Key Takeaways

• What is oral NAD+ supplementation, and how does it work? Oral NAD+ supplementation involves taking NAD+ or its precursors, typically in the form of capsules, pills, or powders.
• Oral NAD+ is ineffective: Because NAD+ is a large, highly charged molecule, it cannot cross cell membranes intact. As a result, taking NAD+ orally has not been shown to reliably increase NAD+ levels in the body.
• NAD+ precursors are the evidence-based oral strategy: Compounds like nicotinamide riboside (NR) are well-studied, absorbed efficiently, and converted into NAD+ through established cellular pathways.
• Not all NAD+ precursors perform equally: Structural differences affect absorption and cellular uptake, making some precursors less reliable than others (e.g., NMN) for increasing NAD+ levels in humans.
• Quality and transparency matter: Industry testing reveals that many NAD+ supplements fail to contain their labeled ingredients, highlighting the importance of third-party testing and verified manufacturing.

In an era of injectable, infusible, and increasingly complex delivery systems, oral supplementation remains one of the most familiar and accessible ways people support their health. Affordable, non-invasive, and practical for long-term daily use, oral supplements are widely used by millions—including those to support nicotinamide adenine dinucleotide (NAD+), a vital coenzyme that has gained growing attention across both consumer wellness and scientific research.

However, increasing attention has also led to more widespread misconceptions. A common assumption is that taking the NAD+ molecule orally will increase NAD+ levels in the body—but from a biochemical and physiological standpoint, this is incorrect. NAD+ is a large, highly charged molecule that faces barriers to absorption and cellular uptake, limiting its ability to effectively raise intracellular NAD+ levels when taken orally.¹

More recently, liposomal NAD+ has been promoted as a potential solution to these limitations, with claims of improved bioavailability. However, current scientific evidence does not support the idea that oral liposomal NAD+ supplements can reliably increase NAD+ levels in humans.

This article explains how oral supplementation and intestinal absorption work, why orally administered NAD+ does not effectively raise NAD+ levels, and why NAD+ precursors—particularly nicotinamide riboside (NR)—are a more evidence-based approach for supporting NAD+ levels.

What Is Oral NAD+ Supplementation and How Does It Work? 

Oral supplementation refers to the delivery of nutrients or bioactive compounds by mouth, typically in the form of capsules, pills, powders, tablets, or liquids. From daily multivitamins to more targeted molecules intended to support health or longevity, oral supplements are commonly used as a way to influence biological processes within the body.

The popularity of oral supplementation is largely driven by its practicality. Oral supplements are easy to take at home, generally lower in cost than injectable or intravenous therapies, simple to incorporate into daily routines, and typically do not require medical supervision for routine use. These factors make oral delivery especially well-suited for long-term or consistent supplementation.

Once ingested, orally administered compounds must pass through several physiological stages before they can exert a biological effect. These stages include digestion in the gastrointestinal tract, absorption across the intestinal lining, and first-pass metabolism in the liver.² Each step influences how much of a compound remains intact, how much enters systemic circulation, and whether it reaches target tissues in a biologically active form.

Therefore, a compound’s stability and bioavailability depend on its ability to withstand these processes. Some nutrients—such as vitamin C, folic acid, and certain minerals—are naturally well suited to oral delivery and are more efficiently absorbed. Others may degrade during digestion, be poorly absorbed, or be extensively metabolized before reaching circulation.

As a result, oral supplementation is best suited for compounds intended to provide steady, long-term support rather than immediate or acute effects. This approach aligns well with strategies aimed at gradually supporting cellular pathways, including those designed to increase NAD+ levels over time.

However, many consumers assume that taking NAD+ itself in oral form will directly increase NAD+ levels in the body. As the next section explains, the science of oral absorption and metabolism tells a very different story.

Why Oral NAD+ Supplements Don’t Work

Despite growing interest in NAD+ supplementation, orally administered NAD+ faces fundamental biological and structural limitations that prevent it from effectively raising NAD+ levels in the body. 

Structurally, NAD+ is a large, highly polar molecule containing two negatively charged phosphate groups. These phosphate groups prevent NAD+ from crossing the cell membrane, meaning it cannot directly enter cells, and must first be broken down into smaller components before it can be utilized.

