NAD+ Dosage Guide: How Much Per Day, by Form

If you search "NAD+ dosage," you'll get a confident-sounding number from almost every supplement brand — and they rarely agree. The honest answer is more useful, and a little less tidy: the doses people quote come from a small set of human trials that measured safety and a blood biomarker (NAD+ levels), not whether you live longer, feel younger, or lose fat. So a dose can be "studied" and still tell you nothing about whether it works for the thing you're hoping for.

This guide gives you the actual numbers from the human studies, organized by form — oral nicotinamide riboside (NR), oral nicotinamide mononucleotide (NMN), niacin and nicotinamide, and IV/injectable NAD+ — and is clear about exactly what each number does and doesn't prove. For the bigger picture of what NAD+ supplementation has and hasn't shown, start with our pillar guide to the NAD+ evidence.

The one rule that matters most: dose is anchored to *what was measured*

Almost every NAD+ human trial to date has a primary endpoint that is either tolerability (did people get side effects?) or a biomarker (did blood or muscle NAD+ go up?). Very few measured a real-world outcome, and the ones that did mostly came back null or mixed. So when a label says "clinically studied dose," what that almost always means is: this dose was shown to be safe and to raise NAD+ in the blood. That is a real and worthwhile thing to know — but it is not the same as "this dose makes you healthier."

Two consequences follow from that, and they run through this entire guide:

• •More is not automatically better. NAD+ blood levels tend to plateau, and the dose-response for raising the biomarker often flattens out well before the highest doses people take. Bigger doses mostly buy you more cost and more flush or GI upset, not more proven benefit.
• •"Studied for safety" is short-term. Most trials ran weeks to a few months. Long-term, high-dose human safety data are thin for NR and NMN. That uncertainty is a reason for restraint, not a license to megadose.

These are supplements, not approved drugs, and none of the doses below is a treatment for any disease. Use this as background for a conversation with a clinician — especially if you're pregnant, on medication, or managing a health condition.

Oral nicotinamide riboside (NR): roughly 250–1,000 mg/day

NR is the NAD+ precursor with the most controlled human dosing data, largely because the branded ingredient (Niagen) funded formal safety and pharmacokinetic work.

The foundational study showed that a single oral dose of NR raises blood NAD+ in humans in a dose-dependent way — the first clear demonstration that an oral precursor actually moves the biomarker¹. A dedicated ascending-dose pharmacokinetic study then gave healthy adults 250 mg, 1,000 mg, and 2,000 mg and confirmed NAD+ rose with dose while the compound was well tolerated across that range². Formal safety work supports the commonly sold band: a randomized trial dosed NR up to 1,000 mg/day and found it safe, with blood NAD+ rising and a favorable tolerability profile³, and an 8-week study comparing 100, 300, and 1,000 mg/day of nicotinamide riboside chloride established dose-dependent NAD+ increases without meaningful safety signals⁴. The manufacturer's toxicology package defined a no-observed-adverse-effect level in animals that underpins the human upper doses⁵.

Higher and split dosing has also been tested: trials in overweight/obese men used 1,000 mg twice daily (2,000 mg/day)⁶, and a study in aged adults gave 1,000 mg/day and confirmed it raised the muscle NAD+ metabolome⁷. The recurring finding in these higher-dose studies, though, is telling — NR reliably raised NAD+ but did not improve the functional or metabolic outcomes the researchers hoped for (insulin sensitivity, muscle mitochondrial function), and even a phase I trial in Parkinson's disease using 1,000 mg/day was designed mainly to confirm target engagement, not to prove a clinical benefit¹⁴.

Bottom line for NR: the human-studied range is roughly 250–1,000 mg/day, with safety data extending to 2,000 mg/day. NAD+ goes up across that band; proven outcomes do not scale with the dose. Going above ~1,000 mg/day buys little but cost. We compare NR head-to-head with NMN in NMN vs NR.

Oral nicotinamide mononucleotide (NMN): roughly 250–900 mg/day

NMN's human dosing is anchored to a cluster of small dose-ranging trials, mostly from Japan and China. An early single-dose safety study in men gave 100, 250, and 500 mg and found NMN was safe with no problematic changes in clinical parameters⁸ — establishing tolerability but, again, not outcomes.

The most-cited dose-ranging trial randomized healthy middle-aged adults to 300, 600, or 900 mg/day for 60 days and reported that blood NAD+ rose dose-dependently and the higher doses were well tolerated, with a walking-distance and biological-age signal that the authors themselves framed cautiously⁹. A separate safety study confirmed that oral NMN up to 1,250 mg/day efficiently raised blood NAD+ metabolites and was safe over the test period¹⁶. In a tighter, mechanism-focused trial, 250 mg/day of NMN improved muscle insulin sensitivity in prediabetic women — a genuine controlled finding, but in a specific population and on a surrogate endpoint, not weight or disease outcomes¹⁰. An exercise trial in amateur runners compared 300, 600, and 1,200 mg/day and reported aerobic-capacity differences, though it was small and unblinded in ways that limit confidence¹¹.

