Overview

What is L-theanine?

What are L-theanine’s main benefits?

What are L-theanine’s main drawbacks?

How does L-theanine work?

Dosage Information

Clinical studies typically use L-theanine at a dosage of 100–400 milligrams (mg) per day.

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Examine Database: Theanine

Health Condition/Goal	Health Outcome	Evidence
Cognitive Improvement	23 outcomes	20 Studies
Focus & Attention	8 outcomes	4 Studies
Stress	18 outcomes	4 Studies
Mental Resilience	7 outcomes	6 Studies
Mood Improvement	15 outcomes	4 Studies
Sleep Health	13 outcomes	10 Studies
General Cardiovascular Health	5 outcomes	3 Studies
Immune Health	13 outcomes	2 Studies
Schizophrenia	9 outcomes	1 Study
Attention Deficit Hyperactivity Disorder	1 outcome	1 Study
Depression	9 outcomes	1 Study
Aerobic Exercise Performance	12 outcomes	1 Study
Generalized Anxiety Disorder	3 outcomes	1 Study
Metabolic Health	3 outcomes	1 Study
Schizoaffective Disorder	3 outcomes	1 Study
General Athletic Performance	13 outcomes	1 Study

Cognitive Improvement

23 outcomes

8 outcomes

18 outcomes

7 outcomes

15 outcomes

13 outcomes

General Cardiovascular Health

5 outcomes

Immune Health

13 outcomes

Schizophrenia

9 outcomes

Attention Deficit Hyperactivity Disorder

1 outcome

Depression

9 outcomes

Aerobic Exercise Performance

12 outcomes

Generalized Anxiety Disorder

3 outcomes

Metabolic Health

3 outcomes

Schizoaffective Disorder

3 outcomes

General Athletic Performance

13 outcomes

Safety InformationNew

Research FeedRead all studies

Frequently Asked Questions

What is the effect of combining L-theanine with caffeine?

What are other names for Theanine?

Update History

September 4, 2025

Safety Information added
major

Research written by

Gregory Lopez

Edited by

Conni Covington

Reviewed by

Katie Jantz

September 27, 2023

Standard FAQ and database update
major

Research written by

Thomas Solomon

Edited by

Natalka Roshak

Reviewed by

Nick Milazzo

References

Examine Database References

Health Condition/Goal	Health Outcome	Evidence
Cognitive Improvement	23 outcomes	20 Studies
Focus & Attention	8 outcomes	4 Studies
Stress	18 outcomes	4 Studies
Mental Resilience	7 outcomes	6 Studies
Mood Improvement	15 outcomes	4 Studies
Sleep Health	13 outcomes	10 Studies
General Cardiovascular Health	5 outcomes	3 Studies
Immune Health	13 outcomes	2 Studies
Schizophrenia	9 outcomes	1 Study
Attention Deficit Hyperactivity Disorder	1 outcome	1 Study
Depression	9 outcomes	1 Study
Aerobic Exercise Performance	12 outcomes	1 Study
Generalized Anxiety Disorder	3 outcomes	1 Study
Metabolic Health	3 outcomes	1 Study
Schizoaffective Disorder	3 outcomes	1 Study
General Athletic Performance	13 outcomes	1 Study

Safety InformationNew

Visit Safety Checker Page

Summary
Side Effects
Interactions
Pregnancy & Lactation
Precautions
WADA Status

Safety Summary

Theanine is generally safe with few to no side effects when taken at dosages up to 400 mg per day for 2 months. Long-term safety evidence is lacking.
Pregnancy and lactation data is lacking. Because theanine can cross the placenta and appears in breast milk, avoidance is warranted.

Side Effects

Theanine is generally safe in the short term. Dosages up to 900 mg per day for up to 2 months don’t have significant side effects,^[31] and more typical dosages of 100–400 mg per day over 1–2 months are also safe with few side effects.^[8]^[32]^[33] Theanine at dosages of 100 mg per day for 6 weeks in children aged 8–12 appears safe as well.^[27]

There is little evidence for safety beyond three months, though.

Effect	Details
^[13]	Route: Oral Dose: 250mg
Full safety information is available to Examine Clinician Edition members. Try free for 14 days.

Interactions

Agent	Effect	Level of Evidence	Level of Severity
	Animal studies suggest theanine could lower blood pressure, raising the possibility of an interaction with hypotensive drugs.^[28]^[29] However, no direct evidence of an interaction exists, and human studies are equivocal on theanine’s ability to significantly lower blood pressure.^[1]^[20]	Level of Evidence: Theoretical	Level of Severity: Unknown
Full safety information is available to Examine Clinician Edition members. Try free for 14 days.

