L-theanine: What It Is, Forms, Cautions, and Clean Brands

L-theanine is an amino acid found in tea leaves. It supports calm, focused relaxation without drowsiness.*

Forms and what to look for on the label

Suntheanine is a well-known branded form. It’s often paired with caffeine.

Before you take it

Talk to your doctor if you take blood pressure medication or sedatives.

What independent doctors say

On his Oct 22, 2026 episode, Dr. Andrew Huberman gave a range of 100–400 mg for theanine.