NAD+: Uses, Benefits, Dosage & Safety

Last updated: August 2026 · Reviewed by the FactoWiki Editorial Team for clarity and source accuracy

What is NAD+?

Nicotinamide adenine dinucleotide, a coenzyme present in every cell, essential to redox reactions and to sirtuin and PARP enzyme activity. NAD+ itself is poorly absorbed orally, so supplements supply precursors instead: nicotinamide riboside (NR), nicotinamide mononucleotide (NMN), niacin or nicotinamide.

What NAD+ is commonly used for

Cellular energy, healthy ageing, mitochondrial function, and DNA repair support — all marketed considerably ahead of the evidence.

How NAD+ works

NAD+ cycles between oxidised and reduced forms in energy metabolism, and is consumed by sirtuins and PARPs during DNA repair and stress responses. Tissue NAD+ declines with age in animals. Restoring it improves multiple markers in mice. The human question is whether raising blood NAD+ produces any outcome that matters, and that has not been demonstrated.

What the evidence says

Each claim below is tied to the specific study behind it, rather than to a general reading list.

• Nicotinamide riboside reliably increases blood NAD+ in humans. Martens et al., Nature Communications, 2018 — randomised, double-blind, placebo-controlled crossover trial. (PubMed)
• Trials have not demonstrated clinical outcome benefits despite raised NAD+. Human NR and NMN trial literature — consistent biomarker effect without outcome data. (PubMed)
• NAD+ declines with age in animal tissue and restoration improves markers in mice. Rajman et al., Cell Metabolism, 2018 — review of NAD-boosting molecules. (PubMed)

Typical dosage used in studies

NR trials commonly use 250–1,000 mg daily; NMN trials 250–500 mg. Both raise blood NAD+ measurably. Plain niacin also raises NAD+ effectively and costs a fraction as much, though it causes flushing.

Side effects and safety

NR and NMN have been well tolerated in trials up to a year, with no serious adverse events attributed. Long-term safety data are limited, and the theoretical concern that raising NAD+ could support existing cancer cell metabolism has not been resolved.

Medication interactions and who should avoid NAD+

Sources & further reading

The claim-level citations above are drawn from these sources:

• Martens et al., Nature Communications, 2018 — randomised, double-blind, placebo-controlled crossover trial — find on PubMed
• Human NR and NMN trial literature — consistent biomarker effect without outcome data — find on PubMed
• Rajman et al., Cell Metabolism, 2018 — review of NAD-boosting molecules — find on PubMed
• NIH Office of Dietary Supplements
• NIH National Center for Complementary and Integrative Health

Frequently asked questions

Does raising NAD+ slow ageing?

Nobody knows. The supplements raise blood NAD+ reliably. No human trial has shown that produces a meaningful health or longevity outcome.

NR or NMN?

NR has more published human trial data. NMN has had regulatory difficulties in the US. Both raise NAD+; neither has outcome evidence.

Is niacin a cheaper alternative?

It raises NAD+ effectively and costs far less. The flushing is the trade-off, and nicotinamide avoids that.

General information, not medical advice.