Received acell + prp injection for hair loss 5 months ago and still have not noticed anything.

There are multiple stages in response to PRP injections. The first stage would be a decrease in hair shedding. Look at the towel and the drain and the shower and see if your hair shedding has decreased. The second stage would be an increase in the rate of hair growth. Along with this stage comes an increase in the diameter of the hair shaft. This means the hair will look thicker and grow faster. The final and last stage, and the one that is the most difficult to predict, is regrowth. Regrowth can start at 1 to 2 months or may take 6 months or longer before it starts. Remember that hair grows at one centimeter per month so that cosmetically acceptable hair growth takes time. Look for short hairs in the first few months. If you notice any of the above changes, you are getting a response.
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Hair loss is a complex multifactorial process. Injecting PRP is the easiest part but in order to get to this point, as doctors- hair restoration specialists, we need to rule out any possible precluding factors/ health problems for successful PRP treatment. You would need to do blood work to look at certain values. Than, a doctor should put you on specific supplements to restore and enhance your nutritional status. And ONLY after those steps, injection of PRP +vitamins( B complex and D)+microneedling followed by Red Light treatments and green tea enriched diet for next 4-5 months finalizing treatment with PRP boost and evaluating results in 9 months from the first PRP treatment. 

I recommend monthly treatments for 4 months to get the best results for PRP. Most patients see their initial growth between the 2nd to 3rd treatment.

Usually PRP requires 4 treatments, done monthly, to yield great results.
Consult with your doctor about follow up appointments for additional procedures.

Unfortunately PRP for hair loss has not been standardized and hair loss is multifactorial.  While Acell as an ECM (extracellular matrix) is popular its not clear there is an adantage.  Also, what type of PRP machine, how much, was it activated properly, did you also have microneedling, etc...  In our office, we use Bio-d which is placental ECM with highly concentrated PRP and microneedle.  This is the method shown to work by Dr. Alan Bauman, one of the worlds experts in hair loss.
You should return to the office that did your prp for a hair check.
Good luck!