What is PRP (platelet-rich plasma) and how does it work?

PRP is a concentrate of your own platelets and growth factors that may speed tissue repair, but results vary with how it is prepared.

PRP (platelet-rich plasma) is a concentrate made from your own blood that contains a high concentration of platelets and growth factors. It is used in orthopedics, dermatology, and aesthetics to promote tissue repair and regeneration.

PRP is not FDA-approved as a drug, but it is widely used as a medical procedure because it uses a patient's own biological material. FDA-cleared devices exist for preparing PRP, and the procedure is performed in clinics across the United States and worldwide.

What you can do

Ask the clinic how its PRP is prepared (spin speed, platelet count, leukocyte content, activation), as these change results⁴.
Expect an in-office visit: a blood draw of about 15–60 mL, 15–30 minutes of preparation, then injection into the target area¹.

Be careful if

PRP is not FDA-approved as a drug; it is used as a medical procedure, with FDA-cleared devices for preparing it.
Two trials using 'PRP' may use very different products, so one study's results may not apply to another clinic's treatment⁴.

Go deeper

How it works What it does in your body, in plain words 2 min

The PRP process involves three basic steps:

Blood draw -- A small amount of blood (typically 15-60 mL) is drawn from the patient's arm, similar to a routine lab draw¹.
Centrifugation -- The blood is placed in a centrifuge and spun at high speed. This separates the blood into three layers: red blood cells at the bottom, a "buffy coat" of white blood cells and platelets in the middle, and platelet-poor plasma on top³.
Concentration and injection -- The platelet-rich layer is extracted, resulting in a concentration of platelets 3-5 times higher than normal blood levels. This concentrate is then injected directly into the target area¹.

The entire preparation takes about 15-30 minutes and is typically done in-office.

Growth Factors in PRP

Platelets contain alpha granules that release several key growth factors upon activation⁴:

PDGF (Platelet-Derived Growth Factor) -- stimulates cell replication and blood vessel formation
TGF-beta (Transforming Growth Factor) -- promotes collagen synthesis and tissue remodeling
VEGF (Vascular Endothelial Growth Factor) -- stimulates new blood vessel growth
EGF (Epidermal Growth Factor) -- promotes cell growth and differentiation
IGF-1 (Insulin-Like Growth Factor) -- mediates cell growth and repair

These growth factors work together to accelerate the body's natural healing cascade⁴.

Common Applications

PRP is used across several medical fields:

Joint healing -- Injected into damaged joints, tendons, and ligaments to reduce pain and promote tissue repair, particularly in knee osteoarthritis and rotator cuff injuries¹.
Hair restoration -- Injected into the scalp to stimulate dormant hair follicles and promote hair growth in androgenetic alopecia².
Skin rejuvenation -- Applied topically after microneedling or injected into the skin to stimulate collagen production and improve skin texture².

The evidence The studies, what they found, and how much to trust them 1 min · 4 sources

Not all PRP is created equal. Several variables in preparation significantly influence clinical results⁴:

Centrifuge speed and time -- Different protocols produce different platelet concentrations. Single-spin protocols yield lower concentrations (2-3x baseline), while double-spin protocols can achieve 5-8x baseline³.
Leukocyte content -- PRP can be leukocyte-rich (LR-PRP) or leukocyte-poor (LP-PRP). LR-PRP contains white blood cells that may increase inflammation, which can be beneficial for tendon injuries but detrimental in joint spaces⁴.
Activation method -- Platelets can be activated with calcium chloride, thrombin, or simply by exposure to collagen at the injection site. The activation method affects growth factor release kinetics¹.
Volume and platelet count -- There is no universal standard for the "ideal" platelet concentration. Studies use widely varying protocols, which contributes to inconsistent results across clinical trials⁴.

Understanding these variables is important when evaluating PRP studies, as two trials using "PRP" may actually be using very different products⁴.

Sources

Platelet-Rich Plasma: New Performance Understandings and Therapeutic Considerations in 2020. Everts P, Onishi K, Jayaram P, Lana JF, Mautner K. International Journal of Molecular Sciences, 2020. PubMed 33096812
Systematic Review of Platelet-Rich Plasma Use in Androgenetic Alopecia Compared with Minoxidil, Finasteride, and Adult Stem Cell-Based Therapy. Gentile P, Garcovich S. International Journal of Molecular Sciences, 2020. PubMed 32295047
Principles and Methods of Preparation of Platelet-Rich Plasma: A Review and Author's Perspective. Dhurat R, Sukesh M. Journal of Cutaneous and Aesthetic Surgery, 2014. PubMed 25722595
Platelet-Rich Plasma: A Narrative Review. Collins T, Alexander D, Barkatali B. EFORT Open Reviews, 2021. PubMed 34040800