Free testosterone or total testosterone: what the difference means
The key points at a glance
Total testosterone includes all testosterone in the blood, both bound and unbound. By far the largest proportion is attached to transport proteins and is not available to the tissues. Free testosterone describes the unbound remainder.
The MSD Manual, professional edition, gives a normal range for total testosterone of 300 to 1,000 nanograms per deciliter, or 10.5 to 35 nanomoles per liter (as of April 2025). The same source notes that after age 50, the total value is a less sensitive parameter because the transport protein SHBG increases with age.
You will first learn how testosterone is transported in the blood. This is followed by the three fractions in numbers, the role of SHBG, three common statements put to the fact check, the question of the measurement method, a comparison of the two values, and the limitations of a single measurement.
What to expect in this article
1. How testosterone travels through the blood
2. Why the total value alone is often not enough
3. SHBG is the reason for the difference
4. The fractions in numbers
5. Measured or calculated: how the free value is determined
6. Three statements about testosterone levels put to the fact check
7. Why the time of day determines both values
8. What else can shift the level
9. Total testosterone, free testosterone, and index compared
10. What a capillary blood test can show here
11. Limitations: what a single measurement cannot answer
12. What matters when it comes to testosterone levels
Frequently asked questions
Sources
How testosterone travels through the blood
Testosterone does not circulate freely in the blood. Most of it is bound to proteins that transport it while also holding on to it.
Two proteins share this task. Sex hormone-binding globulin, or SHBG for short, binds tightly. Albumin, the most abundant protein in the blood, binds loosely. Testosterone attached to SHBG is practically unavailable to tissues. Testosterone attached to albumin is easily released again.
A small unbound fraction remains. This is free testosterone, the part people mean when they talk about its effects.
Why this breakdown matters at all
When a laboratory measures total testosterone, it adds together all three fractions. Two people can have the same total level and still differ in how much of it is available.
The difference, then, is not in the testosterone but in the transport protein. That is precisely why SHBG appears directly next to testosterone on many hormone test results.
The third term: bioavailable testosterone
Some reports list a third term alongside total and free values. Bioavailable testosterone combines the free fraction with the fraction loosely bound to albumin.
The logic behind this is simple. Binding to albumin is weak enough that the hormone can detach again at the target tissue. This fraction therefore also contributes to the effect, even though it is not strictly free.
This gives us three nested quantities. The total value is the outermost shell, bioavailable testosterone lies within it, and the free fraction is the core.
When reading a test report, this means: Three numbers for the same hormone are neither contradictory nor repetitive. They describe three differently defined fractions of the same quantity.
Which of the three a laboratory reports varies from one test report to another. Therefore, rely on the label next to the number rather than assuming that the same thing will appear everywhere.
Why the total value alone is often not enough
The medical literature clearly identifies this limitation, and it also names the group of people in whom it has the greatest impact.
Documented source
“Although free testosterone more accurately reflects functional testosterone levels, determining it requires equilibrium dialysis, which is technically difficult and not available everywhere.”
Masaya Jimbo, MD, PhD
MSD Manual, Professional Edition, Male Hypogonadism, as of April 2025
This one sentence contains both halves of the truth. The free value better reflects the effect, and it is precisely the most difficult one to determine.
This leads to the compromise laboratory medicine has found: Instead of measuring the free fraction laboriously, it is calculated from total testosterone, SHBG, and albumin. This is not a second-rate workaround, but it is a calculation, not a measurement.
SHBG is the reason for the difference
When SHBG rises, it binds more testosterone. The total value may appear unchanged or even higher, while the available fraction decreases.
The MSD Manual, Professional Edition, names a specific trigger for this effect: Because sex hormone-binding globulin rises with age, total testosterone after age 50 is a less sensitive parameter (as of April 2025).
In practice, this means something specific. The older someone is, the less the total value alone tells you, and the more important it becomes to ask how much of it is bound.
