What Causes Low Testosterone in Men? Common and Reversible Causes
Written by the Innovative Men's Health Editorial Team
Medically reviewed by Alessa Lopez-Castor, ARNP, DNP
Last medically reviewed: September 18, 2026
Searching for the causes of low testosterone in men usually means you want a clear explanation—not a sales pitch. Low testosterone can reflect common, potentially reversible factors as well as testicular, pituitary, genetic, medication-related, or chronic-health conditions.
A low laboratory result alone does not automatically mean testosterone replacement therapy is appropriate. Diagnosis starts with compatible symptoms, properly timed confirmatory testing, and evaluation of the underlying cause.
This article provides general education. It does not diagnose readers, replace a clinician, provide testosterone dosing, or guarantee that symptoms or laboratory results will change.
What does “low testosterone” actually mean?
Male hypogonadism describes a condition in which the body does not produce enough testosterone, sperm, or both because of a problem involving the testes or the hormonal signals that control them. Clinicians commonly separate causes into two broad groups:
Primary hypogonadism: the main problem originates in the testes.
Secondary hypogonadism: the problem involves the hypothalamus or pituitary—the brain structures that signal the testes.
Symptoms alone are not diagnostic. Low energy, reduced libido, mood changes, reduced muscle mass, sleep problems, and erectile concerns can have many causes. The Endocrine Society recommends diagnosing hypogonadism only when compatible symptoms or signs occur together with unequivocally and consistently low testosterone measured using accurate testing.
Common and potentially reversible contributors
Obesity and metabolic health
Excess body fat is one of the most frequently discussed contributors. Obesity can alter hormone signaling and lower sex hormone–binding globulin, or SHBG, which can make total testosterone more difficult to interpret. This is one reason a low total value should not be viewed in isolation.
The Endocrine Society’s 2026 statement advises ruling out reversible contributors such as obesity. When overweight or obesity is identified as the driver and no other cause is found, weight loss is typically the first-line approach. Learn more about the relationship between obesity and low testosterone or IMHS medical weight management.
Sleep apnea and disrupted sleep
Obstructive sleep apnea causes repeated breathing pauses during sleep, often producing fragmented rest and intermittent reductions in oxygen. Snoring, witnessed breathing pauses, gasping, morning headaches, and daytime sleepiness warrant medical discussion.
Fatigue and poor concentration caused by sleep disruption can resemble symptoms commonly blamed on low testosterone. Sleep apnea may coexist with obesity and other metabolic risks, so evaluation should not stop at a hormone result.
Medications and substances
Certain medicines can suppress testosterone production or hormonal signaling. Examples discussed in clinical resources include opioids, glucocorticoids or corticosteroids, some chemotherapy, and ketoconazole. Anabolic-steroid use or withdrawal can also suppress the hypothalamic–pituitary–testicular axis.
Never stop a prescribed medicine because of an article or laboratory result. A clinician should review the complete medication and supplement list, why each treatment is being used, and whether an alternative is clinically appropriate.
Acute illness, chronic illness, and inadequate recovery
Serious acute illness can temporarily suppress testosterone, making testing during or shortly after illness difficult to interpret. Chronic systemic disease, undernutrition, excessive training without adequate recovery, and certain organ disorders may also affect the hormonal axis.
This is another reason an isolated result should be confirmed under appropriate conditions rather than triggering immediate treatment.
Testicular causes of low testosterone
Primary hypogonadism occurs when the testes cannot produce expected levels despite hormonal stimulation. Potential causes include:
Klinefelter syndrome and certain other genetic conditions.
Undescended testes.
Testicular injury, torsion, infection, orchitis, or cancer.
Chemotherapy or radiation affecting testicular function.
Other testicular diseases or developmental conditions.
History, examination, testosterone results, and gonadotropins such as LH and FSH help a clinician determine whether the pattern suggests primary testicular dysfunction.
Pituitary and hypothalamic causes
Secondary hypogonadism occurs when the brain’s signaling system does not adequately stimulate the testes. Causes can include pituitary tumors or injury, elevated prolactin, iron overload disorders, genetic conditions, severe obesity, chronic illness, and certain medications.
