The two compounds here most often sold as IV drips, and both share the same structural problem: the molecule being infused is not the one that has to get inside cells.
Side by side
| NAD+ | Glutathione | |
|---|---|---|
| Class | Cellular coenzyme | Antioxidant tripeptide |
| Status | Not a peptide; compounded and gray-market injectable | Compounded injectable |
| Route | Subcutaneous injection | Subcutaneous injection |
| Typical vials | 100 mg, 500 mg, 1,000 mg | 200 mg, 600 mg, 1,200 mg |
| Dose range | 25 mg to 100 mg | 200 mg to 600 mg |
| Frequency | 2 to 3 times weekly | A few times weekly |
| Half-life | No human data | No human data |
| Dosing unit | milligrams | milligrams |
Pharmacokinetics
No curves are shown, on purpose.
No published human pharmacokinetics for NAD+ or Glutathione. Drawing one curve against an absent one would imply a comparison that cannot be made.
What the evidence supports
These grade how well each outcome has been studied in humans, never how well either compound works. A strong grade can sit on a negative result.
Both top out at the same tier of evidence: Human RCT. Where they differ is in which outcomes have been asked about, not in how well either has been studied overall.
NAD+
| Outcome | Evidence |
|---|---|
| Clinical outcomes from precursor supplementation | Human RCT |
| Precursor supplementation raises blood NAD+ | Human RCT |
| Addiction or withdrawal treatment | No data |
| Outcomes from injected or infused NAD+ | No data |
Glutathione
| Outcome | Evidence |
|---|---|
| Oral supplementation raising body stores | Human RCT |
| Oxidative stress markers | Human RCT |
| Skin lightening | Human, observational |
| Safety of intravenous cosmetic use | No data |
How to choose
Nearly all NAD research studies precursors, not NAD+
NAD+ does not readily cross cell membranes. The human trials people cite are usually of nicotinamide riboside or nicotinamide mononucleotide, which are different molecules.
Glutathione is synthesized inside cells
Administered glutathione is largely broken down before it gets there, which is why oral and IV dosing are both contested.
The IV protocols are the least supported part of both
Neither has controlled evidence at the doses and routes actually sold.
At the syringe
At the default setup on each compound's own page, a 500 mg vial in 5 mL puts 1 mg on every insulin unit, while a 600 mg vial in 3 mL puts 2 mg on every unit. That is the number that decides whether a dose lands on a readable mark, and it is set by how much water goes in, not by the compound.