Quick Facts
- Sample: Blood (Morning collection recommended between 7–10 a.m.)
- Fasting: No fasting required. Avoid biotin supplements for at least 72 hours before testing, as biotin may interfere with test results.
- Turnaround: 3-5 days. May take longer based on weather, holidays, or lab delays.
What This Test Measures
This test reports four results from a single blood draw: Total Testosterone (measured by mass spectrometry), Bioavailable Testosterone, Bioavailable Testosterone (%), and Sex Hormone Binding Globulin (SHBG). Total testosterone reflects the full amount of testosterone circulating in your blood, both bound and unbound. Bioavailable testosterone refers to the portion of testosterone not bound to SHBG, while the bioavailable testosterone percentage expresses that fraction as a share of the total.
SHBG is a liver-produced protein that binds testosterone and other sex hormones, carrying them through the bloodstream in an inactive form. SHBG itself is a binding protein, not a hormone, and its result reflects binding capacity rather than testosterone production. Together, these four values give your healthcare provider a picture of how much testosterone is present and how much of it is bound versus available.
Benefits
- Reports total testosterone alongside the bioavailable (non-SHBG-bound) fraction
- Measures SHBG, a protein that affects testosterone availability
- Uses mass spectrometry methodology for total testosterone
- Supports evaluation of possible testosterone excess or deficiency
- Provides results relevant to both men and women
- Single blood draw covers all four reported values
Who Is This Test For?
- Men noticing symptoms linked to low or declining testosterone
- Men or women experiencing changes in sex drive
- Women with irregular or absent periods
- Individuals with changes in hair growth patterns or skin changes like acne
- Individuals with concerns about fertility related to testosterone levels
- Individuals whose provider wants to assess testosterone alongside SHBG
How It Works
- Order Your Test Online
- Visit a Local Lab
- Get Results Online
FAQ
1. What is the purpose of this hormone test?
This test measures total testosterone, bioavailable testosterone, bioavailable testosterone percentage, and SHBG from one blood sample. Total testosterone reflects the full circulating amount of the hormone, while bioavailable testosterone reflects the portion not bound to SHBG. SHBG is a binding protein, not a hormone, and reflects how much testosterone is transported in an inactive form. These results may help a healthcare provider evaluate signs of testosterone excess or deficiency, but this test does not diagnose a condition on its own.
2. Who would benefit from this test?
People noticing symptoms associated with testosterone excess or deficiency, such as changes in sex drive, irregular or absent periods, changes in hair growth or skin, or fertility concerns, may consider this test. It's relevant for both men and women, since testosterone and SHBG levels are measured differently across sexes. A healthcare provider can help determine if this test fits your specific situation.
3. When should I order this test?
You may consider this test if you're experiencing symptoms like decreased sex drive, erectile dysfunction, irregular periods, or changes in hair or skin patterns. It may also be useful when a provider wants to look at testosterone alongside its binding protein, SHBG. This test does not replace a full medical evaluation and is one piece of information your provider may use.
4. How does this test differ from other hormone tests?
This test reports total testosterone (measured directly by mass spectrometry) together with bioavailable testosterone, bioavailable testosterone percentage, and SHBG. Total testosterone includes both bound and unbound hormone, while bioavailable testosterone reflects only the fraction not bound to SHBG. SHBG is a binding protein, not a hormone, and does not directly indicate how much testosterone your body produces. These four results are distinct and are not interchangeable with one another.
5. Do I need to fast before this test?
No fasting is required for this test. You should stop biotin consumption at least 72 hours before your blood collection, as biotin can interfere with results.
6. How quickly will I get results?
Results are typically available in 3-5 days. Turnaround may take longer depending on weather, holidays, or lab delays.
7. How do I interpret the results?
Interpreting total testosterone, bioavailable testosterone, bioavailable testosterone percentage, and SHBG depends on factors like your sex, age, symptoms, and medical history. Because SHBG affects how much testosterone is available to your body, these results are often reviewed together rather than individually. An abnormal result does not automatically confirm a hormonal condition, and a normal result does not rule one out. Your healthcare provider is best positioned to interpret these results in the context of your health.
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.
8. What should I do if my results are abnormal?
If your results fall outside the expected range, review them with a qualified healthcare provider. They can help determine whether additional evaluation or testing is appropriate based on your health history and symptoms. This test result alone does not provide a complete clinical conclusion.
9. How often should I get tested?
Testing frequency should be determined by your healthcare provider based on your individual health needs. There is no set schedule for repeating this test, so follow your provider's guidance on when retesting may be appropriate.
Pre test preparation
No fasting is required for this test. Stop biotin consumption at least 72 hours prior to your blood collection, as biotin can interfere with test results.
