Key Points

  • This page is under construction.
  • Before using this therapy, consult your oncology team about interactions with other treatments and therapies. Also make sure this therapy is safe for use with any other medical conditions you may have.
  • L-theanine is a water soluble amino acid found in green tea and in mushrooms.
  • L-theanine may help to improve sleep quality and does not induce daytime drowsiness.
  • L-theanine is used in a few integrative programs and protocols and traditional medical systems (Ayurveda and traditional Chinese medicine).

BCCT will be adding more information to this page over time. While our summary is in development, you can visit About Herbs: L-Theanine

L-theanine is a water soluble amino acid found in green tea and in mushrooms.

Managing Side Effects and Promoting Wellness

Managing or relieving side effects or symptoms, reducing treatment toxicity, supporting quality of life or promoting general well-being

A 2015 review drew these conclusions from sleep studies based on an actigraph, the obstructive sleep apnea (OSA) sleep inventory questionnaire, wakeup after sleep onset (WASO) and automatic nervous system (ANS) assessment, sympathetic and parasympathetic nerve activities, and a pediatric sleep questionnaire (PSQ):1

  • The administration of 200 mg of L-theanine before bed may support improved sleep quality not by sedation but through anxiolysis
  • Because L-theanine does not induce daytime drowsiness, it may be useful at any time of the day.
  • The no observable adverse effect level (NOAEL) for the oral administration of L-theanine was determined to be above 2000 mg per kilogram of body weight per day.


The About Herbs summary of L-Theanine highlights several cautions, contraindications and herb-drug interactions. See summary for more information. This summary also advises that “patients undergoing chemotherapy should discuss the use of L-theanine with their physicians because these [anticancer] effects are not based on clinical trials, and epigallocatechin-3-gallate (EGCG) in green tea reduces activity of the chemotherapy drug bortezomib.” 


BCCT does not recommend therapies or doses, but only provides information for patients and providers to consider as part of a complete treatment plan. Patients should discuss therapies with their physicians, as contraindications, interactions and side effects must be evaluated.

Dosage recommendations are available from these sources:

Integrative Programs, Protocols and Medical Systems

For more information about programs and protocols, see our Integrative Programs and Protocols page.
  • Programs and protocols
    • Alschuler & Gazella complementary approaches2
    • Block program3
      • Combination stress hormone supplement
      • Coupler to improve effectiveness of chemotherapy (Adriamycin)
      • Combination formula to strengthen cancer-killing effects of conventional treatment
    • MacDonald breast cancer program4
  • Traditional systems

View All References

More Information