The Different Forms of Nicotinamide Riboside: Comparing NR Chloride, NR Hydrogen Malate, NRH, and More

Expert-reviewed by Philip Redpath, Ph.D.

Key Takeaways

• “NR” is not one single compound; it exists in several chemical forms, each with its own structure, stability, and evidence base.
• Salt forms of NR (like NRCl, NRHM, and NR tartrate) contain the same active NR molecule but differ in dosing, regulatory status, and research depth.
• NR derivatives (like NRH and NAR) are chemically distinct molecules with different metabolic pathways that can still overlap with those of NR.
• NRCl currently holds the deepest research base, broadest regulatory acceptance, and only USP monograph among all NR forms.
• No formal head-to-head study has compared bioavailability across all NR forms, so claims of one form being "better absorbed" than another remain unproven.

Nicotinamide adenine dinucleotide (NAD+) is a vital molecule in human biology, playing a central role in cellular energy production, DNA repair, and metabolic function. As interest in aging and longevity research has grown, so too has focus on strategies to support NAD+ levels, which naturally decline with age and in response to stressors like inflammation or metabolic dysfunction. NAD+ precursors—particularly nicotinamide riboside (NR)—have emerged as a widely studied and accessible entry point into this field. 

However, the term “NR” is often used as a catch-all term, implying a single, uniform compound. In reality, NR can exist in multiple salt forms, each with distinct structural characteristics, stability profiles, and levels of scientific evidence behind them. These differences are not always clearly communicated.

As a result, confusion has grown among both consumers and professionals. Individuals comparing “NR” products may in fact be evaluating compounds that are not directly equivalent, with differing safety data, regulatory considerations, and evidence bases. This can make it challenging to interpret claims or make informed decisions. This article aims to provide clarity on the different forms of NR, explain why the specific form matters, and examine the distinctions between the primary forms currently discussed in research and on the market. 

What Is Nicotinamide Riboside? 

Nicotinamide riboside (NR) is a naturally occurring form of vitamin B3, part of the same family as niacin. Structurally, NR consists of a nicotinamide molecule attached to a ribose sugar, which allows it to be efficiently converted into NAD+ within cells. Though NR has been chemically known for decades, its biological significance wasn’t fully understood until 2004 research identified it as a precursor that could be converted directly into NAD+ through a dedicated salvage pathway.¹ This discovery reframed NR from an obscure metabolite into a compound of significant interest in NAD+ research. 

In nature, NR occurs only in trace amounts, appearing in milk,² brewer’s yeast,³ and certain fruits and vegetables,⁴ including wild chicory, bananas, and oranges. However, these dietary levels are too low to meaningfully influence NAD+ levels on their own, which is part of why supplementation has become the primary route for studying and using NR.

However, there is a practical challenge: NR on its own is chemically unstable and prone to degradation.⁵ To create a shelf-stable powder suitable for supplements, NR requires a pairing with a stabilizing counterion—an accompanying molecule that maintains its structural integrity during processing and storage.⁶ This stabilization requirement is exactly what has produced the different “forms” of NR seen on the market today, each defined by the specific counterion (often a salt) used to keep the molecule stable. 

Why the Form of Nicotinamide Riboside Matters

In chemistry, a salt forms when a positively charged ion pairs with a negatively charged ion to create a stable compound. A classic example most people are familiar with is table salt, or NaCl—a sodium ion paired with a chloride ion. The same logic applies to NR, where commonly seen forms include nicotinamide riboside chloride (NRCl), nicotinamide riboside hydrogen malate (NRHM), and nicotinamide riboside tartrate (NR tartrate).⁷ Each of these salt forms pairs the NR molecule with a different counterion—chloride, hydrogen malate, or hydrogen tartrate—just as sodium pairs with chloride to form table salt. 

In practical terms, once these salts are ingested and the salt dissociates in the body, the active NR molecule is essentially the same regardless of which counterion it arrived with. In this sense, the “form” is less about an active ingredient and more about what surrounds the NR molecule during manufacturing, storage, and delivery. Following this logic, you might expect all NR salts to behave similarly once solubilized, with any bioavailability differences between forms being relatively small. However, this has not been formally demonstrated through direct comparison studies, so it can’t be stated with certainty. 

Form also extends into regulatory differences. Some NR salts (discussed in the following section) have secured formal recognition in the United States, such as a New Dietary Ingredient Notification (NDIN)—a filing submitted to the FDA when a new dietary ingredient is introduced to the market—or Generally Recognized as Safe (GRAS) status, a designation indicating a substance is considered safe for its intended use, based on the available scientific evidence. Other NR forms lack these same regulatory standings, affecting how confidently they can be marketed and used. 

This regulatory gap underscores a deeper point: safety and efficacy do not transfer across forms, as a toxicology study conducted on NRCl would say nothing definitive about NRH, for example. Therefore, each form must be evaluated on its own research. Ultimately, it’s difficult to say with certainty which salt form or derivative of NR is “best,” since a true head-to-head study comparing them all has not been performed. Still, by examining what can be compared (i.e., research depth, regulatory status, and manufacturing considerations), it becomes more possible to distinguish which forms carry stronger evidentiary support. 

