NAD+ Injections vs IV vs Oral: Which Route Has the Evidence?

The one-sentence version

Every route raises NAD+. Only one of them — oral precursors — has been through randomized human trials, and even there the results are mixed. The 2026 systematic review that screened 113 studies found no eligible outcomes trial of intravenous or intramuscular NAD+ at all for anti-aging or wellness¹. Those are the two routes telehealth charges most for.

The four routes you will be sold

| Route | What it is | Human outcome trials | |---|---|---| | Oral precursors (NR, NMN) | A capsule of nicotinamide riboside or mononucleotide | Yes — dozens | | Subcutaneous / IM injection | NAD+ itself, self-injected at home | None | | IV infusion | NAD+ itself, in a clinic over several hours | None | | Nasal spray | NAD+ itself, absorbed nasally | None |

That table is the whole article, and it is worth sitting with, because the marketing runs in exactly the opposite direction: the routes with no outcome data are the ones sold as the serious, clinical, higher-dose option.

Why the routes are not interchangeable

The pitch for injecting is bioavailability, and the underlying point is real: swallowed NAD+ is largely broken down before it reaches your cells, which is why oral products sell a precursor — NR or NMN — that survives the trip and is converted inside the body. Injecting NAD+ skips that step.

What does not follow is that skipping the step produces a better outcome. Bioavailability is an input. The trials measure outputs, and the output evidence exists for the route with the worse bioavailability, because that is the route researchers have actually studied.

What the oral trials found

They reliably raise NAD+. Chronic nicotinamide riboside was well tolerated and elevated NAD+ in healthy middle-aged and older adults² — the mechanism is not in doubt.

The functional results are mixed and often null. A 2025 systematic review and meta-analysis of NMN and NR found no significant improvement in skeletal muscle mass or function in older adults³. The NICE randomized clinical trial tested nicotinamide riboside in peripheral artery disease and did not find the walking-performance benefit it was designed to detect⁴.

A few positive signals exist, in specific populations. NMN increased muscle insulin sensitivity in prediabetic women⁵, and improved aerobic capacity in amateur runners⁶. Both are real results and neither is an aging outcome.

The overall verdict. The 2026 PRISMA-guided review's summary is that oral precursors consistently raise NAD+ and are well tolerated, while effects on functional, metabolic and vascular outcomes were "heterogeneous and often null," with clinical effectiveness for anti-aging inconclusive¹.

That is the strongest evidence any NAD+ route has.

What injected, IV and nasal have

Nothing comparable. The same review searched for outcomes trials of intravenous or intramuscular NAD+ for anti-aging or wellness and found none eligible¹.

This is not a claim that they do not work. It is the more specific and more useful claim: nobody has run the study. When a provider tells you injection is "more effective," ask what the comparison is measured against — there is no head-to-head outcome trial of injected versus oral NAD+ to cite.

IV adds a second consideration. It is administered in a clinic over hours, at the highest price of any route, and it is the route where the gap between what is charged and what has been demonstrated is widest.

What each route costs

Prices across the providers we grade are published in shapes that resist comparison — a monthly rate, a block for an estimated multi-week supply, or nothing at all until you have completed an intake. The per-provider figures, with the term each one is really sold on, are on the graded ranking, and the traps to read for are in what longevity care actually costs.

Two patterns worth knowing before you compare anything:

• •A block price is not a monthly price. One graded provider sells NAD+ as $369 for an estimated eight-to-ten-week supply — so the monthly cost is a range, not a number, and which end you land on is not knowable in advance.
• •The advertised figure is often the twelve-month rate, with the month-to-month price in an asterisk.

How to choose, honestly

• •If you want the route with evidence behind it, that is oral NR or NMN — and you should hold modest expectations, because the meta-analyses are largely null on function. Which of the two to pick is NMN vs NR.
• •If you want injection or IV, buy it knowing you are buying bioavailability and convenience, not a demonstrated outcome, and that you are paying the most for the least-studied route.
• •If a provider says injection is proven superior, that specific claim has no trial behind it.

Our broader tour of what this molecule can and cannot do is in NAD+ for longevity, and the wider toolkit is in longevity medicine: what's proven versus hyped.