Total vs Free Testosterone: Which One Should You Test?
Start with morning total testosterone. Add free testosterone when total is borderline or SHBG is likely off. Which test, which method and what it costs.
Educational content · Not medical advice · Provider evaluation required for any treatment
Start with total testosterone, drawn in the morning and repeated to confirm. Add free testosterone, measured by equilibrium dialysis or calculated from total testosterone, SHBG and albumin, when your total is borderline or something is likely to push SHBG up or down, such as aging, obesity, thyroid or liver disease, or certain medications. That's the order the Endocrine Society recommends (Bhasin et al., J Clin Endocrinol Metab 2018).
At Anabolic Insights, you usually don't have to choose. At Quest, Testosterone, Free and Total costs $18 and measures total testosterone by LC/MS and free testosterone by equilibrium dialysis in one test.
The short answer
- Screening or first baseline: total testosterone, morning, fasting, repeated if it's low.
- Total is near the low end of normal: add free testosterone.
- SHBG is likely abnormal: add free testosterone and SHBG.
- On TRT: track total testosterone by uncapped LC/MS. Add free testosterone if SHBG is unusually high or low.
- Method matters for free testosterone: equilibrium dialysis or a validated calculation. Avoid direct "analog" immunoassays.
Total vs free testosterone tests at a glance
| Test | What it measures | Price at Anabolic Insights | Turnaround (our estimate) | When it's useful | Method and lab type |
|---|---|---|---|---|---|
| Total testosterone | All testosterone in blood: SHBG-bound, albumin-bound and free | $14 (Quest, LC/MS), $36 (LabCorp, LC/MS-MS) | About 3 days typical | First test for low testosterone; main number to track on TRT | LC/MS, uncapped. Venous draw at a Quest or LabCorp patient service center |
| Free testosterone, equilibrium dialysis | The unbound fraction, measured directly | $18 with total T by LC/MS (Quest); $39 by equilibrium ultrafiltration (LabCorp) | About 8 days typical | Borderline total, abnormal SHBG, or when total and symptoms don't match | Equilibrium dialysis or ultrafiltration. Venous draw at Quest or LabCorp |
| Calculated free testosterone | The unbound fraction, estimated from total T, SHBG and albumin | $29.99 (Quest), or included in the Basic Panel ($95) | Within our 7–14 day window | Same uses as measured free T, when a validated formula is used | Calculation from measured inputs. Venous draw at Quest |
| Free testosterone, direct analog immunoassay | An antibody estimate that tracks total testosterone, not free | $60 alone, or $50 with total T (LabCorp) | Labcorp lists 4–7 days | Not recommended. Choose another method | Direct analog immunoassay. Venous draw at LabCorp |
| Bioavailable testosterone | Free plus albumin-bound testosterone | Included in the Basic Panel ($95, Quest); not sold on its own | About 8 days for the panel | Rarely adds much beyond free T | Calculated from total T, SHBG and albumin. Venous draw at Quest |
A licensed provider orders every test. There's no lab fee, draw fee or membership required, and results go to your dashboard.
A note on LabCorp options: on our site, the LabCorp versions of "Free Testosterone" and "Testosterone, Free and Total" use the direct analog method. If you're ordering through LabCorp, choose Testosterone Free & Total, LC/MS-MS, Uncapped ($39) instead.
What each number tells you
Most testosterone in blood is bound to proteins. SHBG holds it tightly, and albumin holds it loosely. Free testosterone, the unbound part, is about 2% to 4% of the total, according to Quest's test directory. Total testosterone adds all three together. Free testosterone is only the unbound part.
When SHBG is normal, total and free move together, so total testosterone tells you most of what you need. When SHBG is high or low, they split apart. That's when free testosterone earns its place. For how SHBG shifts the math, read SHBG and free testosterone.
When total testosterone is enough
The Endocrine Society recommends measuring fasting morning total testosterone with an accurate, reliable assay as the first test, then repeating it to confirm a low result (Bhasin et al., 2018). Timing matters because testosterone is highest in the morning. See whether testosterone labs should be drawn in the morning.
A harmonized reference range for healthy, non-obese men aged 19 to 39 is 264 to 916 ng/dL (Travison et al., J Clin Endocrinol Metab 2017). If your total is clearly in that range and you have no reason to suspect an SHBG problem, free testosterone usually won't change the picture.
When to add free testosterone
The guideline recommends a free testosterone result when total testosterone is near the lower limit of normal, or when you have a condition that alters SHBG (Bhasin et al., 2018). Common reasons:
- Aging. SHBG rises with age, so free testosterone falls more than total (Antonio et al., J Clin Endocrinol Metab 2016).
- Obesity. In the European Male Aging Study, men with obesity had lower total and free testosterone (Wu et al., J Clin Endocrinol Metab 2008). Men with low total but normal free testosterone tended to be heavier and had lower SHBG, so total alone can make things look worse than they are (Antonio et al., 2016).
- Thyroid or liver disease, diabetes, and some medications such as certain anticonvulsants. Quest lists these among the conditions that change SHBG.
- Symptoms that don't match a normal total. In the Antonio study of 3,334 men aged 40 to 79, men with normal total but low calculated free testosterone had more sexual and physical symptoms. Men with low total but normal free testosterone didn't (Antonio et al., 2016).
