Free Testosterone Calculator
Easily calculate your free and bioavailable testosterone levels using the clinically established Vermeulen formula. The results are indicative and may not fully reflect individual differences. They do not replace medical advice or diagnosis.
Note: If you do not have a current albumin value, you can use the preset value of 43 g/L.
Testosterone is mostly present in the blood in bound form: approximately 66–78% is tightly bound to sex hormone-binding globulin (SHBG), while another 20–32% binds less strongly to albumin. Only 1–3% circulates as free hormone. The sum of free and loosely bound testosterone is referred to as bioavailable testosterone , which accounts for about 35% of total testosterone.
Since free testosterone is considered the biologically active fraction, its measurement provides valuable information about the actual androgen level in the body. Vermeulen and colleagues described a computational method that allows for the reliable estimation of both free and bioavailable testosterone from the concentrations of total testosterone, SHBG, and albumin.
You can find more information about the importance of relevant lab values in testosterone level determination 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 growth, energy levels, libido, mood, and many other bodily functions. In the blood, testosterone is predominantly bound. Approximately 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 fraction, about 1 to 3 percent, exists as free testosterone. This portion is biologically active and exerts the actual hormonal effects.
Difference between total testosterone and free testosterone
Laboratories typically measure total testosterone. However, this value can be misleading because it doesn't account for how much of it is bound by SHBG or albumin. High SHBG levels can result in low levels of free testosterone despite normal total testosterone levels. Conversely, low SHBG levels can lead to a higher proportion of free testosterone. Therefore, it's advisable to consider not only total testosterone but also to calculate the free testosterone level.
The Vermeulen formula
The Vermeulen formula is a recognized method for calculating free and bioavailable testosterone. It utilizes the concentrations of total testosterone, SHBG, and albumin. From these three laboratory values, the formula calculates the levels of free testosterone and bioavailable testosterone (BAT). BAT comprises both 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 bodily processes. A level that is too low can manifest itself through symptoms such as fatigue, decreased libido, muscle loss, or depressive moods. A level that is too high can also pose health risks. Therefore, accurate assessment is important.
How to 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, expressed 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 occur due to overproduction or testosterone therapy.
Advantages of our computer
The Vermeulen calculator allows you to calculate free testosterone online. You enter total testosterone, SHBG, and albumin, and immediately receive the values for free testosterone and bioavailable testosterone. This gives you a better overview of your hormone levels than a single lab value provides.
You can find even more information on this topic in our glossary entry on free testosterone.
Important NOTE:
The Vermeulen method for calculating free testosterone provides a reliable estimate, but it 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 levels?
What are the symptoms of low testosterone levels?
Possible symptoms of low testosterone levels or testosterone deficiency include:
1. Reduced sex drive/libido
2. Erectile dysfunction/decrease in morning erections
3. Decline in cognitive performance
4. Fatigue/Exhaustion
5. Loss of muscle mass/decline in athletic performance
6. Increase in 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
For whom is testosterone replacement therapy suitable?
For whom is testosterone replacement therapy suitable?
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 (TRT) offers a number of potential benefits, particularly for men with clinically diagnosed testosterone deficiency. It is important to emphasize that TRT should only be used in cases of diagnosed testosterone deficiency and under medical supervision. Potential key benefits include:
1. Improved libido and sexual function: One of the most common effects of testosterone deficiency is a decrease in libido or sexual desire. TRT can help improve sexual desire and erectile function, which can 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 an improved quality of life after starting TRT.
3. Improvement of muscle mass and body composition: Testosterone plays a key role in building and maintaining muscle mass. TRT can increase muscle mass and reduce body fat percentage, especially when combined with regular exercise.
4. Positive effects on bone density: Testosterone contributes to bone health, and a deficiency can lead to a decrease in bone density. TRT can help increase bone density and reduce the risk of osteoporosis and fractures.
5. Improved mood and mental clarity: Testosterone deficiency can lead to mood swings, irritability, and difficulty concentrating. Normalizing testosterone levels can alleviate these symptoms, contributing to better 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 complete.
How much does testosterone replacement therapy cost?
How much does testosterone replacement therapy cost?
The costs for potential testosterone replacement therapy are comprised of various components. Adon Health itself only offers lifestyle tests and, if needed, facilitates contact with independent partner physicians. Medical services and medication supply are handled independently by the treating physicians and pharmacies.
Typical cost examples include:
Initial Lifestyle Test Package (Adon Health): one-time fee starting from €99.90
Medical consultation (by independent physicians): Approximately €70–100 per appointment. The first appointment takes place before any potential therapy, followed by follow-up appointments, usually after 4 weeks and then every 3 months.
Follow-up test (laboratory): approx. €100 every 3 months
Medication (via pharmacies): with a doctor's prescription, approx. €20–70 per month
