Bioavailable testosterone is an assessment of the biologically active testosterone in serum.
The concentrations of free and bioavailable testosterone are derived from mathematical expressions based on constants for the binding of testosterone to albumin and/or sex hormone binding globulin (SHBG).
Testosterone circulates in the blood in three forms:
- Nearly half is bound tightly to a protein called SHBG (sex hormone binding globulin). In this form, testosterone is unable to enter cells.
- The other half is more weakly bound to albumin. In this form, testosterone can eventually detach from albumin and increase the level of biologically active testosterone.
- A very small fraction called “free testosterone” is not bound to any protein and can therefore freely enter cells and be used by the body.
→ The total quantity of albumin-bound (point 2 above) and free forms (point 3 above) is called “bioavailable testosterone.”
→ All non-SHBG bound testosterone is considered bioavailable.
→ Total testosterone is the sum of the three forms of testosterone.
In the vast majority of cases, measuring the level of any fraction will provide the required clinical information. However, there are cases in which the total testosterone level is less representative of biological activity. When this happens, free or bioavailable testosterone must be measured.
Regardless of the fraction measured, it should be remembered that testosterone levels vary throughout the day. In young men, these levels can as much as double between a morning and mid-afternoon sample.
Total testosterone:
Generally represents the biological activity of natural or medicinal testosterone at the tissue level
SHBG:
Helps interpret abnormal testosterone levels
Bioavailable testosterone:
Lowered bioavailable testosterone levels are consistent in men with primary hypogonadism or hypogonadism secondary to a pituitary deficiency.
Free testosterone:
Lowered free testosterone levels are consistent in men with primary hypogonadism or hypogonadism secondary to a pituitary deficiency.
Usually, bioavailable (and free testosterone) levels parallel the total testosterone levels. However, a number of conditions and medications are known to increase or decrease the sex hormone-binding globulin (SHBG) concentration, which may cause total testosterone concentration to change without necessarily influencing the bioavailable or free testosterone concentration, or vice versa:
- Treatment with corticosteroids and sex steroids (particularly oral conjugated estrogen) can result in changes in SHBG levels and availability of sex-steroid binding sites on SHBG. This may make diagnosis of subtle testosterone abnormalities difficult.
- Inherited abnormalities in SHBG binding.
- Liver disease and severe systemic illness.
- In pubertal boys and adult men, mild decreases of total testosterone without LH abnormalities can be associated with delayed puberty or mild hypogonadism. In this case, either bioavailable or free testosterone measurements are better indicators of mild hypogonadism than determination of total testosterone levels.
- In polycystic ovarian syndrome and related conditions, there is often significant insulin resistance, which is associated with low SHBG levels. Consequently, bioavailable or free testosterone levels may be more significantly elevated.
References:
Kumar P, Kumar N, Thakur DS, Patidar A. Male hypogonadism: Symptoms and treatment. J Adv Pharm Technol Res. 2010 Jul;1(3):297-301. doi: 10.4103/0110-5558.72420. PMID: 22247861; PMCID: PMC3255409.
What does it mean if your Testosterone, bioavailable result is too high?
Total testosterone circulates primarily as protein-bound (nearly 50% bound to sex hormone binding globulin (SHBG) and 50% to albumin). Only 2-3% exists in free, biological active form. Testosterone is weakly bound to albumin and can be reversed easily, therefore albumin bound and free testosterone are considered to be bioavailable testosterone.
The highest testosterone level peaks at 30 to 40 years of age in adult men. The levels start to decline steadily after the fourth or fifth decade of adult male life.
The free testosterone test may be used to evaluate infertility, erectile dysfunction, or osteoporosis in men and to evaluate hirsutism, polycystic ovarian disease, and virilization in women. The test may also be used to monitor the efficacy of testosterone-lowering therapies in prostate cancer.
In adult men, testicular or androgen abuse might be suspected if testosterone levels exceed the upper limit of the normal range by more than 50%.
In women, high levels of bioavailable testosterone are consistent with overactive adrenal glands or ovaries (polycystic ovaries).
All Your Lab Results.
One Simple Dashboard.
