Naringin, a bitter plant compound from grapefruit and bitter orange, is explored as a daily scalp solution for regrowing hair, usually self-formulated or pharmacy-prepared. It is inexpensive and, as far as is known, low in risk, but evidence stops at mice and laboratory-grown cells; with no person yet studied, it is an unproven laboratory lead. Main known risks: solvent-related scalp irritation or allergy, and rare allergy to related citrus compounds. (Full Review)
| Marker | Target | Why |
|---|---|---|
| Hair density (trichoscopy, magnified scalp imaging) | No established target; change from own baseline (hairs/cm²) | Primary efficacy measure |
| Hair pull test | 6 or fewer hairs from about 60 pulled | Flags active shedding |
| Ferritin | 50–100 ng/mL | Iron stores for follicle growth |
| TSH (thyroid-stimulating hormone) | 0.5–2.5 mIU/L | Thyroid cause of shedding |
| 25-hydroxyvitamin D | 40–60 ng/mL | Vitamin D status linked to hair cycling |
| Zinc (serum) | 90–120 µg/dL | Deficiency causes shedding |
| Total testosterone and DHEA-S (an adrenal androgen precursor; women) | Testosterone 15–45 ng/dL; DHEA-S about 100–250 µg/dL (age-adjusted) | Screens androgen excess driving pattern loss |
Cadence: Baseline before starting; photographs and pull test at 8 weeks, then every 3 months for the first year, then every 6–12 months; trichoscopy density at 6 and 12 months; blood tests repeated only if shedding worsens or earlier results were abnormal