assays of glutathione peroxidase methods enzymol 105 114-121 1984 Rapid and effective protocol to measure activity | Bulletin the National Research Centre PDF) Assays of Glutathione peroxidase
Description
Determination of glutathione and glutathione disulfide in biological samples: An in-depth review

As fir the cost, it was 100$ less than last clinic I went to with same results

The right question is not which one wins against NAD, but what problem you are actually trying to solve

Most patients find it comfortable, similar to a quick B12 shot