Import, Track, and Share Your Lab Results Easily
Import, Track, and Share Your Lab Results
Import lab results from multiple providers, track changes over time, customize your reference ranges, and get clear explanations for each result. Everything is stored securely, exportable in one organized file, and shareable with your doctor—or anyone you choose.
Cancel or upgrade anytime
What does it mean if your Testosterone, bioavailable result is too low?
In men, low levels of bioavailable testosterone are consistent with primary hypogonadism (testicular impairment) or secondary to a pituitary problem.
Andropause in men (decreased libido, erectile dysfunction, muscle weakness, etc.) is caused by secondary hypogonadism associated with aging.
It is important to determine if low levels of testosterone are due to aging or a pathological disorder.
Laboratories
Bring All Your Lab Results Together — In One Place
We accept reports from any lab, so you can easily collect and organize all your health information in one secure spot.
Pricing Table
Gather Your Lab History — and Finally Make Sense of It
Finally, Your Lab Results Organized and Clear
Personal plans
$79/ year
Advanced Plan
Access your lab reports, explanations, and tracking tools.
- Import lab results from any provider
- Track all results with visual tools
- Customize your reference ranges
- Export your full lab history anytime
- Share results securely with anyone
- Receive 5 reports entered for you
- Cancel or upgrade anytime
$250/ once
Unlimited Account
Pay once, access everything—no monthly fees, no limits.
- Import lab results from any provider
- Track all results with visual tools
- Customize your reference ranges
- Export your full lab history anytime
- Share results securely with anyone
- Receive 10 reports entered for you
- No subscriptions. No extra fees.
$45/ month
Pro Monthly
Designed for professionals managing their clients' lab reports
- Import lab results from any provider
- Track lab results for multiple clients
- Customize reference ranges per client
- Export lab histories and reports
- Begin with first report entered by us
- Cancel or upgrade anytime
About membership
What's included in a Healthmatters membership
Import Lab Results from Any Source
See Your Health Timeline
Understand What Your Results Mean
Visualize Your Results
Data Entry Service for Your Reports
Securely Share With Anyone You Trust
Let Your Lab Results Tell the Full Story
Once your results are in one place, see the bigger picture — track trends over time, compare data side by side, export your full history, and share securely with anyone you trust.
Bring all your results together to compare, track progress, export your history, and share securely.
What Healthmatters Members Are Saying
Frequently asked questions
Healthmatters is a personal health dashboard that helps you organize and understand your lab results. It collects and displays your medical test data from any lab in one secure, easy-to-use platform.
- Individuals who want to track and understand their health over time.
- Health professionals, such as doctors, nutritionists, and wellness coaches, need to manage and interpret lab data for their clients.
With a Healthmatters account, you can:
- Upload lab reports from any lab
- View your data in interactive graphs, tables, and timelines
- Track trends and monitor changes over time
- Customize your reference ranges
- Export and share your full lab history
- Access your results anytime, from any device
Professionals can also analyze client data more efficiently and save time managing lab reports.
Healthmatters.io personal account provides in-depth research on 10000+ biomarkers, including information and suggestions for test panels such as, but not limited to:
- The GI Effects® Comprehensive Stool Profile,
- GI-MAP,
- The NutrEval FMV®,
- The ION Profile,
- Amino Acids Profile,
- Dried Urine Test for Comprehensive Hormones (DUTCH),
- Organic Acids Test,
- Organix Comprehensive Profile,
- Toxic Metals,
- Complete Blood Count (CBC),
- Metabolic panel,
- Thyroid panel,
- Lipid Panel,
- Urinalysis,
- And many, many more.
You can combine all test reports inside your Healthmatters account and keep them in one place. It gives you an excellent overview of all your health data. Once you retest, you can add new results and compare them.
If you are still determining whether Healthmatters support your lab results, the rule is that if you can test it, you can upload it to Healthmatters.
We implement proven measures to keep your data safe.
At HealthMatters, we're committed to maintaining the security and confidentiality of your personal information. We've put industry-leading security standards in place to help protect against the loss, misuse, or alteration of the information under our control. We use procedural, physical, and electronic security methods designed to prevent unauthorized people from getting access to this information. Our internal code of conduct adds additional privacy protection. All data is backed up multiple times a day and encrypted using SSL certificates. See our Privacy Policy for more details.