Applying NMN to the scalp to regrow hair is an early, largely theoretical idea, not a proven treatment. Support rests on a single laboratory and mouse study; no human trials exist, and whether it penetrates skin is doubtful. Safety looks favorable, with local irritation and poor product quality the main concerns. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Ferritin | 40–70 ng/mL | Low iron stores are a common, correctable driver of hair shedding that limits response |
| 25-hydroxy vitamin D | 40–60 ng/mL | Low vitamin D is associated with several hair-loss patterns and is easily corrected |
| TSH | 0.5–2.5 mIU/L | Thyroid dysfunction causes diffuse hair loss that will not respond to a follicle-directed topical |
| Serum zinc | 90–120 µg/dL | Zinc deficiency impairs the hair-growth cycle |
| Total and free testosterone / DHT | Sex- and age-appropriate reference | Helps confirm an androgen-driven pattern that NMN's mechanism targets |
Cadence: Baseline before starting; abnormal labs re-checked ~3 months after correction, otherwise every 6–12 months as clinically indicated. Hair tracked with standardized scalp photos at baseline, 3 and 6 months, then every 6 months.