Decreased Libido
Libido is the desire to engage in sexual activity. About 5% of men have decreased libido, a condition that increases with age. It’s common to lose interest in sex from time to time, and libido levels vary through life. It’s also normal for your interest not to match your partners at times. However, low libido for a long period of time may cause concern for some people. Low libido can sometimes be an indicator of underlying health conditions
 
Causes of decreased libido
Decreased libido often accompanies other sexual disorders. Although most men with erectile dysfunction do not complain of decreased libido, after time, persistent failure with erections and sexual performance can lead to reduced sex drive in some men. Men who have other causes of decreased libido also often have trouble getting erections.
 
Common causes of low libido include:

• medications (SSRI antidepressants; medications that reduce testosterone levels, such as those taken for prostate cancer)
• excessive alcohol use or recreational drug use
• excessive fatigue
• systemic illness (such as chronic lung, heart, kidney and liver failure, cancer)
• low testosterone (male hypogonadism)
• depression
• relationship problems

Low T
While a man's testosterone level gradually falls with aging, there is not necessarily any relationship between hormone levels and the desire for sex. It is just one potential cause for decreased libido and your  doctor may want to look for other causes in addition to just low testosterone.
 
Stress
The body does not react well to stress. Emotional stress may affect physical function, including sexual desire and performance. Realizing what underlying stressors may exist is the first step in treatment. Self-help may work but some people may need to visit a counselor or doctor.
 
Sexual desire requires two to tango. Both partners need to feel connected and women especially need the feeling of being close. Poor communications, a sense of betrayal, lack of trust, and repeated fighting and criticism may create a relationship that lacks closeness and intimacy. Counseling may be the answer if couples find that the issues are too tough to resolve on their own.
 
Too Little Sleep
As with any physical activity, a rested body increases performance. Lack of sleep, including lack of proper sleep, may be the culprit that decreases sex drive. Sleep apnea is a potential cause for lack of good sleep and lack of libido. Medical help may be needed if you or your partner suspect it.
 
Medication
Side effects of many prescription medications include loss of libido and sex drive. Some examples include:
• High blood pressure medications including water pills and beta blockers
• Cold medications that contain antihistamines and decongestants
• Antidepressants
• Birth control pills
• Narcotic pain pills
• Chemotherapy drugs
 
If this is the cause, your doctor may be able to suggest a medication alternative that might have fewer side effects.
 
Erection Problems
Erectile dysfunction (ED) can not only affect the ability to have intercourse but also how a man feels about his ability to perform. There are many options available to treat ED and your doctor can help find the option that is best for you and your partner
 
 
Depression
Depression affects all facets of life including sex drive. Losing pleasure in daily activities often requires treatment including counseling and perhaps medication. Unfortunately, some antidepressants also depress libido. Your doctor and therapist need to know if low sex drive is one of your symptoms of depression.
 
 
Treatment of decreased libido
As is the case with ED, treatment of decreased libido depends on the cause of the condition. For some men, adopting a healthier lifestyle, such as exercising regularly, eating a healthy diet, getting enough sleep, reducing stress, and/or limiting alcohol, can help resolve the problem.
 
Other treatment options may include switching medications, treating an underlying condition, testosterone replacement hormone therapy if the man has hypogonadism, or relationship counseling.