About 30 to 50 percent of men with type 2 diabetes have low testosterone — much higher than the 5 to 10 percent in age-matched men without diabetes. The pattern is usually hypogonadotropic hypogonadism with low or inappropriately normal LH and FSH, driven by obesity, aromatase conversion of testosterone to estrogen in fat tissue, and chronic inflammation. Erectile dysfunction is often the first sign. Diagnosis requires two morning total testosterone measurements below 264 ng/dL plus symptoms. Treatment combines weight loss, optimization of diabetes and sleep apnea, and testosterone replacement therapy when symptoms warrant.
How Diabetes Lowers Testosterone
- Obesity increases aromatase enzyme in fat tissue, converting testosterone to estrogen
- Higher estrogen feeds back on hypothalamus and pituitary to suppress LH and FSH
- Chronic inflammation (elevated TNF-alpha, IL-6) directly suppresses Leydig cell function
- Insulin resistance impairs testicular steroidogenesis
- Sleep apnea (common in T2D) lowers testosterone independently
- Reduced SHBG (sex hormone-binding globulin) in obesity may also reduce total testosterone measurements
- Opioid medications (for pain in neuropathy or other conditions) further suppress the HPG axis
Prevalence by Population
| Group | Approximate Low Testosterone Prevalence |
|---|---|
| General adult men age 40 to 60 | 5 to 10 percent |
| General adult men 60+ | 15 to 20 percent |
| Men with type 2 diabetes | 30 to 50 percent |
| Men with T2D plus obesity (BMI ≥30) | 40 to 60 percent |
| Men with T2D plus obstructive sleep apnea | 50 to 70 percent |
Symptoms
Sexual
- Reduced libido (sex drive)
- Erectile dysfunction — often first or only symptom
- Reduced morning erections
- Decreased ejaculate volume
- Delayed orgasm
Physical
- Decreased muscle mass and strength
- Increased body fat, especially abdominal
- Gynecomastia (breast tissue enlargement)
- Decreased body and facial hair
- Hot flashes in severe deficiency
- Reduced bone density (osteoporosis risk)
- Anemia (mild)
Cognitive and Emotional
- Fatigue, low energy
- Depressed mood or irritability
- Reduced motivation
- Poor concentration
- Sleep disturbance
Diagnosis
Initial Testing
- Total testosterone — must be drawn between 7 and 11 am (diurnal peak)
- Repeat on a separate morning to confirm — single measurements have ~30 percent variability
- Endocrine Society threshold for low: below 264 ng/dL
- Some labs use 300 ng/dL; consider symptoms with borderline results
- SHBG — useful if total is borderline or symptoms are strong despite “normal” total
- Calculate or measure free testosterone (the biologically active fraction)
Further Workup if Low
- LH and FSH — low or inappropriately normal indicates hypogonadotropic (secondary) hypogonadism; high indicates primary (testicular) failure
- Prolactin — rule out pituitary adenoma (prolactinoma)
- Iron, ferritin, transferrin saturation — rule out hemochromatosis (more common in T2D)
- TSH — rule out thyroid disease
- Pituitary MRI if very low testosterone, very high prolactin, or other pituitary symptoms (vision changes, headaches)
- Karyotype if congenital hypogonadism suspected
Causes to Differentiate
| Category | Examples |
|---|---|
| Primary (testicular failure) | Klinefelter syndrome, prior orchitis, testicular trauma, chemotherapy, radiation |
| Secondary (HPG axis) | Obesity, T2D, opioids, chronic illness, pituitary adenoma, Kallmann syndrome, anabolic steroid history |
| Mixed | Aging — both primary and secondary components |
Treatment — Lifestyle and Underlying Causes
Weight Loss
- Strongest non-pharmacologic intervention
- 10 percent weight loss can raise testosterone by 50 to 100 ng/dL on average
- Bariatric surgery often normalizes testosterone in severely obese men
- Mediterranean diet and regular activity improve insulin sensitivity and testosterone
Diabetes Optimization
- Improving glycemic control modestly improves testosterone
- Metformin and GLP-1 receptor agonists both support weight loss and may help
- Reduce or eliminate opioid pain medications if possible
Sleep Apnea Treatment
- CPAP therapy can raise testosterone meaningfully in men with untreated OSA
- Many men diagnosed with low T have undiagnosed sleep apnea — screen with STOP-BANG or home sleep test
Resistance Training
- 2 to 3 sessions weekly improves testosterone and body composition
- Compound movements (squats, deadlifts, presses) preferred
- Sleep 7 to 9 hours nightly
Testosterone Replacement Therapy (TRT)
Indications
- Confirmed low total testosterone (two morning measurements below 264 ng/dL)
- Consistent symptoms of hypogonadism
- No contraindications
- Discussion of risks, benefits, and goals
