It depends on the reason for your hair loss. Sometimes a person loses their hair due to health problems, and it can grow back (assuming that the basic health problem clears up). In these cases there are a variety of products that can strengthen the hair and encourage it to grow.
Many men start losing their hair as they age (I should know
). This is called male pattern baldness, and there is pretty much nothing that can be done about it. I have tried numerous creams, formulas etc, some natural some not, and I have not had any luck with any of them.