A bioavailable testosterone test estimates how much of your testosterone is free or only loosely held by albumin, so your tissues can reach it. It leaves out the share tightly locked to SHBG, which is why it can tell a different story from total testosterone.
It is most useful when SHBG is unusually high or low, for example with ageing, weight gain, the pill or thyroid changes. We read it against optimal ranges, with your SHBG, total testosterone and the patterns between them.
Bioavailable testosterone is included in Vively's Male Hormone Health Test and, for women, the Female Hormone Health Test. You start with your Baseline Health Check, then add the hormone test that fits you.
Every marker in range? Get your $99 back. T&Cs apply.Want to save 25%? Try our 4-Month Reset insteadBioavailable testosterone is the share of your testosterone that is either completely free or loosely bound to albumin, the most common protein in blood. Both forms can reach tissues such as muscle, bone and brain. It excludes testosterone bound tightly to SHBG, which is largely unavailable. It is calculated from your total testosterone, SHBG and albumin.
Testosterone travels in three states. A small share is free testosterone, unbound and active. A larger share sits loosely on albumin, and because albumin's grip is weak, it can come off as blood passes through tissues. The rest is held tightly by sex hormone-binding globulin (SHBG) and mostly stays out of action.
The formula uses the same inputs as calculated free testosterone, so the two usually move together. Bioavailable is the wider measure, so it is reported in nmol/L while free testosterone uses pmol/L.
A bioavailable testosterone test shows how much testosterone your tissues can use, and it matters most when SHBG is pulling your total testosterone result in a misleading direction. It strips out the SHBG-bound share.
Two common situations:
Because SHBG slowly rises over the decades, bioavailable testosterone falls faster with age in men than total testosterone does. Normal does not always mean optimal. A man in his 40s with low-normal bioavailable testosterone and rising SHBG is worth tracking, even if nothing needs treating today.
For adult men, bioavailable testosterone is usually about 2.5 to 12.0 nmol/L. For women, it is much lower, about 0.1 to 1.3 nmol/L when tested on day 2 to 5 of the cycle.
| Range | |
|---|---|
| Typical lab reference range (adult men) | 2.5 to 12.0 nmol/L |
| Vively optimal range (men) | Above 3.0 nmol/L |
| Typical lab reference range (adult women, day 2 to 5) | 0.1 to 1.3 nmol/L |
| Vively optimal range (women) | 0.45 to 1.3 nmol/L |
Because this is a calculated marker, ranges vary more between labs than for most tests, so read your result against the range on your report. Optimal ranges are what we aim for to support long-term health, not diagnostic cut-offs.
High bioavailable testosterone usually means either more testosterone is being made or taken, or SHBG is low so more is available. In women, the most common cause is polycystic ovary syndrome (PCOS).
Men who aren't using testosterone or steroids rarely need to worry about a high-normal result. Women with a high result and symptoms such as acne, excess hair or irregular periods should see a GP.
Low bioavailable testosterone means less testosterone is reaching your tissues, either because you are making less or because high SHBG is locking more of it away. In men, a low result needs repeating with an early morning test before it means much.
Common reasons in men:
Less often, the problem is in the testes or the pituitary gland's signal to them. A GP will check LH, FSH and prolactin to tell these apart.
In women, low bioavailable testosterone is very common on the combined pill or oral HRT, because oestrogen taken by mouth raises SHBG. It is rarely acted on by itself.
Anything that changes testosterone, SHBG or albumin will shift this calculated result. Timing follows the same rules as free testosterone: men test early in the morning, ideally before 10am, and women with periods test on day 2 to 5.
Do you need to fast? No. Men should still test before breakfast, and with your Baseline you'll be fasting anyway.
Bioavailable testosterone is only as meaningful as the SHBG and albumin results behind it.
| Pattern | What it can mean |
|---|---|
| Normal total testosterone, high SHBG, low bioavailable testosterone | Testosterone is there, but more is locked away. Worth checking causes of high SHBG, such as thyroid function, liver health and under-eating. |
| Low bioavailable testosterone with low albumin | The calculation may be less accurate. Low albumin needs broader clinical review. |
| High bioavailable testosterone and high FAI with irregular periods (women) | A pattern often seen with PCOS. Needs GP review to confirm. |
The most useful levers are the ones that move SHBG and insulin towards a healthy range. If the cause sits in the testes or pituitary, treatment comes from your GP or a specialist instead.
See your GP if two early morning tests both come back below your lab's range, especially with low libido, erectile problems, fewer morning erections, low mood or loss of muscle.
Book in promptly if you have a low result plus headaches or changes in your vision, which can signal a pituitary problem. Women should also go promptly for fast-spreading facial or body hair, a deeper voice, or periods that have stopped for three months when not pregnant.
Bioavailable testosterone is included in our Male Hormone Health Test, Female Hormone Health Test, Perimenopause and Menopause Hormone Tests, Weight Management Test and Full Body Health Check, alongside SHBG and total testosterone. Start with your Baseline Health Check, then add whichever test fits. The exact markers can depend on the referring doctor's review.
After we arrange the referral through our GP network, your sample is taken at one of 3,700+ accredited partner collection centres: book early morning if you're a man, or day 2 to 5 of your cycle if you have periods. Results land in the app, usually within a few days, against optimal ranges. Your practitioner explains what your SHBG pattern means, builds a personalised plan with you and sets a retest.
Men can order the Male Hormone Health Test, and women the Female Hormone Health Test.
No fasting is needed for the marker itself, but men should test in the morning, ideally before breakfast and before 10am. Women with periods should test on day 2 to 5. Vively's Baseline needs an overnight fast for glucose and insulin, so if you test with it, you'll be fasting anyway.
No. Free testosterone counts only unbound testosterone. Bioavailable testosterone is free testosterone plus the share loosely bound to albumin, so it is a larger number and is reported in nmol/L instead of pmol/L. Both are calculated from total testosterone, SHBG and albumin, and they usually rise and fall together.
For a man, it is below the typical lower limit of about 2.5 nmol/L. Repeat the test early in the morning before reading much into it, and look at SHBG, total testosterone, LH and symptoms. For a woman, 2.0 nmol/L would be above the usual range and worth reviewing.
This usually means your SHBG is low, so less testosterone is locked away and more is available. It is common in men carrying extra weight or with insulin resistance. Your usable testosterone may be fine, but the low SHBG is worth acting on for your metabolic health.
Yes. The combined oral contraceptive pill raises SHBG, which lowers bioavailable and free testosterone. Your result reflects the pill rather than what your ovaries would produce without it. Oral HRT has a similar effect. Tell your practitioner what contraception or hormones you use.
Many blood tests can be Medicare-funded when a doctor orders them for a clinical reason. With Vively, we arrange the referral through our GP network as part of your hormone test, so you don't need to book a separate GP appointment first.
How to get it: Available as one of our specialty add-on tests. Your test referral is issued straight away when you order. See how a blood test without a referral works.
Related tests: Cortisol/DHEA-S Ratio, Dehydroepiandrosterone Sulfate (DHEA-S), Total testosterone, Sex Hormone-Binding Globulin
The Baseline Health Check reads 70+ markers, then your dietitian turns your results into a plan. $99 a month, first test included.
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