If free testosterone is added, add SHBG too ($14 at Quest). It explains why total and free disagree.
How free testosterone should be measured
This is where many people get a misleading number.
- Equilibrium dialysis separates free from bound testosterone before measuring it. The guideline names it as the method to use (Bhasin et al., 2018).
- Calculated free testosterone uses total testosterone, SHBG and albumin in a formula. In the study behind the widely used Vermeulen formula, calculated free testosterone was almost identical to equilibrium dialysis in every condition tested except pregnancy (Vermeulen et al., J Clin Endocrinol Metab 1999).
- Direct analog immunoassays are the problem. The same study found analog results were only a fraction of the dialysis values, and the gap changed with SHBG (Vermeulen et al., 1999). A later lab study found an analog assay's results followed total testosterone, not free (Fritz et al., Clin Chem 2008). The Endocrine Society says not to use them (Bhasin et al., 2018; Rosner et al., J Clin Endocrinol Metab 2007).
Measured and calculated free testosterone can still disagree a little, and each has its own reference range. Compare like with like. For a deeper look, read measured vs calculated free testosterone.
On TRT: which number to track
On therapy, total testosterone is the main number. The guideline recommends checking it 3 to 6 months after starting, with a target in the mid-normal range (Bhasin et al., 2018). Use an uncapped LC/MS test. Some immunoassays stop at 1,500 ng/dL, so a high result can read ">1500" instead of a number. See immunoassay vs LC/MS testosterone tests.
Free testosterone helps on TRT when SHBG is far from typical. With very low SHBG, total can look modest while free is high. With high SHBG, the reverse can happen. Draw at a consistent point in your schedule each time. See peak vs trough timing. Testosterone is only one part of monitoring on TRT; hematocrit, estradiol, lipids and PSA matter too. See the best blood test on TRT or another hormone protocol.
What to order at Anabolic Insights
- Best value for most people: Testosterone, Free and Total at Quest, $18. Total by LC/MS and free by equilibrium dialysis. Add SHBG for $14.
- Total only, lowest cost: Total Testosterone at Quest (LC/MS), $14.
- Calculated free testosterone: Free Testosterone at Quest, $29.99, calculated from total testosterone, SHBG and albumin. Since the $18 test measures free testosterone directly, most people won't need this one.
- At LabCorp: Testosterone Free & Total, LC/MS-MS, Uncapped, $39.
- Full hormone picture: the Complete Men's Panel ($239 at Quest) includes free testosterone by dialysis, total by LC/MS, SHBG, LH, FSH and sensitive estradiol.
Turnaround is slower than some services. Equilibrium dialysis takes about 8 days at Quest, and our results window is typically 7 to 14 days.
FAQs
Is free testosterone more important than total testosterone?
Not as a first test. Total testosterone is the starting point. Free testosterone becomes more useful when total is borderline or SHBG is abnormal. In those cases it can match symptoms better than total does.
Can I have normal total testosterone and low free testosterone?
Yes. It's most common when SHBG is high, as often happens with aging. In a large European study, men with normal total but low free testosterone reported more symptoms than men with both normal.
What is the most accurate free testosterone test?
Equilibrium dialysis is the reference method. A calculation from total testosterone, SHBG and albumin using a validated formula comes very close. Direct analog immunoassays aren't accurate and the Endocrine Society recommends against them.
Should I test free testosterone on TRT?
Total testosterone by LC/MS is the main number to track on TRT. Free testosterone and SHBG add useful context when SHBG is unusually high or low, or when your results and symptoms don't match. Your provider decides what to monitor.
Is bioavailable testosterone the same as free testosterone?
No. Bioavailable testosterone is free testosterone plus the part loosely bound to albumin. It's usually calculated from the same inputs as free testosterone, so it rarely adds much.
References
- Bhasin S, Brito JP, Cunningham GR, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744.
- Vermeulen A, Verdonck L, Kaufman JM. A critical evaluation of simple methods for the estimation of free testosterone in serum. J Clin Endocrinol Metab. 1999;84(10):3666–3672.
- Rosner W, Auchus RJ, Azziz R, Sluss PM, Raff H. Position statement: utility, limitations, and pitfalls in measuring testosterone: an Endocrine Society position statement. J Clin Endocrinol Metab. 2007;92(2):405–413.
- Travison TG, Vesper HW, Orwoll E, et al. Harmonized reference ranges for circulating testosterone levels in men of four cohort studies in the United States and Europe. J Clin Endocrinol Metab. 2017;102(4):1161–1173.
- Antonio L, Wu FC, O'Neill TW, et al. Low free testosterone is associated with hypogonadal signs and symptoms in men with normal total testosterone. J Clin Endocrinol Metab. 2016;101(7):2647–2657.
- Wu FC, Tajar A, Pye SR, et al. Hypothalamic-pituitary-testicular axis disruptions in older men are differentially linked to age and modifiable risk factors: the European Male Aging Study. J Clin Endocrinol Metab. 2008;93(7):2737–2745.
- Fritz KS, McKean AJ, Nelson JC, Wilcox RB. Analog-based free testosterone test results linked to total testosterone concentrations, not free testosterone concentrations. Clin Chem. 2008;54(3):512–516.
- Quest Diagnostics. Testosterone Free, Calculation (test code 18944).
- Labcorp. Testosterone, Free, Direct (test 144980).