This could be hereditary or it could be a bad diet, lack of exercise, a lot of stress. All of this will cause hair loss eventually. You can take a multi vitamin if you are not getting the nutrients you need in their purest form, food. Finally, because those suggestions are necessary but back longer to see results, you can always go to a hair specialist and find out why you are losing your hair. They will look into things more deeply with you and possibly recommend something you can do for immediate results.