NAD+
Also known as: Nicotinamide Adenine Dinucleotide
What Does NAD+ Measure?
NAD+ (Nicotinamide Adenine Dinucleotide) is a coenzyme found in every living cell that measures the availability of a critical molecule involved in hundreds of metabolic reactions. Blood or cellular NAD+ levels reflect the body's capacity to generate energy, repair DNA, regulate gene expression, and maintain cellular health. NAD+ exists in two forms — the oxidized form (NAD+) and the reduced form (NADH) — and the ratio between them serves as an indicator of metabolic activity and mitochondrial function. Testing can be done via blood samples measuring whole-blood or intracellular NAD+ concentrations, though standardized clinical testing is still evolving.
Why Does NAD+ Matter?
NAD+ levels naturally decline with age — by midlife, most people have roughly half the NAD+ they had in youth — and this decline is now recognized as a key driver of the aging process itself. Low NAD+ impairs mitochondrial function, reduces the body's ability to repair damaged DNA, weakens immune responses, and disrupts circadian rhythms. These downstream effects are linked to increased risk of metabolic diseases, neurodegeneration, cardiovascular disease, and reduced resilience to physical and psychological stress. Monitoring NAD+ offers a window into biological aging speed and metabolic vitality that standard panels often miss.
Normal Ranges
Males
20–50 µmol/L (whole blood); optimal longevity range often cited as 40–60 µmol/L
Females
20–50 µmol/L (whole blood); optimal longevity range often cited as 40–60 µmol/L
Children
Generally higher than adults; specific pediatric reference ranges not yet standardized
Causes of High Levels
- NAD+ precursor supplementation (NMN, NR, or niacin/vitamin B3 at therapeutic doses)
- Regular aerobic exercise and high-intensity interval training (HIIT), which upregulate NAD+ biosynthesis
- Caloric restriction or intermittent fasting, which activates NAMPT enzyme and boosts NAD+ production
- Ketogenic diet or prolonged fasting states that shift metabolism toward NAD+-dependent pathways
- Young biological age — NAD+ is naturally higher in youth and declines progressively with aging
- Genetic variants that favor efficient NAD+ biosynthesis via the salvage pathway
Causes of Low Levels
- Aging — NAD+ declines approximately 50% per decade after age 30–40 due to reduced biosynthesis and increased consumption
- Chronic inflammation and immune activation, which upregulate CD38 (an NAD+-consuming enzyme)
How to Improve Your NAD+
Diet
- Increase niacin-rich foods: chicken breast, tuna, salmon, beef liver, peanuts, and mushrooms provide tryptophan and niacin as NAD+ precursors
- Eat tryptophan-rich foods (turkey, eggs, dairy, legumes) as the body can convert tryptophan to NAD+ via the de novo synthesis pathway
- Practice time-restricted eating or intermittent fasting (16:8 protocol) to activate NAMPT and boost endogenous NAD+ production
- Reduce alcohol intake to below 1 drink/day, as alcohol heavily competes with NAD+ in metabolic pathways
- Include polyphenol-rich foods (green tea, blueberries, resveratrol-containing foods) that support sirtuin activity alongside NAD+
Supplements
- NMN (Nicotinamide Mononucleotide): 250–500 mg/day orally, a direct NAD+ precursor with strong clinical evidence for raising blood NAD+ levels
- NR (Nicotinamide Riboside): 300–500 mg/day, another well-studied precursor shown to raise whole-blood NAD+ by 40–90% in clinical trials
- Niacin (Nicotinic Acid): 250–500 mg/day as a cost-effective NAD+ precursor; note flushing side effect at higher doses
- Resveratrol: 250–500 mg/day to activate SIRT1 and enhance the effectiveness of available NAD+
Related Biomarkers
Frequently Asked Questions
Can you test NAD+ levels through a standard blood test?
NAD+ testing is not yet part of standard clinical blood panels, but it is available through specialized functional medicine labs and direct-to-consumer longevity testing companies. Testing typically measures whole-blood or intracellular NAD+ concentrations. While reference ranges are still being refined, these tests can give you a useful baseline, especially if you're considering supplementation and want to track changes over time. Always interpret results alongside a healthcare provider familiar with NAD+ biology.
What is the difference between NMN and NR for boosting NAD+?
Both NMN (Nicotinamide Mononucleotide) and NR (Nicotinamide Riboside) are direct precursors to NAD+ and have been shown in human clinical trials to significantly raise blood NAD+ levels. NR must first be converted to NMN before becoming NAD+, making NMN one step closer in the biosynthesis pathway. Some researchers argue NMN is more efficient, while others show comparable results with NR. Both are generally well-tolerated and safe. NR tends to be slightly more widely studied in humans, while NMN has gained popularity due to prominent longevity researchers like Dr. David Sinclair advocating its use. Practically, either can be effective, and the best choice may depend on individual response, cost, and availability.
Why does NAD+ decline with age?
NAD+ levels decline with age due to a combination of reduced production and increased consumption. As we age, the activity of NAMPT (the key enzyme in the NAD+ salvage pathway) decreases, meaning the body recycles less NAD+ from its breakdown products. Simultaneously, aging increases chronic low-grade inflammation, which activates CD38 — a highly efficient NAD+-consuming enzyme — leading to accelerated depletion. Additionally, accumulated DNA damage with age triggers excessive PARP enzyme activity, which uses NAD+ as a substrate for repair. The net result is that by age 50–60, many people have NAD+ levels 40–60% lower than in their 20s.