Can i have a hair analysis test from hair that has been cut months prior?

I plan to see a Nutritional Therapist, and they do several tests, including a hair one, which requires 90 days of hair growth, and usually cut from the back of your head for best results. Apparently it's more accurate than a blood test. But i've been having bad scalp problems and my hair is increasingly breaking away due to dry scalp/dandruff, so i want to shave it all off so i can treat it with Jamaican Castor Oil, to prevent any more strands from falling out and grow back the one's i've lost. Can i cut a lock of hair close to the root and keep it in an air locked bag for a few months before testing, with the same results?