9 Warning Signs of Low Testosterone

Written by Ryan Wallace and Kathleen Yoder
Medically Reviewed by Steven Kim, MD on March 19, 2015

Part 1 of 11: Overview

Low Testosterone

Testosterone is a hormone that is produced by the human body. It is mainly produced in the testicles in men. It stimulates sperm production and a man's sex drive and also helps build muscle and bone mass.

Testosterone production typically decreases as men age. Men can experience a range of symptoms if it decreases more than it should. Low T is diagnosed when levels fall below a normal range (300- 1000 ng/dL, according to the U.S. Food and Drug Administration). A blood test (called serum testosterone level) is used to determine your level of circulating testosterone.

A range of symptoms can occur if testosterone production drastically drops. Signs of low T (also called hypogonadism) are often subtle and can be mistaken for a natural part of aging.

Part 2 of 11: Sex Drive

Low Sex Drive

Testosterone plays a key role in libido (sex drive) in both men and women. Men may experience some decline in sex drive as they age. However, someone with low T will likely experience a more drastic drop in his desire to have sex. Low T can also decrease the sex drive in women, along with other factors, such as other hormonal and mood changes.

Part 3 of 11: Erections

Difficulty Achieving Erection

Testosterone stimulates a man's sex drive — and it also aids in achieving an erection. Testosterone alone doesn't cause an erection, but it stimulates receptors in the brain to produce nitric oxide — a molecule that helps trigger an erection. When testosterone levels are too low, a man may have difficulty achieving an erection prior to sex or experience spontaneous erections (for example, during sleep). Other health problems can influence erectile function, so it is important to determine whether low T is causing this symptom.

Part 4 of 11: Semen

Low Semen Volume

Testosterone plays a role in the production of semen, which is the milky fluid that aids in the motility of sperm. It's pretty simple: The more testosterone a man has, the more semen he produces. Men with low T will notice a decrease in the volume of their sperm during ejaculation.

Part 5 of 11: Hair

Hair Loss

Testosterone plays a role in several body functions, including hair production. Balding is a natural part of aging for many men. However, men with low T may experience a loss of body and facial hair.

Part 6 of 11: Energy

Fatigue & Lack of Energy

Men with low T have reported extreme fatigue and a noticeable decrease in energy levels. You might be experiencing symptoms of low T if you are tired all of the time, despite getting plenty of sleep, or if you are finding it harder to get motivated to hit the gym or exercise.

Part 7 of 11: Muscle Mass

Loss of Muscle Mass

Because testosterone plays a role in the building and strengthening of muscle, men with low T might notice a decrease in both muscle mass and strength, according to the Mayo Clinic. Those who try to reverse the muscle loss through weight training might find it difficult to build or rebuild muscle.

Part 8 of 11: Body Fat

Increase In Body Fat

Men with low T may also experience increases in body fat. In particular, they sometimes develop "gynecomastia", a condition in which they develop enlarged breasts. Although the reasons behind this are not entirely clear, research suggests that testosterone influences the way your body stores fat.

Part 9 of 11: Bone Mass

Decrease In Bone Mass

The thinning of bone mass (osteoporosis) is often thought of as a condition that women experience. However, men with low T can also experience bone loss because testosterone aids in the production and strengthening of bone. Men with low T — especially older men who have had low T for years — are more susceptible to bone fractures.

Part 10 of 11: Mood

Mood Changes

Women often experience changes in mood during menopause, when their levels of estrogen drop. Men with low T can experience similar symptoms. Testosterone influences many physical processes in the body. It can also influence mood and mental capacity. Research suggests that men with low T are more likely to experience depression, irritability, or a lack of focus.

Part 11 of 11: Outlook

Outlook and Resources

Testosterone levels decrease naturally over time, so you may experience some degree of change in these symptoms as you age. Your doctor can conduct a blood test and recommend treatment if needed, and discuss any benefits and risks. Here are some resources for you to check out if you think you may be experiencing low T: