Low Testosterone in Men: A Doctor's Guide for 2026

What Is Low Testosterone?

Low testosterone, clinically termed hypogonadism, is the failure of the testes to produce adequate testosterone, often combined with deficient sperm production. The Endocrine Society defines biochemical hypogonadism as a consistently low serum testosterone level accompanied by signs and symptoms of androgen deficiency. Population data from the European Male Ageing Study (N=3,369) found that 2.1% of men aged 40 to 79 met both biochemical and symptomatic criteria for hypogonadism.

Primary vs. Secondary Hypogonadism

Primary hypogonadism originates in the testes themselves. Causes include Klinefelter syndrome, orchitis, chemotherapy, and prior testicular trauma. Lab results show low testosterone with elevated LH and FSH because the pituitary is working hard to stimulate non-responsive testes.

Secondary hypogonadism originates in the hypothalamus or pituitary. Causes include hyperprolactinemia, obesity, opioid use, and pituitary adenomas. LH and FSH are low or inappropriately normal alongside low testosterone. A 2014 analysis in the Journal of Clinical Endocrinology and Metabolism confirmed that obesity is a leading driver of secondary hypogonadism through increased aromatase activity converting testosterone to estradiol.

Age-Related Decline

Testosterone peaks in the late teens and early twenties, then declines approximately 1 to 2% per year after age 30. The Baltimore Longitudinal Study of Aging found that 20% of men over 60, 30% over 70, and nearly 50% over 80 have total testosterone below 325 ng/dL. Age-related decline is real, but it does not automatically justify treatment. Symptoms must be present.

Symptoms of Low Testosterone

Symptoms fall into two categories: sexual and non-sexual. Neither category alone confirms the diagnosis.

Sexual Symptoms

The three most specific sexual symptoms are reduced libido, erectile dysfunction, and fewer spontaneous morning erections. The Endocrine Society's 2018 Clinical Practice Guideline states that "the presence of three sexual symptoms (decreased libido, fewer morning erections, erectile dysfunction) was the strongest predictor of a low total testosterone level." Infertility and reduced ejaculate volume also appear in this group.

Non-Sexual Symptoms

Non-sexual symptoms are more variable and overlap with many other conditions. They include:

• Persistent fatigue and reduced energy
• Loss of lean muscle mass and increased body fat
• Depressed mood, irritability, or difficulty concentrating
• Decreased bone mineral density (osteoporosis risk)
• Reduced body and facial hair
• Hot flashes or sweating episodes

No single non-sexual symptom is diagnostic. Men reporting only fatigue or mood changes should have a thorough workup to rule out thyroid disease, sleep apnea, depression, and anemia before attributing symptoms to testosterone.

How Is Low Testosterone Diagnosed?

Diagnosis requires biochemical confirmation, not symptoms alone. Ordering a testosterone level without the correct timing and fasting state is a common source of misdiagnosis.

Lab Timing and Methodology

Total testosterone should be drawn between 7 a.m. And 10 a.m. After an overnight fast, on at least two separate days. Levels fluctuate by 30 to 35% across the day. The American Urological Association recommends using a reliable assay method, specifically liquid chromatography-tandem mass spectrometry (LC-MS/MS), rather than immunoassay when borderline results are obtained.

A total testosterone below 300 ng/dL on both measurements, in the context of symptoms, meets biochemical criteria.

Additional Lab Work

Free testosterone matters when total testosterone is borderline (300 to 400 ng/dL) or when sex hormone-binding globulin (SHBG) levels may be abnormal, such as in obesity or liver disease. Calculated free testosterone below 65 pg/mL supports the diagnosis in symptomatic men.

The full initial panel includes:

• Total and free testosterone
• LH and FSH (to distinguish primary from secondary)
• Prolactin (to screen for pituitary adenoma)
• CBC (baseline hematocrit before therapy)
• Comprehensive metabolic panel
• PSA if age 40 or older and considering TRT
• Thyroid-stimulating hormone (TSH) to exclude thyroid cause of symptoms

A 2020 review in the Journal of the American Medical Association noted that approximately 25% of men presenting with symptomatic hypogonadism have an underlying secondary cause that requires separate treatment, making the LH/FSH draw diagnostically non-optional.

