If you've started looking into NAD+ supplementation, you've quickly realized something confusing: it's available in three completely different formats, and the people who use each one are absolutely convinced theirs is the best. You can swallow capsules of NMN or NR. You can self-inject NAD+ subcutaneously, like insulin. Or you can sit in a chair at a wellness clinic for two hours while NAD+ drips into your vein. The price differences are dramatic. The bioavailability differences are even more dramatic. And the published research doesn't fully agree with itself.

This guide breaks down what each delivery method actually does, what the data shows, and how to think about choosing among them.

The short answer

Oral NAD+ precursors (NMN and NR) reliably raise blood NAD+ levels and are the most studied, most accessible, and least expensive option. Subcutaneous and intramuscular NAD+ injections bypass digestion and deliver substantially higher bioavailability than oral, at moderate cost, with the convenience of home administration. IV NAD+ infusions deliver the highest plasma concentrations of all, with subjective effects many users describe as transformative, but require clinical administration, take hours per session, and cost significantly more. The right protocol depends on your goals, budget, baseline labs, and what you've already tried.

Oral NAD+ precursors: the foundation

You can't take NAD+ orally in any useful way. The molecule itself is too large and too unstable to survive the digestive tract intact. So oral protocols use precursors: smaller molecules your body converts into NAD+ through its own biosynthesis pathways. The two leading options are nicotinamide riboside (NR) and nicotinamide mononucleotide (NMN).

The strongest data point for oral precursors is consistency: in placebo-controlled human trials at doses of 300 to 1000 mg per day, both NR and NMN reliably double or more-than-double circulating NAD+ levels within two weeks of supplementation. A 2026 head-to-head Norwegian study found NR raised blood NAD+ by approximately 161% versus 69% for NMN at the same gram dose. A separate Nestlé-led 2025 study found both raised NAD+ comparably after 14 days. The exact comparison depends on the study design, but the conclusion that both work is well established.

What oral precursors do well: they're convenient (just swallow a capsule), affordable (mid-range monthly cost), supported by the most published human clinical data, and well tolerated even at higher doses.

What oral precursors don't do well: they hit a bioavailability ceiling. Some of the dose is degraded by gut bacteria. Some is converted to nicotinamide in the liver before reaching tissues. The peak blood concentrations achievable through oral dosing are an order of magnitude below what injectable forms can produce.

Subcutaneous and intramuscular injections: the middle ground

Self-administered NAD+ injections work the same way insulin does. A small needle, a small volume of solution, a quick subcutaneous or intramuscular dose, two or three times per week. The NAD+ bypasses the digestive tract entirely and is absorbed directly from the injection site into circulation.

The bioavailability case for injections is strong. Without first-pass metabolism through the liver, more of the dose enters systemic circulation. A 2023 pharmacokinetic study found that parenteral NAD+ delivery produced peak plasma NAD+ levels several times higher than matched oral dosing, with tissue uptake measurable within hours.

What injections do well: they hit pharmacokinetic levels that oral can't reach. They're administered at home, taking only minutes per dose. Cost sits between oral and IV. Many users report meaningful subjective improvements in energy, mental clarity, and recovery within the first few weeks, often more noticeable than with oral protocols alone.

What injections don't do well: they require some willingness to handle a needle (most people adjust quickly). They require a physician to prescribe and monitor. Site reactions (mild redness or tenderness) occur in a small minority of users. And while the bioavailability story is strong, large-scale clinical trials specifically on injectable NAD+ for healthy aging are still limited; most of the human evidence comes from clinical practice rather than randomized controlled trials.

IV infusions: the maximum-bioavailability option

IV NAD+ infusions deliver the molecule directly into venous circulation. Bioavailability is essentially 100%. Plasma concentrations climb to levels that are simply not achievable by any other route.

A typical protocol involves sessions lasting 60 minutes to several hours, depending on the dose. High-dose protocols (1000 mg or more per infusion) require slow administration to avoid side effects like chest discomfort, GI symptoms, or hot flashes during the drip.

What IV infusions do well: peak plasma levels are unmatched. Users frequently report the most noticeable subjective effects of any delivery method, particularly the first few sessions. High-dose IV NAD+ has the most clinical data in specific therapeutic contexts (addiction recovery, neurological recovery), where the protocol has been studied at substantial doses.