Further testing may include LH, FSH, prolactin, iron studies, or other laboratory work based on the individual picture. Pituitary imaging is selective—not something every man with one low testosterone result needs.
Aging and low testosterone
Average testosterone levels may decline gradually with age, but aging alone does not establish hypogonadism. The Endocrine Society cautions that labels such as “age-related” or “late-onset” hypogonadism can blur the line between normal aging and treatable disease.
The relevant question is not simply whether a man is older or below a favorite internet cutoff. Clinicians consider symptoms, repeated accurate measurements, possible reversible factors, and the benefits and risks of any proposed treatment.
Low testosterone does not automatically mean TRT
Some men need weight, sleep, medication, illness, or metabolic factors addressed first. Others need additional testing to distinguish testicular from pituitary causes. Men with confirmed hypogonadism may discuss testosterone therapy only after reviewing fertility goals, contraindications, monitoring, and individual risks and benefits.
Evaluation is not a promise of treatment. This article provides no dosing instructions and should not be used to begin, stop, or change hormone therapy.
How low testosterone is confirmed
The Endocrine Society frames diagnosis around compatible symptoms or signs plus consistently low, accurately measured testosterone. Its 2026 statement describes at least two early-morning, fasting testosterone tests, with a commonly used clinical threshold near 300 ng/dL.
The exact interpretation depends on the laboratory, assay, clinical context, and whether SHBG is altered. Free testosterone may be useful when total testosterone is borderline or SHBG conditions complicate interpretation. Further testing can help identify the cause.
Do not self-diagnose from one afternoon result, a home test, or an online reference range.
Care at IMHS Bellevue—and eligible Washington telehealth
At Innovative Men's Health, evaluation begins with history, symptoms, appropriately timed laboratory testing, and review of possible reversible contributors. Explore testosterone replacement therapy, browse services, contact the clinic, or learn about Washington telehealth for eligible adults when clinically appropriate.
Innovative Men's Health is located at 1940 116th Ave NE Unit 201, Bellevue, WA 98004. Phone: (425) 455-1700. Evaluation is required, treatment is individualized, results vary, and an inquiry does not guarantee a diagnosis or prescription.
Key takeaways
Low testosterone can arise from obesity, sleep disruption, medications, illness, testicular disease, pituitary or hypothalamic conditions, genetic conditions, and aging-related context.
Some contributors may be reversible or modifiable under clinician guidance.
Symptoms alone are not diagnostic, and one low laboratory result is not enough.
Guideline-aligned diagnosis generally uses at least two early-morning fasting testosterone measurements.
LH, FSH, and selective additional testing can help distinguish testicular from pituitary causes.
Low testosterone does not automatically mean TRT.
Frequently asked questions
What are the most common causes of low testosterone in men?
Common contributors include obesity, certain medications, sleep disruption, chronic or acute illness, and aging-related changes. Less common causes involve the testes, pituitary, hypothalamus, or genetic conditions.
Can low testosterone be reversible?
Sometimes. Weight loss, recovery from illness, sleep evaluation, or clinician-directed medication changes may help when those factors are responsible. Not every cause is reversible.
Does a low testosterone result mean I need TRT?
No. Diagnosis requires symptoms or signs plus consistently low, properly measured testosterone and evaluation of the cause. Treatment decisions are individualized.
How is low testosterone confirmed?
Guideline-aligned evaluation generally uses at least two early-morning fasting testosterone tests. Free testosterone and other labs may be considered when indicated.
Can I start with a telehealth consultation?
Eligible Washington adults may use Washington telehealth for appropriate portions of care. Laboratory testing and any necessary in-person examination remain clinician-directed.
Sources and further reading
Keep reading
Obesity and Low Testosterone • Difference Between Total and Free Testosterone • What to Expect at a Testosterone Evaluation
Medical disclaimer
This article is for general educational information only. It is not medical advice, diagnosis, or treatment; it does not create a clinician–patient relationship; and it does not guarantee a diagnosis, therapy eligibility, symptom improvement, testosterone-level change, or any outcome. Do not start, stop, or change testosterone, prescribed medications, supplements, or other treatment without guidance from a licensed clinician who knows your history. Low testosterone does not automatically mean TRT; proper evaluation and confirmatory testing are required.
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