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MEN’S HORMONE HEALTH
What Causes Low Testosterone in Men? Evaluation and Next Steps
A low result is the beginning of an evaluation. Understanding why testosterone is low helps determine which treatment, if any, makes sense.
Medically reviewed by Dr. Timothy Mackey
Medical Director, NovaGenix
Updated September 2026
Low testosterone has more than one cause
Low testosterone can reflect a problem in the testicles, reduced signaling from the brain, or suppression associated with another health condition or medication. Several contributors can coexist.
A single low blood test does not establish hypogonadism or explain its cause. Doctors combine symptoms, repeat measurements, medical history and selected additional tests. Treating a reversible contributor may help; some men have persistent deficiency that needs a different approach.
Primary vs. secondary hypogonadism
Primary: the testicles
The testicles do not produce adequate testosterone despite signals to do so. With low testosterone, LH is typically elevated; FSH may also rise.
Examples include certain genetic conditions, testicular injury and damage from cancer treatment.
Secondary: the signaling system
The hypothalamus or pituitary does not provide adequate stimulation. LH and FSH can be low or inappropriately normal for the low testosterone level.
Possible contributors include obesity, certain medicines, elevated prolactin and pituitary disease.
LH (luteinizing hormone) stimulates testosterone production; FSH (follicle-stimulating hormone) supports sperm production. These patterns guide evaluation, but do not establish a specific diagnosis alone. Some men have mixed causes. See the Endocrine Society’s overview of hypogonadism.
Obesity and metabolic health
Obesity is a common contributor to low testosterone. It can reduce sex hormone-binding globulin (SHBG), lowering measured total testosterone without necessarily producing the same change in free testosterone. More substantial obesity can also suppress the reproductive hormone signaling system.
Weight, diabetes, medications and sleep apnea often overlap. A clinician considers these together rather than assuming one number proves permanent testicular failure. The Endocrine Society’s 2026 statement identifies weight loss as typically first-line when excess weight is the identified cause and other causes have been excluded. Testosterone response varies; improvement is not guaranteed.
Sleep and sleep apnea
Insufficient sleep and sleep disorders can complicate hormone evaluation. Obstructive sleep apnea deserves particular attention when there is loud snoring, witnessed pauses in breathing or marked daytime sleepiness.
Treating sleep apnea matters for overall health, whether or not testosterone rises. Do not assume CPAP will normalize every low result. Sleep assessment and repeat hormone testing can answer different parts of the problem.
Medications and previous hormone use
Long-term opioids and systemic glucocorticoids can suppress hormone production. Medicines that raise prolactin may also affect reproductive signaling. Review all prescriptions, supplements and previous testosterone or anabolic-steroid use with your physician.
External testosterone can suppress the body’s own production and sperm production. Recovery after stopping varies. Sexual side effects from an antidepressant, however, do not automatically mean testosterone is low.
Do not stop a prescribed medicine on your own. The prescriber can assess alternatives or dose changes when medically appropriate.
Pituitary and hypothalamic causes
The pituitary and hypothalamus coordinate hormone signals. Pituitary tumors, elevated prolactin, iron overload, head injury and certain inherited conditions can interfere with this system. A low result does not mean a tumor is present.
Very low testosterone with low or low-normal LH, persistent prolactin elevation, other pituitary hormone abnormalities, or relevant symptoms may prompt specialist assessment and imaging. New severe headache with visual changes needs urgent medical assessment.
Testicular causes
Primary hypogonadism can follow significant testicular injury, torsion, inflammation, chemotherapy or radiation. A history of undescended testes or a genetic condition such as Klinefelter syndrome can also be relevant.
Examination, treatment history and fertility history help determine which investigations are useful. A new testicular lump should be evaluated; sudden severe testicular pain requires urgent care.
Acute and chronic illness
Acute illness can temporarily lower testosterone. Severe or longstanding conditions, including kidney or liver disease, may also affect production, hormone binding and general health. Testing during illness can therefore be misleading if interpreted as a permanent baseline.
The timing of reassessment depends on recovery and the clinical situation. Treating the underlying illness and reassessing symptoms may be more useful than immediately starting hormone therapy.
Aging is not the same as hypogonadism
Testosterone tends to decline with age, but an age-related trend does not explain every low result. Health conditions, weight and medications may account for part of the change.
Being in your 40s, 50s or 60s is not a diagnosis. Fatigue, reduced libido and erectile symptoms deserve evaluation, including causes unrelated to testosterone. Treatment decisions depend on persistent biochemical deficiency, symptoms and individual circumstances.
Lifestyle factors: useful changes, realistic expectations
Severe calorie restriction, inadequate nutrition, excessive training without recovery and heavy alcohol use can be relevant. Adequate sleep, sustainable activity and appropriate nutrition support health, but no single food, exercise or supplement reliably corrects every cause of low testosterone.
Correct a documented deficiency when indicated. Avoid interpreting “testosterone booster” claims as a substitute for diagnosis. Our guide to supporting testosterone naturally explains where lifestyle measures fit.
