The short answer
It supports what you still have
PRP for hair loss supports what you still have: in androgenetic hair loss, follicles do not disappear suddenly. They miniaturize — producing progressively finer, shorter, weaker hairs over years. PRP delivers concentrated growth factors into the scalp to support those follicles while they are still viable.
The pooled evidence is genuinely positive. A meta-analysis of 9 trials in 257 patients, published in the International Journal of Trichology, found a standardized mean change in hair density of 1.21 (95% CI 0.59–1.82, p < 0.01). That figure measures change from each patient's own baseline, not a comparison with placebo; against saline, the gain is real but modest, as the evidence-quality section below explains.
Book a scalp assessmentMechanism
What the injection is doing
The injection delivers concentrated platelets from your own blood: a small amount of blood is drawn and processed to concentrate the platelet fraction. Platelets carry growth factors that influence the hair cycle — including signaling that helps push follicles from the resting phase back into active growth, and that supports the small blood vessels feeding them.
It is your own blood, so there is no drug to tolerate and no daily routine to maintain, which is a large part of the appeal for people who cannot or would rather not take oral medication. What a session involves in practice is set out on our PRP hair restoration page. In short, the injection puts your own platelet growth factors where the follicles are.
The number that should decide where you go
Double-spin versus single-spin
Double-spin versus single-spin preparation is the variable most worth asking about.
PRP is not a standardized product. In the same International Journal of Trichology meta-analysis, preparation method split the results dramatically:
| Preparation | Effect on hair density (SMCC) | Heterogeneity |
|---|---|---|
| Double-spin | 2.66 | I² = 0% |
| Single-spin | 0.52 | I² = 46% |
That is a five-fold difference in effect. The three double-spin trials agreed with each other closely, while the six single-spin trials varied more. The subgroups are small, but preparation may explain much of why PRP works well in one clinic and poorly in another.
The evidence
What else the research shows
The research also shows that platelet concentration, session schedule and preparation all shape results. A 2025 systematic review in Cureus covering 11 studies and 684 participants, 514 men and 170 women, found the majority reporting positive outcomes, with a dose relationship worth noting: in one included trial, the group receiving the highest platelet concentration saw a 42% increase in hair density. Most protocols used three sessions at monthly intervals.
- Most, but not all, placebo-controlled trials in the review showed increased hair density or shaft thickness; at least two found no significant difference from saline.
- Differences reach statistical significance most consistently at three and six months.
- In one split-scalp trial, density and thickness rose with both activated and non-activated PRP; the activated side did better on density at four months and thickness at six.
- Platelet concentration appears to matter — higher counts produced larger density gains in the reviewed trials.
- Trial protocols cluster around three monthly sessions, though some ran to six. No single regimen has emerged as definitively optimal.
PRP is also used to support hair transplantation rather than compete with it. A 2025 Cureus review of three controlled studies in 217 patients found PRP associated with better outcomes across all three; in one of the included trials, graft survival at six months was 82.2% with PRP versus 74.0% without (p = 0.002), with earlier onset of growth — 17.7 days versus 20.1 (p = 0.015).
The honest summary: the effect is real and reasonably large, the optimal schedule is still unsettled, and how your PRP is prepared matters more than almost any other variable. Every review cited here names preparation variability as a major reason results differ between clinics.
Evidence quality
How strong is the evidence for PRP for hair loss, and is it safe?
The evidence for PRP for hair loss is encouraging but not yet high quality. A 2023 systematic review and meta-analysis from Italy's National Institute of Health pooled 27 controlled trials with 1,117 people, 18 of them in androgenetic (pattern) hair loss (Cruciani et al., 2023). Compared with saline injections, PRP increased hair density by an average of about 25.6 hairs per square centimeter over medium-term follow-up.
The same review rated that evidence as low quality, because trials differed in how PRP was prepared and given and several carried a risk of bias. That matches the double-spin versus single-spin finding above: when the product itself varies, so do the results. The review's conclusion was that benefit is supported by limited, mostly low-quality evidence, which is a fair way to set expectations.
On safety, the review found no serious adverse events related to PRP injections. Because PRP is made from your own blood, there is no foreign drug to react to, though the injections themselves can cause short-lived discomfort. PRP for hair loss is not an FDA-approved drug treatment for hair loss; it is an in-office procedure, which is one more reason to have it done by a physician-led team.
Before you treat
Find out why you are losing hair first
Find out why you are losing hair first, because not all hair loss is genetic and the treatable causes are common. Injecting a scalp while ignoring a thyroid problem wastes both the treatment and the money.
