Typical male pattern baldness is usually diagnosed based on the appearance and pattern of the hair loss, along with a detailed medical history, including questions about the prevalence of hair loss in your family. An experienced medical hair loss expert should examine the scalp under magnification (preferably with a device called a densitometer), in order to assess the degree of miniaturization of the hair follicles. This assessment is very important when recommending the proper course of treatment.
Some advertised "clinics" might recommend a costly hair analysis or a scalp biopsy to properly diagnose your hair loss. The only reason to have a hair analysis is to assess the possibility of poison induced hair loss. A hair analysis may reveal substances such as arsenic or lead, however, hair loss caused by poising does not present itself in a typical male pattern. You should avoid these clinics and seek the advice of a physician who can properly examine you and help you treat your hair loss.