Testosterone Blood Test: Complete Guide to Testing

Master testosterone testing: learn which tests to order, optimal timing, reference ranges by age and sex, factors affecting results, and how to interpret findings. Understand why morning fasting tests matter and when additional testing is warranted.

Why Test Testosterone? Symptoms Indicating Testing

Testosterone testing helps diagnose hypogonadism (low testosterone) and guide treatment decisions. Understanding which symptoms warrant testing helps you and your provider determine whether testing is appropriate.

In men, low testosterone may cause: Persistent fatigue and low energy despite adequate sleep; decreased sexual desire (libido) or erectile dysfunction; reduced muscle mass despite resistance training; increased body fat, especially abdominal; depression, anxiety, or mood instability; decreased motivation or focus; insomnia or poor sleep quality; hot flashes or temperature regulation issues; reduced bone density; joint or muscle pain disproportionate to activity.

Not all these symptoms indicate low testosterone—many conditions (depression, thyroid dysfunction, diabetes, sleep apnea) produce similar symptoms. However, if several symptoms cluster, testosterone testing is reasonable. Your provider considers symptom pattern and medical history before recommending testing.

In women, elevated testosterone may cause: Unexpected facial or body hair growth; male-pattern baldness or increased hair loss; acne; deepening voice; clitoral enlargement; irregular menstrual periods; reduced breast tissue; increased muscle mass without training; fertility issues. These symptoms suggest possible PCOS, adrenal disorder, or androgen-secreting tumor, warranting testosterone testing to evaluate.

Testing thresholds: There's no universal agreement on which testosterone level is "too low" requiring treatment. Many endocrinologists consider testing patients with symptoms and total testosterone below 400 ng/dL. Some advocate testing anyone below 300 ng/dL. The decision depends on your symptoms, age, and provider judgment. Generally, symptoms plus testosterone below 300 ng/dL warrant consideration of treatment.

Types of Testosterone Tests: Which to Order

Multiple testosterone tests exist, each providing different information. Understanding what each measures helps you choose appropriate testing.

Total Testosterone: Measures all testosterone in your blood—both bound (attached to proteins) and free (bioavailable). This is the standard screening test. Normal total testosterone doesn't exclude functional hypogonadism (low free testosterone despite adequate total). However, it's the appropriate starting point because it's inexpensive, widely available, and sufficient for initial diagnosis in most men. Most men with symptoms and low total testosterone benefit from treatment regardless of free testosterone levels.

Free Testosterone: Measures testosterone not bound to proteins—the portion available to exert biological effects. Free testosterone is more specific for bioactive hormone status than total testosterone. It's particularly useful if total testosterone is low-normal (250-400 ng/dL) with persistent symptoms, or if SHBG is abnormally high or low. Reference ranges for free testosterone differ from total testosterone and by sex—female free testosterone is about 50-fold lower than male free testosterone.

Bioavailable Testosterone: Calculates testosterone bound to albumin plus free testosterone—essentially, total testosterone minus SHBG-bound testosterone. This measures the testosterone available to tissues. Some clinicians prefer bioavailable testosterone over free testosterone because it's more stable and easier to measure accurately. However, free testosterone is more commonly ordered.

SHBG (Sex Hormone-Binding Globulin): A protein binding testosterone and estrogen in blood. High SHBG reduces free testosterone despite adequate total testosterone. Conditions increasing SHBG include hyperthyroidism, cirrhosis, certain medications. Low SHBG (seen in obesity, diabetes, insulin resistance) reduces SHBG-bound testosterone, potentially increasing free testosterone despite low or normal total. Testing SHBG explains why free testosterone may be disproportionate to total testosterone.

Recommended testing approach: Start with total testosterone. If total testosterone is low (<300 ng/dL) with symptoms, that's usually sufficient to initiate treatment discussion. If total testosterone is 300-400 ng/dL with persistent symptoms, add free testosterone and SHBG. If total testosterone is normal but symptoms persist, test free testosterone to assess bioavailable hormone status.

