I am an 18 years old male, my hair are falling is falling out day by day. What do you suggest?

I suggest that you work with a doctor who specializes in
hair restoration. He or she would need to determine what is causing your hair
loss. If this is a medical issue (e.g.
thyroid imbalance), then treatment would be recommended.

If Finasteride is a safe and appropriate choice, this may be
considered. If not, Rogaine may be used as a resource. FDA approved medications
are not guaranteed to grow back your hair. They are considered for controlling
the extent of your hair loss.

Along with your active forms of treatment, also make sure to
maintain healthy lifestyle habits as a long term commitment.

The
inner health of your body matters for the well being of your hair follicles.
Dietary choices can also be discussed with your doctor 

There are many reasons to lose hair so see a knowlegable specialist to get the correct diagnosis and get on a proper treatment plan. It's normal to lose 50 to 100 hairs per day.  Excessive shedding beyond that occurs with high stress, thyroid problems, crash diets, alopecia areata, medications, drugs and the early stages of male balding. The "most likely" diagnosis in an 18 year old male with hair loss (by far) is genetic hair loss, also called androgenetic alopecia or male pattern balding (mpb). FDA approved treatments include topical minoxidil and oral finasteride. Hair transplants are not an option until mid 20s