During a PRP procedure, the Medical Staff separates platelets from your blood and processes them to concentrate the growth factors. Once injected into your scalp, PRP increases blood flow to the hair follicles, stimulates the growth of new follicles, and lengthens the anagen (active) phase of the hair cycle to promote hair growth.

“It stimulates the dormant hair follicles to grow,” explains Dr. David Berman, a plastic surgeon in Sterling, Virginia. “Studies suggest that you get an increased number of hair follicles and increased thickness in the hair shaft.”

PRP injections originated in Europe more than a decade ago. Today, doctors use it for a variety of medical applications, including helping injured joints and wounds to heal more quickly and treating aging skin and hair loss.

When will you see PRP for hair loss results?

Research on the results of PRP injections in both men and women has been generally positive, although most of the studies have been small. For a 2016 study published in the journal Dermatologic Surgery, researchers tested PRP in 25 people with hair loss. They injected PRP in one half of participants’ heads and an inactive treatment (placebo) in the other half, to see the difference. After three treatments, spaced one month apart, there were improvements in the number and thickness of hairs. Another 2015 study found improvements in hair counts, thickness, and root strength.

Hair restoration as a result of PRP injections will depend a lot on your gender, your age, your genes, your hormones, and other factors, including the amount of hair you had to begin with. “You do have to have some hair,” Dr. Berman says. “If somebody has a huge bald spot, it’s not going to work.”

He adds that there’s a lot of variability from person to person. “You can’t predict whether it’s going to work on a particular person and, if so, how much better their hair is going to be,” he adds. “I tell most patients to allow four months to see a difference. If it hasn’t helped by four months, it probably isn’t going to help you.”

Adopting a healthier lifestyle will increase your chance of success. Eat a balanced diet and stop smoking and using other nicotine products, which disrupt the blood supply your hair needs to grow.

You’ll need repeated injections to see results. The exact number will depend on factors like the amount and pattern of hair loss and your age. Typically, you’ll start with one injection every four to six weeks, for three to six treatments months. Then you’ll space them out to once every three to four months, for up to two years.