# NAD+ Dosage in the Research: Doses Studied, Routes, and Clearance > NAD+ dosage as studied in the literature — oral NMN and NR dose ranges, IV infusion protocols, tolerability, and why infused NAD+ is rapidly cleared. Research context only, no dosing advice. The oral-precursor dose ranges used in human trials, the IV protocols reported in the literature, and the pharmacokinetics behind both — described as research, not as instructions. ## The short version This is a research digest, and it gives no NAD+ dosage instructions. Here is the landscape it describes. Almost all the controlled human data use precursors (building blocks like NR and NMN) taken by mouth, not NAD+ itself — because NAD+ is poorly absorbed intact. Oral NMN was studied around 250-900 mg/day; oral NR around 250-1000 mg/day, with 3000 mg/day tested only to check safety. IV NAD+ uses much larger infused amounts but has the weakest evidence. The numbers below are study doses, full stop — not recommendations. ## Doses studied in the published research These are the NAD+ dosage figures reported in human trials, presented as study doses with no recommendation attached. Oral NMN (a precursor) was studied at 250-900 mg/day; 250 mg/day is the most-replicated dose [6], and a multicenter trial compared 300, 600 and 900 mg/day, identifying 600 mg/day as optimal [3]. Oral NR (a precursor) was studied at 100-1000 mg/day for efficacy [4][14], with 3000 mg/day (1500 mg twice daily) tested for 30 days purely to establish a safety ceiling [9]. Nicotinamide (NAM) has been studied at 500 mg twice daily in a different context, skin-cancer chemoprevention. IV NAD+ — the coenzyme itself, infused — is reported in wellness and clinical settings at roughly 250-1000 mg per session over several hours; one pharmacokinetic study used a continuous 3 µmol/min infusion over 6 hours. Historical addiction protocols used 500-1000 mg IV NAD+ daily over several days [8]. These IV figures rest on far weaker evidence than the oral-precursor trials. ## Why most oral products are precursors, not NAD+ itself Oral "NAD+" capsules face a basic absorption problem: NAD+ is a large, charged dinucleotide (663.43 Da) that is not freely taken up intact by most cells and is largely broken down before absorption [12]. In human skin fibroblasts, extracellular NAD was degraded by surface ecto-enzymes into nicotinamide, NMN and purine metabolites before any cellular uptake, with adenosine the principal product taken in [12]. That is why most experts consider precursors — NMN, NR, niacin/nicotinamide — the rational oral approach, and why oral NMN and NR, not oral NAD+, are the molecules with reproducible blood-NAD+ trial data [3][4]. ## How long does NAD+ persist? Clearance and precursor pharmacokinetics The NAD+ half life question splits by route. Infused NAD+ itself is cleared from plasma rapidly — a pilot pharmacokinetic study found near-complete plasma removal within roughly the first two hours of infusion, because extracellular NAD is metabolized by ecto-enzymes before uptake [12]. So an IV bolus does not persist as circulating NAD+. Oral precursors behave differently: NR and NMN are absorbed and raise *whole-blood* NAD+ over days to weeks, with the elevation sustained through chronic dosing across 8-12 week trials [4][3]. The precursor route builds the pool gradually; the IV route spikes and clears. ## Routes studied Four route categories appear in the literature, with sharply different evidence weight. **Oral** (capsules or powder of NMN, NR or nicotinamide) carries the bulk of controlled human evidence [3][4][6]. **Intravenous** NAD+ infusion is used in wellness clinics with limited, mostly pilot or retrospective data [8]. **Subcutaneous / intramuscular** compounded NAD+ injection has minimal peer-reviewed pharmacokinetic data. **Sublingual, intranasal, topical and transdermal patches** are marketed but have little controlled evidence — no randomized trial in this digest supports patches or sprays raising NAD+. The oral-precursor route is where the data live. ## Why the oral and IV dose figures are not comparable It is tempting to line up an oral 1000 mg NR capsule against a 1000 mg IV NAD+ infusion as if they were the same dose of the same thing. They are not. The oral figures are *precursor* doses — NR or NMN — that the body converts into NAD+ along the salvage pipeline and that raise the pool gradually over days to weeks [3][4]. The IV figures are *the coenzyme itself*, pushed into plasma where it is rapidly degraded and cleared, much of it broken down extracellularly before any cell takes it up [12]. Same number on the label, entirely different molecule, route, and fate. The dose-response evidence — the part that is actually quantified and reproducible — lives almost entirely on the oral-precursor side [4]. ## Tolerability and reported adverse events in the trials In the controlled oral-precursor trials, tolerability was good. NR at 100-1000 mg/day for 8 weeks showed no significant adverse-event difference from placebo and no flushing [4]. High-dose NR at 3000 mg/day for 30 days reported no moderate or severe adverse events and met its primary safety endpoint [9]. NMN at 250-900 mg/day reported no safety issues across trials [3][6]. The risk profile shifts by route. IV infusions can cause chest tightness, abdominal discomfort, flushing or nausea if run too fast [8]. Compounded injectable NAD+ has carried a Class I FDA recall for elevated bacterial endotoxin — the most serious recall class. A separate, theoretical concern is that boosting NAD+ could support the metabolism of existing cancers, since NAD+ fuels proliferating cells; its role in oncology is dual and context-dependent. None of this is medical advice — it is what the studies and recalls report. --- A build-log reading of the NAD+ literature, traced from salvage pathway to brain — the coenzyme kept distinct from its NMN and NR precursors, the oral trials kept apart from the rapidly-cleared IV route, and the contested NMN supplement status logged as filed; no clinic compiles behind this console and nothing here is dosed, compounded, prescribed, or sold.