Male fertility generally depends on the quantity and quality of his sperm. There 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 number of sperm is low, it has a 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.