The rationale for measuring glutathione levels across multiple time points, rather than a single time point, is that inter-individual variation in absorption is common across various supplements and pharmacological products, and data from a single time point may not be an accurate representative of ability to increase glutathione pool
You may wish to bring doctor's notes, original prescription bottles or containers, and other documentation to make the screening process go more quickly
10.1182/blood-2013-01-478651 47 Wei G., Twomey D., Lamb J., Schlis K., Agarwal J., Stam R
& Yu, Z
Common side effects are minimal and may include mild nausea, dizziness, or injection site discomfort