Before NAD+ can be used inside cells, it must first be broken down into smaller precursor molecules, such as nicotinamide riboside (NR) or nicotinamide (NAM). These precursors can cross cell membranes, be transported into cells, and then be enzymatically converted back into NAD+ through different pathways. In other words, the body does not absorb NAD+ directly; it rebuilds NAD+ internally from precursor compounds.

In addition to these biochemical constraints, NAD+ is chemically unstable. It is highly susceptible to degradation when exposed to heat, light, or moisture, making it difficult to stabilize in supplement form under conditions commonly encountered during manufacturing, storage, or typical at-home use.

In an FDA briefing document evaluating NAD+ as a dietary ingredient, regulators concluded that NAD+ is unlikely to remain stable in capsule form under standard storage conditions, further limiting its effectiveness as an oral supplement. Additionally, multiple published studies¹ and review articles³ support this conclusion, reinforcing the lack of evidence for oral NAD+’s efficacy in boosting NAD+ levels. 

Taken together, these factors explain why there is currently no published scientific evidence showing that oral NAD+ increases NAD+ levels in humans. Claims suggesting otherwise are not supported by clinical data. For an oral supplement to efficiently elevate NAD+, the active ingredient must effectively cross the cell membrane and be synthesized inside cells from smaller, bioavailable precursors such as NR.

Why NAD+ Precursors Are Effective Orally: The Body’s Natural NAD+ Building Blocks

While oral NAD+ itself is not effective, supplementation with certain NAD+ precursors has been extensively studied and represents a practical approach to increasing NAD+ levels in the body. A precursor is a smaller molecule that cells can convert, through a series of chemical reactions, into a larger, more complex compound—in this case, NAD+.

NAD+ precursors serve as the natural building blocks the body uses to synthesize NAD+, supporting essential cellular processes like energy metabolism, DNA repair, and cellular health.

Common NAD+ precursors include:

• Niacin (nicotinic acid or NA)
• Nicotinamide (niacinamide or NAM)
• Nicotinamide riboside (NR)
• Nicotinamide mononucleotide (NMN) 
• Tryptophan

Each of these compounds enters NAD+ metabolism through distinct biochemical pathways, which can influence how efficiently they increase NAD+ levels.

Once ingested, these smaller molecules are absorbed into the bloodstream and transported into cells through established uptake mechanisms. Inside the cell, they are enzymatically converted into NAD+, effectively increasing NAD+ levels in circulation and within tissues. In contrast, oral NAD+ has not been shown to raise NAD+ levels in humans, as it cannot cross cell membranes in its intact form.

Not all precursors, however, are equally efficient. NMN, for example, faces challenges with direct cellular uptake due to its nucleotide structure, which includes the presence of a phosphate group. As a result, NMN must first be broken down into NR before it can enter cells and contribute to NAD+ synthesis. 

While preclinical research in mice suggests that NMN can enter cells and support NAD+ production,⁴ these findings have not yet been confirmed in other mammals, including humans, calling into question claims that NMN provides a faster or more direct route to NAD+ replenishment. 

Collectively, these differences underscore an important point: raising NAD+ levels depends not only on the choice of molecule, but also on its bioavailability, stability, and proven ability to enter cells. These factors are crucial for ensuring that supplements actually deliver the intended biological effects—a reality that becomes especially evident when looking at the current NAD+ supplement market.

Industry Testing Uncovers Widespread Quality Issues in the NAD+ Supplement Market

Third-party testing is the gold standard for ensuring supplement purity and potency. This is especially important for complex, high-demand ingredients like NAD+ and its precursors, where consumers often pay a premium for products intended to support cellular health. Ingredient and/or product testing helps uncover whether brands prioritize quality and integrity—or whether what’s on the label doesn’t actually match what’s in the bottle.

Over the past few years, three lab-accredited testing reports conducted by Niagen Bioscience have revealed details about just how much—or rather, how little—NR is actually found in your supplement bottle.

• In October 2021, a quantitative analysis of 22 NMN products with the highest market share on Amazon revealed that only 14% met or exceeded their label claims. Even more concerning, 64% had NMN levels below detectable limits (under 1%), and 14% contained no NMN at all.

• Next, in February 2025, Niagen Bioscience analyzed 39 NR products and found that only five met or exceeded 100% of their label claims. About one-third contained less than advertised, and over 70% had significantly less—or even undetectable—amounts of NR. Not only that, but seven counterfeit Tru Niagen products being sold on Amazon were also identified, none of which provided the amount of NR claimed on their labels.