Environmental exposures: what the evidence supports
NIEHS describes endocrine-disrupting chemicals that can interfere with hormone activity. Evidence includes laboratory, animal and population studies; the strength and meaning of findings differ by substance and exposure.
These findings do not establish that a particular cosmetic or plastic product caused an individual’s low testosterone. Follow occupational protections and product safety guidance, and discuss significant exposures with a clinician. Routine “toxin panels” and detox products are not a substitute for a standard hormone evaluation.
Can low testosterone be temporary?
Yes. Illness, poor sleep, undernutrition and some medication effects can produce a low measurement or reversible suppression. Other causes are persistent. Repeat testing under appropriate conditions helps distinguish a temporary finding from ongoing deficiency.
The question is not simply whether a later number is higher: symptoms, the degree of change and the likely cause all matter.
How doctors confirm low testosterone and determine the cause
- Clarify the symptoms. Reduced sexual desire, fewer spontaneous erections, infertility and other findings may be relevant. Fatigue alone is nonspecific.
- Confirm the biochemical finding. Obtain two separate early-morning total testosterone measurements. The Endocrine Society recommends morning fasting samples; follow the clinician’s instructions. Shift workers should discuss sampling timing.
- Interpret the result in context. The AUA uses below 300 ng/dL as a reasonable cutoff supporting diagnosis, alongside symptoms and repeat testing. Borderline results or altered SHBG may warrant free testosterone assessment.
- Identify the pattern. LH, and when appropriate FSH, help distinguish testicular dysfunction from reduced signaling.
- Investigate selectively. History, examination and initial results determine whether prolactin, iron studies, other hormone tests, imaging or referral are needed.
These steps reflect the AUA diagnostic guidance and Endocrine Society recommendations. Keep copies of prior results, including collection times, and bring your medication list and fertility goals.
What labs may be ordered?
| Test | What it can help answer |
|---|---|
| Total testosterone, repeated | Is the low measurement persistent under appropriate sampling conditions? |
| SHBG and free testosterone | Could altered binding proteins or a borderline total result affect interpretation? |
| LH and FSH | Does the pattern suggest testicular dysfunction or inadequate signaling? |
| Prolactin | Could elevated prolactin contribute, particularly with low or low-normal LH? |
| Selected thyroid, iron or other tests | Is another condition suggested by the history, examination or hormone pattern? |
| Semen analysis | What is sperm production like when fertility is a concern? |
Not every patient needs every test. Pituitary MRI is selected for specific findings, not routinely ordered for every low value. CBC/hematocrit and prostate assessment may be needed when considering TRT; they address treatment safety rather than explaining every cause of deficiency.
Learn about testosterone testing and interpreting total and free testosterone results.
Can treating the cause raise testosterone?
Sometimes. Managing obesity, correcting undernutrition, changing a contributing medicine when appropriate, or treating a specific hormonal disorder may improve testosterone. The response depends on the cause and whether lasting damage is present.
Doctors may reassess symptoms and laboratory results after addressing a contributor. There is no universal recovery timetable, and lifestyle changes cannot reverse every genetic or testicular condition.
When TRT is—and is not—the next step
TRT may be appropriate for men with confirmed, symptomatic hypogonadism after evaluation and discussion of benefits, risks and monitoring. It should not bypass the search for a treatable cause or follow automatically from age, fatigue or one low result.
Fertility goals matter because external testosterone suppresses sperm production. Men seeking fertility may need reproductive or endocrine evaluation and a different treatment strategy. Untreated severe sleep apnea, elevated hematocrit and certain prostate or cardiovascular conditions require additional attention before treatment.
See our testosterone replacement therapy overview for treatment and monitoring considerations.
Frequently asked questions
What is the most common cause of low testosterone?
Obesity, health conditions and medications are common contributors, but the likely cause depends on the patient. Testing is needed to distinguish reversible suppression from testicular or pituitary disease.
Does one low testosterone test mean I need TRT?
No. Diagnosis requires symptoms or signs plus consistently low measurements. A low result during illness or under unusual conditions may need reassessment.
Can I have low testosterone with normal LH?
Yes. If testosterone is low, an LH result within the laboratory range may still be inappropriately normal. Your physician interprets the results together.
Does low testosterone mean I have a pituitary tumor?
No. Many other causes exist. Imaging is considered when hormone patterns, symptoms or other findings warrant it.
Can sleep apnea or weight loss treatment fix low testosterone?
Addressing these contributors may help some men, but hormone recovery is not assured. Treatment remains worthwhile for broader health reasons.
Which test shows why testosterone is low?
There is no single cause-finding test. Repeat testosterone, LH/FSH and selected additional investigations are combined with history and examination.
Can testosterone return to normal without TRT?
It can when a reversible contributor improves. Persistent testicular or pituitary disorders may need specific treatment; repeat assessment guides the decision.
Find the reason behind your symptoms
At NovaGenix in Jupiter, Dr. Timothy Mackey evaluates symptoms, medical history and appropriate laboratory results to help determine next steps. Bring prior blood work, your medication list and any fertility concerns.
Patients in Jupiter and Palm Beach County can schedule a consultation to discuss evaluation and an individualized plan.
