How do NMN and NR become NAD+? In human trials, both raised blood NAD+

Two common ways to raise the energy molecule NAD+ are nicotinamide mononucleotide (NMN) and nicotinamide riboside (NR). The useful version is not the molecule you swallow, but the NAD+ it becomes inside the body. In people, both precursors raise the blood NAD+ level, and a 2026 head-to-head found the two did it comparably. Two NMN trials also found better walking results, and one found better sleep scores. Whether a higher blood level shows up as more energy or faster recovery is still an open question.

The short version

• Your cells rebuild most of their own NAD+ from recycled parts. NAD+ cannot be taken directly from food, and one enzyme, NAMPT, is the key step in rebuilding it (Navas 2021, a review; Zhang 2025, a review).
• NMN and NR are two NAD+ precursors. In human trials, both raise the blood NAD+ level (Yi 2023, Pencina 2023, Orr 2024).
• In a 2026 randomized head-to-head of 65 healthy adults, 14 days of NR or NMN raised blood NAD+ by a comparable amount, while plain nicotinamide did not (Christen 2026).
• Two NMN trials also found functional gains over placebo: longer six-minute walks in 80 middle-aged adults (Yi 2023), and a faster 4-meter walk and better sleep scores in 60 older adults (Morifuji 2024). Two NR trials in people with mild cognitive impairment raised blood NAD+ but did not improve cognition (Orr 2024, Martens 2026).
• A review of the human trials finds the effect is smaller than earlier lab work predicted, and the gut makes it more complicated (Yaku 2023).

Show the scienceHow it works

How it works

NAD+ sits at the center of energy metabolism. NAD+ and its partner NADH are swapped back and forth in the cell’s main energy-making reactions, such as glycolysis, the TCA cycle and oxidative phosphorylation (Navas 2021, a review). The enzyme NAMPT is a key rate-limiting step in rebuilding a cell’s NAD+ pool (Zhang 2025, a review).

The cell recycles rather than imports. NAD+ cannot be taken directly from food. Instead, NAMPT recovers NAD+ from nicotinamide, and this recycling generates most of the cell’s NAD+ (Navas 2021, a review). That is why precursors are the way supplements try to raise it.

The two precursors can take different routes. NR and NMN both end up as NAD+, but they can behave differently in the body, and where each one goes depends on the tissue and on the enzymes and transporters it has (Yoshino 2018, a review).

• NMN itself reaches the blood: in a trial of 32 adults aged 55 to 80, 1,000 mg of NMN once or twice a day for 14 days raised blood NMN, and blood NAD+ rose in a dose-related way (Pencina 2023).
• The gut adds a second route. In the 2026 head-to-head, lab tests with human gut bacteria found that NR and NMN both give rise to nicotinic acid, and nicotinic acid was a potent NAD+ booster in blood samples. The authors propose that NR and NMN raise blood NAD+ mainly through this gut-dependent route, the Preiss-Handler pathway, rather than the recycling loop (Christen 2026). That route has been shown in the lab, not yet inside the body.

Why the tissue matters. The NAMPT recycling loop helps sustain NAD+ especially in high-energy tissues such as skeletal muscle, and a review discusses exercise and NAD+ boosters as ways to support it (Su 2024). The level the trials measure, however, is the blood.

What the trials measured

Blood NAD+ is the reliable finding. In a randomized trial of 80 healthy middle-aged adults taking 300, 600 or 900 mg of NMN by mouth for 60 days, blood NAD+ rose at every dose versus placebo at days 30 and 60, highest at 600 and 900 mg (Yi 2023). In the same trial, six-minute walking distance rose more than with placebo at every dose, general health scores were better, and a blood-based biological age measure stayed unchanged with NMN while it rose with placebo (Yi 2023). In 32 overweight or obese adults aged 55 to 80, 1,000 mg of NMN once or twice a day for 14 days brought substantial, dose-related rises in blood NAD+ (Pencina 2023).

Both precursors, about equal. The 2026 head-to-head is the closest thing to an NR-versus-NMN answer yet. In 65 healthy adults over 14 days, NR and NMN raised blood NAD+ comparably; nicotinamide did not raise it over the two weeks, and only nicotinamide had a short-lived effect on the blood NAD+ profile right after it was taken (Christen 2026).

Walking and sleep. A randomized trial of 60 older adults found 250 mg of NMN a day for 12 weeks raised blood NAD+, gave a faster 4-meter walk than placebo and improved sleep quality scores; a stepping test did not differ (Morifuji 2024).

Higher doses of NR. In 20 older adults with mild cognitive impairment, NR built up to 1 gram a day for 10 weeks raised blood NAD+ 2.6-fold, and an exploratory analysis found a modest drop in epigenetic age; cognition stayed stable (Orr 2024). In 42 adults with amnestic mild cognitive impairment, 12 weeks of NR raised blood NAD+ twofold but did not improve cognitive function, total blood flow to the brain or blood pressure (Martens 2026). In a four-week safety trial in 20 people with Parkinson’s disease, 1,500 mg of NR twice a day raised blood NAD+ up to fivefold, with no moderate or severe adverse events (Berven 2023).

Muscle. In a five-month study of 20 identical twin pairs, NR at 250 to 1,000 mg a day raised muscle mitochondrial number and changed NAD+ metabolism and gut bacteria, but did not improve body fat or metabolic health (Lapatto 2023).

One caveat. Across the field, oral NR and NMN are safe and raise NAD+ in people, but the effect has been smaller than the earlier lab work predicted, and the gut microbiome adds complexity (Yaku 2023).

Next step

If you would rather see the numbers for yourself, the dose story walks through how far blood NAD+ rose with each dose the trials tested. Read Does a bigger NMN dose raise NAD+ more? next.