NAD+ injections: mechanism, evidence, and why the dose matters

NAD+ is not a peptide — it's a coenzyme. It sits at the centre of cellular energy metabolism and DNA-repair signalling, and its levels decline steadily with age. Subcutaneous NAD+ injection has emerged as the most direct way to restore depleted levels. Understanding why the dose matters — and why the common "micro-dose" protocols don't — is key to using NAD+ effectively.

What NAD+ is#

NAD+ (nicotinamide adenine dinucleotide) is a coenzyme found in every cell. It exists in two states — the oxidised form (NAD+) and the reduced form (NADH) — and the ratio between them is one of the most important signals of cellular metabolic state. NAD+ serves two main functions:

• Electron transport in ATP production. Cellular respiration requires NAD+ to accept electrons during glycolysis, the citric acid cycle, and beta-oxidation of fats. Without adequate NAD+, ATP production slows.
• Substrate for sirtuins, PARPs, and CD38. A set of enzymes involved in DNA repair, mitochondrial biogenesis, and longevity signalling (the sirtuin family) uses NAD+ as a substrate. So does PARP (DNA damage response) and CD38 (immune and metabolic signalling).

Tissue NAD+ levels decline progressively with age — roughly 50% reduction from young-adult baselines by age 60 in muscle and skin. That decline correlates with reduced mitochondrial function, increased DNA damage accumulation, and diminished cellular resilience. The supplementation rationale is direct: restore NAD+, restore the downstream biology.

Why injectable delivery#

Oral NAD+ precursors (nicotinamide riboside, nicotinamide mononucleotide) are widely marketed. They work — but the efficiency is limited by first-pass metabolism. Most orally consumed NAD precursors are degraded in the gut or liver before reaching peripheral tissues. Oral supplementation raises NAD+ modestly but tops out well below the levels achievable with parenteral delivery.

Subcutaneous NAD+ injection bypasses first-pass metabolism. The peptide enters the systemic circulation directly and distributes to peripheral tissues. Subcutaneous delivery is less aggressive than IV (slower peak, longer tail) and doesn't require clinical administration.

IV NAD+ infusion is the aggressive end of the delivery spectrum. Clinic-administered 250 mg to 1,000 mg infusions over 2–4 hours produce high peak levels but are substantially more expensive per milligram and logistically demanding.

For most research-use protocols, subcutaneous NAD+ at 50–200 mg 2–3× weekly strikes the efficacy-to-cost balance.

Dosing (and why many protocols get this wrong)#

NAD+ is dosed in milligrams, not micrograms. Most peptide protocols work at doses measured in micrograms; NAD+ is a clear exception. The therapeutic range is at least 1,000× higher than typical peptide doses:

• Starting dose: 50 mg subcutaneously, 2–3× weekly
• Standard dose: 100 mg subcutaneously, 2–3× weekly
• Maximum common dose: 200 mg subcutaneously, 2–3× weekly
• Typical cycle length: 8–12 weeks, with or without off-cycle

Doses below 10 mg per injection are common in consumer-marketed "NAD nasal sprays" or "NAD drops" — but these are well below the threshold needed to meaningfully affect tissue NAD+ levels. Effective parenteral NAD+ dosing requires milligrams per dose; anything in the microgram range is effectively cosmetic.

Reconstitution math: a 500 mg NAD+ vial (pen format) reconstituted with 5 mL of bacteriostatic water gives 100 mg/mL. A 100 mg dose = 1 mL = 100 syringe units. The peptide calculator handles any vial size.

What users typically notice#

NAD+ effects are cumulative. Users don't report acute post-injection effects (beyond occasional transient warmth or mild flushing at higher doses). The benefits show up across weeks:

• Weeks 1–2: mild subjective energy improvement, possibly better sleep quality
• Weeks 3–6: more stable energy across the day, reduced afternoon fatigue
• Weeks 6–12: cognitive clarity improvements, some users report skin texture or appearance changes
• Longer-term: cumulative benefits to metabolic markers and perceived vitality, with individual variation

The effects are subtle compared to, say, the appetite suppression of a GLP-1 agonist or the sleep quality of a GH-axis peptide. NAD+ is a metabolic foundation rather than an acute signal.

Side effects#

NAD+ is well tolerated at typical research-use doses:

• Flushing or warmth in the hour after injection (more common at doses >100 mg)
• Mild transient nausea in some users
• Injection-site irritation (mild, transient)
• Occasional headache particularly if dehydrated

IV NAD+ infusions have a more pronounced side-effect profile — the "infusion rush" of chest pressure, anxiety, and flushing is well documented and is why clinical IV protocols use slow titration.

Regulatory status#

NAD+ sits in regulatory grey zone. Oral NAD+ precursors (nicotinamide riboside, NMN) are sold as dietary supplements in most jurisdictions. Injectable NAD+ has no FDA or EMA approval as a medicine for any indication. Legemiddelverket has not authorised injectable NAD+. Clinic-administered IV NAD+ exists in many markets operating under varying regulatory frameworks.

Syntho stocks NAD+ in pen (500 mg) and vial (1000 mg) formats for research-use access.

The practical framework#

Three factors determine whether NAD+ fits a protocol:

1. Goals. NAD+ is a metabolic-foundation peptide. For energy, cognition, and generalised cellular-health goals, it fits naturally. For acute body-composition or recovery goals, other peptides are better matches.
2. Dose commitment. NAD+ requires milligrams, not micrograms. Cost per cycle is meaningfully higher than for most peptide protocols. For users expecting peptide-sized monthly cost, NAD+ breaks the budget.
3. Cycle integration. NAD+ pairs well with GH-axis peptides (cellular energy + growth signal) and with longevity-focused protocols. It doesn't typically stack with acute recovery or weight-loss peptides because the mechanism targets different biology.

For protocol planning, Syntho's questionnaire handles screening. The peptide calculator handles dose math at the appropriate mg scale. For the related longevity context, see the Epitalon guide.

NAD+ is the foundation-level supplementation peptide. It works on a longer timescale and at a different dose magnitude than most peptides in the catalogue. Use it when the goal is cellular-energy foundation rather than acute effect — and accept the mg-scale dosing discipline that effective NAD+ protocols require.