What shifts the transport protein level
SHBG is not a fixed value. It responds to metabolism, the thyroid, and medications, and these responses can go in both directions.
Because the calculated free value is derived from SHBG, it changes along with it. A change in free testosterone may therefore originate in the testosterone itself or in the transport protein, and the two cases look identical on the report.
That is precisely why both values belong on the same report. Knowing only one of them does not allow this question to be distinguished.
Two reports, one total value, two situations
The effect can be illustrated with a hypothetical example, explicitly as a calculation example rather than a real-world case. Two men have the same total value in the middle range. One has low SHBG, while the other has high SHBG.
In the first case, more testosterone remains unbound; in the second, less does. The report shows the same total value in both cases, while the calculated free values differ.
Without SHBG, this difference cannot be seen. That is the entire reason the transport protein appears on a hormone report, and also why a total value alone is often insufficient.
The reverse is also true. Anyone with an abnormal free value should check whether the testosterone or the transport protein has changed. The two cases lead to different next questions.
The fractions in figures
Three figures from the same source help put the proportions into perspective.
Documented testosterone figures
300–1000
Nanograms per deciliter: normal range for total testosterone (MSD Manual, professional edition, as of April 2025)
10,5–35
Nanomoles per liter: the same range in the second commonly used unit (as of April 2025)
before 10 a.m.
Time window for sample collection to confirm hypogonadism (as of April 2025)
The normal range is strikingly broad. Between 300 and 1000 nanograms per deciliter, the value increases more than threefold, and both ends are considered unremarkable.
This breadth is the second reason why the free value matters. A total value in the lower range says little on its own unless it is clear how much of it is bound.
The classification by the Institute for Quality and Efficiency in Health Care remains important: the decisive factor is always the reference range stated on the laboratory report, and reference ranges may vary from one laboratory to another (as of April 2, 2025).
Measured or calculated: how the free value is obtained
There are two ways to determine free testosterone, and they differ considerably in complexity and availability.
The measured approach
Direct determination is performed using equilibrium dialysis. The unbound fraction is physically separated from the bound fractions and then measured.
This method is considered the most accurate. At the same time, as the MSD Manual notes, it is technically difficult and not available everywhere (as of April 2025). It is used least often in routine practice.
The calculated approach
The commonly used approach is calculation. The free fraction can be estimated from total testosterone, SHBG, and albumin using their known binding properties.
This approach requires three measured values instead of a specialized laboratory. Its trade-off is dependence: if one of the three values is inaccurate, the error carries over into the result.
When reading a test report, this means: If it lists free testosterone with the qualifier “calculated,” it is a derived value. This is common and acceptable, but it is not a second independent measurement.
Why two laboratories may report different free testosterone values
Having the same test report calculated by two laboratories does not necessarily produce the same number. There are two reasons for this, and both lie in the method.
The first is the formula. Several calculation methods are commonly used to determine the free fraction, and they are based on different assumptions about binding strength.
The second reason concerns the input values. Total testosterone and SHBG are already determined using different testing methods, and these differences carry over into the calculation.
IQWiG describes this situation generally for laboratory values: reference ranges may vary from one laboratory to another, and the range on your own test report is always the relevant one (as of April 2, 2025). For a calculated value, this matters twice over.
The practical consequence is unremarkable. For comparison over time, using the same laboratory is the simpler choice because the method and formula then remain the same.
Three statements about testosterone levels: a fact check
These three statements come up regularly. All three can be assessed against the evidence.
Checked against the evidence
Widespread
“The total value is entirely sufficient.”
Substantiated
Because SHBG levels rise with age, total testosterone after age 50 is a less sensitive parameter for confirming hypogonadism (MSD Manual, Professional Edition, as of April 2025).
Widespread
“Free testosterone is measured just like any other value.”
Substantiated
Direct measurement requires equilibrium dialysis, which is technically difficult and not available everywhere (as of April 2025). Most test reports therefore list a calculated value.