• Finally, in May 2025, Niagen Bioscience tested 22 of the best-selling NAD+ products on Amazon, including softgels, capsules, liquids, and liposomal delivery systems, finding that 55% of the products contained little to no actual NAD+.

Liposomal formulations, which are often marketed as a more bioavailable delivery method, were also found to fail testing. Certain “liposomal NAD+” softgel products contained no detectable NR or NAD+, reinforcing that liposomal encapsulation is not a reliable strategy for delivering NAD+, NR, or other NAD+ precursors.

These findings underscore the importance of rigorous testing and quality verification when choosing NAD+ supplements and highlight why clinically researched, third-party tested products offer consumers both safety and confidence.

For more information on liposomal formulations and why they may not deliver what they promise, see our article What Is Liposomal NAD+ Delivery?

What Consumers Should Look for in an NAD+ Supplement

With the variability in quality revealed by industry testing, it’s more important than ever for consumers to know how to evaluate NAD+ supplements. Choosing products backed by science, safety, and transparency can make all the difference.

When considering an NAD+ supplement, look for the following:

• Clinically studied ingredients: The ingredient or finished product should be supported by published research demonstrating safety and efficacy in humans.
• Transparent manufacturing and third-party testing: Independent verification confirms that the product contains the labeled amount of active ingredient and is free from contaminants.
• Clear labeling and dosage disclosure: The supplement should specify exact amounts of active ingredients per serving.
• Strict quality control and verified retail channels: Choose brands with rigorous manufacturing standards and traceable distribution.

Ultimately, marketing claims should not be the deciding factor. Science, safety, and transparency are far more important than hype or wellness buzzwords. By choosing supplements from reputable brands that prioritize these principles, consumers can feel confident they are taking products that are both effective and reliable.

Conclusion: Choose Science Over Trends: Effective Oral NAD+ Supplementation Comes from NAD+ Precursors

Oral supplementation offers a convenient and accessible way to support health, but not all compounds are equally effective—especially NAD+. While taking NAD+ directly may seem intuitive, structural and biochemical limitations prevent it from reliably increasing levels in the body.

Therefore, research shows that NAD+ precursors like nicotinamide riboside (NR) provide a scientifically supported pathway to elevate NAD+ consistently and safely.

As industry testing consistently highlights that many NAD+ precursors on the market do not contain the listed ingredients or amounts advertised, it’s increasingly important to choose brands that value trust, transparency, and third-party verification.

For consumers seeking reliable NAD+ support over time, the choice is clear: focus on supplements that are tested, proven, and well-regulated, using clinically researched NAD+ precursors. By choosing science-backed ingredients, you can take a confident step toward long-term cellular support and NAD+ optimization.

References

1. Nikiforov, A., Dölle, C., Niere, M., & Ziegler, M. (2011). Pathways and Subcellular Compartmentation of NAD Biosynthesis in Human Cells FROM ENTRY OF EXTRACELLULAR PRECURSORS TO MITOCHONDRIAL NAD GENERATION*. Journal of Biological Chemistry, 286(24), 21767–21778. https://doi.org/10.1074/jbc.m110.213298
2. BACK, D. J., & ROGERS, S. M. (1987). Review: first‐pass metabolism by the gastrointestinal mucosa. Alimentary Pharmacology & Therapeutics, 1(5), 339–357. https://doi.org/10.1111/j.1365-2036.1987.tb00634.x
3. Vinten, K. T., Trętowicz, M. M., Coskun, E., Weeghel, M. van, Cantó, C., Zapata-Pérez, R., Janssens, G. E., & Houtkooper, R. H. (2025). NAD+ precursor supplementation in human ageing: clinical evidence and challenges. Nature Metabolism, 1–17. https://doi.org/10.1038/s42255-025-01387-7
4. Grozio, A., Mills, K. F., Yoshino, J., Bruzzone, S., Sociali, G., Tokizane, K., Lei, H. C., Cunningham, R., Sasaki, Y., Migaud, M. E., & Imai, S. (2019). Slc12a8 is a nicotinamide mononucleotide transporter. Nature Metabolism, 1(1), 47–57. https://doi.org/10.1038/s42255-018-0009-4