Can You Take L-Theanine With Levothyroxine?

In our latest question and answer, the pharmacist discusses whether or not there is an interaction between L-Theanine and levothyroxine.


Hello, I take 100 mcg of levothyroxine per day for hypothyroidism. Am I able to also take L-Theanine for anxiety without it causing any problems with my thyroid? Thank you!

Asked by Amy On Aug 29, 2023

Answered by
Medical Content Reviewed By HelloPharmacist Staff

Published Aug 30, 2023
Last updated May 20, 2024

Key points

  • There is no known interaction between L-theanine and levothyroxine. However, be sure to follow the appropriate administration instructions for levothyroxine to optimize absorption.

Quick Answer

In general, it is considered safe to take L-Theanine along with levothyroxine, as there are currently no known interactions between the two. However, it's important to note that levothyroxine has specific administration instructions to ensure maximum absorption. It is generally recommended to take it on an empty stomach, at least 30 minutes before food and other medications.

Detailed Answer

L-Theanine is an amino acid naturally found in green and black teas, as well as in certain types of mushrooms. It is often utilized as a dietary supplement due to its potential to reduce anxiety and induce calming effects.

Its mechanism is thought to involve the promotion of brain chemicals like serotonin and dopamine, which elevate mood and create a sense of calmness. As far as we know, it does not impact thyroid hormone levels or interfere with thyroid medication.

Levothyroxine is a medication used to treat hypothyroidism. It is a synthetic version of thyroxine (T4), a hormone that the thyroid gland fails to produce adequately in cases of hypothyroidism.

While there is no known interaction between L-Theanine and levothyroxine, it's important to understand that levothyroxine comes with specific administration requirements. Adhering to these instructions is crucial for optimal drug absorption. Generally, unless instructed otherwise by your doctor, levothyroxine should be taken on an empty stomach, at least 30 minutes before consuming food, other supplements, or medications.

Therefore, even though no specific interaction exists, it's advisable to take supplements like L-Theanine separately from levothyroxine.

Final Words

As always, it's best to consult your doctor or pharmacist before initiating any new medication or supplement, especially if you have existing health conditions or are taking other medications. This ensures that you can be appropriately monitored.


  • Synthroid Prescribing Information, AccessFDA
  • L-theanine, a natural constituent in tea, and its effect on mental state, PubMed

About the Pharmacist

Dr. Brian Staiger, PharmD

Dr. Brian has been practicing pharmacy for over 13 years and has wide-ranging experiences in many different areas of the profession. From retail, clinical, program development, and administrative responsibilities, he's your knowledgeable and go-to source for all your pharmacy and medication-related questions! Dr. Brian Staiger also has herbalist training and educational certificates in the field of medical ethnobotany. Feel free to send him an email at [email protected]! You can also connect with Dr. Brian Staiger on LinkedIn.

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