NAD+ injections for energy and aging: what the evidence shows

What did @lose.weight.with.kate actually say?

The creator said she's taking NAD+ injections that came with instructions for either intramuscular (IM) or subcutaneous (sub-Q) administration. Because she's already familiar with sub-Q from GLP-1 shots, she's starting there. She added that she's "already noticed the difference" and that IM might be more effective, but IV is "definitely the best way" — something she attributes to celebrities — while calling it too expensive and inconvenient for her budget.

This is a pretty honest, experience-first framing. She's not selling anything, and she's clear about what she knows versus what she's heard. That matters when we're evaluating credibility. She's also working with instructions from whoever supplied her injections, which raises its own set of questions about sourcing and oversight.

Does the science back this up?

Partially. The IV-versus-injection hierarchy she describes has some biological plausibility, but the human evidence is thin across all three routes. Most clinical research on NAD+ precursors uses oral formulations, not injections, and head-to-head comparison studies between administration routes in humans basically don't exist yet.

NAD+ itself does not survive oral ingestion well because it's broken down in the gut before reaching systemic circulation. That's the argument for injectable routes. A 2023 review by Covarrubias et al. in Nature Aging noted that while NAD+ boosting strategies show metabolic and neuroprotective signals in animal models, translation to human outcomes remains early-stage. IV infusions do bypass first-pass metabolism entirely, which is the pharmacokinetic argument for their superiority. But whether sub-Q absorption is meaningfully inferior to IM for NAD+ specifically has not been tested in any published randomized trial. The creator's claim that IM is more effective than sub-Q is biologically reasonable but not yet evidence-confirmed.

What did they get wrong (or right)?

She got the general hierarchy roughly right on pharmacokinetic logic, even if she didn't know the mechanism. IV does deliver the fastest, most complete absorption. IM generally absorbs faster than sub-Q because muscle tissue is more vascularized. That part checks out as plausible science.

Where she's on shakier ground: saying she's "already noticed the difference" after starting sub-Q injections. That's a personal observation with no baseline measurement, no control, and a strong expectation effect baked in. This is not a criticism unique to her. It's the core problem with self-reported outcomes in unblinded, uncontrolled self-experimentation. The placebo response to injections specifically is well-documented and tends to be stronger than for oral interventions (Schedlowski et al., 2015, Pharmacological Reviews).

She also frames IV as what "all the celebrities do," which is a credibility appeal that doesn't mean much scientifically. IV NAD+ clinics are a wellness industry product, not an FDA-regulated therapy with a proven outcomes record.

What should you actually know?

A few things worth understanding if you're looking at NAD+ injections yourself. First, NAD+ is not a peptide despite being grouped in peptide-adjacent biohacking content. It's a coenzyme. Second, injectable NAD+ sits outside FDA-approved indications and is typically administered through compounding pharmacies or grey-market suppliers, which means quality control varies significantly. Third, IV NAD+ infusions are associated with side effects including nausea, chest tightness, and flushing, which are less commonly reported with IM or sub-Q routes (Braidy et al., 2019, Antioxidants and Redox Signaling).

The honest summary: the route-of-administration logic the creator outlines is pharmacologically coherent. But the idea that any route of NAD+ supplementation produces a noticeable subjective effect within days is not well-supported by controlled human data. If you're considering this, that conversation belongs with a licensed clinician who can assess your individual situation, not a TikTok comment thread.