As of 2015, there is not enough evidence to calculate dosing of L-theanine for anxiety, according to WebMD. Multiple factors determine a proper dosage, including a consumer's health and age. Consumers should talk to their doctors, pharmacists or medical providers before using the products, and follow the product directions.
L-theanine, an amino acid found in green tea, is typically used to aid relaxation. In a study reported in 2004, healthy participants consumed 200 milligrams of L-theanine to evaluate its effect under conditions of experimentally induced anxiety and relaxation, according to the National Center for Biotechnology Information. The results indicated that L-theanine produces some relaxing effects under conditions of rest, but it does not reduce anxiety under situations of increased anxiety.