# NAD+ Injection: Administration Routes in the Research Literature

> NAD+ injection routes — IV infusion, subcutaneous, and intramuscular administration — reviewed from the published clinical and preclinical literature. Doses, tolerability, and protocols cited.

## What Is an NAD+ Injection?

An NAD+ injection delivers nicotinamide adenine dinucleotide directly into tissue (subcutaneously or intramuscularly) or into the bloodstream via intravenous infusion. The mechanism is to bypass the oral bioavailability limitation: intact NAD+ is rapidly hydrolyzed in the gastrointestinal tract [10][11].

During a 6-hour intravenous infusion of 750 mg NAD+ in healthy males (infusion rate approximately 2 mg/min in normal saline), plasma NAD+ and metabolites — NMN, AMP, and nicotinamide — rose substantially, establishing the first pharmacokinetic characterization of IV NAD+ administration in humans [10].

Two parenteral routes have clinical evidence: intravenous infusion (two published human studies) and subcutaneous injection (predominantly rodent data). Intramuscular use is described in some clinical protocols but lacks published PK data in humans [10].

## NAD+ IV Therapy vs Subcutaneous Injection

The key difference between IV infusion and subcutaneous injection is delivery rate and resulting plasma concentration profile. IV infusion delivers the full dose directly into the bloodstream (near-100% bioavailability). Subcutaneous injection delivers into interstitial tissue with slower absorption.

In preclinical rodent studies on cognitive endpoints, a single subcutaneous injection of NMN at 1.2 g/kg proved ineffective — suggesting that duration and route interact, and that repeated parenteral dosing over 7–28 days was required to see cognitive effects [26].

## Safety Profile of NAD+ IV Therapy

Published infusion trials report a consistent adverse-event pattern: nausea, chest tightness, elevated heart rate, and burning at the infusion site. These events are rate-dependent and resolve when infusion speed is slowed. No serious adverse events were reported in either published IV NAD+ human study [10][11].

The Reyna et al. 2026 retrospective real-world study compared IV NAD+ (500 mg) to IV NR (500 mg) over 4 consecutive days. IV NAD+ required a mean infusion time of 97 minutes and was associated with moderate-to-severe GI symptoms. IV NR required only 37 minutes on average and caused only mild tingling. All symptoms resolved upon infusion completion [11].

## IV NAD+ vs Oral: Bioavailability Comparison

IV infusion delivers NAD+ with near-100% bioavailability. Oral NAD+ itself is poorly absorbed as an intact molecule — gut extracellular enzymes (CD38, CD73, ENPP1) degrade most of the intact NAD+ before it can enter systemic circulation [10]. Oral precursors at equivalent milligram doses produce substantially lower peak plasma NAD+, but are the only route studied over multi-week periods with consistent blood NAD+ elevation confirmed [1][2][3].

## Injection Efficacy

Published human trials show injections raise blood NAD+ more reliably than oral dosing in terms of peak plasma concentration and speed of onset. No published human RCT has used injectable NAD+ as the primary study arm over a multi-week period [10][11][26].

## Injection Frequency in Research Protocols

The Reyna et al. 2026 real-world study administered IV NAD+ (500 mg) over 4 consecutive days [11]. Oral studies use daily dosing for 8–12 weeks, producing sustained blood NAD+ elevation confirmed at weeks 4, 8, and 12 [2][3].

## Compounded vs Oral Formulations

Injectable NAD+ formulations used in research are pharmaceutical-grade lyophilized powders reconstituted in sterile water or normal saline — not the same as oral supplement capsule contents. Oral supplement capsules contain excipients formulated for gastrointestinal tolerance, not for parenteral administration [10].

## Published Infusion Protocols

Grant et al. 2019: single 6-hour infusion of 750 mg NAD+ at approximately 2 mg/min in normal saline [10]. Reyna et al. 2026: 4-consecutive-day protocol at 500 mg per day for both IV NAD+ and IV NR, with mean infusion times of 97 minutes (IV NAD+) and 37 minutes (IV NR) [11].

## References

[1] Irie J, et al. Endocrine Journal. 2020;67(2):153-160. https://pubmed.ncbi.nlm.nih.gov/31685720/
[2] Okabe K, et al. Frontiers in Nutrition. 2022. https://pubmed.ncbi.nlm.nih.gov/35309539/
[3] Yi L, et al. GeroScience. 2022;45(1):29-43. https://pubmed.ncbi.nlm.nih.gov/36482258/
[10] Grant R, et al. Frontiers in Aging Neuroscience. 2019;11:257. https://pubmed.ncbi.nlm.nih.gov/31572171/
[11] Reyna K, et al. Frontiers in Aging. 2026. https://pubmed.ncbi.nlm.nih.gov/41704678/
[26] Qader MA, et al. BMC Neuroscience. 2025. https://pubmed.ncbi.nlm.nih.gov/40033213/

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The NAD+ administration and dosing literature — routes weighed, protocols indexed, evidence disclosed — compiled here with no protocol to sell and no prescription to fill.