Nothing published shows that 1000 mg of NAD⁺ works better than 500 mg. The tiers exist because a seller needs a second price point, and the only proper dose-ranging trial in this area found its highest dose no better than the middle one.
That trial was of an oral precursor rather than an injection, which matters — but it is the closest thing to evidence anyone has, and injectable NAD⁺ has no dose-ranging data at all.
What the dose-ranging trial found
A randomized, multicenter, double-blind, placebo-controlled trial randomized 80 healthy middle-aged adults (n = 80) to placebo or 300, 600 or 900 mg of NMN once daily for 60 days. Blood NAD concentrations rose significantly in every treated group at day 30 and day 60 against both placebo and baseline (all p ≤ 0.001), and were highest in the 600 mg and 900 mg groups. Six-minute walking distance improved in all three treated groups against placebo at both time points (all p < 0.01), with the longest distances in the 600 mg and 900 mg groups. The authors’ own conclusion was that clinical efficacy, measured by blood NAD concentration and physical performance, reaches its highest at 600 mg daily [1].
Read the shape rather than the headline. Going from 300 to 600 bought something. Going from 600 to 900 — a 50% increase in dose and in cost — did not buy more. That is what a flattening dose-response curve looks like, and it is the normal shape for a nutrient your body already regulates.
There is a dose-response in the biomarker, so this is not an argument that dose does not matter at all. In an eight-week randomized, placebo-controlled trial of nicotinamide riboside, 100, 300 and 1,000 mg raised whole blood NAD⁺ by 22%, 51% and 142% within two weeks [2]. Blood levels keep climbing. Whether anything you can feel climbs with them is the question nobody has answered.
What the tiers actually are
Look at how they are presented on the sellers we have verified. Eden lists a 500 mg vial at $186 with a 1000 mg option also available. System Labs states a 1000 mg monthly supply at $149. The IV Doc sells a 250 mg starting infusion at $799 with add-ons of a further 250 mg, 500 mg or 750 mg.
Three things follow. The first is that these are not comparable units — a vial, a monthly supply and a single session — which is why our dose-value tool keeps the basis attached to every figure. The second is that at 1000 mg System Labs is cheaper in absolute terms than Eden is at 500 mg, so the tier you pick matters far less than the seller you pick. The third is that no page presenting these tiers cites anything for the difference between them.
The most expensive version of this choice is the IV add-on. Going from 250 mg to 500 mg in a session roughly doubles the milligrams on a product that already costs about $3.20 a milligram — against roughly $0.15–$0.25 a milligram for injection sellers that publish a dose. Doubling the dose on the most expensive format is the single costliest decision available in this category, and the least supported.
Is more ever justified?
High doses have been tested for safety, which is not the same as being tested for benefit. The NR-SAFE trial randomized 20 people with Parkinson’s disease to nicotinamide riboside 1,500 mg twice daily (n = 10) or placebo (n = 10) for four weeks; all completed, there were no moderate or severe adverse events, blood NAD⁺ rose up to five-fold, and the authors supported extending the dose range to 3,000 mg a day in phase II trials with appropriate safety monitoring [3]. Separately, 1,250 mg of β-NMN once daily for up to four weeks in 31 healthy adults produced no severe adverse events [4].
So high doses appear to be tolerated in the short term by small numbers of people. What no trial has shown is that they deliver more of what you are buying them for. Tolerated and worthwhile are different findings, and only one of them is on the shelf.
How to make the choice
Ask the prescriber what the higher tier is based on. A good answer names something specific about you. A weak answer describes the higher tier as “optimal” or “for advanced protocols”, which is pricing language wearing a lab coat.
Then compare on cost per milligram rather than on tier. The cost calculator turns any two offers into the same unit, and the cheapest NAD⁺ therapy board ranks what is actually on the market once you do. In most cases the 1000 mg tier at a cheaper seller costs less than the 500 mg tier at an expensive one, which makes the whole dropdown a distraction from the decision that matters.
And keep the format question upstream of the dose question. Everything injectable here is compounded, meaning not FDA-approved and not reviewed by the FDA for safety, efficacy or quality before dispensing; the doses actually used in trials are all on the oral side, which is also where the evidence is.