glutathione supplements do they work 9 Health Benefits of Vitamin C and glutathione supplementation:

Cancer cells and normal cells potentially use different food sources, Harris explained, and we discovered how cancer cells, specifically, break down this antioxidant and use it as fuel. The new role for glutathione is notable, Harris said, because until now, most scientists who study glutathione have focused on the way it can prevent or repair cell damage, rather than its ability to feed cancer cells

Medicines Some types of medicine can lead to a reduction in the amount of vitamin B12 in your body

Cycling protocols Users typically cycle peptides (e.g., eight to 12 weeks) to avoid desensitization and minimize potential side effects, though optimal protocols are not firmly established in long-term clinical trials

CNS effects on dopaminergic and serotonergic systems are documented in injury models but remain less mechanistically resolved

So you're really not getting accurate readings there