They Tested 22 NAD+ Supplements. What They Found Inside Should Have Made Headlines. What They Found in the Gut Is Worse.

There is a version of this story where the problem is simple: the capsules were empty. You bought garbage and you didn't know it. For 64% of NAD+ supplements tested, that is the accurate version. But the uncomfortable finding — the one the supplement industry has been much quieter about — is that even the capsules that passed every purity test still produced nothing for most of the people taking them. Blood levels went up. The lab results looked right. And the person swallowing the pills every morning felt exactly the same. That gap — between what the bloodwork says and what the body actually experiences — is what this investigation is about. The purity crisis is real. But it is the smaller problem.

When Marcus, 44, decided to take NAD+ supplementation seriously, he did not buy the cheapest option on Amazon. He read the research. He listened to the podcasts. He cross-referenced David Sinclair's published work and Andrew Huberman's protocol recommendations. He bought from a brand he trusted. He took it every day for six months.

He felt nothing.

He did everything right. He spent over £1,200. The line didn't move.

"Not nothing as in subtle benefits I couldn't detect," he said. "Nothing as in absolutely zero difference. I was tracking everything. HRV, sleep quality, energy. The line didn't move."

He switched brands. He tried NMN instead of NR. He experimented with sublingual delivery. He added TMG to the protocol. He spent, by his own calculation, somewhere between £800 and £1,200 over eighteen months on products that collectively produced no measurable result.

"At some point," he said, "you start to wonder if the whole category is a scam."

Marcus is not alone. Across longevity forums, supplement communities, and consumer review platforms, a pattern repeats with striking consistency: buyers who have done the research, paid the premium prices, and committed to the protocol are walking away convinced that NAD+ does not work.

New evidence suggests they are wrong about that conclusion — but right about almost everything else.

THE PURITY PROBLEM

In 2023, independent laboratory analysis of NAD+ and NMN products sold through major online retailers found that 64% of products tested contained substantially less active ingredient than their labels claimed. Some contained almost none at all.

The analysis examined 22 products across categories including NMN, NR (nicotinamide riboside), and direct NAD+ supplements. Of the eight products that passed purity testing with meaningful active content, several still failed on dosing accuracy. Only a small minority delivered what was promised on the label.

For consumers like Marcus, this explains a great deal. The supplement that felt like nothing may have contained nothing. The money spent on premium brands may have purchased little more than capsule filler.

Consumer protection advocates have described the supplement industry as largely self-regulated, with manufacturers responsible for their own quality verification. Third-party testing exists, but it is not mandatory, and certification standards vary significantly across brands and markets.

This is the problem that the industry has begun — slowly, reluctantly — to acknowledge.

But researchers studying NAD+ metabolism say the purity crisis is real and serious, and that fixing it would still leave buyers with a second problem they have not yet confronted. One that is structural. And one that has nothing to do with what is written on the label.

THE DELIVERY PROBLEM: WHY EVEN PURE SUPPLEMENTS FALL SHORT

NAD+ is not a vitamin. It is not absorbed and deployed the way most supplements are.

To understand why, it helps to understand what NAD+ actually does. Nicotinamide adenine dinucleotide is a molecule present in every cell in the human body. It is involved in more than 500 enzymatic reactions. It regulates energy metabolism, DNA repair, and cellular maintenance. Without adequate NAD+, cellular function degrades. After forty, the body's own production declines steeply — in some research, dropping by 50% or more between the ages of 40 and 60.

The supplement industry responded to this discovery by offering precursor molecules: NMN and NR. The logic was sound. Feed the body the raw material, and the body will convert it into NAD+. Take the capsule. Let biology do the rest.

The problem is not what's on the label. It's what happens after you swallow it.

The problem is the conversion process.

Oral NMN and NR are ingested, survive partial degradation in the gut, enter the bloodstream as precursors, and then must be converted through a multi-step enzymatic chain before arriving as functional NAD+. Each conversion step involves losses. Each step depends on conditions — gut health, enzyme availability, cellular uptake efficiency — that vary significantly between individuals and decline with age.

