NAD+: blood tests and everyday life

The blood result

The number that makes this subject so tempting is 142%. In an eight-week NR trial in healthy overweight adults, that was the rise in whole-blood NAD+ at 1000 mg/day. The response grew with the amount given. Something measurable happened, and I think that deserves its due.

Then comes the much larger question: how much better did life become? That blood test cannot supply the answer. The 2025 review of human ageing trials found limited clinical efficacy and sparse measurements inside particular tissues. A striking laboratory result and a useful health result can be separated by a great deal of unfinished work.

Order is the word I reach for here. Start with the ingredient, follow it to the measurement, then see how far the finding travels. A claim that jumps straight to the end irritates me. The NMN and NR comparison begins at the ingredient; muscle and walking studies get closer to the life outside the blood test.

What does NAD+ do in the body?

Nicotinamide adenine dinucleotide is already at work in cells. The plus sign identifies the form that accepts electrons; NADH carries them onward as cells release energy from food. A coenzyme is a helper molecule for enzymes, the proteins that make chemical reactions happen. NAD+ also gets consumed in work involving DNA repair and cellular signalling, as the review of NAD+ metabolism during ageing describes.

That double job appeals to me: a molecule can circulate through energy reactions and also be spent on repairs. Replenishing it involves production, reuse and consumption. The body builds NAD+ from materials including niacin, nicotinamide and NR, members of the vitamin B3 family. NAD+ itself has a dinucleotide structure; peptides have chains of amino acids. Those names describe different chemistry.

NAD supplement ingredients

A NAD supplement commonly supplies NMN or NR, the smaller precursors from which cells make NAD+. Intact swallowed NAD+ is poorly absorbed. The human precursor trials reviewed in Nature Metabolism therefore need to be read with the actual ingredient in mind.

NMN means nicotinamide mononucleotide. NR means nicotinamide riboside. The structural work on the enzyme that processes NR describes how NR enters the route to NAD+. I enjoy that chemistry, but the supplement comparison turns on the human outcomes. Here are the separate NR and NMN results.

NAD+ benefits: movement and metabolism

The muscle insulin-sensitivity finding has earned a longer look from me. Women with prediabetes who were past menopause received NMN in a ten-week trial; their muscles became more sensitive to insulin, the hormone that helps control blood sugar. Body composition and HbA1c, a measure of longer-term blood sugar, stayed unchanged. That combination sharpens the finding. It locates a change precisely.

Another NMN trial reported greater walking distance. Walking is a recognisable activity, much closer to the reason someone becomes interested in this research. The finding still comes from a short trial. The research page follows both studies and the unusually small Werner syndrome trial, where the population matters enormously.

Memory, infusions and the next question

In the long-COVID trial, NR raised NAD+, while the randomised comparison found no significant cognitive advantage over placebo. The randomised comparison gets priority in my judgement. It separates the NR group’s changes from changes with placebo. It asks the question the hopeful story tends to skip.

NAD IV therapy has a much thinner controlled record. The small intravenous cognition pilot reported improved test scores, leaving everyday memory and lasting benefit unresolved. The brain page starts with the long-COVID result and works outward to the mouse experiments and the infusion pilot.

For amounts and adverse events, there is a separate account of NAD+ dosage and side effects in studies. NAD+ has no FDA approval as a treatment for disease, and compounded injections are unapproved. A useful effect still has an unfinished journey from measurement to daily life. That stretch is the reason I’m still interested.