- Low ferritin — a common reversible contributor to shedding, particularly in menstruating women, and worth checking directly because a normal blood count does not rule it out
- Thyroid dysfunction — both underactive and overactive thyroid can cause hair loss
- Hormonal change — perimenopause, post-partum shifts and androgen changes all affect the hair cycle
- Rapid weight loss — including on GLP-1 medication, where shedding has been reported and is easier to manage if someone is watching for it
- Vitamin D deficiency and inadequate protein intake
Protocol Health's scalp assessment includes bloodwork for these causes before PRP is offered, and because this is a hormone clinic, that conversation happens here rather than being referred out. Testosterone's relationship with hair is its own subject — we cover it in does TRT cause hair loss.
Candidates
Who it suits, and who it does not
PRP suits people with thinning hair and living follicles, and it does not suit bare areas or anyone expecting fast regrowth.
- Good fit: early-to-moderate thinning with living follicles — crown and mid-scalp in men, widening part in women
- Good fit: increased shedding after pregnancy, illness, stress or rapid weight loss
- Good fit: people supporting a hair transplant result, or who cannot tolerate daily medication
- Poor fit: areas that are completely bare — grafting, not PRP, is what puts hair there
- Poor fit: anyone expecting visible regrowth within a few weeks
PRP is used across our practice for more than hair — the joint and tendon applications are covered on PRP for joint, tendon and cartilage restoration, and the overall approach on our PRP therapy page.
Practicalities
What a course looks like
A course of PRP for hair loss looks like an assessment, a series of sessions over several months, and a reassessment.
Assessment and bloodwork
Assessment and bloodwork come first: examine the pattern of loss and test for thyroid, iron and hormonal causes before assuming it is genetic.
Draw and preparation
A small blood draw in the office, processed using a double-spin protocol — the preparation the comparative evidence supports.
Scalp injection
A series of small injections across the thinning areas, with topical numbing. Most patients find it very tolerable.
The series
The series is sessions spaced over several months rather than a one-off. Trials mostly used three monthly sessions, and some used up to six; you should be told your expected schedule before you begin.
Review and maintenance
Density is reassessed before planning maintenance treatment.
You can see the whole pathway from first consultation to ongoing care on our how it works page, and Dr. Dentico's credentials on our team page. The course runs over months, not a single visit.
After the injection
Side effects and aftercare of PRP for hair loss
Side effects of PRP for hair loss are usually minor, and aftercare comes with specific instructions. Most people have scalp tenderness, mild swelling or pinpoint bleeding at the injection sites for a day or two. A dull headache or a tight feeling in the scalp is also common and usually settles quickly. Your clinician will give you specific aftercare instructions, typically covering when you can wash your hair, whether to avoid anti-inflammatory painkillers for a short window, and when to resume hair products or minoxidil.
Before-and-after photos are useful only if they are taken under the same lighting and angles, at three and six months, which is when trials most consistently show a difference. Density is assessed at baseline and reassessed before maintenance, so your own results can be judged honestly rather than against someone else's marketing images.
PRP for hair loss can increase density where follicles are still alive, with the clearest results at three and six months and a double-spin preparation. The average benefit over saline is modest, the evidence is rated low quality, and it does not regrow a bare scalp. Bloodwork for thyroid, iron and hormonal causes comes first.
FAQ
Frequently Asked Questions
How many PRP sessions do I need for hair?
A series over several months, followed by maintenance. Anyone quoting a single session as a complete treatment is not describing how the trials were run.
When will I see results?
Improvement is usually measured first as reduced shedding, then as increased density over months. Trials report significant differences at three and six months, not weeks.
Does PRP work for women?
It can. Women were included in the PRP trials, although most participants were men. Female pattern thinning is treated here with the same seriousness as male pattern loss, and hormonal and iron causes are often more relevant in women.
Will PRP regrow hair on a bald area?
No. PRP supports follicles that are still viable. A completely bare scalp needs grafting, and we will tell you that rather than sell you a course that will not work.
Does PRP for hair loss work?
For many people with early-to-moderate pattern thinning, yes, modestly. A 2023 meta-analysis found PRP increased hair density compared with saline injections, but rated the evidence low quality because trials and preparation methods varied. It does not regrow hair where follicles are gone.
Can I combine PRP with minoxidil or finasteride?
Yes — PRP is commonly used alongside them rather than instead of them, and combination approaches are typical in practice.
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Book a scalp assessmentThis article is educational and is not medical advice. It does not diagnose, prevent, treat or cure any condition. Talk with a licensed clinician about your own situation.