Male fertility generally depends on the quantity and quality of his sperm. There are no symptoms and obvious signs of male infertility. There could be a lot of causes: different diseases, hormone disorders, smoking, genetic health problems, using steroids for body building.
Medical examinations should be done to know if a male is fertile. Usually, sperm analysis and general health tests are taken. If the number of sperm is low or of poor quality, it will be difficult, and sometimes impossible, for a male to cause a pregnancy. In some cases, additional tests are needed, for example, DNA fragmentation, genentic diagnosis, FISH, oxydative stress level in semen, hormone testing and so forth.
IVF/ICSI are one of the most effective ways to treat male infertility.