Free Testosterone Testing in Bangkok: Calculated vs Measured, and Which to Order

Men's hormone testing guide · 2026

Free testosterone is the number most people want and the one most often measured badly. The fix is cheap: order the three inputs and calculate it.

By MedEx · Updated September 2026 · Approx. 7-minute read

Quick answer

Free testosterone is the small unbound fraction of circulating testosterone. It can be estimated in two ways: measured directly by immunoassay, or calculated from total testosterone, SHBG and albumin. Analogue immunoassays for free testosterone perform poorly at low concentrations and are not recommended by major guidelines. In most Bangkok laboratories the practical, accurate and inexpensive route is to order total testosterone, SHBG and albumin on one morning sample and calculate the free fraction from those three values.

In this guide

1. Why anyone bothers with the free fraction
2. The three ways it gets estimated
3. What to order, in one draw
4. Common ways the number misleads

Why anyone bothers with the free fraction

Only a small proportion of testosterone in blood is unbound. The rest is held by sex hormone binding globulin, which binds tightly, and albumin, which binds loosely. The unbound and albumin-bound fractions are the portion generally considered available to tissue.

This matters whenever SHBG is abnormal. Obesity, insulin resistance, hypothyroidism and nephrotic syndrome lower SHBG; ageing, hyperthyroidism, liver disease, HIV and some anticonvulsants raise it. In both directions, total testosterone drifts away from the functional picture and a free estimate resolves the discrepancy.

Where SHBG is normal and total testosterone is comfortably mid-range, a free testosterone adds very little. Order it for a reason, not by default.

The three ways it gets estimated

1. Calculated free testosterone. Uses total testosterone, SHBG and albumin in a published binding equation. Inexpensive, reproducible, and the pragmatic choice for most clinical questions.
2. Equilibrium dialysis with mass spectrometry. The reference method. Accurate but slower, more expensive and generally reserved for research or difficult cases.
3. Direct analogue immunoassay. Cheap and widely offered, but it correlates poorly with dialysis at the low end — exactly where a decision is likely to hinge on the number. Several professional bodies advise against relying on it.

If a provider quotes a “free testosterone” price without specifying the method, ask. You can check which biomarkers a laboratory offers through the MedEx lab directory.

What to order, in one draw

For a complete and defensible male hormone picture, a single morning draw can cover:

• Total testosterone
• SHBG
• Albumin (often already included in a liver or metabolic panel)
• LH and FSH, to localise the problem if testosterone is low
• Prolactin, where libido is low or LH is suppressed
• Estradiol, where gynaecomastia is present or aromatase inhibition is being discussed

Adding HbA1c, a lipid profile and TSH to the same sample costs little extra and frequently explains more than the hormone panel does. This combination sits comfortably inside a MedEx checkup package.

Common ways the number misleads

Different equations give different answers. The Vermeulen and Sodergard formulas, among others, return values that are not interchangeable. Keep to one method when tracking change.

Albumin is frequently assumed rather than measured. Many online calculators default to a fixed albumin. In liver disease, malnutrition or inflammation, that assumption breaks the calculation.

Reference ranges are method-specific. A calculated free testosterone should be compared against a range derived the same way, not against a range from a direct assay.

The clinical picture still leads. A calculated free testosterone slightly below a cut-off, in someone with no specific symptoms, is not a reason to start treatment. Review the result with a MedEx clinician before acting on it.

Frequently asked questions

Is calculated free testosterone accurate?

It correlates well with equilibrium dialysis when total testosterone, SHBG and a measured albumin are used, and is far more reliable than a direct analogue immunoassay. It is the pragmatic choice for most clinical questions.

Why do guidelines advise against direct free testosterone immunoassays?

Analogue immunoassays correlate poorly with the reference method at low concentrations, which is precisely where a treatment decision is most likely to depend on the result.

Do I need albumin measured, or can it be assumed?

Measure it where possible. Many calculators assume a fixed albumin, which breaks the calculation in liver disease, malnutrition or significant inflammation.

Can free testosterone be normal when total testosterone is low?

Yes. Low SHBG – common with obesity, insulin resistance and hypothyroidism – drags total testosterone down while the free fraction stays adequate. This is a frequent source of unnecessary treatment.

Should free testosterone be drawn in the morning too?

Yes. The same 8-10am timing applies, since the free fraction tracks the total testosterone rhythm.

Sources and further reading

1. MedEx lab test catalogue
2. Endocrine Society: Testosterone Therapy in Men With Hypogonadism
3. MedEx lab directory

Medical disclaimer: This article is general health information and does not replace medical advice, diagnosis or treatment. Laboratory reference ranges differ between laboratories and results must be interpreted alongside your symptoms, medicines and medical history. Speak with a qualified clinician before starting, stopping or changing any treatment. Service details, inclusions and prices can change — confirm them with MedEx before booking.