Widespread
“A low value in the afternoon counts just as much.”
Substantiated
Testosterone levels should be measured in the morning before 10 a.m. because they are highest in the early morning and decline over the course of the day (as of April 2025).
The third point is the one that causes the most unnecessary uncertainty. A value measured in the afternoon may look low without that implying anything.
What the three points have in common
All three statements share the same oversimplification. They treat a number as though it spoke for itself and leave out the conditions under which it was produced.
For testosterone, these conditions are unusually numerous: the time of day, age, the transport protein, and the calculation method. Four variables affecting one number are more than most laboratory values involve.
This does not call the measurement into question; it establishes an order for interpreting it. First check the conditions, then put the number into context. Those who start the other way around may end up interpreting a morning rather than a hormonal state.
Why the time of day determines both values
Testosterone follows a daily rhythm. It peaks in the early morning, then declines throughout the day.
A testosterone value without a time of day is difficult to interpret, whether total or free.
The MSD Manual therefore gives a clear recommendation: testosterone levels should be measured in the morning before 10 a.m. to confirm hypogonadism (as of April 2025).
Because the free value is derived from the total value, the same applies to it. A calculation cannot be better than the numbers that go into it.
The companion article Measuring cortisol in the blood: which time matters explains how narrow this time window is and what it means for repeat testing. The rule is the same; the hormone is different.
What else shifts the value
In addition to the time of day, there are three other factors that should be included with every test result.
Age
The age-related increase in SHBG is the best-documented effect in this context (MSD Manual, professional edition, as of April 2025). It shifts the ratio of bound to free without necessarily changing production.
An acute illness
An infection, a hospital stay, or surgery: during such phases, hormone levels are generally difficult to interpret. A measurement taken during an acute illness does not answer the question of what is normal.
Medications and preparations
Every preparation should be listed on the form that accompanies the test results. This explicitly also applies to over-the-counter products advertised as having an effect on hormone levels.
Anyone already using a testosterone preparation is measuring something other than their own baseline anyway. This situation belongs under medical supervision, not in a self-test.
Why sleep and exertion belong on the same sheet
Testosterone’s daily rhythm is tied to the sleep–wake cycle. The peak occurs in the early morning, and that peak requires a night worthy of the name.
Anyone who tests after a night shift or after four hours of sleep encounters the curve at a different point. That is not a measurement error, but a different starting situation, and it belongs as a note on the report.
The same applies to the symptoms that lead people to have their testosterone levels tested in the first place. Sleep deprivation and inadequate recovery rank high among the causes of persistent fatigue (MSD Manual, professional edition, as of April 2025). Anyone who tests because of exhaustion while sleeping too little has already obtained part of the answer before the blood is drawn.
This does not argue against testing. It argues for noting sleep duration and the period of exertion alongside the results, because both are part of the interpretation.
Total value, free value, and index compared
Three values appear side by side on hormone test reports. The table compares them according to the same four criteria.
| Criterion | Total testosterone | Free testosterone | SHBG |
|---|---|---|---|
| What it describes | The sum of bound and unbound testosterone | The unbound fraction, which more accurately reflects functional levels | The amount of tightly binding transport protein |
| How it is determined | Direct measurement in serum | Usually calculated from total testosterone, SHBG, and albumin; directly measurable only by equilibrium dialysis | Direct measurement in serum |
| Where its weakness lies | Less sensitive after age 50 because SHBG increases | As a calculated value, it depends on the quality of the three input values | On its own, it means nothing; it only becomes interpretable in relation to other values |
| When it makes the difference | As an initial guide for younger men | When the total value and the symptoms do not match | When it needs to be clarified whether the shift is caused by transport |
The fourth row is the most important in practice. The free value becomes relevant whenever the total value appears unremarkable but the symptoms persist.
The fourth measure: the free androgen index
Some lab reports show a fourth number alongside the table’s three columns. The free androgen index relates total testosterone to SHBG and indicates what proportion of the hormone is theoretically not tightly bound.
