"NAD+ supplement vs injection" is a question about routes, and the evidence for each route was gathered in different studies, in different people, measuring different things. That makes this a page about two separate records and the gap between them — not a ranking. The capsule side mostly concerns NAD+ precursors, because that is what oral supplements contain and what oral trials tested.
What the precursor trials found, molecule by molecule, is on our NAD+ vs NMN page; this page does not repeat that table. What injected NAD+ has been shown to do is on our NAD+ injection benefits page, doses on our NAD+ dosage page. Nothing here is a recommendation.
Three things sold as "NAD+"
| Form | What it is | How it is sold |
|---|---|---|
| NAD+ itself | The coenzyme, about 663 daltons, charged | Intravenous drips, intramuscular or subcutaneous injections, nasal sprays, some capsules |
| NADH | The reduced form of the same molecule | Capsules and lozenges (the brand studied was ENADA) |
| Precursors: nicotinamide riboside (NR), nicotinamide mononucleotide (NMN) | Smaller molecules cells convert into NAD+ | Capsules and powders, as dietary supplements |
A buyer comparing "an NAD+ shot" with "an NAD+ supplement" is usually comparing NAD+ itself by injection with a precursor by mouth. The two records below follow that split.
The injection record: what happened in the blood
The only published study of infused NAD+'s fate in people (Grant et al. 2019, PMID 31572171) infused 3 µmol per minute for six hours and sampled blood and urine. For the first two hours, plasma NAD+ and its metabolites — nicotinamide, methylnicotinamide, ADP-ribose, NMN — did not change. The authors concluded that at this rate NAD+ "is rapidly and completely removed from the plasma." By six hours, NAD+ itself and methylnicotinamide had risen in urine. The metabolite pattern pointed to enzymes that break NAD+ down outside cells.
What the study did not measure: NAD+ inside blood cells, muscle or brain, and any outcome a person would feel. No later study of injected NAD+ has filled those gaps.
Two registered US studies would add to this record, and neither has posted results as of 15 October 2026: one compares 100 mg of NAD+ given into muscle, under the skin or as an IV push with the precursor NR and with bacteriostatic water, measuring injection pain (NCT06919328); the other compares intravenous NR with intravenous NAD+ (NCT06382688).
The oral record: what rose, and where
The precursor trials measured the thing the injection study could not show — a rise.
| Study | People | What was given | What rose |
|---|---|---|---|
| Trammell et al. 2016, Nat Commun | Healthy adults (plus one pilot volunteer) | Single NR doses of 100, 300, 1,000 mg | Blood NAD+ metabolome, dose-dependent; up to 2.7-fold in the pilot volunteer |
| Airhart et al. 2017, PLoS One | 8 healthy volunteers | NR up to 1,000 mg twice daily, 9 days | Whole-blood NAD+ at steady state |
| Martens et al. 2018, Nat Commun | Healthy middle-aged and older adults, crossover | NR 1,000 mg a day, 6 weeks | NAD+ metabolism in blood |
| Nanga et al. 2024, Magn Reson Med | 10 healthy volunteers | One 900 mg NR dose | Brain NAD+, 0.392 → 0.458 mM on 7-tesla scan at 4 hours |
The brain result is the only human measurement of NAD+ in an organ after any NAD-boosting product, and it came after a capsule. Repeat baseline scans without NR did not change, which is what makes the rise readable.
Three caveats sit on this side too. Raised NAD+ is chemistry, not benefit — the outcome trials of oral precursors are mixed and often null, as our NAD+ vs NMN page shows. Several of these studies had company authors (Trammell 2016 lists ChromaDex stockholders and employees). And a 2026 Nestlé trial (Christen et al., Nat Metab, PMID 41540253) suggested that NR and NMN raise circulating NAD partly after gut bacteria turn them into nicotinic acid — so "it reaches the blood" may describe a detour, not the capsule's molecule arriving intact.
Swallowing NAD+ or NADH itself
Capsules of NAD+ itself, rather than a precursor, have almost no human record. The oral trials located used NADH:
- Chronic fatigue, 1999 (Forsyth et al., PMID 10071523): 26 patients, 10 mg NADH or placebo for four weeks each, crossover. 8 of 26 responded on NADH against 2 of 26 on placebo. The authors called it a pilot.
- Dementia, 2000 (Rainer et al., PMID 11459000): "no evidence for cognitive improvement."
- Parkinson's disease, 1993 (Birkmayer et al., PMID 8101414): 885 patients, open label, about half by IV and half by capsule. The authors reported the oral form gave improvement "comparable to that of the parenterally applied form." There was no placebo group, so it compares two uncontrolled results.
None of these measured blood NAD+. The 1993 report is the only one located that put an oral and an injected form side by side, and it was not designed to separate either from placebo.
Time, tolerability and what a session involves
| Intravenous NAD+ | Intramuscular or subcutaneous NAD+ | Oral precursor | |
|---|---|---|---|
| Doses on record | 500 mg (a US registration and a vendor vial); 10 mg a day in the heart-failure trial | 100 mg (a US registration); 5 mg a day in a Chinese trial | 100–1,000 mg (NR trials above) |
| Time | 97 minutes average for 500 mg in one chain's records | Seconds; injection-site pain is the measured outcome of a registered trial | Seconds |
| Measured rise in NAD+ | None in plasma for 2 hours (one study) | Not measured | Blood rise in several trials; brain rise in one |
| Main recorded discomfort | Nausea, chest pressure, faster heart rate when run fast | Not yet reported | Mild; mostly similar to placebo in trials |
The 97-minute figure and the symptoms come from a 2026 retrospective review of a wellness chain's own client records (Reyna et al., PMID 41704678), in which the same 500 mg dose of intravenous NR averaged 37 minutes. Why infusion speed drives the symptoms is set out on our NAD+ injection side effects page. The injection doses are as recorded on our dosage page and the oral ones are the doses the trials above used; they describe what sources state, not a plan.
What the comparison would need
A trial that settled "injection or oral" would give matched groups NAD+ by injection and a precursor by mouth, measure NAD+ inside cells over days and weeks, and track an outcome people care about. None is registered. Until one is, the honest reading is narrow: the oral route has evidence of raising NAD+; the injection route has one study in which it did not, at first; neither has evidence of a benefit in healthy adults.
For what each form costs per milligram, see our peptide cost survey for the method used across this site.
Sources and dates
Read 15 October 2026: abstracts of PMIDs 31572171, 27721479, 29211728, 29599478, 39044608, 41540253, 10071523, 11459000, 8101414 and 41704678; ClinicalTrials.gov records NCT06919328 and NCT06382688. NMN's dietary-supplement status and the precursor trial table are as recorded on our NAD+ vs NMN page.