The Different Forms of Nicotinamide Riboside, Explained

Most compounds discussed in the NR landscape can be organized into two broad categories: salt forms, which pair NR with a different counterion for stability, and NR-related derivatives, which are chemically related to NR but structurally distinct. 

Salt Forms of Nicotinamide Riboside

The primary salt forms of NR include NRCl, NRHM, and NR tartrate. These forms differ in the counterion paired with NR, while retaining the NR component.

Nicotinamide Riboside Chloride (NRCl)

Nicotinamide riboside chloride (NRCl) pairs NR with a chloride counterion and stands as the first and most extensively studied NR salt. Its research history dates back to 2016,⁸ when it was the subject of the first human NR supplementation study, showing that oral NR safely increased blood NAD+ levels in a dose-dependent manner and without serious side effects.

In the decade since, NRCl has built a remarkably deep research base for a single ingredient, with nearly 200 preclinical studies and close to 50 clinical studies, spanning areas from cardiovascular health and orphan disease to metabolism and healthy aging. This breadth of research is part of what distinguishes NRCl from other salt forms that have far less data. 

The regulatory position of NRCl mirrors its depth of research. It is the only NR salt reviewed twice under the FDA’s NDIN program, corresponding to filings NDI 882 and NDI 1062, and it has also received a formal GRAS notification in the U.S. Internationally, NRCl has secured regulatory acceptance from the European Commission, the Australian Therapeutic Goods Administration (TGA), Food Standards Australia New Zealand (FSANZ), Health Canada, the Brazilian Health Regulatory Agency (ANVISA), and Turkey's Ministry of Agriculture and Forestry.

Most recently, the United States Pharmacopeia (USP) published an ingredient monograph for NRCl, making it one of the only NAD+ precursors to receive this type of pharmaceutical-related quality standard. In practical terms, a USP monograph functions as a publicly available rulebook defining an ingredient’s identity, purity, potency, and required testing methods—the same kind of standard that historically was reserved for pharmaceutical ingredients. For those interested in what this designation means, this article explores the topic further.

Nicotinamide Riboside Hydrogen Malate (NRHM)

Nicotinamide riboside hydrogen malate (NRHM) pairs the NR molecule with a hydrogen malate counterion, but its evidence picture looks different from NRCl’s decade-long research base. Structurally, NRHM combines NR with a hydrogen malate counterion rather than chloride—beyond this difference, no direct comparative research has established whether NRHM functions differently from NRCl in the body. 

The current evidence base for NRHM remains comparatively limited. To date, there is only one published toxicology study, which found NRHM to be non-genotoxic and well-tolerated in rats across a 90-day sub-chronic assessment.⁹ There are no standalone human clinical studies; the only clinical preprint involving NRHM tested it exclusively as part of a multi-ingredient formulation, alongside magnesium beta-hydroxybutyrate, glutathione, and CoQ10, for brain function, meaning NRHM’s independent safety and efficacy profile remains unestablished.¹⁰ One ongoing trial is currently examining NRHM’s effects on cardiovascular health in healthy adults, though results are not yet available.  

The regulatory history of NRHM is also more complicated than NRCl’s, as its first NDIN, NDI 1243, was unsuccessful, followed by a successful no-objection response to a subsequent filing (NDI 1312). A third notification, NDI 1393, submitted by a different company, was also unsuccessful. NRHM additionally holds self-affirmed GRAS status, a designation that differs meaningfully from NRCl’s FDA-reviewed GRAS notice, as self-affirmed GRAS relies on a company’s own internal expert panel review without FDA involvement or public disclosure. Conversely, an FDA-notified GRAS determination is submitted to the agency for review and results in a public “no questions” response. Separately, NRHM has secured a Canadian Natural Health Product (NHP) ingredient record, authorizing its use as a source of NR within Health Canada’s natural health product framework. 

Nicotinamide Riboside Hydrogen Tartrate (NR Tartrate)

Nicotinamide riboside hydrogen tartrate (NR tartrate) pairs NR with hydrogen tartrate as its counterion, positioning it a step further out on the same evidence spectrum as NRHM. As a newer entrant to the NR landscape, it currently lacks any preclinical or human clinical studies, having been described so far only in technical and production-oriented literature, along with a single peer-reviewed lab synthesis and characterization study.⁷

Regulatory recognition for NR tartrate remains largely absent. There are no known NDINs or GRAS submissions on record for this form in the United States. However, like NRHM, it has secured a Canadian Natural Health Product (NHP) ingredient record, authorizing its use through a natural health product registration as a source of NR. 

Nicotinamide Riboside Fumarate (NR Fumarate)

Nicotinamide riboside fumarate pairs NR with a hydrogen fumarate counterion and is currently the newest and least characterized of the NR salts. Its evidence base consists of a single, recently published preclinical study, which compared it against NRCl and nicotinamide mononucleotide (NMN) in aged mice and reported greater increases in blood NAD+ at matched and even lower doses.¹¹ It is important to note that this finding is still preliminary, has not been independently replicated, and does not extend to toxicology or human data.