What IV infusions don't do well: they're the most expensive option by a significant margin. Sessions are time-intensive. They require clinical setting and IV access. And here is where the contested science enters: some leading NAD+ researchers, including Dr. Eric Verdin of the Buck Institute, have argued that the NAD+ molecule may be too large to cross cell membranes intact, meaning that the dramatic plasma elevations from IV may not translate into proportional intracellular NAD+ in target tissues. Other researchers and clinicians dispute this, citing the consistent functional improvements reported by IV NAD+ patients and the clinical results in addiction recovery and other applications. The honest answer is that the question of how much IV NAD+ enters cells versus how much is broken down extracellularly is genuinely open.

How to think about choosing

The framework most longevity-focused clinicians use is roughly this:

If you're new to NAD+ optimization and don't have specific clinical goals: start with oral NR or NMN. It's the lowest-friction entry point with the strongest research base. Give it three to six months and see how you respond.

If you've used oral precursors and want to escalate, or if you have higher baseline metabolic demand: add subcutaneous injections under physician guidance. The pharmacokinetic step up is real, and many users notice clearer effects on energy and recovery than oral alone produces.

If you have specific therapeutic goals (recovery from significant illness, addiction medicine, neurological rehabilitation) or want the highest possible peak concentrations: IV infusions in a clinical setting are the most aggressive option. Cost and time investment are real but justified for specific use cases.

Many people combine routes. Daily oral precursors as a foundation, weekly or twice-weekly injections for sustained elevation, and occasional IV protocols for specific recovery or performance windows. This stacked approach is becoming more common in clinics that take NAD+ optimization seriously.

Cost comparison: a rough sketch

Pricing varies widely by provider, but these are typical 2026 ranges in the U.S. cash-pay market:

Note that these are out-of-pocket costs. Insurance generally does not cover NAD+ protocols for healthspan or longevity indications. Some HSA/FSA accounts may apply depending on the documentation and your plan.

What about side effects?

All three routes have favorable safety profiles in clinical use, but each has its own signature:

Oral: Mild GI symptoms (nausea, gas) occasionally at higher doses. Liver enzyme elevations have been reported in rare cases at very high chronic doses. Generally well tolerated.

Subcutaneous: Local injection site reactions (redness, mild swelling, occasional bruising). Rarely a flushing or warm sensation immediately post-injection that subsides within minutes.

IV: The classic IV NAD+ side effects, especially at higher doses or faster infusion rates, are chest tightness, GI cramping, anxiety-like sensations, and warmth. These are typically managed by slowing the infusion rate. Once the infusion is complete, side effects resolve quickly.

Frequently asked questions

Does oral NMN raise tissue NAD+ or only blood NAD+? Trials reliably show blood NAD+ elevation. Tissue elevation in muscle has been demonstrated in some studies. Brain NAD+ elevation has been demonstrated for NR over 4 weeks in healthy adults. The translation from blood levels to tissue levels in every organ is still being studied.

Are NAD+ injections legal? Yes, with a valid prescription from a licensed provider. Compounded injectable NAD+ is available through 503A pharmacies under physician supervision.

Can you do IV NAD+ at home? Some mobile IV services will administer NAD+ infusions at home with a nurse present. This adds convenience but is generally more expensive than clinic-based sessions.

How often should I dose injections? Common protocols are twice or three times per week, with the exact frequency adjusted by your provider based on goals and response.

Is one route safer than another? All three have strong safety records in standard clinical use. IV requires the most clinical oversight and has the most acute infusion-related side effects to manage. Oral is the most forgiving for self-management. Injections sit in the middle.

The Bottom Line

Bioavailability differs dramatically among the three routes. Oral precursors are the foundation: well-studied, affordable, convenient. Injectable NAD+ steps up bioavailability significantly and is increasingly the format of choice for sustained, physician-supervised optimization. IV NAD+ produces the highest plasma concentrations and the most striking subjective effects, at the highest cost and time commitment. None of them are mutually exclusive, and many sophisticated protocols use combinations.

If you're considering NAD+ injections, CLYR Health offers physician-supervised injectable NAD+ as part of our longevity catalog. Licensed providers, 503A compounding pharmacy, transparent pricing. Start your assessment.