When to Test: Timing and Preparation

Time of day: Morning is essential. Testosterone naturally peaks between 7-9am and declines steadily throughout the day, dropping 15-30% by late afternoon. Testing at 3pm versus 8am can produce a difference of 100+ ng/dL in the same person on the same day. For valid results, test between 7-11am ideally. If you can't test before 11am, note the time so your provider can account for diurnal variation. Never compare a 3pm test to a previous 8am test—the timing difference confounds interpretation.

Fasting status: Most testosterone testing doesn't require strict fasting, but some labs recommend it. Check with your lab beforehand. If fasting is recommended, avoid eating for 8-12 hours before testing (overnight fasting is typical). You can usually drink water. Eating significantly doesn't change testosterone levels, but fasting may be advised to ensure consistent conditions for other blood work being done simultaneously.

Sleep and physical activity: Test when you're well-rested. Sleep deprivation (even one poor night) reduces testosterone 10-15%, so ensure adequate sleep 2-3 nights before testing. Avoid intense exercise for 48 hours before testing—strenuous workouts temporarily suppress testosterone. Moderate activity is fine; just avoid heavy lifting or cardio the day before testing.

Illness and stress: Illness, fever, infection, and acute illness suppress testosterone. Wait until you're fully recovered (at least 1 week post-illness) before testing to avoid artificially low results. Acute stress also suppresses testosterone, so test during calm periods. Chronic stress elevates cortisol, which suppresses testosterone—if you're under chronic stress, that's something to address regardless, but it affects test interpretation.

Medications: Certain medications affect testosterone. Opioids (even short-term use), glucocorticoids (prednisone), some psychiatric medications, and anticonvulsants suppress testosterone. If you're on these, inform your provider—stopping them may not be feasible, but they should interpret results accounting for these effects. Discuss with your doctor whether stopping or adjusting medications before testing is appropriate.

Repeat testing: A single testosterone test is insufficient for diagnosis. Repeat testing 2-8 weeks later confirms abnormal results. This accounts for day-to-day variation and eliminates isolated low results from temporary causes (illness, poor sleep). Two consistently low results strongly support hypogonadism diagnosis. Do repeat testing at similar times of day for valid comparison.

Reference Ranges: By Age and Sex

Adult males, total testosterone: General reference range is 300-1000 ng/dL (10-35 nmol/L in SI units). However, ranges vary by lab—check your specific lab's reference. Additionally, normal testosterone declines about 1% annually after age 30, so age-specific ranges are more accurate.

Age 20-30: 600-900 ng/dL average
Age 30-40: 500-850 ng/dL average
Age 40-50: 450-750 ng/dL average
Age 50-60: 350-650 ng/dL average
Age 60-70: 300-550 ng/dL average
Age 70+: 250-500 ng/dL average

These are approximations—individual variation is substantial. Some 70-year-olds have testosterone levels comparable to 40-year-olds; others have much lower levels. Age-adjusted ranges provide context but shouldn't replace symptoms in decision-making.

Low testosterone definition: Total testosterone below 300 ng/dL is generally considered low by most endocrinologists. Below 250 ng/dL is definitely low, increasing disease risk. Between 300-400 ng/dL is ambiguous—some men have symptoms attributable to low testosterone; others don't. Clinical symptoms plus lab values together determine whether treatment is appropriate.

Adult females, total testosterone: 15-70 ng/dL is standard reference. Women naturally produce 10-15x less testosterone than men. Female testosterone peaks at ovulation mid-cycle. Testing on specific cycle days standardizes results if needed, though most labs don't require this. Testosterone >70 ng/dL in women suggests PCOS, adrenal disorders, or androgen-secreting tumors—further investigation is warranted. Below 15 ng/dL is very low and may indicate adrenal insufficiency.

Free testosterone reference ranges: Adult male: 46-224 pg/mL (varies slightly by lab). Adult female: 0-4.2 pg/mL. Free testosterone (<10 pg/mL in men) with normal or elevated total testosterone suggests elevated SHBG.

SHBG reference ranges: Male: 19-76 nmol/L (varies by lab). Female: 24-122 nmol/L. Women have higher SHBG; estrogen increases it. Obesity, diabetes, and insulin resistance lower SHBG; these conditions affect free testosterone interpretation.

