008 Jan;31(1):1-7. (source)

[xvi] Tamano H., Fukura K., Suzuki M., Sakamoto K., Yokogoshi H., Takeda A. “Preventive effect of theanine intake on stress-induced impairments of hippocamapal long-term potentiation and recognition memory.” Brain Research Bulletin. 2013 Jun;95:1-6. (source)

[xvii] “L-Theanine Supplement Review” Cleveland Clinic Wellnessclevelandclinicwellness.com Retrieved June 3, 2016 (source)

[xviii] Owen G.N., Parnell H., De Bruin E.A., Rycroft J.A. “The combined effects of L-theanine and caffeine on cognitive performance and mood.”Nutritional Neuroscience. 2008 Aug;11(4):193-8. (source)

[xix] Vuong Q.V., Stathopoulos C.E., Golding J.B., Nguyen M.H., Roach P.D. “Optimum conditions for the water extraction of L-theanine from green tea.” Journal of Separation Science. 2011 Sep;34(18):2468-74. (source)

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Join The Discussion - 315 comments

February 16, 2023

what do you think about AlphaWave®?
It’s cheaper, research has been done, 98% L-theanine, but I don’t know how natural it is, and what is contained in those 2%, but in any case it is better than buying an unknown version of L-theanine

    David Tomen
    February 17, 2023

    Dan, AlphaWave® is another patented form of L-Theanine just like Suntheanine® is patented form. I usually prefer when a manufacturer uses a patented ingredient in their supplement because they pay a licensing fee to use that ingredient. It is more expensive to produce. But chances are much higher that what it says on the label is actually what is in the capsule.

February 10, 2023

Hi David, do you know how many bags of green tea (e.g. standard Lipton pure green tea) must one drink to get 400 mg of L-Theanine?

    David Tomen
    February 13, 2023

    Mark, scroll up to the section called “L-Theanine Recommended Dosage” and I think it is the 3rd paragraph.

    February 16, 2023

    about 20 cups.
    If it is a quality tea, NOT in bags, about 10+, if the matcha is about 8+, but this is very very approximate.

    July 27, 2023

    You might also want to try Guayusa tea.

January 23, 2023

Hi David,

I have been taking 250mg of L-Theanine every morning and have had amazing focus and “get to work” effects. My friend on the other hand takes 100 mg and says that he is afraid that going to 250mg will make him sleepy.

What could I tell him to get him to take a slightly bigger dose, like me?

This is a close family friend and I really want him to experience the same effects as me.

    David Tomen
    January 25, 2023

    Dmitriy, 250 mg L-Theanine makes me sleepy as well. Chances are high that your friend will not have the same experience that you do. We are all wired different from each other with different body and brain chemistry, different food and air, different living environment, etc.

    February 6, 2023

    Very strange, I tried a few grams and it did not cause absolutely no drowsiness, rather the opposite.

January 9, 2023

Hello David! Which is best company for EGCG supplements? Please share a link . Thanks

    David Tomen
    January 10, 2023

    I prefer this form of EGCG because it is pure without any other toxic “other ingredients”: https://geni.us/glMW (Amazon)

January 7, 2023

“Research has shown that some supplement makers using their own extraction method for L-Theanine, contain more than just the “L” form of Theanine. Turns out if it’s not done exactly right, you end up with a “D” form of Theanine.”
can you link to the source?

    David Tomen
    January 10, 2023

    Daniel, I do not remember where I got that info from. When I originally wrote this review I took a deep dive into different manufacturing methods for L-Theanine. Clearly I missed linking to the source for that sentence.

January 7, 2023

NOW Foods, L-Theanine Pure Powder,
do you think it could be a falsification? I ordered it without even knowing about the “Suntheanine”…

    David Tomen
    January 10, 2023

    How could it be “false”? NOW Supplements is a very trustworthy source of supplements and they are telling you directly that that product is L-Theanine powder.

December 25, 2022

Could you please help me?
What can you recommend for s successful astral projection?
I am a beginner. I need solic stack of nootropics for that.

Thanks in advance

    David Tomen
    December 26, 2022

    Nick, astral project is typically associated with the use of hallucinogenic drugs and not nootropic supplements. You’re in the wrong place for advice on astral projection.

November 19, 2022

This is really interesting. A couple of questions: Does the Mind Lab Pro supplement contain caffeine? I can’t have any caffeine at all, but am interested in this supplement anyway. Also, do you know if it’s safe to take with anti-seizure meds like Lamotrigine? Thanks.

    David Tomen
    November 19, 2022

    Janice, Mind Lab Pro does NOT contain caffeine. And while it is unlikely that any of the ingredients are contraindicated with Lamotrigine you need to be careful increasing dopamine while on the drug according to this list: https://www.drugs.com/drug-interactions/lamotrigine-index.html.

    Mind Lab Pro contains 175 mg NALT which increases dopamine. NALT is nothing like levodopa but it is related. If you can, it would be best to ask your doctor about this before using Mind Lab Pro.

      November 19, 2022

      Awesome, thanks! I think I could ask my pharmacist as they seem to know more. Neurologists don’t tend to know anything about nutritional supplements. So they just automatically say not to use them. (At least, that’s been my experience so far).

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