# NMN vs NR: How NAD+ Precursors Compare in the Research > NMN vs NR compared from the trials: oral bioavailability, the dose-dependent blood NAD+ rises, the functional endpoints, and the coenzyme-versus-precursor distinction. A cited NAD+ digest. Two oral NAD+ precursors, two biosynthetic routes, two trial records — set side by side and stamped to source. ## The short version NMN vs NR is the comparison most NAD+ shoppers actually want. Both are precursors — building blocks the body converts into NAD+ — and neither is NAD+ itself, which is barely absorbed when swallowed [6][8]. NR (nicotinamide riboside) is the most-studied: a randomized trial raised blood NAD+ by 22%/51%/142% at 100/300/1000 mg/day [4]. NMN (nicotinamide mononucleotide) sits one step closer to NAD+ and has the muscle insulin-sensitivity trial behind it [1]. They take slightly different routes into the cell. This page reads both records and keeps the precursor-versus-coenzyme line sharp. ## NAD+ vs NMN: the coenzyme versus its precursor Start with the distinction that marketing and forums blur: NAD+ is the coenzyme; NMN is a precursor to it. NMN (nicotinamide mononucleotide) is one biochemical step from NAD+, converted by the NMNAT enzymes [9]. NAD+ is the finished molecule the cell actually uses for redox and signaling [5]. You cannot effectively swallow NAD+ itself — it is large and charged and poorly absorbed intact [6] — so a product labeled for raising NAD+ delivers a precursor instead. This is why every figure on this page is attributed to the precursor that produced it. When NMN at 250 mg/day improved muscle insulin sensitivity, that was NMN, the precursor, raising the downstream NAD+ pool [1]. Calling it 'taking NAD+' would be wrong. The same holds for NR. ## Nicotinamide riboside (NR): the most-studied oral NAD+ precursor Nicotinamide riboside (NR) has the deepest human dataset of any oral NAD+ precursor. It enters the NAD+ pool through a dedicated route: NR is converted to NMN by the NRK1/NRK2 kinases, then to NAD+ — a path independent of the Preiss-Handler pathway [6]. It is uniquely and orally bioavailable: single doses of 100-1000 mg dose-dependently raised whole-blood NAD+, a 1000 mg dose by about 2.7-fold over 24 hours [6]. The controlled chronic data are consistent. Eight weeks at 100/300/1000 mg/day raised whole-blood NAD+ by 22%/51%/142%, with no flushing and no adverse-event difference from placebo [4]. Six weeks at 1000 mg/day raised blood NAD+ about 60% in older adults, well tolerated, with a trend toward reduced aortic stiffness [7]. NR's strength is reproducible, dose-scalable, well-tolerated NAD+ elevation. ## Nicotinamide mononucleotide (NMN): one step from NAD+ Nicotinamide mononucleotide (NMN) is structurally one step closer to NAD+ than NR — it is the molecule NR is converted into on the way to NAD+ [6][9]. Whether that proximity matters for absorption is debated: a proposed direct intestinal transporter, Slc12a8, was reported in mice, but other groups have questioned it, and some NMN is thought to be dephosphorylated to NR before uptake [9]. NMN's human record includes the functional endpoint that draws the most interest: 250 mg/day for 10 weeks improved muscle insulin sensitivity in prediabetic, postmenopausal women [1]. A multicenter RCT at 300/600/900 mg/day for 60 days raised blood NAD+ across all groups, named 600 mg/day optimal, and reported improved walking distance, with no safety issues [3]. Single doses up to 500 mg were safely absorbed in healthy men [8]. ## Side by side: what each precursor has shown Both NMN and NR reliably raise blood NAD+ in randomized trials; that is the shared, well-supported finding [4][3]. NR has the larger and more replicated blood-NAD+ dataset, including direct dose-ranging (22%/51%/142% at 100/300/1000 mg/day) and a clear single-dose pharmacokinetic profile [4][6]. NMN has the standout metabolic functional result (muscle insulin sensitivity at 250 mg/day) and a multicenter dose-finding trial [1][3]. No cited head-to-head trial declares one precursor superior on hard clinical outcomes, and the 2025 Nature Metabolism review concluded human efficacy for clinical endpoints remains limited for the category as a whole [15]. The defensible comparison is at the level of blood NAD+ and tolerability, where both perform; it is not yet a comparison of proven health benefits. The regulatory footing also differs: NMN faces a contested FDA position on its supplement status, discussed in the [frequently asked questions about NAD+](/faq). ## Is taking NAD orally effective? Oral NAD+ itself is poorly absorbed intact, so most products use precursors [6][8]. Taking a precursor orally is effective at raising blood NAD+: randomized human trials show oral NMN and NR reliably and dose-dependently raise whole-blood NAD+ — NR by 22%/51%/142% at 100/300/1000 mg/day [4]. 'Effective' here means a measured biomarker rise; whether that produces a clinical benefit is a separate, less-settled question [15]. --- A specimen sheet of the NAD+ record — every precursor effect-size stamped to its study and every gap stamped just as plainly; no clinic behind the concrete and nothing here dispensed, priced, or sold.