Pregnancy and Lactation

Condition	Safety Information
Pregnancy Avoid	While theanine is naturally found in tea,^[1] the health effects of supplemental dosages during pregnancy have not been studied in humans. Because animal evidence suggests theanine crosses the placenta,^[30] avoiding theanine supplementation during pregnancy is warranted.
Lactation Avoid	While theanine is naturally found in tea, the health effects of supplemental dosages on breastfeeding infants have not been studied in humans. Because animal evidence suggests that theanine can cross into breast milk, avoiding theanine supplementation while breastfeeding is warranted.

Precautions

Precautions for specific demographics, populations, and/or conditions

Population/Condition	Details
	A child with preexisting history of facial tics experienced a bout of mild tics that ceased upon withdrawal of theanine.^[27]
Full safety information is available to Examine Clinician Edition members. Try free for 14 days.

World Anti-Doping Agency
Not Prohibited

According to the 2026 WADA List of Prohibited Substances, theanine is not prohibited.

Route: Oral
Dose: 250mg

Full safety information is available to Examine Clinician Edition members. Try free for 14 days.

Animal studies suggest theanine could lower blood pressure, raising the possibility of an interaction with hypotensive drugs.^[28]^[29] However, no direct evidence of an interaction exists, and human studies are equivocal on theanine’s ability to significantly lower blood pressure.^[1]^[20]

Level of Evidence:

Theoretical

Level of Severity:

Unknown

Full safety information is available to Examine Clinician Edition members. Try free for 14 days.

Pregnancy

Avoid

While theanine is naturally found in tea,^[1] the health effects of supplemental dosages during pregnancy have not been studied in humans. Because animal evidence suggests theanine crosses the placenta,^[30] avoiding theanine supplementation during pregnancy is warranted.

Lactation

Avoid

While theanine is naturally found in tea, the health effects of supplemental dosages on breastfeeding infants have not been studied in humans. Because animal evidence suggests that theanine can cross into breast milk, avoiding theanine supplementation while breastfeeding is warranted.

Population/Condition	Details
	A child with preexisting history of facial tics experienced a bout of mild tics that ceased upon withdrawal of theanine.^[27]
Full safety information is available to Examine Clinician Edition members. Try free for 14 days.

A child with preexisting history of facial tics experienced a bout of mild tics that ceased upon withdrawal of theanine.^[27]

Full safety information is available to Examine Clinician Edition members. Try free for 14 days.

Theanine

Overview

What is L-theanine?

What are L-theanine’s main benefits?

What are L-theanine’s main drawbacks?

How does L-theanine work?

Dosage Information

Supplements Demystified: Get Our Unbiased, Evidence-Based Guide

Examine Database: Theanine

Safety InformationNew

Research FeedRead all studies

Frequently Asked Questions

What is the effect of combining L-theanine with caffeine?

What are other names for Theanine?

Update History

Safety Information added
major

Standard FAQ and database update
major

References

Examine Database References

Examine Database: Theanine

Safety InformationNew

Table of Contents

Safety Summary

Side Effects

Interactions

Pregnancy and Lactation

Precautions

Precautions for specific demographics, populations, and/or conditions

World Anti-Doping Agency
Not Prohibited

Table of Contents

Safety Summary

Side Effects

Interactions

Pregnancy and Lactation

Precautions

Precautions for specific demographics, populations, and/or conditions

World Anti-Doping Agency
Not Prohibited

Theanine

Overview

What is L-theanine?

What are L-theanine’s main benefits?

What are L-theanine’s main drawbacks?

How does L-theanine work?

Dosage InformationMedical disclaimer

Supplements Demystified: Get Our Unbiased, Evidence-Based Guide

Examine Database: Theanine

Safety InformationNew

Research FeedRead all studies

Frequently Asked Questions

What is the effect of combining L-theanine with caffeine?

What are other names for Theanine?

Update History

Safety Information addedmajor

Standard FAQ and database updatemajor

References

Examine Database References

Examine Database: Theanine

Safety InformationNew

Table of Contents

Safety Summary

Side Effects

Interactions

Pregnancy and Lactation

Precautions

Precautions for specific demographics, populations, and/or conditions

World Anti-Doping Agency Not Prohibited

Table of Contents

Safety Summary

Side Effects

Interactions

Pregnancy and Lactation

Precautions

Precautions for specific demographics, populations, and/or conditions

World Anti-Doping Agency Not Prohibited

Dosage Information

Safety Information added
major

Standard FAQ and database update
major

World Anti-Doping Agency
Not Prohibited

World Anti-Doping Agency
Not Prohibited