NAD+

NAD+ (Nicotinamide Adenine Dinucleotide) is a coenzyme found in every living cell, playing a central role in cellular energy metabolism (as a carrier in the electron transport chain) and in DNA damage repair (as a required substrate for sirtuins and PARP enzymes). Research over the past two decades has established that NAD+ levels decline with age, by roughly 50% between ages 40 and 60 in most tissues, and that restoring NAD+ levels in aged animal models produces significant metabolic and longevity benefits.

The connection to aging was substantially advanced by David Sinclair's lab at Harvard, which demonstrated that NAD+ supplementation reversed several markers of aging in mice, including muscle function, endurance, and mitochondrial density. Sirtuins, the longevity proteins activated by NAD+, regulate gene expression, mitochondrial biogenesis, and inflammatory pathways. The more NAD+ is available, the more active sirtuins can be. Similarly, PARP enzymes (DNA repair proteins) consume NAD+ rapidly during DNA damage response, and chronically elevated DNA damage in aged cells creates a drain on NAD+ pools.

Injectable NAD+ bypasses GI absorption limitations that constrain oral supplementation. Oral precursors (NMN, NR, niacin) must be converted to NAD+ intracellularly, with variable conversion efficiency. Subcutaneous NAD+ injection delivers NAD+ directly to the bloodstream, where it is available for cellular uptake. Subcutaneous doses range from 100 to 500 mg per injection. IV infusions deliver higher doses (500–1,000 mg) more rapidly and are done in clinical settings.

Reconstituting NAD+ for injection requires bacteriostatic water. NAD+ is light-sensitive, store the vial away from light both before and after reconstitution. A common preparation is 500 mg in 5 mL BAC water, giving 100 mg/mL. A 100 mg dose would be 1 mL (100 units on U-100). Inject subcutaneously in the abdomen. Unlike peptides, NAD+ degrades faster in solution; some researchers prefer preparing smaller volumes and using within 7–14 days rather than the full 28-day window.

The clinical evidence for injectable NAD+ in humans is still developing. Published human trials are small, and most longevity benefits have been demonstrated in animal models. What is well-established is that NAD+ levels are measurable and decline with age, and that subcutaneous injection does raise circulating NAD+ levels. The subjective reports from users, improved energy, better sleep, mental clarity, are consistent enough to be notable, but await rigorous double-blind trial confirmation.