Interpreting Your Results

Low total testosterone (<300 ng/dL) in symptomatic men: Strongly suggests hypogonadism (low testosterone production by testes or problems with hypothalamic-pituitary signaling). This warrants discussion of testosterone replacement therapy (TRT) if symptoms are significant and other causes are ruled out. Next steps typically include testing LH (luteinizing hormone) and FSH (follicle-stimulating hormone) to differentiate primary hypogonadism (testes problem) from secondary hypogonadism (pituitary problem). Primary hypogonadism shows low testosterone with elevated LH/FSH; secondary shows low testosterone with low-normal LH/FSH.

Normal total testosterone with low free testosterone: Suggests elevated SHBG. This can occur with hyperthyroidism, cirrhosis, estrogen excess, or certain medications. Investigating SHBG causes is important because treating underlying conditions may normalize free testosterone. Additionally, some men with this pattern benefit from TRT because they lack sufficient bioavailable hormone despite adequate total testosterone.

Elevated total testosterone in women (>70 ng/dL): Suggests possible PCOS (polycystic ovary syndrome), adrenal excess, or androgen-secreting tumor. PCOS is most common; diagnosis requires ultrasound findings plus hormone levels plus clinical features. Some women with mild elevations (70-100 ng/dL) have no PCOS features—retest to confirm elevation before investigation. Significant elevations (>150 ng/dL) warrant specialist referral to endocrinology to rule out tumors.

Disproportionate free/bioavailable testosterone to total: If total testosterone is normal but free testosterone is low, elevated SHBG is likely. Check SHBG level. If SHBG is elevated, investigate thyroid function, liver function, and estrogen excess. If SHBG is low-normal, consider insulin resistance (diabetes, obesity, metabolic syndrome) as cause.

What Affects Testosterone Test Results

Sleep quality and quantity: One night of poor sleep reduces testosterone 10-15%. Chronic sleep deprivation (sleep apnea, insomnia, shift work) causes sustained testosterone suppression. Testing after good sleep provides accurate baseline; testing after poor sleep underestimates true testosterone levels. If you have sleep issues, address them before interpreting low testosterone as primary hypogonadism—sleep treatment alone may normalize testosterone.

Stress and cortisol: Acute stress elevates cortisol, which suppresses testosterone acutely. Chronic stress sustains cortisol elevation, chronically suppressing testosterone. Testing during stressful periods (job crisis, illness in family, financial stress) may show artificially low testosterone. Stress reduction—meditation, exercise, therapy—can raise testosterone independent of other treatment. If testosterone is low and stress is high, addressing stress is a prerequisite before TRT.

Obesity and body composition: Excess body fat—especially abdominal fat—suppresses testosterone and elevates aromatase enzyme activity, converting testosterone to estrogen. Overweight men often have low testosterone partly due to adipose tissue hormone effects. Weight loss through diet and exercise can increase testosterone 10-20% for significant weight loss. Additionally, obesity increases SHBG, further lowering free testosterone. This creates a vicious cycle where low testosterone promotes weight gain, which further suppresses testosterone. TRT combined with weight loss is more effective than either alone.

Alcohol use: Acute alcohol consumption suppresses testosterone 10-20%, with effects worst after heavy drinking or binge drinking. Chronic heavy alcohol use causes sustained testosterone suppression and testicular damage. Moderate alcohol (1-2 drinks daily) has minimal testosterone effect. If you drink heavily and have low testosterone, reducing alcohol consumption may normalize testosterone partially or fully. If alcohol use is excessive, addiction treatment should precede testosterone testing.

Medications affecting testosterone: Opioid medications (hydrocodone, oxycodone, morphine, etc.) suppress testosterone even at therapeutic doses. Glucocorticoids (prednisone, dexamethasone) suppress testosterone when used chronically or at high doses. Some psychiatric medications (SSRIs rarely, antipsychotics sometimes) may suppress testosterone. Antiseizure medications can suppress testosterone. If you're on these medications and have low testosterone, discuss with your prescriber whether stopping or reducing them is feasible. If stopping isn't possible, testosterone supplementation may still be appropriate.