Full Menu of Treatment Options

Once the diagnosis is confirmed, several FDA-approved delivery routes are available. Choice depends on patient preference, lifestyle, insurance coverage, and clinical factors like fertility goals and hematocrit.

Testosterone Injections

Injections remain the most widely used and studied formulation. Testosterone cypionate and testosterone enanthate are bioequivalent long-acting esters. Standard dosing is 100 to 200 mg intramuscularly (IM) or subcutaneously (SQ) every 1 to 2 weeks. Some clinicians prefer weekly injections to reduce peak-to-trough fluctuation.

A head-to-head pharmacokinetic study published in the Journal of Clinical Pharmacology demonstrated that subcutaneous testosterone cypionate at 75 mg weekly produced steadier serum levels than 150 mg IM every two weeks, with fewer hematocrit elevations.

Testosterone undecanoate (Aveed) is a longer-acting injectable given at 750 mg IM at baseline, 4 weeks, then every 10 weeks. It carries an FDA-mandated REMS program due to rare oil microembolism risk.

Evidence grade: High (multiple RCTs, long-term safety data)

Transdermal Gels and Solutions

Gels (AndroGel 1% and 1.62%, Testim, Vogelxo) are applied daily to the shoulders, upper arms, or abdomen. They are convenient but carry a transfer risk to partners and children. The FDA issued a black-box warning in 2009 on secondary exposure, particularly in pediatric patients who had inadvertent contact with gel-treated skin.

Typical dosing starts at 40 to 50 mg applied daily, titrated based on serum levels at 2 to 4 weeks.

Evidence grade: High (phase III trials, multiple approvals)

Topical Solutions and Nasal Gel

Axiron is a topical solution applied to the axilla. Natesto is a nasal testosterone gel dosed at 11 mg (5.5 mg per nostril) three times daily. Natesto has a notable advantage: a 2015 study in the International Journal of Impotence Research (N=306) found that Natesto preserved gonadotropin secretion (LH, FSH) and sperm parameters better than IM injections, making it an option for men who want treatment but have not completed their family.

Oral Testosterone

Testosterone undecanoate (Jatenzo, 237 mg twice daily; Tlando, 225 mg twice daily) received FDA approval in 2019 and 2022, respectively. Both are taken with food to optimize lymphatic absorption and bypass first-pass liver metabolism. The key trial for Jatenzo (N=166) achieved testosterone levels in the normal range in 87% of men at day 90.

Blood pressure elevation is a class effect of oral testosterone undecanoate: the Jatenzo label carries a warning for hypertension. Monitor blood pressure at baseline and at 3 months.

Evidence grade: Moderate (phase III, shorter follow-up than injectables)

Testosterone Pellets

Subcutaneous pellets (Testopel) are implanted in the upper gluteal area under local anesthesia every 3 to 6 months. Each pellet contains 75 mg of testosterone; typical implantation uses 6 to 12 pellets per session (450 to 900 mg). The main advantage is no daily or weekly compliance requirement. Disadvantages include minor surgical risk, inability to quickly adjust dose if adverse effects occur, and variable insurance coverage.

Evidence grade: Moderate (observational data, limited RCTs)

Testosterone Patches

Androderm patches deliver 2 mg or 4 mg per day applied nightly to the back, abdomen, thigh, or upper arm. Skin irritation at the application site affects up to 37% of users, which limits long-term adherence. Package labeling from the FDA notes that 37% of men in clinical trials experienced application-site reactions requiring medical treatment.

Evidence grade: High (phase III)

Comparison of Testosterone Replacement Options

| Formulation | Dose | Frequency | Key Advantage | Key Limitation | |---|---|---|---|---| | Testosterone cypionate injection | 100 to 200 mg IM/SQ | Weekly or biweekly | Low cost, well-studied | Peaks and troughs; requires injection | | Testosterone enanthate injection | 100 to 200 mg IM | Weekly or biweekly | Generic availability | Same as cypionate | | Testosterone undecanoate (Aveed) | 750 mg IM | Q10 weeks | Infrequent dosing | REMS; oil embolism risk | | AndroGel 1.62% | 40.5 mg daily | Daily | Non-invasive | Transfer risk; skin irritation | | Natesto nasal gel | 11 mg | Three times daily | Preserves fertility markers | Frequent dosing; nasal irritation | | Jatenzo oral | 237 mg twice daily | Twice daily | No injection, no transfer | Hypertension risk; must take with food | | Testopel pellets | 450 to 900 mg SC | Q3 to 6 months | Compliance-free | Minor procedure; non-reversible short-term | | Androderm patch | 2 to 4 mg | Daily | Steady levels | 37% skin reaction rate |

