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10 L-Theanine Benefits, According to Science

White capsule pills on grey table with words Benefits of L-theanine written on the image

L-theanine is an amino acid touted for its mood-boosting, sleep-inducing and cognitive-enhancing properties, but how do you know if it’s right for you? This guide details what it is and how it works, plus lists L-theanine benefits to help you decide whether to try this popular supplement. 

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  • What is L-theanine?
  • Benefits
  • Dosage
  • Side effects
  • Safety
  • Precautions
  • Dependency and overdose
  • Long-term use
  • Drug interactions
  • How long does it take to work?
  • How long does it last?
  • When to take it
  • L-theanine sources
  • How to choose the best supplement

L-theanine benefits, at a glance

1. Enhanced Mood

2. Anti-Anxiety

3. Better Sleep

4. Anti-Depressant

5. Improved Focus in ADHD Patients

6. Lower Blood Pressure

7. Weight Loss

8. Reduced OCD, Panic Disorder & Bipolar Symptoms

9. Bolstered Immunity

10. Cognitive Enhancement

What is L-theanine?

L-theanine (pronounced el thee-uh-neen) is a non-protein, non-dietary amino acid that’s primarily found in green tea leaves (Camellia sinensis, Thea sinensis) and some mushrooms (Boletus badius), but can also be found in other types of tea. Often taken as a dietary supplement, it’s related to glutamine and can increase GABA, serotonin and dopamine levels.

Read: 20 reishi mushroom benefits

“L-theanine is an amino acid naturally found in green tea that is commonly used to support relaxation in the human body via its effects on the nervous system,” says Dr. Sydney Baker, a naturopathic doctor at Oasis Hormone Therapy and Wellness Center in San Diego. “L-theanine has been shown to increase serotonin, dopamine and GABA in the brain while simultaneously decreasing the effects of glutamate, which is an excitatory neurotransmitter.”

A woven basket containing green tea leaves that contain L-theanine

10 L-theanine benefits

Research shows that L-theanine offers the following benefits. 

1. Enhanced mood

L-theanine has been shown to improve mood by increasing brain serotonin, dopamine and GABA

A headshot of a man smiling broadly

Serotonin is a natural mood booster. According to Harvard Medical School, serotonin can ward off depression and induce euphoric feelings. 

Dopamine has been called the pathway to pleasure. Increased dopamine levels make you feel good, satisfied and motivated

Increased GABA levels have also been shown to have mood-enhancing effects. L-theanine, then, might stimulate the perfect mood-boosting trifecta. 

Related: 5 drink recipes to help boost your mood

2. Anti-anxiety

Studies show that L-theanine may have anti-anxiety and anti-stress properties, as it promotes calmness and relaxation by increasing alpha wave activity and GABA. L-theanine also decreases levels of cortisol, known as the stress hormone. 

In fact, one study found that L-theanine significantly decreased stress levels just one hour after taking it. Another study confirmed that L-theanine supplements can reduce stress and anxiety for those experiencing stressful situations. It’s even been shown to reduce stress and anxiety in schizophrenia and schizoaffective patients. 

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“Because L-theanine promotes ‘calming’ neurotransmitters and blocks ‘excitatory’ signals, it can leave users feeling calmer and less anxious,” says Dr. Baker. 

Unlike benzodiazepines and other anti-anxiety drugs, L-theanine doesn’t cause drowsiness or slowed reflexes, and it doesn’t impair concentration (Psychology Today). 


3. Better sleep

L-theanine isn’t a sedative and doesn’t make you tired, but it can still promote sleep by inducing a calm, relaxed state

A man sleeping peacefully.

One double-blind, randomized, placebo-controlled trial found that participants who took L-theanine reported greater sleep satisfaction, and several studies suggest that L-theanine users have better sleep quality. It’s also been shown to improve sleep for ADHD patients

“L-theanine works not only to relax the mind, but also the body, and can improve sleep in those who take it regularly,” says Dr. Baker. 

Thinking about melatonin for sleep? Read our guide to melatonin, including uses, side effects, safety & FAQs

4. Anti-depressant

L-theanine may offer relief for those suffering from depression. In one study, researchers found that an 8-week regimen of L-theanine reduced depression and anxiety in patients with major depressive disorder. 

5. Improved focus in ADHD patients

ADHD patients may benefit from taking L-theanine, especially when paired with caffeine. At least one study has shown that children with ADHD who take L-theanine and caffeine in combination may have better sustained attention, less impulsivity and enhanced cognitive performance while reduced mind wandering. 

6. Lower blood pressure

L-theanine supplements can lower blood pressure, especially for those who have high-stress responses. They’ve also been found to lower resting heart rate. Those are positive effects for most people, but consult a doctor before taking L-theanine if you already take blood pressure medicine. 

A close-up of a person holding a blood pressure monitor and taking their blood pressure

7. Weight loss

Mice studies suggest that L-theanine may help combat diet-induced obesity. The supplement may also help suppress body weight increase and fat accumulation. According to Psychology Today, L-theanine might also be a source of umami, contributing to a healthy weight. 

Further Reading: Activities that improve your mood

8. Reduced symptoms of OCD, panic disorder and bipolar disorder

Studies have found that L-theanine may reduce symptoms of obsessive-compulsive disorder (OCD), panic disorder and bipolar disorder. Of course, consult your doctor to see if L-theanine is an appropriate treatment for any medical condition. 

9. Bolstered immunity

Rodent studies suggest that L-theanine may improve immunity by altering TH2/TH1 cytokine balance, brain neurotransmitters and expression of Phospholipase C. Similar effects have been observed in athletes exposed to strenuous exercise

L-theanine is an anti-inflammatory and antioxidant – a free radical scavenger that can reduce the oxidation that damages cells. 

