READER QUESTIONS / THE FAQ DESK
Common questions about NAD+
Definitional, safety, and efficacy questions answered straight from the cited record — the coenzyme kept distinct from its precursors throughout.
What is the downside of taking NAD+?
Oral NAD+ itself is poorly absorbed, so the coenzyme in a plain pill largely does not reach cells intact [9]. IV NAD+ rests on minimal controlled evidence and a compounded injectable was recalled by the FDA for endotoxin [8]. Precursor trials report good tolerability but unproven hard clinical benefit beyond raising blood NAD+ [8][14].
Is it safe to take NAD daily?
Randomized trials of oral precursors reported no serious adverse events — NR up to 2,000 mg/day for 20 weeks, and NMN trials running to 24 weeks [8]. Those are research findings on specific products at specific doses, not a recommendation or a dosing instruction. Supplement purity also varies, so safety is study-specific rather than a blanket guarantee [8].
Does NAD cause weight gain?
No cited trial shows precursor supplementation causes weight gain. In the prediabetic-women NMN trial, muscle insulin sensitivity improved while body composition did not change [1], and the 2023 review found body-composition endpoints unmoved across multiple trials [8]. Weight gain is not among the reported effects of NAD+ precursors in the human record.
What is an NAD injection?
An NAD injection is an injectable or IV form of NAD+ given in wellness settings. It is a compounded, not FDA-approved, preparation with limited controlled data, and it carries a documented contamination risk — a compounded NAD+ injection was subject to an FDA Class I endotoxin recall [8]. Infused NAD+ is also cleared from plasma within hours [14].
When should you inject NAD+?
There is no established, evidence-based injection schedule. Injectable NAD+ is compounded and off-protocol, and the controlled data behind the route are minimal [14]. This digest reads the research record and gives no dosing or timing instructions for human use — including for the injectable route.
Does NAD help with fertility?
Fertility claims circulate from preclinical work, but no cited human trial in this digest establishes a fertility benefit from NAD+ or its precursors. It remains a research-stage question rather than a demonstrated outcome, and nothing here should be read as a recommendation to use NAD+ for fertility.
Is NAD safe?
Oral precursors showed good tolerability across randomized trials [4][8], but the answer is route-specific. Compounded IV NAD+ carries a contamination risk — the FDA Class I endotoxin recall — and supplement purity varies between products [8]. Safety here is study-specific and route-specific, not a single blanket guarantee for everything sold as "NAD+."
What is the best time to take NAD, morning or night?
NAMPT — the rate-limiting salvage enzyme that recycles nicotinamide into NAD+ — follows a circadian rhythm, which is why the timing question gets asked [9]. But no trial has established an optimal time of day to dose, and this digest does not recommend a dosing schedule. The question is biologically reasonable and empirically unanswered.
How long do NAD side effects last?
Infusion-related discomfort from IV NAD+ run too fast — flushing, nausea, chest or abdominal pressure — is transient and tied to infusion rate [14]. Oral precursor trials reported no significant adverse-event difference from placebo, so there was little in the way of lasting side effects to measure [4][8]. Effects are route-dependent.