It is purely a calculated value and answers the same question as calculated free testosterone, just by a shorter route. Instead of three values, it needs two because it does not take albumin into account.
This makes it simpler and, at the same time, more approximate. Anyone who sees the index on their report has a point of reference, not a second independent measurement.
How it is calculated and where its limitations lie is covered in the companion article Free Androgen Index: How It Is Calculated. This article focuses on the difference between total and free values.
What a capillary blood test can show here
A self-test from capillary blood does not provide a diagnosis. It shows where several values stand at a given point in time, and for testosterone, the deciding question is whether SHBG is included.
Two tests by mybody®x (MYBODY Lab GmbH) measure testosterone, and they differ precisely at this point. What they do and do not measure is shown in the cards.
Blood test from capillary blood
HormoneCheck | Men’s Hormone Test
Measures testosterone, calculated free testosterone, SHBG, and albumin together, as well as estradiol, DHEA-S, LH, FSH, prolactin, and TSH. This provides all three values from which the free fraction is derived. What the test does not do: The free value is calculated, not measured by equilibrium dialysis. The test does not provide a diagnosis and does not replace a medical examination.
Laboratory results 3–5 business days after receipt of the sample
Product page information, accessed 08/13/2026
Blood test from capillary blood
Men’s Wellness Check | Men’s Health Test
Measures 17 values, including total testosterone, as well as cortisol, TSH, the cholesterol profile, homocysteine, liver and kidney values, and PSA. What the test does not measure: It includes neither SHBG nor albumin and therefore does not provide a free value. It is not the right test for determining the available fraction. It does not provide a diagnosis.
Laboratory results 3–5 business days after receipt of the sample
Product page information, accessed 08/13/2026
Four points determine whether a measurement becomes useful information.
Have the sample taken before 10 a.m.
This is the time window to which the information in the specialist literature refers.
Include SHBG
Without the transport protein, it remains unclear how much of the total value is available.
Note the circumstances
The time, age, medications, and acute illnesses should be recorded on the same sheet.
Discuss anything unusual
A low value accompanied by symptoms should be taken, together with the test report, to a medical practice.
Chapter at a glance
A capillary blood self-test provides values from a single point in time, not a diagnosis. For the question of how much testosterone is available, it matters whether SHBG and albumin are included, because the free value is calculated from them. Four points are crucial to the test’s usefulness: take the sample before 10 a.m., include SHBG, note the circumstances, and discuss anything unusual.
Limitations: what a single value cannot answer
The first limitation is the calculation itself. Calculated free testosterone is a derived value, and the formulas used do not produce the same result in every case.
The second limitation is a single measurement. The MSD Manual states that total testosterone as well as FSH and LH should be measured simultaneously to confirm hypogonadism (as of April 2025). One value alone cannot answer this question.
The third limitation concerns symptoms. Fatigue, lack of drive, and declining libido are nonspecific and have many possible causes. A hormone level helps assess one of them but does not rule out the others.
The fourth limitation is a gap in the sources. We found no consistent information on the calculated free level at which a deficiency should be diagnosed. That is why the text does not give a number for it.
What the level does and does not say about causes
A low testosterone level does not answer where it comes from. That is precisely why FSH and LH appear on the same test report, and why the specialist literature describes measuring them simultaneously.
The logic behind this concerns regulation. FSH and LH come from the pituitary gland and signal the testicles. If both are high while testosterone is low, that points to a different level than when all three are low.
This distinction belongs in a medical practice, not in the interpretation of a self-test. What a test can do is provide the values together, so that the question can be raised in the first place.
For you, this means when reading the results: A single low testosterone level is a reason to have a conversation. It is not a diagnosis, and on its own it says nothing about where something in the regulatory system is working differently.
What matters when it comes to the testosterone level
If you take away one action from this article, let it be this: Check your test report to see whether SHBG is listed alongside testosterone.
