What PRP for hair loss is, how well it works, and what the evidence shows.

To make PRP, a small amount of blood is drawn and spun in a centrifuge, which separates the platelets from the red blood cells. The platelet-rich layer is then injected into areas of thinning hair. Platelets release growth factors that are thought to support hair follicles and prolong the growing phase of the hair cycle.

There is no single standard recipe. Studies differ in how many times the blood is spun, whether the PRP is activated before injection, and how many sessions are given.² These differences affect results, which is one reason the evidence is hard to summarize.³

PRP is mostly studied in androgenetic alopecia, the common pattern hair loss that affects both men and women.² A meta-analysis focused on women with pattern hair loss found that PRP increased the density of thick, terminal hairs compared with control treatments.⁵

For alopecia areata, an autoimmune cause of patchy hair loss, it is unclear whether PRP works better than steroid injections.² PRP does not regrow hair in areas where follicles have been permanently lost, such as scarred or completely bald scalp.

• Sessions: In a network meta-analysis, more sessions given at shorter intervals were linked to better results.³
• Treatment: Blood is drawn, processed, and injected across the thinning scalp, which usually takes under an hour.
• Recovery: Mild tenderness, pinpoint bleeding and temporary scalp soreness are common for a day or two.
• Results: Changes develop gradually over months, and ongoing treatment is usually needed to maintain them.

PRP is often added to established treatments rather than used alone. In a meta-analysis of 6 randomized trials and 343 participants, PRP combined with minoxidil improved hair density and thickness more than either treatment alone.⁴ In a network meta-analysis, PRP, finasteride and minoxidil produced roughly similar gains in hair count, although the quality of evidence for PRP was very low.⁶

A combined approach called PRP hybridized adipose transplant (PHAT) mixes PRP with a person's own fat before injecting it into the scalp. In a 3-patient case series, hair density improved after a brief period of shedding, with new growth starting around 4 weeks and results maintained at 6 months to 1 year.⁷ This is early evidence, and larger studies are needed.⁷

PRP aims to strengthen existing hairs, while a hair transplant moves healthy follicles from the back of the scalp to thinning areas. In a meta-analysis of surgical hair restoration, graft survival averaged 85.0% - 93.1% in nonscarring hair loss, and patient satisfaction averaged 89.7% - 97.0%.⁸ PRP and fat grafting have also been used to improve scalp and hair quality before a transplant.⁷

PRP uses a person's own blood, so allergic reactions and disease transmission are not expected. Across controlled trials, no serious adverse events were reported, and side effects were mostly temporary pain, redness or swelling at injection sites.^1,2

• Best Protocol: The ideal preparation, dose and session schedule have not been established.³
• Quality: Most evidence is rated low or very low quality.^2,6
• Durability: Long-term results after treatment stops are not well studied.¹