Glutathione Dosage Chart & Schedule Guide.

Technically yes: it's a tripeptide of glutamate, cysteine and glycine, but it doesn't behave like the peptides it sits next to on a vendor list. The bond between glutamate and cysteine is a gamma-linkage rather than the usual alpha-peptide bond, which makes it resistant to ordinary peptidases and instead a substrate for one specific enzyme, gamma-glutamyl transpeptidase. It's an endogenous antioxidant your liver already makes and exports in gram quantities, not a signalling peptide like BPC-157 or a secretagogue like ipamorelin. That difference is why the dosing logic is completely unlike the rest of the category.

Counterintuitively, oral has the better evidence. A 6-month randomised, double-blind, placebo-controlled trial in 54 adults found 250 mg/day raised blood glutathione by 17% and 1,000 mg/day raised red cell, plasma and lymphocyte glutathione by 30–35%, with buccal cells up 260%. There is no comparable controlled trial showing that injected glutathione raises body stores at all. The rationale for injecting is bypassing first-pass metabolism, but that logic runs into a 14-minute plasma half-life and the fact that cells cannot import glutathione intact anyway. If your goal is simply higher glutathione status, oral (or the cysteine/glycine precursor route) is the better-supported choice; injection is the less-evidenced one.

Because it's acidic. Glutathione dissolved in plain bacteriostatic water sits well below physiological pH, and pharmaceutical glutathione injection formulations are explicitly pH-adjusted into the 6.0–7.0 range with sodium hydroxide before they're considered injectable. A research vial you reconstitute yourself has had no such adjustment. Injecting IM into a large muscle rather than SubQ, and using the smallest volume you can, both help. Persistent lumps or welts are not something to push through.

Compounded 200 mg/mL glutathione injection is stored refrigerated at 2–8 °C, protected from light, not frozen, and discarded 28 days after first puncture, and the solution is expected to look clear and colourless to slightly pale yellow. Treat that as your outer limit, and tighter if your vial is preservative-free (a self-reconstituted research vial usually is). Glutathione’s whole function is being easily oxidised, so a solution that has gone cloudy, dark or particulate is chemically not what you started with. Discard it.

There is a modest measurable effect and a genuinely poor risk profile. The protocol behind the effect was 1,200 mg IV twice weekly for 6 weeks, and 8 of those 25 patients developed abnormal liver function tests. The Philippine FDA issued a public warning against IV glutathione for skin lightening back in 2011, citing liver, kidney and thyroid dysfunction, Stevens-Johnson syndrome and toxic epidermal necrolysis. The US FDA has never approved any injectable skin-lightening drug. If lightening is the goal, the oral and topical trials reported far better tolerability for a smaller effect.

There's a coherent argument for it, because they target the actual bottleneck. Intracellular cysteine sits right at the Km of the rate-limiting synthesis enzyme, so cysteine supply, not glutathione supply, is what constrains how much your cells can build. NAC and glycine (the 'GlyNAC' approach) feed exactly that step, orally and cheaply. What you should not expect is additivity from stacking a bigger injection on top: the same enzyme is feedback-inhibited by glutathione itself, so once the substrate is there the ceiling is enzymatic, not logistical.

No, not for any indication, by any route. It exists only as a compounded preparation under section 503A/503B or as a research chemical, and the compounders themselves state that safety and efficacy for the formulation have not been evaluated by the FDA. In February 2019 the FDA specifically warned compounders not to use one distributor's glutathione powder for sterile drugs after seven patients had adverse reactions (from nausea and vomiting through to difficulty breathing requiring immediate hospitalisation) linked to endotoxin contamination. The powder in question was labelled 'Caution: Dietary Supplement', which is why sourcing matters more here than dose does.

Nothing dramatic: no rebound, no crash, no suppression of your own production to withdraw from. In the 6-month oral trial the gains simply reversed to baseline after a 1-month washout. So cycling is not damage control, it is just an honest recognition that the effect tracks ongoing supply. A common pattern is 8–12 weeks on, 4 weeks off, using the break to check whether anything you attributed to the compound actually goes away.