The reason is unremarkable. Without this second value, the most common confusion cannot be resolved: the confusion between having little testosterone and having a lot of bound testosterone.
The starting question was which of the two values is the correct one. The answer is that the free value better reflects the effect, and it can only be determined when both the total value and the transport protein are available. The question of which single value is the correct one therefore misses the point.
Frequently asked questions
What is the difference between free and total testosterone?
Total testosterone includes all testosterone in the blood, both bound and unbound. Free testosterone describes only the unbound fraction. According to the MSD Manual, professional edition, free testosterone more accurately reflects functional levels, but direct measurement requires equilibrium dialysis, which is technically difficult and not available everywhere (as of April 2025).
Which value is more informative?
It depends on age. The MSD Manual states that after age 50, total testosterone is a less sensitive parameter because SHBG increases with age (as of April 2025). In younger men, total testosterone is often sufficient as an initial guide; with increasing age, the free value becomes more important.
When should testosterone be measured?
In the morning, before 10 a.m. The MSD Manual explains that testosterone levels are highest in the early morning and decline throughout the day (as of April 2025). A value measured in the afternoon may be low without this implying anything.
What does the term calculated mean for free testosterone?
The value was not measured directly but derived from total testosterone, SHBG, and albumin. This is the usual method because direct measurement requires a specialized laboratory. In practice, this means the value is only as good as the three numbers from which it is derived, and it is not a second independent measurement.
What is a normal testosterone level?
The MSD Manual gives a normal range for total testosterone of 300 to 1,000 nanograms per deciliter, equivalent to 10.5 to 35 nanomoles per liter (as of April 2025). The range is intentionally broad. What remains decisive is the reference range shown on your own lab report, because reference values can vary from one laboratory to another (IQWiG, as of April 2, 2025).
Next step
SHBG first, then interpretation
If your lab report lists only the total value, half the information is missing. HormonCheck combines testosterone, SHBG, and albumin and uses them to calculate the free value. It does not provide a diagnosis and does not replace medical evaluation.
Zum HormonCheck Zum Men’s Wellness CheckGo to the HormoneCheck Go to the Men’s Wellness Check
Read more
The reference article on the numerical ranges themselves.
The same rule for another hormone, explained in detail.
Sources
- MSD Manual, Professional Edition: Male Hypogonadism, Jimbo M (as of April 2025) – msdmanuals.com
- Institute for Quality and Efficiency in Health Care (IQWiG): Understanding Laboratory Values Correctly, as of 2 April 2025 – gesundheitsinformation.de
- MSD Manual, Professional Edition: Fatigue, Wasserman MR (as of April 2025) – msdmanuals.com
The verbatim quotation on equilibrium dialysis, the normal range for total testosterone, the statement about the increase in SHBG with age, the requirement to collect the sample before 10 a.m., and the note on determining FSH and LH at the same time are taken from source [1]. The explanation of the reference range and the note about variations between laboratories are taken from [2]. The classification of sleep deprivation as a cause of persistent fatigue is based on [3]. We found no reliable information in the sources reviewed on a uniform threshold for deficiency in calculated free testosterone; therefore, no number is given in the text. Information on price, values, sample type, and laboratory comes from the mybody®x product pages, accessed on 13 August 2026; processing times follow the central specification for blood tests. All sources were accessed and reviewed on 13 August 2026.
mybody®x Editorial & Expert Team
Laboratory diagnostics Blood analysis interpretation Nutritional science Nutrigenetics
This article was created by the mybody®x editorial and expert team. The team combines laboratory diagnostics, nutritional science, and the interpretation of blood analyses. Everyone who contributes to it is listed on the authors’ page.
Published on 13 August 2026 · Last updated on 13 August 2026
The content is intended for general information and does not replace medical advice, diagnosis, or treatment. Reference ranges depend on the laboratory, method, and age; the information on your test report is always authoritative.
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