Alternatives to TRT When Fertility Is a Priority

Exogenous testosterone suppresses the hypothalamic-pituitary-gonadal (HPG) axis. Spermatogenesis often drops to near zero within 3 months of starting TRT. Men who want to conceive should not use standard testosterone therapy.

Clomiphene Citrate

Clomiphene citrate (Clomid) is an off-label but widely used option. It blocks estrogen receptors in the hypothalamus, triggering increased LH and FSH output, which in turn stimulates endogenous testosterone production. Typical dosing is 25 to 50 mg orally every day or every other day. A 2003 study in the Journal of Urology (N=178) found that clomiphene raised mean testosterone from 232 ng/dL to 612 ng/dL over 4 to 6 months while preserving or improving sperm parameters. Clomiphene is not FDA-approved for male hypogonadism, so it is prescribed off-label.

Human Chorionic Gonadotropin (hCG)

HCG mimics LH and directly stimulates Leydig cell testosterone production. Standard dosing is 1,500 to 5,000 IU subcutaneously 2 to 3 times per week. It maintains testicular volume and spermatogenesis, unlike exogenous testosterone. A 2005 Fertility and Sterility study demonstrated that hCG monotherapy raised serum testosterone to normal in 84% of men with secondary hypogonadism while preserving sperm production. Note that the original Pregnyl and Novarel brands are derived from human urine; Ovidrel is recombinant hCG.

Enclomiphene

Enclomiphene (the trans-isomer of clomiphene) is in late-stage development for male hypogonadism. Unlike clomiphene, it lacks the cis-isomer (zuclomiphene), which may accumulate and have estrogenic effects. Phase III data showed normalization of testosterone in 74% of men at 3 months. FDA correspondence on the enclomiphene NDA is publicly available through the FDA drug database.

Who Should NOT Use Testosterone Therapy

The Endocrine Society's 2018 guidelines specify absolute and relative contraindications. Prescribers must screen all patients before initiating therapy.

Absolute Contraindications

• Active or suspected prostate cancer
• Active or suspected male breast cancer
• Desire to maintain fertility in the near term (use clomiphene or hCG instead)
• Hematocrit above 54%
• Untreated severe obstructive sleep apnea
• Uncontrolled heart failure (class III or IV)

The 2018 Endocrine Society guideline states: "We recommend against starting testosterone therapy in patients with any of the following conditions: metastatic prostate cancer, breast cancer, hematocrit >54%, uncontrolled heart failure, untreated severe obstructive sleep apnea, or active desire for fertility."

Relative Contraindications

• PSA above 4 ng/mL without urological evaluation
• Lower urinary tract symptoms (LUTS) with IPSS score above 19
• Poorly controlled type 2 diabetes
• Recent cardiovascular event (within 3 to 6 months)

The cardiovascular safety debate merits attention. The TRAVERSE trial (N=5,246), published in the New England Journal of Medicine in 2023, found that testosterone therapy did not increase major adverse cardiovascular events (MACE) compared to placebo in men with hypogonadism and high cardiovascular risk, with a hazard ratio of 0.96 (95% CI 0.78 to 1.17). This trial provides the most strong cardiovascular safety data available for TRT to date.

Monitoring During Testosterone Therapy

Starting TRT is not a set-and-forget decision. Lab monitoring protects against the therapy's known adverse effects: polycythemia, PSA changes, and lipid alterations.

