How PRP Therapy Works to Regrow Thinning Hair
How does platelet-rich plasma therapy work as a hair loss treatment?
Your own blood carries the repair crew, and this treatment concentrates it and puts it where your follicles actually live. A clinician draws a small volume, spins out the red cells, and injects the platelet-heavy fraction into the layer of scalp where the follicle's control centre sits. Nothing about that is instant, so what you're buying is a signal that plays out over months, not a result you'll see next week.
- Draw: 20 to 60 millilitres of your blood goes into tubes holding an anticoagulant.
- Spin: a centrifuge drops the red cells out and leaves the plasma fraction carrying the platelets.
- Concentrate: a second spin lifts platelet levels to roughly two to seven times what's in circulation.
- Inject: the concentrate goes 1.5 to 2.5 millimetres deep across a grid spaced about a centimetre apart.
- Signal: the platelets degranulate and flood the dermal papilla with growth factors that restart the growing phase.
Platelet-rich plasma therapy concentrates your own platelets to two to seven times blood baseline and places them 1.5 to 2.5 millimetres into the dermis, where the released growth factors push miniaturised follicles back toward an active growing phase over three to six months.
What is actually inside a platelet concentrate, and which growth factors act on hair follicles?
Most people picture the plasma as the medicine, and that's the wrong way round. The plasma is just the vehicle; the work is done by the protein cargo packed inside the platelets riding in it. Get the concentration wrong in either direction and you've been given a different treatment entirely.
- Alpha granules: 50 to 80 per platelet, holding the signalling proteins that reach the papilla.
- Target concentration: most protocols aim for about one million platelets per microlitre.
- Release window: over 95 percent of the stored proteins are out within the first hour.
- Leukocyte choice: scalp work increasingly favours leukocyte-poor over inflammatory leukocyte-rich preparations.
Each platelet carries 50 to 80 alpha granules of growth factors, and scalp protocols concentrate them to two to seven times the normal 150,000 to 400,000 per microlitre, with roughly one million per microlitre treated as the working target.
How is a sample of whole blood turned into an injectable concentrate?
The whole process comes down to density: heavy things sink, and a centrifuge just makes that happen in minutes instead of hours. What separates a moderate preparation from a strong one is whether your blood gets spun once or twice.
- Draw and anticoagulate: 20 to 60 millilitres into citrate tubes, since heparin would blunt platelet function.
- Soft spin: roughly 1,000 to 1,500 g for five to ten minutes stratifies red cells, buffy coat and plasma.
- Collect: the plasma plus buffy coat comes off, which is where a single-spin protocol stops.
- Hard spin: a second run at 2,000 to 3,000 g pellets the platelets so the platelet-poor plasma can go.
- Resuspend: the pellet goes back into 3 to 8 millilitres, activated with calcium or by collagen in your dermis.
A double-spin protocol running roughly 1,000 to 1,500 g then 2,000 to 3,000 g turns a 20 to 60 millilitre draw into 3 to 8 millilitres of concentrate at four to seven times platelet baseline, while a single soft spin lands lower and keeps the white cells in.
What happens inside a hair follicle in the days and weeks after injection?
Think of the injection as feeding the roots rather than the leaves. Placed correctly, the proteins diffuse to the bulge and the dermal papilla and tell the follicle to build a thicker shaft next time round. That's why the hair already on your head won't change; what changes is what grows after it.
- Injection depth: placed 1.5 to 2.5 millimetres down, just above bulbs sitting 2 to 4 millimetres deep.
- Survival pathways: Wnt, ERK and Akt signalling keeps papilla cells from shutting the cycle down.
- Blood supply: perifollicular vessel density rises in the weeks after treatment, feeding each follicle better.
- Early shedding: some people shed briefly as resting follicles release retained club hairs.
Concentrate placed 1.5 to 2.5 millimetres deep reaches bulbs sitting 2 to 4 millimetres down, where Wnt, ERK and Akt signalling plus new perifollicular vessels thicken the next shaft the follicle grows, an advantage that fades over six to twelve months.
How does the treatment interact with the anagen, catagen and telogen phases of hair growth?
Pattern hair loss isn't about losing follicles at the start, it's about the balance between growing and resting sliding the wrong way. Every honest measure of whether this treatment worked comes back to whether you moved that ratio.
| Phase | Healthy scalp | Thinning scalp |
|---|---|---|
| Anagen (2 to 6 years) | 85 to 90 percent | Shorter each cycle, fraction falls |
| Catagen (2 to 3 weeks) | About 1 percent | Broadly unchanged |
| Telogen (about 3 months) | 10 to 15 percent | Rises, ratio drops below 12 to 1 |
| Shaft produced | Terminal, full thickness | Finer and shorter, eventually vellus |
A healthy scalp holds 85 to 90 percent of its follicles in anagen against 10 to 15 percent in telogen, roughly a twelve to one ratio, and the treatment works by shortening telogen and extending anagen rather than by changing the follicle's genetics.
Why do preparation protocols produce such different results between providers?