Illicit drug use: Cannabis (marijuana) can suppress testosterone acutely and chronically in heavy users. Cocaine and methamphetamine suppress testosterone acutely; chronic use causes sustained suppression. If you use illicit drugs and have low testosterone, reduction or cessation may improve testosterone. Testing should include substance use history.

Illness and infection: Acute illness, fever, viral infection, or bacterial infection temporarily suppresses testosterone. Chronic infections (TB, HIV) cause sustained suppression. Cancer and cancer treatment (chemotherapy, radiation) suppress testosterone. If you're acutely ill, defer testing until you've recovered fully (at least 1 week post-illness). If chronic illness is present, that's important context for low testosterone interpretation.

Getting a Testosterone Test: Where and How

Through your doctor: Request testosterone testing from your primary care physician or a specialist (urologist, endocrinologist). Your doctor can order the appropriate test(s) based on symptoms and medical history. Most insurance covers testosterone testing if indicated by symptoms and medical necessity. This approach provides clinical context for results—your doctor interprets them alongside your presentation and other findings.

Online lab ordering: Services like EverlyWell, LetsGetChecked, Ulta Lab Tests, and others allow you to order testosterone tests without seeing a doctor first. You order online, choose a local blood collection center or do finger-prick at home, and receive results via an online portal. Cost is typically $30-100 depending on which test(s) you order. Advantages: no doctor appointment needed, quick results, privacy. Disadvantages: no provider context or recommendations, you interpret results alone. This works for baseline self-assessment but isn't ideal if you have symptoms or plan to start treatment.

Through specialist clinics: Urologists, endocrinologists, men's health clinics, and some weight loss/anti-aging clinics routinely test and manage testosterone. These specialists have expertise in interpretation and treatment decisions. Insurance coverage depends on your plan and indication (symptomatic hypogonadism is covered; elective optimization is sometimes not).

Testosterone Test Accuracy and Lab Variation

Lab-to-lab variation: Reference ranges vary between laboratories—a result of 350 ng/dL might be "low-normal" at one lab and "low" at another depending on their ranges. Always check your lab's specific reference range, not a generic range. This variation is why repeat testing at the same lab is preferable—you can track changes accurately at one lab.

Testing method variation: Different testing methods (liquid chromatography-mass spectrometry LC-MS, immunoassay, enzyme immunoassay) have different accuracy. LC-MS is most accurate, especially for low testosterone. Some labs use older immunoassays with greater variability. High-quality labs use LC-MS; ask your lab which method they use. If you're considering TRT based on borderline results, requesting LC-MS testing may provide more accurate results.

Day-to-day variation: Individual testosterone levels vary 10-20% day-to-day even at the same time. This normal variation is why repeat testing confirms diagnosis—isolated low results could be random variation. Two consistently low results (at similar times) confirm hypogonadism.

Follow-Up Testing and Monitoring

After starting testosterone therapy: Test testosterone 4-6 weeks after starting treatment to assess dose adequacy. Check whether testosterone has risen to desired range (typically 500-700 ng/dL). If too low, dose increases. If very high (>900 ng/dL), dose decreases. Hematocrit (red blood cell concentration) also increases with testosterone—test at 4-6 weeks and ensure it remains <54% (some recommend <50%). Additionally, test PSA (prostate specific antigen) if you're over 40 or have prostate cancer risk, and estradiol if you have breast tissue gynecomastia.

Ongoing monitoring on testosterone therapy: Once dose is optimized, test testosterone every 6-12 months to ensure levels remain stable. Test hematocrit annually—if elevated (>54%), you may need blood donation or dose reduction. Periodically check PSA, lipids, liver function, and blood pressure. Annual physical exams and symptom assessment ensure testosterone therapy remains beneficial and safe.

Age-appropriate screening: For men not on TRT, routine screening becomes reasonable around age 50-60. Annual or biennial testing allows early detection of age-related decline. Some men choose to start TRT when testosterone drops significantly; others simply monitor.

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