PRP: how a session goes

“We’ll use your own blood.” Put like that, PRP sounds reassuring: nothing foreign to your body. Then you hear the rest. A blood draw, a centrifuge, and small injections into your scalp, repeated for months. Before you say yes, you want to know how it goes and whether it really works.

What is PRP?

PRP stands for platelet-rich plasma. Plasma is the liquid part of your blood; platelets are the small cells that help wounds heal. Once prepared, PRP usually contains two to five times more platelets than normal blood¹.

The idea is that platelets release growth factors that might extend the hair’s growth phase and support the small blood vessels around the follicle. These are hypotheses. A fact sheet from the American Academy of Dermatology (AAD), written for dermatology residents, admits that the mechanism is still poorly understood, and that in the US no PRP preparation device has been cleared for hair loss¹.

How a session goes

The AAD describes it in three steps²:

1. A small amount of blood is drawn, as for a blood test.
2. A machine separates the blood into parts; the plasma is kept.
3. That plasma is injected into the skin where the hair is thinning.

The whole thing takes about 10 minutes, and usually there’s no downtime². Spanish dermatologists mention 2 to 4 mL of plasma injected per session³.

Everything varies from one clinic to the next: the kit used, the number of spins in the centrifuge, whether a product is added to “activate” the platelets. There’s no agreed method¹. Two PRP sessions with two different doctors aren’t necessarily the same treatment.

After the session

The most common side effects appear straight away and clear up on their own within 24 hours: pain, swelling, a little bleeding, redness, sometimes light-headedness with a drop in blood pressure. Pain is the most commonly reported¹. To limit light-headedness, the AAD fact sheet suggests doctors ask patients to arrive well hydrated and after a meal¹.

On a forum, a 29-year-old woman and another member, a regular at sessions, describe very different experiences⁴:

Testimonials posted on the HairLossTalk forum⁴.

How many sessions?

The schedule most often described is the same at the AAD and among Spanish dermatologists: one session a month for 3 months, then one every 3 to 6 months for maintenance²³. This schedule rests on expert opinion, the lowest level of evidence in the Spanish consensus³. Other teams space the first sessions 1 to 2 months apart, or suggest more frequent maintenance¹.

So PRP isn’t a one-off. If you stop, the effect doesn’t last forever: in the study described below, hair loss came back in some patients a year after their last session⁵. According to the AAD, you may notice less shedding within the first few months².

What the studies show

The most telling study compares PRP with a placebo on the same people. A team treated 23 men aged 19 to 63 with mild to moderate inherited baldness. Each received PRP on one half of the scalp and a placebo on the other, over 3 sessions 30 days apart. An assessor who didn’t know which half had received what counted the hairs. Twenty men completed the study⁵.

In terms of density, the treated half gained 45.9 hairs per cm², while the placebo half lost 3.8. No side effects were noted⁵. But it’s a small study, run by a single team, using two different preparation devices. And in 4 men, hair loss returned after 12 months, more clearly around 16 months after the last session; they were treated again⁵.

In women, the results are less clear. A small double-blind pilot study found no significant difference in hair count or hair mass between PRP and a saline placebo. Yet 13.3% of the treated women, against none on placebo, felt their hair had improved substantially⁶. How it feels and what’s measured don’t always agree.

A recent review of several studies, cited by the AAD, concludes that PRP increases hair count, thickness and density compared with placebo in androgenetic alopecia¹. That’s the type of hair loss with the strongest evidence. For scarring alopecias, the evidence is still at the level of individual cases¹.

The limits to know about

PRP isn’t cleared for hair loss in the US, and there’s no agreed protocol¹. The Spanish consensus lists it among second-line treatments for female pattern hair loss, and describes its efficacy as “proven but variable” alongside other treatments³. The AAD presents it as an option for people who can’t tolerate the usual treatments or don’t improve with them¹.

Two more points matter. First, PRP won’t fix hair loss that has another cause: an iron or vitamin deficiency is found with a blood test, not treated with an injection. Second, it can be combined with something else. The AAD cites studies in which microneedling combined with PRP helps hair growth².

Before you start, ask a dermatologist whether your hair loss is the right type for this treatment: here’s which doctor to see. Your doctor can also suggest a treatment to pair it with.

Judging your sessions in photos

With PRP, the question isn’t whether it works in general, but whether it works for you. Studies count hairs in a marked area, always in the same spot. The mirror doesn’t mark anything.

Take a first set of photos before your first session: parting, crown, temples, in the same room and the same light. Then retake them every week. With Calvap, the ghost overlay shows your previous photo so you can line up the same framing, and each session goes in the journal, on the same timeline as your photos. At 3 months, then at 6 months, you compare images that are truly comparable and decide whether to carry on with the facts in front of you.