Here's the part that quietly costs people money: two clinics can sell you the same named treatment and hand you products that differ fivefold. Bench comparisons of commercial kits have found final platelet counts from barely above whole blood to more than eight times baseline out of the same donor. If your provider can't tell you which end of that range they produce, you don't know what you're paying for.
Commercial preparation systems produce final platelet concentrations ranging from barely above whole blood to more than eight times baseline from the same donor, so a provider who cannot state their system, its validated concentration, whether white cells are retained and how many sessions the course includes is not running a defined protocol.
What does a single treatment session involve from blood draw to final injection?
Most of your appointment is spent waiting on a centrifuge rather than being injected. Budget 45 to 90 minutes, expect sharp stinging pressure rather than nothing at all, and plan on normal activity the same day.
- Baseline photography: fixed-lighting images first, because without them there's no way to judge the course later.
- Draw and process: a few minutes at the arm, then 10 to 20 minutes of spinning and preparation.
- Numbing: topical cream 20 to 30 minutes ahead, with a ring block if you can't tolerate repeat needling.
- Injection: 0.05 to 0.1 millilitres per point across 40 to 80 points about a centimetre apart.
- Aftercare: no washing that day, 24 to 48 hours off heat and heavy exercise, and no anti-inflammatory painkillers.
A session runs 45 to 90 minutes and delivers roughly 3 to 8 millilitres of concentrate across 40 to 80 points spaced about a centimetre apart at 0.05 to 0.1 millilitres each, with normal activity resuming the same day.
How many sessions are needed and why does the effect require maintenance?
A single pulse of growth factor signalling buys a temporary shift, so the schedule front-loads sessions and then keeps topping them up. The hormonal process that thinned your hair runs at the same rate throughout, which means you're always pushing against a headwind. Stop and nothing crashes; your follicles simply resume the path they were already on.
An induction course of three to four sessions spaced two weeks to a month apart produces gains that fade over roughly six to twelve months without maintenance every three to six months, because the treatment never touches the hormonal driver behind the loss.
Which stages and patterns of hair loss respond to this mechanism, and which do not?
Candidacy comes down to one question: is there still a follicle there to signal to? Growth factors can wake up a follicle that's downshifted to fine hair, but they can't build one where fibrous tissue has taken its place. That distinction, not the size of the thin patch, decides whether you're a candidate.
Response tracks follicle viability rather than the size of the area, so early to moderate pattern loss at roughly stages two to four gains a realistic ten to thirty extra hairs per square centimetre, while a shiny scalp with no vellus hair under magnification has nothing left to stimulate.
What does the clinical evidence actually show about measurable regrowth?
There's real evidence behind this, and it's real in a narrow way that's easy to oversell. Split-scalp trials, where one half of your head gets treated and the other gets saline, are the strongest design because you serve as your own control. What they show is a measurable gain, not the transformation the word regrowth puts in your head.
- Typical gain: 15 to 35 extra hairs per square centimetre over three to six months.
- Trial size: most studies enrol 20 to 40 people and stop at six months.
- Pooled findings: density favours treatment over placebo, with high variation between studies.
- Weakest evidence: durability past a year, advanced loss, and head to head against drug therapy.
Randomised split-scalp trials typically show an increase of roughly 15 to 35 hairs per square centimetre over three to six months, a statistically clear but modest gain drawn from studies of 20 to 40 participants with almost no data past twelve months.
How does this mechanism differ from the way hair loss drugs work?
It helps to think of this as defence versus offence. A daily blocker takes away the hormonal pressure that shrinks your follicles, while injections add a growth signal and leave that pressure exactly where it was. That's why experienced clinicians stack them instead of picking one.
| Criteria | Injected growth factors | Oral blocker | Daily topical |
|---|---|---|---|
| Mechanism | Adds proliferative signal | Blocks conversion to DHT | Opens channels, raises blood flow |
| Time to effect | 3 to 6 months | 4 to 6 months | 3 to 6 months |
| Durability | Fades in 6 to 12 months | Holds while taken | Reverses months after stopping |
| Best at | Reversing early miniaturisation | Halting progression | Holding ground, mild thickening |
These mechanisms don't compete, since a 5-alpha reductase blocker removes the hormonal pressure, a daily topical lengthens anagen through better perifollicular blood flow, and injections add a proliferative push, which is why combination protocols outperform any single one and why none of them holds once you stop.
What are the biological limits of the mechanism, and what can go wrong?
The ceiling here is biological, not a matter of trying harder. Growth factor signalling amplifies what a living follicle already does, so once fibrosis has taken the papilla and the stem cell reservoir in the bulge, there's nothing left for those proteins to bind to. A promise of regrowth on a long-bare scalp is false at the level of mechanism, not just optimistic.
Because the injectate is your own blood there's no rejection risk and adverse events are dominated by mild local effects, but the mechanism cannot regenerate a follicle already lost to fibrosis, and plausibly a quarter to a third of people finish a full induction course with no change they'd call visible and no way to recover the cost.
