Quick Facts
- Sample: Blood (serum)
- Fasting: Overnight fasting recommended
- Turn-around: 7-9 business days. May take longer based on weather, holiday, or lab delays.
Benefits
- Accurate hormone assessment — measures bioavailable testosterone by accounting for SHBG, reducing misdiagnosis by up to 15% (Mayo Clinic 2024)
- Convenient direct access — order online without a doctor's visit and monitor testosterone health discreetly
- Fast results — receive comprehensive hormone analysis typically within 7-9 business days
- Better therapy monitoring — track testosterone replacement therapy effectiveness and adjust treatment as needed
- Complete picture — reveals true testosterone availability even when total testosterone appears normal
Who Is This Test For?
- Men experiencing low libido, fatigue, or erectile dysfunction who suspect testosterone deficiency
- Individuals with symptoms of hormone imbalance such as infertility or decreased muscle mass
- People monitoring testosterone replacement therapy to ensure optimal dosing and effectiveness
- Women with androgen excess symptoms including irregular periods, excess hair growth, or acne
- Anyone with borderline total testosterone results needing clarification of bioavailable levels
How It Works – Just 3 Steps
- Order online — purchase your test without a doctor's visit and receive a lab requisition form
- Visit a lab — get your blood drawn at a nearby patient service center, preferably 6–10 a.m. after fasting
- Get results — access your confidential results online within 7-9 business days.
FAQ
What does this test measure? Total testosterone, SHBG levels, and calculated bioavailable testosterone—the fraction of hormone actually available to your tissues (CDC 2024).
Why measure SHBG along with testosterone? SHBG binds testosterone tightly, making it unavailable; higher SHBG lowers bioavailable testosterone even when total levels appear normal.
Do I need to fast for this test? Yes, overnight fasting is recommended for accurate results; schedule your blood draw in the early morning for peak hormone levels.
Can women take this test? Absolutely—women produce testosterone in smaller amounts, and this test helps diagnose conditions like PCOS or adrenal disorders.
How soon will I receive my results? Results are typically available within 7-9 business days for your convenience and peace of mind.
What if my total testosterone is normal but I have symptoms? This test reveals bioavailable testosterone, which often correlates better with symptoms than total testosterone alone (NIH 2025).
More Details
What is the purpose of this test?
This test measures the biologically active fraction of testosterone in your bloodstream by quantifying both total testosterone and sex hormone binding globulin (SHBG). While total testosterone includes all circulating testosterone—both bound and unbound—bioavailable testosterone represents the hormone actually available to your body's tissues. This includes free testosterone plus testosterone loosely bound to albumin, but excludes testosterone tightly bound to SHBG. Since SHBG modulates how much testosterone your body can use, measuring both values together provides a clearer, more accurate picture of your true hormone status (Mayo Clinic 2024).
Testosterone is essential for male physical development and reproductive function, including muscle growth, body hair development, deepening voice, sex drive regulation, and sperm production. Women also produce testosterone in smaller amounts through the ovaries and adrenal glands. This test uses sensitive immunoassay methods on a serum sample to deliver precise, quantitative measurements that help diagnose hormone imbalances and guide treatment decisions.
Who would benefit from this test?
This test is valuable for individuals experiencing symptoms of hormone imbalance that affect quality of life and health. Men with signs of testosterone deficiency—such as low libido, erectile dysfunction, fatigue, decreased muscle mass, or infertility—can benefit from this comprehensive hormone assessment. About 38% of men over age 45 have low total testosterone, but bioavailable levels correlate better with actual clinical symptoms (NIH 2025).
Women experiencing androgen excess symptoms also benefit from this test. Conditions like polycystic ovary syndrome (PCOS), ovarian or adrenal tumors, and pituitary disorders can cause elevated testosterone. Symptoms include irregular or absent periods, excess facial or body hair, acne, and voice changes. Additionally, individuals on testosterone replacement therapy should use this test to monitor treatment effectiveness and ensure optimal dosing for their specific needs.
When should I order Testosterone BIO With Sex Hormone Binding Globulin (SHBG) Blood Test?
Order this test when your total testosterone results are borderline or when symptoms suggest hormone imbalance despite normal total testosterone levels. SHBG levels increase with age, obesity, liver disease, and certain medications, affecting testosterone bioavailability—about 20–30% of variation in testosterone availability is attributed to SHBG changes (AUA 2017).
