Free Testosterone Calculator
Easily calculate your free testosterone and bioavailable testosterone now using the clinically established Vermeulen formula. The results are estimates and may not fully reflect individual differences. They are not a substitute for medical advice or diagnosis.
Note: If you do not have a current albumin level, you can use the preset value of 43 g/L.
Important: This value alone does not indicate the presence or absence of a medical condition (e.g., testosterone deficiency). Laboratory results can only be interpreted by a doctor in the overall clinical context. We deliberately do not assess them in isolation as "normal" or "abnormal".
In the blood, testosterone is mostly bound: around 66–78 % is bound to sex hormone-binding globulin (SHBG), while another 20–32 % is weakly bound to albumin. Only 1–3 % circulates as free hormone. The sum of free and loosely albumin-bound testosterone is known as bioavailable testosterone, which accounts for approximately 35 % of total testosterone.
Since free testosterone is considered the biologically active fraction, its determination provides valuable information about the actual androgen level in the body. Vermeulen and colleagues described a calculation method for this purpose, which allows both free and bioavailable testosterone to be reliably estimated from the concentrations of total testosterone, SHBG, and albumin.
You can find more about the significance of the relevant laboratory values in determining testosterone levels in our blog post.
Source: 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.
Calculate free testosterone using the Vermeulen formula
Testosterone is the most important male sex hormone. It influences muscle building, energy, libido, mood, and many other bodily functions. In the blood, testosterone is predominantly bound. About 65 to 80 percent is bound to SHBG (sex hormone-binding globulin). Another 20 to 30 percent is bound to albumin. Only a very small proportion of approximately 1 to 3 percent exists as free testosterone. This part is biologically active and exerts the actual hormonal effect.
Difference between total testosterone and free testosterone
Laboratories usually measure total testosterone. However, this value can be misleading because it does not take into account how much of it is bound by SHBG or albumin. High SHBG levels can lead to only a small amount of free testosterone being available despite normal total testosterone. Conversely, low SHBG levels can result in a higher proportion of free testosterone. That is why it makes sense not only to look at total testosterone but also to calculate the value for free testosterone.
The Vermeulen formula
The Vermeulen formula is a recognized method for calculating free and bioavailable testosterone. It uses the concentrations of total testosterone, SHBG, and albumin. These three laboratory values can be used with the formula to calculate the levels of free testosterone and bioavailable testosterone (BAT). BAT includes free testosterone and testosterone loosely bound to albumin. Both forms are considered biologically available.
Why is free testosterone important?
Free testosterone is the active form of the hormone and is responsible for many physiological processes. A value that is too low can become noticeable through symptoms such as fatigue, declining libido, muscle loss, or depressive moods. A value that is too high can also pose health risks. That is why the correct interpretation is important.
How do I interpret the value?
- Normal range: Depending on the laboratory and age, the reference range for free testosterone is usually between 0.04 and 0.25 µg/L or stated in pmol/L between 140 and 850.
- Below the reference range: May indicate a testosterone deficiency.
- Above the reference range: In rare cases, this can be caused by overproduction or testosterone therapy.
Advantages of our calculator
With the Vermeulen calculator, free testosterone can be calculated online. You enter total testosterone, SHBG, and albumin and immediately receive the value for free testosterone and bioavailable testosterone. This gives you a better overview of your hormonal status than a single laboratory value allows.
You can find even more on the topic in our encyclopedia entry on free testosterone.
Important note:
The calculation of free testosterone using the Vermeulen method provides a reliable estimate but does not replace a medical diagnosis. Only a doctor can assess your values in the context of your symptoms and overall health.
Do you have any questions?
Here is an overview of the most frequently asked questions and answers.
What are the symptoms of low testosterone?
What are the symptoms of low testosterone?
Possible symptoms of low testosterone levels or testosterone deficiency include:
1. Reduced sex drive/libido
2. Erectile dysfunction/decrease in morning erections
3. Impaired cognitive performance
4. Fatigue/exhaustion
5. Loss of muscle mass/decreased athletic performance
6. Increased body fat/increased waist circumference
7. Reduced body hair
8. Lack of motivation and depressive mood
9. General mood swings
10. Sleep problems/restless sleep
Who is suitable for testosterone replacement therapy?
Who is suitable for testosterone replacement therapy?
Testosterone replacement therapy may be suitable for men of any age with low or borderline low testosterone levels who exhibit signs and symptoms of hypogonadism and for whom contraindications to therapy have been medically ruled out.
What are the benefits of testosterone replacement therapy?
What are the benefits of testosterone replacement therapy?
Testosterone replacement therapy offers a number of potential benefits, particularly for men with clinically diagnosed testosterone deficiency. It is important to emphasize that TRT should only be undertaken for diagnosed testosterone deficiency and under medical supervision. Some of the key potential benefits include:
1. Improved libido and sexual function: One of the most common effects of testosterone deficiency is a decline in libido or sexual desire. TRT can help improve sexual desire and erectile function, which may lead to a more satisfying sex life.
2. Increased energy and overall well-being: Low testosterone levels can lead to fatigue, lack of energy and a general feeling of malaise. Many men report increased energy and improved quality of life after starting TRT.
3. Improved muscle mass and body composition: Testosterone plays a key role in building and maintaining muscle mass. TRT can help increase muscle mass and reduce body fat, particularly when combined with regular exercise.
4. Positive effects on bone density: Testosterone contributes to bone health, and a deficiency can lead to reduced bone density. TRT can help increase bone density and reduce the risk of osteoporosis and bone fractures.
5. Improved mood and mental clarity: Testosterone deficiency can lead to mood swings, irritability and difficulty concentrating. Normalising testosterone levels can help alleviate these symptoms, contributing to improved mental clarity and a more stable mood.
6. Possible positive effects on the cardiovascular system: Some studies suggest that well-monitored TRT may have positive effects on the cardiovascular system, although research in this area is not yet conclusive.
How much does testosterone replacement therapy cost?
How much does testosterone replacement therapy cost?
The costs of a possible testosterone replacement therapy consist of various components. Adon Health itself exclusively offers lifestyle tests and, if necessary, provides contact with independent cooperating doctors. The medical services and medication supply are carried out independently by the treating doctors and pharmacies.
Typical cost examples can be:
Initial lifestyle test package (Adon Health): one-time from €99.90
Medical consultation (by independent doctors): approx. €70–100 per appointment. The first appointment takes place before a possible therapy, followed by follow-up checks usually for the first time after 4 weeks and then every 3 months.
Follow-up test (laboratory): approx. €100 every 3 months
Medication (via pharmacies): with a medical prescription approx. €20–70 per month