Total testosterone is the starting point
Total testosterone measures both bound and unbound hormone. Most testosterone is bound to SHBG or albumin, while a small fraction circulates freely. Free testosterone means the unbound fraction. Bioavailable testosterone conventionally includes free testosterone and the fraction loosely bound to albumin; these are different quantities.
Changes in SHBG can affect the relationship between total and free testosterone. For a man with compatible symptoms or a borderline total result, the clinician may use SHBG and a suitable method of assessing free testosterone to clarify the result. Not everyone needs a separate free testosterone test, and no single hormone result diagnoses deficiency.
What SHBG and albumin add
SHBG is a binding protein made in the liver. Age, thyroid function, liver disease, body composition and hormone treatment can influence its concentration. A lower total testosterone with low SHBG does not necessarily mean testosterone deficiency.
Albumin is another binding protein. SHBG and albumin can provide context for interpreting total testosterone and are inputs to some validated calculations. Whether a calculation is useful depends on symptoms, the assay and the clinical question; the presence of the component tests does not mean a calculated result is automatically reported.
Free testosterone and a simple ratio are different
A suitable free testosterone measurement or validated calculation can be useful in selected cases. The result depends on the method, and free and bioavailable testosterone must be identified separately on the report.
A simple testosterone/SHBG ratio is an index, not a measured free testosterone concentration. It is not an interchangeable substitute for an appropriate free testosterone assessment in men. Enkel Health’s Testosterone Basics profile contains total testosterone, SHBG and albumin; it does not include a separately reported free or bioavailable testosterone result or the ratio.
Testosterone Basics includes total testosterone, SHBG and albumin for a selected testosterone question. A separate free or bioavailable testosterone result and a testosterone/SHBG ratio are not included.
Testosterone Basics
Sampling conditions matter
For Testosterone Basics, fast for 10 hours and sample at 07:00-10:00 after normal sleep. Water is allowed. Acute illness, disrupted sleep, medicines and strenuous activity can affect the result. Tell the clinician about hormone treatment and shift work, and follow the order-specific advice.
A low result in a man is usually confirmed on another morning and assessed with symptoms before a diagnosis is made. Do not change prescribed treatment or begin testosterone treatment based on a test result alone.
Reading the result and choosing follow-up
Symptoms, repeated results and medical history determine what to investigate next. After a confirmed low testosterone, LH, FSH or prolactin may help assess the cause. Hormone treatment, other medicines, obesity and illness can also affect interpretation.
The next step may be a targeted clinical assessment, a repeat morning sample or treatment of another condition. A routine yearly hormone panel is not required for men without symptoms, and a test result does not establish the need for testosterone treatment.
Markers in this article
More articles in the same area
- Normal testosterone levels by ageNormal testosterone levels by age: Swedish reference intervals in nmol per liter, how the value changes over the years and when a level counts as low.
- Free testosterone, total testosterone and SHBG: the differenceFree testosterone, total testosterone and SHBG explained: what each value shows, why a total value can mislead and how the three fit together.
- PMOS (previously called PCOS) and blood tests: the values that bring clarityWhich blood values matter when PMOS (previously called PCOS) is suspected? A guide to testosterone, SHBG, LH, FSH and more, and what they can and cannot show.
- Men’s health after 40: choosing blood tests for your risk and symptomsHow lipids, glucose, kidney tests, hormones and PSA are selected after 40. Testing and follow-up depend on risk, symptoms and previous findings.
This article is general health information, not medical advice and not an assessment of your values. If you have symptoms or concerns, contact your healthcare provider.