At the higher end, a pharmaceutical-grade NMN (MIB-626) was tested at 1,000 mg once or twice daily in overweight/older adults; it robustly raised NAD+ but was explicitly described as a physiologic study — biomarker movement, not a clinical-outcome win¹².

Bottom line for NMN: the studied range is roughly 250–900 mg/day (with safety data to ~1,250 mg), and 300–600 mg/day captures most of what the trials used. As with NR, NAD+ rises reliably; durable human outcomes remain unproven. (NMN also sits under a regulatory cloud in the US after the FDA's position that it can't be sold as a supplement — context we cover in NMN vs NAD+ and our best NMN supplements roundup. And if you're wondering whether to pair NMN with a methyl donor at these doses, see should you take TMG with NMN?. Once you've settled on a dose, the best time to take NMN is a smaller question than the marketing suggests — consistency matters more than the hour.)

Niacin and nicotinamide: the old, cheap NAD+ precursors

Niacin (nicotinic acid) and nicotinamide (niacinamide) are the original vitamin-B3 NAD+ precursors, and they're dramatically cheaper than NR or NMN — but they come with their own dosing realities.

The recommended dietary allowance for niacin is only about 14–16 mg/day (as niacin equivalents) — enough to prevent deficiency. The doses studied for raising NAD+ are far higher and behave differently:

• •Niacin (nicotinic acid) was tested at escalating doses up to 750–1,000 mg/day in patients with a mitochondrial myopathy and genuine NAD+ deficiency, where it corrected systemic NAD+ levels and improved muscle performance — a striking result, but in a rare disease state, not in healthy people¹³. Niacin's signature limitation is the flush: a prostaglandin-mediated reaction (acting through skin Langerhans cells and the GPR109A receptor) that causes intense warmth, redness and itching, which is why high-dose niacin is hard to tolerate¹⁵.
• •Nicotinamide (niacinamide) doesn't cause flushing, which is why it shows up in NAD+ blends. But at high chronic doses it carries its own caution — large amounts can raise liver-enzyme concerns and may blunt some of the very NAD+-dependent (sirtuin) signaling people are chasing. It's effective at correcting deficiency, but not a free lunch at megadoses.

Bottom line for B3: these forms do raise NAD+ and cost pennies, but flush (niacin) and high-dose liver/signaling concerns (nicotinamide) make them less popular as "NAD+ optimizers," even though the precursor logic is the same. Cheaper isn't automatically worse — but the tolerability tradeoffs are real.

IV and injectable NAD+: clinic protocols, weakest evidence

Intravenous NAD+ is the most aggressively marketed and the least supported by controlled data. Clinic protocols vary enormously — commonly cited drips run 250 mg to 1,000 mg per session, with some "high-dose" programs advertising multi-day courses totaling several grams. These numbers come from clinic marketing and small case reports, not from dose-ranging trials with real endpoints. There is no established, evidence-based IV NAD+ dose because there are essentially no rigorous outcome trials to anchor one. Infusing too fast reliably causes chest tightness, nausea and a flushing/anxiety sensation, which is why drips are run slowly over hours.

We go deep on what's actually known (and what isn't) in NAD+ IV therapy: evidence and cost and NAD+ injections: what the research shows. The short version: the route is plausible for getting NAD+ into the blood, but the dose is set by clinics and convenience, not by trials — so treat any specific IV number with skepticism.

A realistic dosing summary (not medical advice)

Putting the trials together, here's what the human evidence actually supports as studied doses — each of which moved the NAD+ biomarker and was generally tolerated, with outcomes still unproven:

• •Oral NR: ~250–1,000 mg/day (safety data to 2,000 mg/day).
• •Oral NMN: ~250–900 mg/day (safety data to ~1,250 mg/day); 300–600 mg/day is the common research band.
• •Niacin: RDA is ~14–16 mg/day; NAD+-raising doses studied at hundreds of mg but flush-limited.
• •Nicotinamide: raises NAD+ cheaply, no flush, but high chronic doses carry liver/signaling cautions.
• •IV NAD+: no evidence-based dose; clinic protocols (~250–1,000 mg/session) are marketing-derived, not trial-derived.

Three honest caveats to carry with those numbers. First, "studied" means studied for safety and NAD+ levels — not for living longer or feeling better. Second, the dose-response for the biomarker plateaus, so chasing ever-higher doses is mostly chasing cost and side effects. Third, long-term high-dose safety is genuinely unknown for NR and NMN; the trials were short. Before starting any of these, talk to a clinician — and review the realistic NAD+ side effects first.

If you want to see how specific products map onto these studied doses, with third-party-testing and value caveats, see our evidence-rated best NAD+ supplements and best NMN supplements roundups, and our hub of vetted NAD+ options.