You should consider this test if you experience persistent fatigue, decreased sexual desire, erectile dysfunction, difficulty building muscle, or fertility problems. Women should order when experiencing irregular periods, excess hair growth, or suspected PCOS. It's also appropriate for monitoring testosterone therapy effectiveness—regular testing ensures your treatment is optimized and identifies when dosage adjustments are needed. Schedule your blood draw between 6–10 a.m. when testosterone levels peak for most accurate results.
How do I interpret the results?
Your results include three key measurements that work together to reveal your true hormone status. Total testosterone reflects all circulating testosterone; SHBG indicates how much protein is binding your hormones; and bioavailable testosterone shows the hormone fraction actually available to your tissues. Low bioavailable testosterone suggests androgen deficiency even when total testosterone appears normal—this occurs when high SHBG levels bind too much hormone.
Low total, low bioavailable testosterone
- Meaning: True testosterone deficiency
- Typical action: Consult an endocrinologist; consider hormone replacement therapy
Normal total, low bioavailable testosterone
- Meaning: High SHBG reducing availability
- Typical action: Investigate causes of elevated SHBG; address underlying conditions
High total, high bioavailable testosterone
- Meaning: Possible androgen excess
- Typical action: Evaluate for tumors, PCOS, or adrenal disorders
Normal range across all values
- Meaning: Balanced hormone status
- Typical action: Maintain a healthy lifestyle; retest if symptoms develop
Accurate bioavailable testosterone measurement improves diagnosis of hypogonadism and reduces misdiagnosis by up to 15% compared to total testosterone alone (Mayo Clinic 2024).
Compare your results to age- and sex-specific reference ranges provided with your report. Always consider your symptoms alongside lab values—hormone deficiency symptoms with borderline bioavailable testosterone warrant consultation with a specialist, even if numbers fall within normal ranges.
Disclaimer: Reference ranges may vary by laboratory. Listed ranges are general guidelines and may differ from those used by the performing lab. Always consult your healthcare provider for interpretation.
Pre-test preparation
Fast overnight before your blood draw—avoid eating or drinking anything except water for 8–12 hours before your appointment. Schedule your blood collection between 6–10 a.m. when testosterone levels naturally peak, ensuring the most accurate measurement of your hormone status. Avoid strenuous exercise 24 hours before testing, as intense workouts can temporarily affect hormone levels.
Inform your healthcare provider about all medications and supplements you're taking, as certain drugs affect testosterone and SHBG levels. Medications like corticosteroids, opioids, and some blood pressure drugs can lower testosterone, while others may increase SHBG. Don't stop prescribed medications without medical guidance—simply note them when ordering your test.
How often should I get tested?
- Initial evaluation of symptoms: once to establish baseline
- Starting testosterone replacement therapy: 3–6 months after initiation, then adjust
- Stable on testosterone therapy: every 6–12 months
- Monitoring PCOS or androgen excess: every 6–12 months or as directed
- After lifestyle changes (weight loss, exercise): 3–6 months to assess implemented changes
Your healthcare provider may recommend more frequent testing based on your specific condition, symptoms, or treatment response. Consistent monitoring helps detect changes early and allows timely treatment adjustments.
Why early detection matters
Identifying testosterone deficiency or excess early prevents serious long-term health consequences and improves quality of life. Untreated low testosterone in men contributes to osteoporosis, cardiovascular disease, diabetes, depression, and cognitive decline. Early detection allows intervention before irreversible complications develop. For women, undiagnosed androgen excess from conditions like PCOS leads to infertility, metabolic syndrome, and increased cardiovascular risk.
Bioavailable testosterone measurement provides diagnostic accuracy that total testosterone alone cannot achieve. Since SHBG levels vary significantly with age, obesity, and medical conditions, relying only on total testosterone misses many cases of true hormone deficiency or excess. This comprehensive test reveals your actual hormone status, enabling precise treatment decisions and better health outcomes.
Related tests you may consider
Testosterone Free Serum Test - Measures unattached testosterone levels in the blood to help diagnose and monitor hormonal imbalances in men and women.
Luteinizing Hormone (LH) Serum Test - Measures LH levels and helps screen for issues with fertility or reproductive organs, ovulation, and pituitary function.
Prolactin Serum Test - Helps screen for a pituitary tumor by measuing the level of prolactin in the blood.
Estradiol (E2) Blood Test - measures the E2 hormone levels in the blood to detect an abnormal level or hormone imbalance.
