Does a NAD+ infusion do something that an NMN pill does not?
No study directly compares a NAD+ infusion with an oral NMN pill, so an advantage of the infusion has not been demonstrated. Oral NMN demonstrably raises blood NAD+ levels, but whether you notice any health benefit from this remains unclear for now.
A NAD+ infusion presumably does not do more than an NMN pill, but this has never been directly investigated. No study exists that compares both in the same people, so an advantage of the infusion has simply not been demonstrated.
What an oral NMN capsule or tablet does do is reasonably well documented. In a study of 80 healthy middle-aged adults comparing NMN with a placebo, blood NAD+ levels rose measurably at 300, 600 and 900 mg per day, with the highest levels seen at 600 and 900 mg. On the label, look for the designation NMN (nicotinamide mononucleotide) and the number of milligrams per capsule or tablet. Whether you take NMN or NR (nicotinamide riboside) does not matter: both raise blood NAD+ levels to a comparable degree. Doses above 600 mg produce no additional rise. If you want to try it for improved walking distance, 600 mg per day for at least 60 days is the amount used in research. For general NAD+ support, it has been too little studied to recommend. Note: NMN may not (yet) be sold as a supplement in the EU, whereas NR may.
Whether higher blood levels also raise NAD+ levels in the heart, muscles, brain or liver sufficiently remains unclear. In people with obesity and fatty liver disease, the clinical effects in available studies were modest.
Regarding the infusion: intravenous administration of NADH, a related molecule, was studied in 1996 in 15 people with Parkinson's disease. In that study, people with Parkinson's disease received 10 mg of NADH per day intravenously for 7 days, which produced an improvement in motor symptoms and higher levodopa levels in the blood. This says nothing about NAD+ infusions in healthy or ageing individuals. The level of evidence from that single small study without a comparison group is too weak for firm conclusions. If you are considering an infusion for Parkinson's symptoms, discuss this with your doctor. The theory that an infusion bypasses the intestinal barrier and produces better peak levels has never been tested in comparative research.
The claims are based on several small to medium-sized RCTs and open-label studies of oral NMN (PMID 36482258, 36797393, 38191197), two review articles on the gap between animal and human studies (PMID 37335049, 33932956), and one small observational study of intravenous NADH in Parkinson's disease (PMID 9013405). No comparative study between a NAD+ infusion and oral NMN is available in the source texts.
Are NAD+ supplements (NMN/NR) worth it?
NMN and NR demonstrably raise NAD+ in your blood and appear to be safe, but whether you will notice any benefit in muscle strength, heart function or memory has not yet been proven in humans. Note also: NR is authorised in the EU as a supplement; NMN is not (yet).
Which is better for raising NAD+: NMN or NR?
NMN and NR raise NAD+ equally well, so the choice between the two probably makes no difference to the end result. Whether that rise in NAD+ actually does anything for your health is far from certain.
What does a NAD supplement do, and does it work in people?
NAD supplements demonstrably raise NAD levels in your blood, but whether you actually benefit from that remains uncertain. If you want to try them, keep your expectations realistic and choose a dose with the best available evidence behind it.
Which supplements or medications are best not combined with NAD+?
The combination of NAD+ supplements, particularly nicotinamide, with platinum-based chemotherapy is the most concrete reason for caution. For other interactions the indications are preliminary, but worth discussing if you use multiple substances.
What is NAD+ and what does it do in your body?
NAD+ is an indispensable molecule for energy, DNA repair and cell maintenance, and its levels measurably decline with age. Whether that decline can be corrected with supplements, and what benefit that would bring, is a separate question.
What does NAD+ do for your brain?
NAD+ matters for your brain and declines with age. Whether topping it up via NMN (a substance your body converts into NAD+) or other means actually helps has not yet been convincingly demonstrated in people. Wait for the results of larger studies in people before drawing firm conclusions.