How Long Does L-Theanine Stay in the Body?

Aside from hemp-derived cannabinoids, there are a plethora of natural compounds that people today embrace and incorporate into their wellness routines.

Take L-theanine, for example. While this amino acid is found in a variety of beverages and foods, many consumers are gravitating toward the isolated substance, which can now be found in health food and supplement shops.

While consumers are already enjoying the benefits of L-theanine, you may find yourself wondering what exactly it’s good for and more specifically, how long it stays in your body. Today, we’re taking a closer look at the amino acid and how long L-theanine stays in your system.

green froth of matcha tea

Key Takeaways

  • L-theanine is an amino acid found in green tea. Research has found that the compound may hold a number of potential benefits, namely helping consumers to relax.
  • L-theanine is fast-acting. Some feel the effects within a half hour.
  • There is limited research surrounding how long L-theanine stays in the system, though available studies give us a general indication. While this knowledge can be nice to have, consumers don’t have to worry about this compound appearing on a drug test.

What is L-Theanine?

L-theanine is a water-soluble amino acid found in green tea, certain mushrooms, and many types of black tea. It offers the subtle but distinct umami flavor of green tea, and it's speculated that it's responsible for many of the benefits of green and black tea.

Research has shown that L-theanine may hold the potential to promote mental health benefits, especially for those with stress-related ailments and cognitive impairments. Specifically, it may help to elevate your levels of GABA, dopamine, and serotonin, which promote relaxation and reduce anxiety levels. This may be why a cup of tea is associated with calming effects.

How Fast Does L-Theanine Take to Kick In?

Before we look at how long l-theanine stays in the system, many consumers may be curious how long it takes to actually feel the effects of the amino acid. L-theanine is typically fast-acting, with its effects being felt within 30 minutes. This may be a suitable option for those looking for anxiety relief or a quick, mellowing effect.

sleep powder with clouds


How Long Does L-Theanine Stay in Your System?

There is limited data available surrounding L-theanine’s absorption, distribution, and elimination within the body. One study found that the plasma concentrations of L-theanine were essentially zero after 24 hours, though urine tests of individuals who consumed 100 mg of L-theanine in capsule form or 250 ml of green tea still produced measurable results after 24 hours.

Based on these findings, we can safely confirm that most of an L-theanine dose will exit the body through urine between three and 24 hours, though a small amount may still be retained in the red blood cells which release the compound slowly over time.

Will L-Theanine Make Me Fail a Drug Test?

It’s always good to be more informed about a substance before adding it to your wellness routine. Some consumers may simply want to know how long L-theanine stays in their bodies, while others may question whether or not L-theanine will appear on a drug test.

Not to worry — since L-theanine is naturally occurring, it will not cause you to fail a drug test.

Final Thoughts

L-theanine is safe to consume and widely embraced for its calming effects. While there is limited research surrounding the time L-theanine stays in the body, it’s likely that the majority of a dose exits the body through urine within 24 hours.

When it comes to L-theanine, you won’t have to worry about drug testing, though it’s always good to be mindful of how new compounds and substances interact with our bodies as we integrate them into our wellness routines!


Hidese, S., Ogawa, S., Ota, M., Ishida, I., Yasukawa, Z., Ozeki, M., & Kunugi, H. (2019). Effects of L-Theanine Administration on Stress-Related Symptoms and Cognitive Functions in Healthy Adults: A Randomized Controlled Trial. Nutrients, 11(10), 2362.

Kakuda, T. (2002). Neuroprotective Effects of the Green Tea Components Theanine and Catechins. Biological & Pharmaceutical Bulletin, 25(12), 1513–1518.

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