In addition, L-theanine has been shown to play a role in regulating the immune system and metabolic processes, protect the cardiovascular system, kidneys and liver, and serve as a neuroprotector in the brain. It may also help prevent and treat cancer and potentially help anti-cancer and chemotherapy drugs work better. 

Read: How melatonin boosts immunity, according to experts

10. Cognitive enhancement

L-theanine is a nootropic that could enhance cognitive performance. 


A male college student holding a pencil and sitting at a desk o take a test, with other students in the background


Studies demonstrate better attention and memory after L-theanine administration and that the supplement can improve performance during cognitive-demanding tasks (particularly when paired with caffeine). It’s also been shown to improve concentration, especially for those who experience high anxiety.

Other studies have found that L-theanine could enhance reaction time response and performance during tasks that require visual attention, improve vigilance, and help focus attention during demanding tasks. 

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L-theanine dosage

L-theanine dosage varies. It’s considered safe to take up to 400mg per day, though some studies use higher doses – up to 900mg per day – while some supplements instruct users to take 25mg two to three times per day as needed. 

“To fully benefit from the effects that L-theanine has to offer, a dosage of 200 to 400mg daily is what you should aim for,” says Dr. Baker. “For reference, on average, one cup of matcha green tea has around 50mg of L-theanine in it.”


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L-theanine side effects

Side effects of L-theanine are typically mild and usually only experienced when taking high doses. Potential side effects include:

  • Headache
  • Nausea
  • Irritability
  • Loss of appetite
  • Diarrhea

Is L-theanine safe?

L-theanine is considered safe when taken in recommended doses. 

“There are no known risks to consuming L-theanine on a daily basis, whether from green tea, matcha or a supplemental version,” says Dr. Baker. 


Though side effects are rare and typically mild, there are a few precautions to consider before taking L-theanine: 

  • Blood pressure: Since L-theanine can lower blood pressure, people who take medications to control blood pressure should consult their doctors
  • Pregnancy and nursing: Though L-theanine is safe, some sources do not recommend taking it if you’re pregnant or nursing. Other sources say it’s safe in recommended doses. Again, consult your doctor

“The main precaution with L-theanine has to do with the fact that some research shows it has an antihypertensive effect, meaning it has the ability to lower blood pressure. This is only of concern in patients already taking blood pressure medication, as adding on L-theanine could theoretically cause their blood pressure to drop too low,” explains Dr. Baker. “Otherwise, L-theanine is safe for consumption, even in pregnant and breastfeeding women.”

Close up of a round pregnant belly and woman holding it

Can you develop a dependency or overdose on L-theanine?

L-theanine has been tested in extremely high doses – up to 6,500mg per day – and was not toxic to participants. That doesn’t mean it’s impossible to overdose, but it does mean you won’t overdose when you take recommended doses. 

In addition, L-theanine is not habit-forming, so you can’t become addicted to it and won’t develop a dependency. 

Can you take L-theanine long-term?

Studies suggest that L-theanine is safe and continues to offer benefits when taken long-term (eight weeks). 

Drug interactions

L-theanine may interact with blood pressure medications, sedatives, stimulants and caffeine. Always consult your doctor before taking any supplement alongside other medicines. 

How long does L-theanine take to work?

L-theanine kicks in relatively quickly, with estimates ranging from 20 to 30 minutes to 40 to 60 minutes. In general, you can expect L-theanine to start working within an hour.

How long does L-theanine last? How long does it stay in the body?

L-theanine lasts around 8 to 10 hours

When should you take L-theanine?

The time of day you take L-theanine depends on what you want to use it for. 

  • For sleep: 30 to 60 minutes before bed
  • For focus: Take it in the morning when you wake up
  • For mood: Take it as needed

Depending on the dosage, you can take L-theanine two to three times per day as needed so long as you stay under the recommended 400mg daily limit. 

An analog alarm clock with text describing when to take L-theanine for sleep, focus and mood


L-theanine sources

L-theanine is available naturally in some foods and as dietary supplements.


  • Tea (primarily green tea, but some black teas contain it as well)
  • Some mushrooms


  • Lozenges
  • Gummies
  • Powder
  • Drinks
  • Pills and capsules
  • Chewables
  • Liquid drops
Kindroot lozenges flying out of a bag


How to choose the best L-theanine supplement

L-theanine supplements are easily accessible, but they’re not created equal. Look for:

  • Reputable brands with quality control processes
  • Accurate and consistent dosing
    • Pairings: Some supplements pair L-theanine with other elements, such as reishi mushrooms, to increase its mood-enhancing effect. Others may pair it with caffeine for focus or melatonin for sleep
    • Flavor: Choose an L-theanine supplement that agrees with your palate
    • Delivery method: Some people struggle with swallowing pills, so alternatives such as L-theanine lozenges make good alternatives
    • Other ingredients: People with dietary restrictions should pay attention to all supplement ingredients, not just the active ingredients. For example, some gummies might be high in sugar, which isn’t ideal for those who have diabetes or are watching their calorie intake

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    “When choosing an L-theanine supplement, consumers should ensure that they are purchasing the correct form (L-theanine) and that the product contains ‘L-theanine extract’ versus whole green tea,” says Dr. Baker. “This is because whole green tea still contains caffeine, which can be stimulating and is typically the opposite of what those taking L-theanine are trying to achieve.”

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    Disclaimer: The information stated in this article is for educational purposes only. The information stated is not intended to treat, diagnose or cure any disease, condition, or other physical or mental ailment of the human body. The desire to make any changes to one's dietary habits or supplementation should be consulted and discussed with a licensed medical professional. 


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