Monitoring Schedule

At 3 months post-initiation:

• Total testosterone (target: 400 to 700 ng/dL mid-cycle for injectables)
• Hematocrit (hold or reduce dose if above 54%)
• PSA (hold if rise exceeds 1.4 ng/mL within 12 months or absolute level exceeds 4 ng/mL)
• Blood pressure (especially for oral formulations)

Every 6 to 12 months thereafter:

• Total testosterone, hematocrit, PSA
• Fasting lipid panel
• Bone mineral density (DXA scan) at baseline and every 1 to 2 years in men with osteoporosis

The American Urological Association 2022 guideline update recommends checking a CBC at 3 to 6 months to screen for polycythemia, given that erythrocytosis affects up to 6.5% of men on TRT.

Managing Polycythemia

If hematocrit rises above 54%, the first step is dose reduction or extending the injection interval. Therapeutic phlebotomy is an option for men who require TRT but develop persistent erythrocytosis. Switching from IM injections to daily transdermal therapy typically lowers the erythrocytosis risk.

Managing Estradiol Elevation

Some men on TRT develop elevated estradiol, leading to gynecomastia, fluid retention, or mood changes. Aromatase inhibitors (anastrozole 0.5 to 1 mg twice weekly) may be used when estradiol exceeds 40 to 50 pg/mL and symptoms are present, though routine co-prescription without symptoms is not supported by current guidelines.

Lifestyle Factors That Affect Testosterone Levels

Medication is not always the first step. For men with borderline low testosterone (300 to 400 ng/dL) and mild symptoms, lifestyle modification may restore levels without medication.

Body Weight and Exercise

Adipose tissue expresses aromatase, which converts testosterone to estradiol. A 2013 meta-analysis in Obesity Reviews (N=24 studies) found that a 10% reduction in body weight raised total testosterone by approximately 2.9 nmol/L (83 ng/dL) in overweight men. Resistance training 3 to 4 days per week adds an independent testosterone benefit.

Sleep

Testosterone secretion is closely tied to sleep architecture. An experimental study published in JAMA (N=10) demonstrated that restricting sleep to 5 hours per night for one week reduced daytime testosterone levels by 10 to 15%. Men with untreated obstructive sleep apnea frequently present with low testosterone that improves substantially after CPAP therapy.

Alcohol and Medications

Chronic heavy alcohol use directly suppresses Leydig cell function. Opioids suppress GnRH secretion dose-dependently. Men on chronic opioid therapy have secondary hypogonadism rates exceeding 70% in some series. Statins, particularly at high doses, may modestly lower testosterone through effects on cholesterol availability, though the clinical significance is debated.

What to Expect From Treatment: Clinical Outcomes

Realistic expectations prevent premature discontinuation and over-medication. Responses vary by symptom domain and baseline health.

Sexual Function

Libido responds fastest, often within 3 to 6 weeks. Erectile function improves more slowly and may require a phosphodiesterase-5 inhibitor (sildenafil, tadalafil) alongside TRT in men with vascular or neurogenic contributions to ED. A 2016 meta-analysis in the Journal of Sexual Medicine (N=1,792 across 14 RCTs) found that testosterone therapy significantly improved sexual desire (weighted mean difference 0.54, P<0.001) but had only modest effects on erectile function compared to placebo.

Body Composition

Lean mass increases and fat mass decreases over 6 to 12 months of therapy. Effects are more pronounced with resistance training. Men should not expect dramatic physique changes in the first 3 months.

Bone Density

The T-Trial bone sub-study (N=211) published in the Journal of Bone and Mineral Research showed that testosterone therapy for one year increased volumetric bone mineral density in the spine by 7.5% and in the hip by 3.4% compared to placebo.

Mood and Cognition

Depressed mood, irritability, and difficulty concentrating improve in many men, though the response is less predictable than sexual symptom improvement. Men with a primary psychiatric diagnosis require concurrent psychiatric care.

Finding a Qualified Provider

Board-certified endocrinologists, urologists, and men's health-focused internists are the most appropriate prescribers. Telehealth TRT platforms are legal and convenient but should perform all required labs and document informed consent before prescribing. The Endocrine Society's clinical practice guidelines are freely available for patient review and provide a standard against which any provider's approach can be measured.

Patients should avoid any provider who prescribes testosterone without confirming two low morning testosterone measurements with symptoms, or who does not perform baseline PSA, hematocrit, and lipid assessment.