The only truly natural male fertility test is actually causing a pregnancy! If pregnancy isn’t occurring within 12 months (or 6 months if your female partner is over 35), an evaluation of some sort needs to take place, and most of the time this begins with a semen analysis. I assume this question is from someone who either is unable to collect a semen analysis, or is unwilling to do one. Reasons for this often center around not wanting to masturbate or not wanting to ejaculate anywhere other than within their partner’s vagina with the intention to cause a pregnancy. There is often a religious component to this concern, which I am sensitive to.  Fertility specialists have a variety of things we can do during an initial evaluation which can act as a surrogate marker for fertility instead of a semen analysis. These include physical examination of the testicles as well as blood reproductive hormone levels which often correlate with the status of sperm production. Lastly, when there are religious reasons for not wanting to ejaculate at any other time or place than when trying to conceive, many couples will find an excellent solution which is to use a special perforated condom. These condoms allow for ejaculation to occur during intercourse, and a few sperm can sneak out of the perforations technically still allowing for potential conception, while the majority of the sample can still be submitted for a semen analysis. Men who are unable to ejaculate or have such severe sexual problems limiting the ability to collect a semen sample should be evaluated–often the treatments will involve improving sexual function sufficiently to allow for standard semen collection.