NAD⁺ injections are sold for both subcutaneous and intramuscular use, and which one applies to your vial is set by the prescription and the concentration — not by a general rule you can look up. That is the honest answer, and it is worth more than the confident diagram you were hoping to find.
Nothing on this page is technique instruction. What follows is what the two routes are, what sellers in this category actually tell buyers, and what the published literature has to say about either — which, as you will see, is close to nothing.
The difference between the two routes
Subcutaneous means into the fat layer beneath the skin, typically with a short fine needle at a shallow angle. Absorption is slower and steadier, because fat is less vascular. It is the route most home-injected medications use, and it is the one most NAD⁺ telehealth programs default to.
Intramuscular means deeper — through the fat and into the muscle, with a longer needle held perpendicular. Muscle has a richer blood supply, so absorption is faster, and larger volumes can generally be given than fat will accept comfortably.
Those are real pharmacological differences. What does not exist is evidence about which of them is appropriate for NAD⁺ specifically, because no one has run the study. Our injection explainer covers what the format involves in practice; this page is about why the route question has no published answer.
The census behind that claim
We ran the searches rather than assuming. In September 2026, PubMed returned 13 records for (“nicotinamide adenine dinucleotide”[Title] OR NAD[Title]) AND (subcutaneous[Title/Abstract] OR intramuscular[Title/Abstract]) AND humans[MeSH Terms]. We screened all 13 titles. Not one is a study administering NAD⁺ to people by either route: they are studies of adipose tissue biology, oxidative-stress enzymes and imaging methods that happen to carry the letters. Narrowing to intramuscular alone returned 8 records, with the same result.
That is our own search, so here is an independent one. Reviewers working to PRISMA protocol swept the NAD literature from January 2010 to October 2025 and screened it down to 113 eligible studies, 33 of them human intervention studies and 28 of those randomized. Their finding on this exact point: no eligible outcomes trial evaluated intravenous or intramuscular NAD⁺ itself for anti-aging or wellness indications [1].
The closest thing to a trial-derived parenteral dose comes from a different route and a different population entirely. A randomized, placebo-controlled trial enrolled 180 adults with heart failure from ischemic cardiomyopathy and gave 10 mg of NAD⁺ a day intravenously for seven days alongside standard therapy, reporting a greater one-month improvement in ejection fraction than placebo (45.44 ± 8.55% vs 42.44 ± 9.09%, p = 0.024) [2]. If you are searching for how much to inject, that is the only published human dosing figure for NAD⁺ given parenterally — ten milligrams a day, intravenously, in supervised cardiac patients. It is not a wellness protocol and it is not transferable to one.
So: two independent searches, the same finding, and the one parenteral dose anyone has published is from cardiology. When a provider tells you subcutaneous is the right route for NAD⁺, or that intramuscular “works better”, they are describing a practice convention, not a trial result.
What sellers actually instruct
The pattern across the programs on our injection board is a subcutaneous protocol with a rotating site — abdomen, outer thigh, back of the arm — on a weekly or twice-weekly schedule, with the vial shipped alongside syringes and an instruction card. Some programs use intramuscular protocols instead, usually at larger volumes.
Two things vary far more than they should. The first is the milligram figure: most sellers publish a monthly price and no dose at all, which makes it impossible to know how much you are drawing up or what it is worth. Among those that do publish, System Labs states a 1000 mg monthly supply at $149 and Eden a 500 mg vial at $186.
The second is the schedule. Weekly, twice weekly and monthly protocols all exist, sold with equal confidence, and there is nothing in the literature that distinguishes them. When intervals vary that much between sellers, the interval is not coming from evidence.
The limits of self-administration
Compounded NAD⁺ is not FDA-approved, and is not reviewed by the FDA for safety, efficacy or quality before it is dispensed. A pharmacy may be FDA-registered, which describes the facility rather than the product in the vial — a distinction worth holding on to when a page uses the phrase as reassurance. The regulatory picture is worth reading in full before a first injection.
What that means practically is that you are performing a clinical procedure at home, with a preparation whose contents have not been independently verified, on a schedule nobody has validated. The prescribing clinician is the only person who can tell you the route, the needle, the volume and the site rotation for your prescription, and the only person who should.
Reactions at the injection site — redness, swelling, a lump, tenderness — are the most commonly reported issue with subcutaneous injectables generally. Anything beyond that, and anything systemic, is a call to the prescriber rather than a search engine. What is known about NAD⁺ side effects is thinner than most sellers imply, and it is format-dependent.
The questions to ask before the first dose
Which route, and why that one for this concentration. How many milligrams per injection, and how many in the vial. What the schedule is based on. Who to call if something looks wrong at 9pm on a Sunday.
If those answers are not forthcoming, that is itself information. Our question checklist puts them in an order that tends to get responses, and the cost board shows what you should be paying once you finally have a milligram figure to compare on.