Low testosterone assessment
- First line
Assessment of low testosterone or hypogonadism with total testosterone, SHBG, albumin, calculated free testosterone, FSH, LH, prolactin and thyroid function. It is designed to confirm a low result and indicate whether the cause may lie in the testes, in the pituitary gland or in a related hormonal cause.
No prescription or appointment needed
Results in 1-2 working days
Includes: Total testosterone · SHBG · Albumin · Calculated free testosterone · FSH · LH · Prolactin · TSH · Free T4. See what each one measures
What it is for
It is used to investigate why testosterone is low. Raised FSH and LH point towards a primary problem of the testis. If they are low or do not rise as would be expected, the cause may lie in the pituitary gland or the hypothalamus, or in functional suppression linked to obesity, illness, medication or lack of sleep.
Prolactin and the thyroid extend the investigation to hormonal causes that can produce similar symptoms or alter the reproductive axis. The result guides the next step, but it does not replace clinical confirmation or any further tests that may be required.
When it is recommended
- Low testosterone that has been confirmed, or repeatedly borderline
- Loss of sexual desire, spontaneous erections or sexual characteristics together with abnormal testosterone
- Male infertility when the hormonal axis needs to be assessed
- Gynaecomastia accompanied by signs of androgen deficiency
- Before considering testosterone therapy
Clinical comment
Low testosterone is a finding, not a cause. FSH and LH make it possible to separate a testicular pattern from a central or functional one, and that distinction completely changes the investigation that follows.
Prolactin is included because a persistent rise can suppress the hormonal axis. A high result must be confirmed under good conditions, and common causes such as stress, medicines or macroprolactin must be considered before thinking about a pituitary lesion. TSH and free T4 are included because both hypothyroidism and hyperthyroidism can alter SHBG, sexual function and testosterone.
We have not included oestradiol or DHEA-S routinely, as they are not part of the usual first assessment of hypogonadism. Free testosterone is calculated from total testosterone, SHBG and albumin to avoid the direct immunoassay, which guidelines consider inaccurate.
The diagnosis requires compatible symptoms and two low results on different mornings. If this is the first low result, it will still have to be confirmed before any treatment is decided.
Dr. Antonio Mas
What is tested
- Total testosterone
- Measures all circulating testosterone.
- SHBG
- The main protein that carries testosterone, and it affects how the total value is interpreted.
- Albumin
- Used together with total testosterone and SHBG to calculate the free fraction.
- Calculated free testosterone
- Estimates the fraction not bound to proteins using a validated formula.
- FSH
- A pituitary hormone linked to testicular function and sperm production.
- LH
- The pituitary signal that stimulates testosterone production in the testis.
- Prolactin
- A persistent rise can lower FSH, LH and testosterone.
- TSH
- The first test of thyroid function, and it helps identify abnormalities that can change symptoms or SHBG.
- Free T4
- Completes the thyroid assessment and makes it possible to interpret an abnormal TSH.
These tests are used to calculate Testosterona libre calculada. They are not separate tests.
How to prepare
Have the sample taken in the morning, preferably before 10:00, after 8 hours of fasting. Avoid intense exercise and a very short night's sleep. Arrive in good time so you can rest for a few minutes, because stress can temporarily raise prolactin.
You can add
Without another needle. It is offered when you order, so you do not have to decide now.
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Related blood tests
We have other profiles in Men with more or fewer tests:
- Total testosterone, free testosterone and SHBG test€59.00
- Testosterone therapy monitoring€89.00
- Gynaecomastia assessment€129.00
- Full male hormone blood test€169.00
The most comprehensive is not always the most useful. This is the one we recommend to start with; the others cover specific situations.
What it is based on
Endocrine Society · J Clin Endocrinol Metab 103(5):1715-1744
Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline
Advises against the direct immunoassay for free testosterone, because it is inaccurate, and recommends obtaining it by equilibrium dialysis or calculating it from total testosterone, SHBG and albumin. It also asks for total testosterone to be measured, fasting, on two different mornings before hypogonadism is taken as established.
Protocol designed by Dr. Antonio Mas, specialist in Endocrinology and Nutrition, Spanish medical licence no. 080846289, and reviewed in September 2026.
This blood test is a standardised protocol and does not replace a medical consultation. If you have symptoms, a known condition or a complex clinical situation, speak to your doctor.