L-theanine, an amino acid found in tea leaves, is often promoted to reduce stress and for use in a variety of conditions including ADHD, but does it really work? In this report, ConsumerLab.com reviews the evidence for this supplement, explains how L-theanine is used and, most importantly, shows you which L-theanine supplements are high-quality, provide the right dose for your needs, and offer the best value. We found, for example, that you can get the same, high-quality L-theanine for nearly one-third the price of other supplements if you choose the right product. Be aware that the suggested dosing on products may much higher or lower than you want.