Oral and intravenous NAD+ are not competing answers to one question. They are answers to two different questions — and most people arrive here having accidentally asked the expensive one.
The one-paragraph version
An IV infusion delivers essentially all of a dose to your bloodstream, which no oral product can match. It also costs orders of magnitude more per session, takes hours in a chair, and has to be repeated. Oral is for maintaining a level over years. Infusion is for raising one sharply over hours. Choosing between them means deciding which of those you are actually after.
The bioavailability gap is real
Start with the point in favour of infusion, because it is not in dispute.
Anything swallowed has to survive stomach acid, digestive enzymes and the intestinal wall, then pass through the liver before it reaches general circulation. That last step — first-pass metabolism — removes a substantial share of many compounds before they ever get anywhere. An intravenous route skips every one of those obstacles by definition. Bioavailability is one hundred percent because the dose is placed directly into the blood.
For NAD+ specifically this gap is unusually wide, because NAD+ is a poor oral candidate to begin with: a large, charged dinucleotide that is largely broken apart before absorption. Infused NAD+ does not face that problem at all.
So if the question is "which route gets more of the molecule into my bloodstream," infusion wins decisively, and anyone telling you otherwise is wrong.
Why that is not the end of it
Bioavailability is a measure of delivery, not of benefit. Three things complicate the picture.
Infusion is a spike, not a level
A session produces a sharp rise followed by a decline. Your NAD+ status over a year is better described by what you do most days than by what happens during a handful of sessions. For a maintenance goal, a modest daily input can matter more than occasional large ones.
The cost structure is completely different
A daily oral capsule is a monthly expense in the tens of dollars. Infusion sessions are priced per session, at clinic rates, and the protocols people are typically sold involve a series rather than a single visit. The multiple is large enough that it changes the question from "which is better" to "is the difference worth that."
The time cost is underrated
NAD+ infusions are typically run slowly — often over several hours — because pushing them quickly is poorly tolerated. People describe flushing, chest tightness, nausea and cramping when the rate is too high. That is a known characteristic of this particular infusion, and it is why appointments are long. A capsule costs you five seconds.
Side by side
| Oral capsule | IV infusion | |
|---|---|---|
| Bioavailability | Low and indirect | Complete, by definition |
| Pattern | Steady daily input | Sharp intermittent spike |
| Cost | Tens of dollars monthly | Clinic session rates, usually as a series |
| Time per dose | Seconds | Several hours, on site |
| Access | Over the counter | Clinic appointment required |
| Tolerability | Generally uneventful | Rate-dependent side effects are common |
| Suits | Long-term maintenance | Short, intensive protocols |
The option most people miss
Framing this as oral-versus-IV leaves out the format that has grown fastest, and for most people considering infusion it is the more sensible comparison.
Subcutaneous injection — a small self-administered injection under the skin — bypasses the digestive tract and first-pass metabolism just as an infusion does, but without the clinic visit, the chair time, or the per-session clinic pricing. In the US this route is prescription-only and generally runs through a telehealth consultation followed by a compounding pharmacy.
If your reason for looking at IV is "I want to skip digestion," injection achieves that. If your reason is "I want a supervised clinical procedure," it does not. Being clear about which reason is yours resolves most of this decision.
How to decide, in three questions
- Am I maintaining or intervening? Maintenance over years points to oral. A short intensive push points to the injected or infused routes.
- Is the clinic part a feature or a cost? Some people want supervision and a scheduled appointment. Others are paying for a room they did not need.
- What happens in month four? Protocols that end tend to end quietly. The route you will still be using next year is usually the right one.
Related: IV infusion in detail · Injectable NAD+ in detail · The case for capsules