NAD+ Index.

What does this test assess?

The NAD+ Index is a comprehensive panel that quantifies the key molecules of NAD+ metabolism from a single dried blood spot. It measures both oxidised and reduced forms of the two principal nicotinamide coenzymes (NAD+ / NADH and NADP+ / NADPH), along with two vitamin B3 precursors (nicotinamide and nicotinic acid), producing a composite Niacin Number that reflects overall cellular energy status.

Clinical indications include:

• Assessment of mitochondrial function and cellular energy production capacity
• Evaluation of age-related NAD+ decline — tissue levels may halve between ages 20 and 60
• Monitoring the efficacy of NAD+ precursor supplementation (NMN, NR, niacin)
• Investigation of chronic fatigue, exercise intolerance, and metabolic resilience
• Assessment of redox balance in chronic inflammation, where CD38 and PARP enzymes consume NAD+
• Evaluation of DNA repair capacity and sirtuin-mediated longevity pathways
• Screening for niacin (vitamin B3) insufficiency affecting NAD+ biosynthesis

Measured analytes

Analyte	Role	Clinical Significance
NAD+	Nicotinamide adenine dinucleotide (oxidised)	Central coenzyme in catabolic energy metabolism; electron carrier in mitochondrial respiration
NADH	Reduced NAD+	Delivers electrons to the electron transport chain for ATP production; elevated levels may indicate metabolic bottleneck
NADP+	Nicotinamide adenine dinucleotide phosphate (oxidised)	Coenzyme in anabolic biosynthetic pathways including fatty acid and cholesterol synthesis
NADPH	Reduced NADP+	Essential for glutathione regeneration, antioxidant defence, and reductive biosynthesis
Nicotinamide (NAM)	Vitamin B3 form; NAD+ precursor (salvage pathway)	Elevated levels may indicate recent B3 supplementation; very high levels may inhibit sirtuin activity
Nicotinic Acid (NA)	Niacin; NAD+ precursor (Preiss–Handler pathway)	Found in meat, fish, and fortified foods; supports NAD+ synthesis via an alternative biosynthetic route

The Niacin Number (NAD/NADP Index) is a composite score calculated as (NAD+/NADH × NADP+/NADPH) × 100. This integrates the catabolic (energy production) and anabolic (biosynthetic) redox systems into a single metric reflecting overall NAD+ metabolic health. The optimal range is 90–350.

About NAD+ metabolism

Nicotinamide adenine dinucleotide (NAD+) is one of the most important molecules in human biology. Present in every living cell, it serves as a critical coenzyme in over 500 enzymatic reactions, functioning as an electron carrier in mitochondrial energy production and as a co-substrate for key regulatory enzymes including sirtuins, PARPs, and CD38.

In its role as an electron shuttle, NAD+ accepts electrons during glycolysis and the citric acid cycle (becoming NADH), which then delivers them to the mitochondrial electron transport chain to drive ATP synthesis. This redox cycling between NAD+ and NADH is fundamental to cellular energy production, and the NAD+/NADH ratio serves as a key indicator of catabolic metabolic health.

The phosphorylated counterpart, NADP+/NADPH, operates in parallel but supports anabolic processes — fatty acid synthesis, cholesterol biosynthesis, and critically, the regeneration of glutathione, the cell's primary antioxidant defence molecule. The balance between these two redox couples provides a comprehensive picture of cellular metabolic function.

NAD+ levels decline with age through multiple mechanisms: increased consumption by CD38 (an enzyme upregulated by chronic inflammation), increased PARP activation due to accumulated DNA damage, and reduced biosynthetic capacity. This decline has been implicated in mitochondrial dysfunction, metabolic disease, neurodegeneration, and accelerated ageing. Restoring NAD+ levels through precursor supplementation (NMN, NR, niacin) has emerged as a major area of longevity and metabolic research.

Analytical technique

All six analytes are measured simultaneously from a single DBS sample using liquid chromatography with tandem mass spectrometry (LC-MS/MS), the gold standard method for NAD+ biomarker measurement. Isotope-labelled internal standards are employed for each analyte to ensure accurate and reproducible quantification across the full dynamic range.

LC-MS/MS provides the sensitivity and specificity required to resolve structurally similar nicotinamide coenzymes (NAD+, NADH, NADP+, NADPH) within a single chromatographic run, while simultaneously quantifying the B3 precursors nicotinamide and nicotinic acid. The Niacin Number composite score is calculated from the measured ratios.

Literature

1. Yoshino J, Baur JA, Imai S. “NAD+ intermediates: the biology and therapeutic potential of NMN and NR.” Cell Metabolism, 2018, 27(3):513–528. 10.1016/j.cmet.2017.11.002
2. Covarrubias AJ, Perrone R, Grozio A, Verdin E. “NAD+ metabolism and its roles in cellular processes during ageing.” Nature Reviews Molecular Cell Biology, 2021, 22(2):119–141. 10.1038/s41580-020-00313-x
3. Verdin E. “NAD+ in aging, metabolism, and neurodegeneration.” Science, 2015, 350(6265):1208–1213. 10.1126/science.aac4854
4. Rajman L, Chwalek K, Sinclair DA. “Therapeutic potential of NAD-boosting molecules: the in vivo evidence.” Cell Metabolism, 2018, 27(3):529–547. 10.1016/j.cmet.2018.02.011
5. Cantó C, Menzies KJ, Auwerx J. “NAD+ metabolism and the control of energy homeostasis: a balancing act between mitochondria and the nucleus.” Cell Metabolism, 2015, 22(1):31–53. 10.1016/j.cmet.2015.05.023