Free testosterone not calculated: what this means and what you can do now

Free testosterone cannot be calculated when testosterone levels are very low (below approximately 0.09 nmol/L), because the formula becomes unreliable at those levels. This does not mean you’re missing information; rather, it means that the low level itself is significant. The appropriate next step is to conduct additional hormone testing and evaluate your overall hormonal balance.

You had a blood test done, and your results say: “Free testosterone could not be calculated.” That’s pretty annoying, because that was exactly the value you wanted to know.

But there’s a more important story behind this than meets the eye. If free testosterone can’t be calculated, that often tells you more than the result itself would have. In this blog, you’ll learn why the calculation sometimes fails, what that might mean for your health, and what you can do about it.

What exactly is free testosterone?

Testosterone in your blood exists in three forms: bound to SHBG and therefore inactive, partially active when bound to albumin, and free testosterone, the portion that is directly biologically available. It is precisely this last portion that is often considered the most important value, because your body can use it directly.

In practice, free testosterone isn’t usually measured directly. It’s calculated.

See also: When should you have your testosterone levels checked?

How free testosterone is calculated

That calculation is done using formulas such as the Vermeulen formula, based on your total testosterone, SHBG, and albumin levels. As long as these values fall within a reliable measurement range, it works just fine.

When does the calculation fail?

Most laboratories have a lower limit: if your total testosterone is lower than approximately 0.09 to 0.10 nmol/L, free testosterone is not calculated. This is not a lab error, but a deliberate decision.

The reason behind a failed calculation

When testosterone levels are very low, the calculation itself becomes problematic. The ratio with SHBG becomes unstable; even small measurement differences can then lead to large deviations, and the result is no longer mathematically reliable.

You would then receive a number that looks precise on paper but, in reality, doesn't mean much. That's why labs prefer to report nothing rather than present a misleading value.

You aren't missing any information

It might feel like something is missing, but that’s not the case. If your testosterone level is so low that it can’t be calculated, that low level itself is already the most important finding. The question then naturally shifts: no longer “how high is my free testosterone,” but “why is my testosterone so low.”

Does direct measurement of free testosterone actually work?

It sounds logical to simply measure free testosterone directly, but that’s usually not a good solution. Many direct tests, such as immunoassays, are susceptible to interference, do not adequately account for SHBG, and are often inaccurate, especially at low levels and in women.

There are more accurate methods, such as equilibrium dialysis or ultrafiltration. However, these are expensive, not widely available, and rarely necessary in practice, so direct measurement is of little benefit in most cases.

What a low testosterone level can mean

A very low testosterone level can have various causes. In women, for example, this can occur around (peri)menopause, with the use of hormonal birth control, with reduced adrenal function accompanied by low DHEA levels, or as part of a broader hormonal imbalance.

In addition, there are causes that can apply to anyone, such as chronic stress, malnutrition, certain medications, or hormonal imbalances.

Symptoms associated with low testosterone

• Decreased libido
• Fatigue
• Reduced muscle strength
• Depression
• Reduced motivation

These symptoms don’t tell the whole story on their own, but they should be taken into account when interpreting your results.

What can you do now?

Instead of focusing solely on free testosterone, it’s better to take a broader view.

Additional testing

Consider testing for:

• SHBG
• DHEA-S
• Androstenedione
• LH and FSH
• Estradiol

Consider the context

Consider the following:

• Age
• Menstrual cycle or menopausal status
• Use of Hormones
• Symptoms

Discuss the results with a doctor

Especially with such low levels, it’s wise to actually discuss this with a doctor or specialist, rather than continuing to search for an explanation on your own.

Testing Recommendations for Your Hormonal Balance

If you’d like a better understanding of your hormonal balance, you can choose a comprehensive hormone profile through Bloedwaardentest. This test measures DHEA-S and estrogen, among other hormones, providing a broader picture than just looking at testosterone alone.

Blood draws are available at more than 1,000 locations in the Netherlands, and a phone consultation or lifestyle consultation is available as an option. If any abnormalities are found that may require immediate medical follow-up, you will always be contacted first by a doctor or medical expert.

In a nutshell

If free testosterone cannot be calculated, that’s not a problem—it’s actually an important indicator. The low total level is the key finding in your results, and the right next step is not to retest, but to find out why this level is so low.

Frequently Asked Questions

Why isn’t my free testosterone measured?

Usually because your total testosterone is too low—below about 0.09 nmol/L. Below that level, the calculation simply becomes unreliable.

Is measuring direct free testosterone better?

Not necessarily. These tests are often less reliable at low levels and are therefore usually not recommended.

Should I be concerned if my testosterone is low?

Not right away, but it’s still worth having the cause investigated and taking your symptoms seriously.

Have a question about your results?

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