Formulations
| Form | Frequency | Notes |
|---|---|---|
| Topical gel (AndroGel, Testim, Fortesta) | Daily | Apply to upper arms/shoulders; risk of transfer to female partners and children |
| Topical solution (Axiron) | Daily underarm | Roll-on applicator |
| Transdermal patch (Androderm) | Daily | Skin irritation common |
| Intramuscular injection (testosterone cypionate or enanthate) | Every 1 to 2 weeks | Self-injected or in clinic; peak-trough fluctuations |
| Long-acting injection (testosterone undecanoate, Aveed) | Every 10 weeks after loading doses | Pulmonary oil microembolism risk requires in-office observation |
| Subcutaneous pellet (Testopel) | Every 3 to 6 months | In-office implant procedure |
| Oral testosterone undecanoate (Jatenzo, Tlando) | Twice daily with food | Newer; needs dietary fat for absorption; BP monitoring |
| Nasal gel (Natesto) | Three times daily | Less HPG axis suppression — fertility preservation |
Monitoring on TRT
- Total testosterone 2 to 4 weeks after starting (target mid-normal range)
- Hematocrit at 3, 6, 12 months then annually — stop or reduce if above 54 percent
- PSA at baseline, 3 to 12 months, then annually for men ≥40
- Digital rectal exam baseline and yearly
- Lipid panel
- Bone density at baseline and every 1 to 2 years if osteoporosis
- Symptom review and side effect screening
Contraindications
- Active prostate cancer or unevaluated suspicious prostate nodule
- Male breast cancer
- Untreated severe sleep apnea
- Hematocrit above 50 percent at baseline
- Severe heart failure
- Recent (within 6 months) myocardial infarction or stroke
- Active desire for fertility — TRT suppresses spermatogenesis
- Severe untreated lower urinary tract symptoms (high IPSS)
Cardiovascular Safety — TRAVERSE
- TRAVERSE trial (2023) enrolled 5,246 men age 45 to 80 with hypogonadism and CV risk factors
- Topical testosterone gel vs placebo
- Primary endpoint: composite of CV death, MI, stroke
- Result: TRT non-inferior to placebo — no significant increase in major adverse CV events
- Modest increases in atrial fibrillation, pulmonary embolism, acute kidney injury observed
- Findings reassure but cautions persist for high-risk individuals
Fertility Considerations
- TRT suppresses LH and FSH, reducing spermatogenesis — often to zero
- Recovery of sperm production after stopping TRT can take 6 to 24 months and may be incomplete
- Alternatives for fertility-desiring men: clomiphene citrate, hCG, aromatase inhibitors (anastrozole), gonadotropin therapy
- Sperm cryopreservation before TRT if future fertility may be desired
Effects of TRT on Diabetes
- Modest improvement in insulin sensitivity in hypogonadal men with T2D
- Improvement in body composition (less fat, more muscle)
- Variable effect on HbA1c
- Improved energy, libido, mood
- TRT is not a primary treatment for diabetes — weight loss and standard diabetes care remain central
Erectile Dysfunction Treatment Beyond TRT
- PDE5 inhibitors (sildenafil, tadalafil, vardenafil) — first-line for ED regardless of testosterone status
- Vacuum erection devices
- Intracavernosal injections (alprostadil)
- Intraurethral suppositories
- Penile implants for refractory cases
- Psychotherapy or counseling when psychogenic component present
When to See an Endocrinologist or Urologist
- Very low testosterone (below 150 ng/dL)
- Elevated prolactin or other pituitary abnormalities
- Suspected primary hypogonadism (high LH/FSH)
- Desired fertility
- Complicated medical history
- Lack of response to standard TRT
- Polycythemia or other TRT side effects
- Prostate concerns
Related Reading
See our overviews on complications and related conditions, diabetes and fertility, and diabetes treatment options. The Endocrine Society 2018 guideline outlines diagnosis and treatment of male hypogonadism.
The Bottom Line
Low testosterone is common in men with type 2 diabetes — affecting 30 to 50 percent — most often through hypogonadotropic hypogonadism driven by obesity, aromatase activity in fat, and chronic inflammation. Erectile dysfunction is frequently the first sign. Diagnosis requires two morning total testosterone measurements below 264 ng/dL plus consistent symptoms, with LH, FSH, SHBG, and prolactin to characterize the cause. Weight loss is the most effective intervention. Testosterone replacement (gels, injections, patches, pellets, oral) is appropriate when symptoms warrant; TRAVERSE trial data reassure on cardiovascular safety. Monitoring includes hematocrit, PSA, and lipids. Talk to your doctor about evaluation if symptoms are present and consider sperm preservation before starting TRT if fertility is desired.
