Once you start using a shampoo to regrow hair, do you have to always use it to keep growing hair?

Yes and No.. you would have to maintain your new hair growth with weekly treatments at least. If you stop you might experience loss again.Once you start using a shampoo to regrow hair, do you have to always use it to keep growing hair?
No, you don't have to necessarily. It's actually not good to stick to only one product for the fact the hair may become use to it. (This doesn't always happen though because I know some people swear by certain products and will only use them.) You should look into alternating between at least two products though. Just make sure they all work well with your hair.Once you start using a shampoo to regrow hair, do you have to always use it to keep growing hair?
If it is Rogaine, yes.