In addition to medical reasons for low sex drive, there are also psychological reasonssuch as depression, chronic stress, or relationship problemsthat could explain why a man might be experiencing low libido.
If your sex drive is waning, the first step is to get a complete physical assessment. If your primary care provider can't find a specific health problem, a consultation with a specialist in sexual medicine could be helpful. A certified sex therapist may be able to pinpoint any psychological issues behind the loss of desire, and help you and your partner cope with the problem while your doctors are tracking down any hidden physical causes.
Treatment may involve something as logical as testosterone replacement or couples counseling, or something as unexpected as treatment for a thyroid problem or of previously undiagnosed diabetes.