The three routes
| IV infusion | Injection under the skin | Oral precursors (NR, NMN) | |
|---|---|---|---|
| What you get | NAD+ itself | NAD+ itself | Building blocks the body converts |
| Human data | Small pilots: infused NAD+ is cleared from the blood quickly at first | Very little published | Randomized studies show NR and NMN raise blood NAD+ |
| Common complaints | Nausea, stomach cramps, chest pressure and faster heart rate during infusion | Injection-site discomfort, flushing | Generally mild stomach upset |
| Time | Often one to several hours | Minutes | Daily capsule |
What the evidence does not show
Raising NAD+ on a blood test is not the same as a health benefit. Reviews describe real uncertainty about which approach, if any, improves outcomes in people, and about long-term safety. Claims that NAD+ reverses aging, cures fatigue or treats addiction are not established.
IV vs injection: tolerability
In a 2026 review of clinic records, people receiving IV NAD+ reported moderate to severe stomach symptoms, faster heart rate and chest pressure during infusions, which lengthened infusion times; symptoms resolved when the infusion ended. Injections deliver smaller amounts over a short time, but they have not been compared head to head in a published trial.