How much scalp coverage from a single PRP injection?

Hi, How are you? Typically if the PRP treatment is performed correctly, the DR will inject the whole scalp. However, it will not be coverage from new hairs that you will notice. It will be the small, miniaturized hair that you will see begin to get thicker and stronger. Giving you back volume and fullness. If you are looking for a certain amount of coverage you are going to need a hair transplant. PRP is just a prevention. 

There are many factors that can impact how far PRP may migrate and still remain effective. In an ideal world, when prepared and delivered correctly as I use in my protocol, the effective migration range of PRP is not far. My observation have generally been between 0.5cm and 0.75cm. 
If combined with other materials such as exosomes, most of the exosomes will remain in the injection site area. However, the size of exosomes does permit them to migrate significantly further. Other material such as Acell will remain very lose to the injection site due to the particulate size of the material.
Hope I have helped.
Warmly,
Arbella Sarkis, MD