Unlike the other salt forms, no regulatory recognition currently exists for NR fumarate, leaving its safety and efficacy profile entirely unestablished at this stage.

Chemical Derivatives of Nicotinamide Riboside

The remaining compounds often discussed alongside NR—dihydronicotinamide riboside (NRH) and nicotinic acid riboside (NAR)—are better described as NR-related derivatives rather than alternative salt forms of NR. Both are ribosides that are structurally related to NR, but each has a distinct chemical identity and metabolic pathway. Neither compound is currently available for human consumption. 

Dihydronicotinamide Riboside (NRH)

Dihydronicotinamide riboside (NRH) is a reduced form of NR, chemically distinct from it rather than a salt pairing. NRH began receiving increased attention around 2019 and follows a metabolic pathway different from NR’s,¹² bypassing the NRK enzymes NR relies on and instead converting into NMNH (through the action of an enzyme called adenosine kinase) before becoming NADH and ultimately NAD+.

This distinct pathway is part of what drew early scientific attention, as initial cell studies showed that NRH produced faster, larger NAD+ increases than other precursors, raising levels 2.5- to 10-fold within an hour and suggesting notably higher potency.¹³ Since then, a growing body of preclinical research has produced mixed results. Some studies confirm NRH’s potency and highlight potential benefits,¹⁴ such as supporting immune cell metabolism,¹⁵ attenuating age-related hearing loss,¹⁶ and improving glucose tolerance and lipid metabolism.¹⁷ However, others have raised some concerns, with one study finding NRH supplementation activated a pro-inflammatory phenotype and signs of toxicity at higher doses.¹⁴ Overall, these studies suggest NRH’s effects vary meaningfully depending on the tissue type, dosage, and biological context. 

These preclinical findings come with caveats, as NRH is chemically unstable and prone to degradation,¹⁸ breaking down through oxidation and hydrolysis even under controlled storage conditions, a practical stability challenge that may be addressed through appropriate formulation and handling strategies. Just as importantly, there are currently no published human safety, bioavailability, or long-term studies on NRH, nor any public regulatory submissions or authorizations, leaving it firmly still in the experimental stage of research. 

Nicotinic Acid Riboside (NAR)

Nicotinic acid riboside (NAR) is not a salt form of NR—it is a structurally distinct molecule composed of nicotinic acid linked to a ribose sugar. However, NAR is not entirely separate from NR metabolically, as it can also be phosphorylated by NRK enzymes into its corresponding nucleotide, nicotinic acid mononucleotide (NaMN), connecting it to the same broader NAD+ biosynthetic pathway.

Unlike the salt forms of NR discussed above, NAR is not NR paired with a separate counterion. Instead, it can exist as an “inner salt,” or zwitterion, in which the positive and negative charges are contained within the same molecule, representing its more stable form that can be readily produced.

First identified in 2007,¹⁹ NAR converts to NAD+ through the Preiss-Handler pathway by being phosphorylated to NAMN, the same route used by niacin.

Preclinical research on NAR remains limited, but emerging evidence suggests it may exhibit more tissue-specific activity than NR, with recent findings showing NAR is produced and used by specific organs, such as the liver and kidneys, in a targeted way.²⁰ This hints at selective effects depending on cell or organ type. However, no regulatory submissions or authorizations for NAR currently exist. 

Other Forms of NR

Beyond the salt and non-salt forms covered above, a handful of other NR variants, including NR bromide, NR acetate, NR triflate, and NR tosylate, exist. However, public information on these forms comes almost entirely from patent filings and publications describing possible salt or formulation variants, with little to no published research, regulatory submissions, or independent verification available. 

For a brief comparison of all the NR forms covered above, please see Table 1.

Table 1. Comparison of Nicotinamide Riboside Salt Forms / Derivatives

Nicotinamide Riboside Forms: A Summary of the Evidence

NR consistently converts into NAD+, but the compounds surrounding it differ meaningfully in structure, depth of research, and regulatory standing. Salt forms like NRCl, NRHM, and NR tartrate share the same active NR molecule but pair it with different counterions, whereas non-salt derivatives such as NRH and NAR are chemically distinct molecules with separate metabolic pathways. 

Among the available NR forms discussed, NRCl is distinguished by the strength and breadth of the evidence supporting its use, including a decade of clinical research, multiple regulatory acceptances, and a USP monograph. By comparison, newer forms and derivatives, including NRHM, NR tartrate, NRH, and NAR, carry more uncertainty, with less extensive safety data, limited or no human trials, and, in some cases, no regulatory recognition at all. 

For anyone evaluating a supplement label, this distinction matters. A product listing NRCl reflects a form with a well-established safety and research record, while a label listing a newer salt or derivative may carry less certainty, even if it’s marked with similar claims. Understanding this difference is a useful starting point for anyone doing further research or making informed choices about NAD+ precursors. 

As research on newer forms continues to expand, the evidence supporting their distinct characteristics will continue to evolve. At present, however, NRCl is supported by a strong and growing body of evidence, providing a strong basis for its use and highlighting the importance of considering the depth and quality of available research when comparing different forms and derivatives.

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