NAD+ and glutathione are often sold as a pair, in the same IV bag or as back-to-back injections, on the idea that one supports the other. There is a real biochemical connection between them, but it runs through a third molecule, and the claim that combining them helps has never been put to a trial in people.
This page walks the connection from enzyme to enzyme, marks where it stops being measured, and sets out what the human studies of each molecule, and of the one precursor mix that targets both, actually found.
What each molecule does
NAD+ is a coenzyme that shuttles electrons in energy metabolism and is also consumed by enzymes such as the sirtuins, and one major review describes NAD+ levels declining during aging [1]. The same review notes that the benefits of raising it have been shown in preclinical settings, and the claims made for injecting it are weighed in NAD+ injections.
Glutathione is a small peptide that the body uses as its most abundant internal antioxidant, and once it has neutralized an oxidant it sits in an oxidized, spent form until it is recycled [5].
The link runs through NADPH
The connection is this: an enzyme called NAD kinase adds a phosphate to NAD+ to make NADP+. In its reduced form, NADPH, that molecule is the fuel glutathione reductase burns to turn spent glutathione back into its active form.
In human cell lines, cutting NAD kinase by about 70% cut NADPH by a similar amount and made the cells more sensitive to hydrogen peroxide [2]. A separate cell study tracked glutathione reductase using up NADPH in both the cytosol and the mitochondria of macrophages [3].
What happens to NAD+ given by IV
The first published study of what happens to IV NAD+ in people gave 750 mg over six hours to 8 men, with 3 controls [4]. For the first two hours plasma NAD+ did not rise at all, which the authors read as the molecule being cleared from the blood as fast as it arrived.
Changes appeared only after that, and NAD+ itself and methylnicotinamide turned up in the urine by six hours. The study did not measure glutathione, and it did not measure any health outcome. The wider record is in NAD IV therapy.
What happens to glutathione taken by mouth
Whether oral glutathione raises body stores in people had not been established when a 6-month randomized trial in 54 healthy non-smoking adults found stores rising with daily supplements [5].
On 1,000 mg a day, glutathione rose 30% to 35% in red blood cells, plasma and lymphocytes by six months, and it fell back to baseline within a month of stopping. The study measured stores and immune markers, not disease.
Injected and liposomal forms have their own records, set out in glutathione injections and liposomal glutathione.
The closest thing to a combination trial
No trial has given NAD+ and glutathione together. What has been tested in people is a mix of precursors, called combined metabolic activators, that feeds both pathways at once: nicotinamide riboside for NAD+, and N-acetylcysteine and serine for glutathione, plus L-carnitine.
| Trial | Who and how long | What it reported |
|---|---|---|
| Fatty liver disease | 31 adults with NAFLD (20 on the mix, 11 on placebo), 10 weeks | Less liver fat and lower ALT and AST on the mix after adjusting for weight loss |
| Alzheimer's disease | 69 adults over 50 with mild to moderate disease (47 on the mix, 22 on placebo), 84 days | ADAS-Cog score improved 29% from baseline on the mix; versus placebo, only in the higher-score subgroup |
The fatty liver trial was cut short by pandemic restrictions, enrolling 32 of a planned 45, and only 7 women took part, which the authors list among its limits [6].
In the Alzheimer’s trial, plasma markers of NAD+ and glutathione metabolism improved on the mix [7]. Against placebo, though, the improvement reached significance only among patients with higher baseline scores.
Both trials tested oral precursors in daily doses of several grams, not NAD+ or glutathione themselves, so they say nothing direct about an NAD+ and glutathione drip.
Regulatory status
Both substances sit in Category 1 of the FDA’s 503A list, bulk drug substances under evaluation, in the update dated May 14, 2026 [8]. That placement lets pharmacies compound them under the FDA’s interim policy while the evaluation continues; it is not an approval of either one for any use.
What this means if you are considering both
The case for pairing them is a pathway drawn from cell studies, and the one human trial design that fed both pathways used different molecules, by mouth, in small groups of people with specific diseases. A combination product is therefore being sold ahead of any evidence that the second molecule adds to the first.
Each has its own side-effect record, covered in NAD side effects and glutathione side effects, and the broader longevity picture is in peptides for anti-aging.
To compare prescribers, see the NAD+ injection or nasal rankings and the longevity peptide rankings.