The result, according to research published in longevity science journals, is that what arrives at the cellular level after oral supplementation is a fraction of what was swallowed. Estimates for oral bioavailability in the NAD+ precursor category vary, but the consensus among researchers is that absorption losses are significant enough to matter.

Some manufacturers have responded with liposomal formulations, sublingual delivery, and time-release capsules. Each claims to improve on the standard capsule. None has produced data demonstrating clinical equivalence to direct delivery formats.

WHAT DIRECT DELIVERY CHANGES

For a small but growing number of NAD+ users, the conversation has shifted from which precursor to take to whether precursors are the right format at all.

Subcutaneous injection — the same delivery method used by diabetics managing insulin and by patients receiving a range of pharmaceutical therapies — bypasses the oral conversion chain entirely. The molecule does not need to survive digestion. It does not require enzymatic conversion. It enters systemic circulation directly.

Among users on longevity forums who have switched from oral NMN or NR to injectable NAD+, the experiential reports follow a consistent pattern: outcomes they did not achieve after months of oral supplementation began appearing within weeks of switching format.

THE SECOND BARRIER: CD38 AND WHY IT MATTERS AFTER 40

For users willing to go deeper into the mechanism, there is a third layer that most supplement brands do not discuss.

An enzyme called CD38 — part of the immune system's normal cellular signalling — degrades NAD+ as one of its functions. In published research, CD38 activity approximately doubles between the ages of 20 and 50. By some estimates, the CD38-driven drain accounts for the majority of NAD+ decline in older adults — not insufficient production, but accelerated destruction.

This means that even a well-absorbed NAD+ supplement arriving in the bloodstream faces a cellular environment working against it. The drain is active. The supplement is trying to fill a depleted tank while the drain is open.

Understanding this changes the supplementation logic. The goal is not just to get the molecule past the gut. It is to get it there efficiently enough, in sufficient quantity, that it can meaningfully raise tissue NAD+ levels despite an active degradation process.

This is the argument that has shifted serious longevity researchers toward injection formats: not that oral supplements are worthless, but that for adults over 40 dealing with both the conversion problem and the CD38 drain, the margin for error on delivery format is narrow.

A DIFFERENT KIND OF PRODUCT

NADPure is a powder-form subcutaneous injection pen designed for at-home use without clinical supervision. Each pen ships as high-purity NAD+ powder and is activated at point of use — mixed with sterile solution in approximately 30 seconds before application.

Each pen contains high-purity NAD+ in a precise, batch-verified dose. Independent laboratory testing accompanies every production batch — the results are available on request, not hidden behind a certificate of authenticity buried in a FAQ.

The delivery format is a fine-gauge subcutaneous needle, identical in mechanism and user experience to the auto-injectors used by millions of people daily for metabolic health management. The injection is typically administered to abdominal tissue. Most users describe a mild, brief sensation.

It is not a supplement in the conventional sense. There is no capsule. There is no conversion chain. There is no question of whether the molecule survived the journey. It arrives as NAD+ because it was always NAD+.

Each pen ships with a silicone cool-pack. No dry ice. No refrigeration required on receipt — store up to 25°C, away from direct sunlight, and use within 45 days of mixing. Powder form is the highest-integrity format for sensitive injectables: the compound does not enter solution until you activate it.

WHO THIS IS FOR — AND WHO IT IS NOT

NADPure is a protocol for adults who have already done the research, already spent money on formats that did not deliver, and are now asking a different kind of question.

It is not a shortcut. The pen requires consistency. NAD+ levels return to baseline over approximately four weeks if the protocol is discontinued — this is biology, not dependency. The protocol is designed to be maintained, not cycled.

It is not appropriate for everyone. Individuals with certain medical conditions or on specific medications should consult a physician before beginning. The product carries a 30-day satisfaction guarantee, and the company's support address — support@trynadpure.com — is answered by humans, not autoresponders.

For people who have spent a year or more trying oral NMN or NR and experienced nothing, NADPure is not asking for blind trust. It is asking for one question: what if the problem was never the molecule?