PDRN is a salmon- or trout-derived DNA injection placed into the thinning scalp to improve blood supply, calm inflammation, and support hair follicles. Reported gains in hair thickness and density are modest, with a possible slowing of further thinning. It is generally well tolerated and works best for early thinning rather than established baldness. (Full Review)

Protocol

Route

Scalp injection

Intradermal / intra-perifollicular across the thinning area

Schedule

Sessions 2–4 weeks apart

Series over several months; the main hair study used 12 weekly sessions

Approach

Monotherapy or with PRP

Combining with platelet-rich plasma produced greater thickness gains

Time to effect

Hair density

~1 month

Density changes begin to appear around one month and accumulate thereafter

Hair thickness

~1 month

Diameter changes begin to appear around one month after starting

Fair trial

3–6 months

Several sessions over roughly 3–6 months before judging response

Benefits

Low: Increased hair density; increased hair thickness

Speculative: Slowed progression / follicle stabilization; improved scalp skin quality

Contraindications

Active scalp infection or inflammation

Significant fish or seafood allergy

Pregnancy or breastfeeding (untested)

Key Interactions

Anticoagulants and antiplatelet drugs (warfarin, apixaban, clopidogrel)

OTC blood thinners (aspirin, ibuprofen and other NSAIDs, high-dose fish oil)

Antiplatelet supplements (high-dose fish oil, vitamin E, ginkgo)

Risk & Side Effects

Medium: Injection-site reactions

Low: Allergic / hypersensitivity reaction; infection at injection sites

Speculative: Temporary shedding after treatment; unknown long-term effects of repeated injection

Monitoring

Marker	Target	Why
Ferritin (iron stores)	≥ 40–70 ng/mL	Low iron stores worsen hair shedding and can blunt response
Vitamin D (25-hydroxyvitamin D)	40–60 ng/mL	Deficiency is linked to hair loss and impaired follicle cycling
Thyroid-stimulating hormone (TSH)	1.0–2.0 mIU/L	Thyroid dysfunction is a common reversible cause of hair loss
Zinc	Mid-to-upper reference range	Deficiency contributes to hair shedding and poor tissue repair
Hemoglobin / complete blood count	Within normal range	Identifies anemia as a contributor to diffuse hair loss

Cadence: Baseline, around 3 months, then every 6 months

Qualitative Assessment

Reduced daily hair shedding on the pillow, in the shower, or on a brush
Subjective improvement in scalp coverage, "thickness," and styling
Improved scalp comfort with less itching or irritation
Overall satisfaction and confidence in appearance

PDRN for Hair Regrowth

Protocol

Benefits

Risk & Side Effects

Monitoring

Qualitative Assessment