NAD+ Injection vs Supplement: Not the Same Molecule by Two Routes

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme involved in cellular energy production, and it declines with age. It is a relatively large molecule, and the better-designed oral products do not try to deliver it intact. They supply a precursor instead.

Nicotinamide riboside (NR) has the most developed human dataset. A 2016 study found that NR is orally bioavailable in people and raises blood NAD+ metabolism, and a 2018 randomized, placebo-controlled crossover trial in healthy middle-aged and older adults found chronic NR well tolerated and effective at raising NAD+. What those trials have been less able to show is a lasting functional benefit; that work is ongoing.

NMN is the other common precursor. Niacin and nicotinamide are forms of vitamin B3 with long histories as vitamins, and niacin is also a prescription drug. The B3, NR, NMN and NAD+ explainer sets out how they differ from one another.

A product labeled simply "NAD+" and swallowed is a different proposition from either route above; what reaches the blood from it is not well established.

An injection removes the absorption and conversion questions entirely. The research base in people is small, largely because administered treatments are harder and more expensive to study than capsules. A 2019 pilot study tracked the NAD+ metabolome in blood and urine during an intravenous infusion, and a 2026 retrospective study noted that NAD+ infusions are commonly associated with side effects such as nausea, and that slow, prolonged infusions are used to limit them, though formal studies of that approach are lacking.

ACT 2 does not run infusion rooms. The NAD+ injection is a subcutaneous injection you give yourself at home, prescribed and reviewed by telehealth. Injection-site reactions are the most commonly reported effect, and flushing or nausea may occur, more often with rapid administration. NAD+ side effects covers what to expect and what to report.

The evidence position at ACT 2 is stated plainly on the treatment page: robust long-term human evidence for many claimed benefits is limited, so the program has a defined point at which you and your clinician ask whether it is doing anything for you, and a genuine willingness to answer no.

Injectable NAD+ is not an FDA-approved drug product. What ACT 2 prescribes is prepared by a licensed compounding pharmacy, and the FDA does not verify the safety, effectiveness or quality of compounded drugs before they are marketed. Any use for energy or healthspan is off-label. Is NAD+ FDA-approved? covers the detail.

Oral precursors vary. Niacin and nicotinamide are established vitamins, and niacin is also sold as a prescription drug. NR is marketed as a dietary supplement. NMN has had a more contested position: the FDA had taken the view that it was excluded from the dietary supplement definition, then in September 2025 concluded that it is not excluded, because it was marketed as a supplement before it was authorized for investigation as a drug. Dietary supplements are not reviewed by the FDA for effectiveness before sale either.

Routine. A daily capsule against a self-injection on a schedule. For some people that settles it.

Experience. Oral precursors generally produce nothing you notice, with the exception of niacin's flush, which is harmless but unpleasant enough that many people stop. The injection carries injection-site reactions and, sometimes, flushing or nausea.

Supervision. The injection is prescribed after an eligibility review and reviewed by a clinician. A supplement is taken on your own, which is worth mentioning to whoever manages your care rather than treating as separate from it.

Cost. NAD+ injections at ACT 2 cost $199 a month, with the clinician's oversight and the medication included. Supplements are priced by whoever sells them. The NAD+ injection cost page sets out a full year.

• When fatigue or brain fog is the reason. The common correctable causes come first: thyroid, ferritin, B12, vitamin D, glucose and sleep. Correcting one of those changes more than either route. What your tiredness pattern says is a good start.
• When the foundations are not in place. Sleep, training and nutrition are what the NAD+ program assumes you have already handled.
• During pregnancy or breastfeeding, when NAD+ injections are not used.
• When you will not keep it up. A routine abandoned after a month delivers little either way.