Low Energy and Low Libido in Men: What's Behind It and What to Do

Why do low energy and low sex drive often come together in men?

Libido and energy share common physiological drivers. Testosterone plays a role in both — it supports sex drive, muscle maintenance, mood, and a baseline sense of vitality. When testosterone is lower than optimal, both energy and libido can fall together. But the same two symptoms also appear when sleep is chronically disrupted, when mood is low, when the thyroid is underactive, or when chronic illness or excess weight places strain on the body. That is why evaluation needs to look at the whole picture, not just order a testosterone test in isolation.

What is low testosterone (hypogonadism) and when does it matter?

Testosterone levels decline naturally with age — a gradual process beginning in the mid-30s. Not every man with low-normal testosterone will have symptoms, and not every man with symptoms has abnormally low testosterone by lab standards. When testosterone is genuinely low and causing symptoms, it is called hypogonadism — a real clinical diagnosis with specific treatment options 1Ref 1Mulhall JP, Trost LW, Brannigan RE, Kurtz EG, Redmon JB, Chiles KA, Lightner DJ, Miner MM, Murad MH, Nelson CJ, Platz EA, Ramanathan LV, Lewis RW (2018).Evaluation and Management of Testosterone Deficiency: AUA Guideline.Clinical diagnosis and management of hypogonadism, including the need to confirm with more than one measurement and identify underlying cause before treatment.

A single testosterone result is not always the full story: levels vary significantly by time of day (highest in the morning), so clinicians typically confirm with a second measurement and check related hormones before making a treatment decision.

Testosterone supplementation is not risk-free — there are cardiovascular and other considerations that require clinical assessment and monitoring 2Ref 2Jaiswal V, Sawhney A, Nebuwa C, Borra V, Deb N, Halder A, Rajak K, Jha M, Wajid Z, Thachil R, Bandyopadhyay D, Mattumpuram J, Lavie CJ (2024).Association between Testosterone Replacement Therapy and Cardiovascular Outcomes: A Meta-analysis of 30 Randomized Controlled Trials.Testosterone replacement therapy carries cardiovascular considerations requiring clinical monitoring. Over-the-counter supplements marketed for testosterone have far less evidence behind them than a clinician-supervised approach.

What else commonly causes low energy and low libido in men?

Sleep apnea is one of the most underappreciated drivers of both symptoms. Obstructive sleep apnea — where breathing is repeatedly interrupted during sleep — dramatically reduces testosterone production and causes profound fatigue. Many men with sleep apnea have never been diagnosed, and treating it can meaningfully improve both energy and hormonal status 3Ref 3Kapur VK, Auckley DH, Chowdhuri S, et al. (2017).Clinical Practice Guideline for Diagnostic Testing for Adult Obstructive Sleep Apnea: An American Academy of Sleep Medicine Clinical Practice Guideline.Sleep apnea as a prevalent undiagnosed condition causing fatigue; sleep study as the diagnostic test.

Depression and anxiety frequently cause low libido and low energy in men, and can exist independently of testosterone levels. Men often experience depression as flat affect, low motivation, and reduced interest rather than overt sadness — making it easy to miss 4Ref 4O'Connor E, Henninger M, Perdue LA, et al. (2023).Screening for Depression and Suicide Risk in Adults: US Preventive Services Task Force Recommendation Statement.Depression as a common and treatable condition that often presents with fatigue and low motivation rather than obvious sadness.

Hypothyroidism (underactive thyroid) causes fatigue, low motivation, and decreased libido and is easy to overlook if only testosterone is tested 5Ref 5Jonklaas J, Bianco AC, Bauer AJ, et al. (2014).Guidelines for the Treatment of Hypothyroidism: Prepared by the American Thyroid Association Task Force on Thyroid Hormone Replacement.Hypothyroidism as a cause of fatigue, low libido, and low motivation in men; importance of TSH testing.

Excess body weight, particularly around the abdomen, is associated with lower testosterone levels — excess fat tissue increases conversion of testosterone to estrogen. Weight loss can meaningfully improve hormonal status.

Certain medications — including some antidepressants, blood pressure drugs, opioids, corticosteroids, and finasteride (used for hair loss or prostate) — directly suppress libido and energy. Never stop a medication without discussing it with your prescriber.

Diabetes is strongly associated with both lower testosterone and fatigue. If blood sugar has not been checked recently, it is part of a complete workup 6Ref 6American Diabetes Association Professional Practice Committee (2024).Standards of Care in Diabetes—2024.Diabetes as a condition strongly associated with fatigue and lower testosterone in men; importance of glucose screening.

What will a clinician do, and what tests are involved?

A primary care clinician is the right starting point. They will take a thorough history — asking about sleep, mood, medications, and other health conditions — and order an appropriate panel of tests. This typically includes:

• Total and free testosterone (morning draw)
• Luteinizing hormone (LH) and follicle-stimulating hormone (FSH) — to distinguish between testicular failure and a pituitary/hypothalamic cause
• Thyroid-stimulating hormone (TSH)
• Complete blood count (CBC) — anemia is an underappreciated cause of fatigue in men
• Fasting glucose and hemoglobin A1c
• Prolactin level if testosterone is clearly low (a small pituitary adenoma can suppress testosterone)
• Sleep study, if sleep apnea is suspected based on history

If testosterone is low and treatment is being considered, the clinician will also want to identify any underlying cause before recommending testosterone therapy — because some causes (such as a pituitary problem) require their own treatment first 1Ref 1Mulhall JP, Trost LW, Brannigan RE, Kurtz EG, Redmon JB, Chiles KA, Lightner DJ, Miner MM, Murad MH, Nelson CJ, Platz EA, Ramanathan LV, Lewis RW (2018).Evaluation and Management of Testosterone Deficiency: AUA Guideline.Clinical diagnosis and management of hypogonadism, including the need to confirm with more than one measurement and identify underlying cause before treatment.

What role does alcohol use play?

Heavy or regular alcohol use directly suppresses testosterone production and disrupts sleep quality, compounding both symptoms. Prior use of anabolic steroids can also suppress the body's own testosterone production for months to years after stopping — be honest with your clinician about this history.