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The testosterone in your body exists in two states: free testosterone and total testosterone.
Testosterone is the most important male hormone; however, women’s bodies make and need testosterone as well. In both men and women, most of the testosterone in your blood is attached or bound to proteins. There is some testosterone in the bloodstream that is not attached to protein and is traveling unbound through the bloodstream. This is what doctors refer to as “free testosterone.” The combination of the two is known as your total testosterone. Only free testosterone is active and available to your body.
Think of it this way: if all of the testosterone in your body was traveling in a fleet of Amazon package delivery trucks, your total testosterone would be all of the “boxes” of testosterone in every truck, whether they were parked at the warehouse, stuck in traffic, in a lunch break or whatever, and free testosterone would be only the trucks that are actively dropping “boxes” of testosterone at people’s doorsteps.
It’s important for doctors to know your total testosterone just as it is important for Amazon to know where all of their packages are at any given time, but you, the consumer, their delivery is the most important thing, just as two your body and overall health, your free testosterone level is more important than you “total testosterone.”
Testosterone is the most important male hormone or “androgen.” Testosterone is largely responsible for building muscle and bones in boys and the ongoing development of the sex organs. Once a child reaches the age of puberty, testosterone levels spike dramatically. It is this increased production and release of testosterone that brings on the secondary characteristics typical of “maleness,” such as facial hair and a deeper voice.
While it is a male hormone, women’s bodies make and need testosterone too. In both men and women, testosterone is needed to build muscle and healthy bones. It also is vital for:
Most of the time, the testosterone in your blood is “bound” to proteins. But, less frequently, it glides through the blood unbound as “free testosterone.” Free testosterone is the part of testosterone that is active and available for your body to use right away. It’s like having money in your pocket that you can spend whenever you want. This type of testosterone helps with things like energy, protein synthesis and muscle growth, mood, and sex drive.
“Total testosterone” represents all the testosterone in your system in any state— both bound to proteins and the testosterone that is “free” or unbound.
Both free and bound testosterone levels decrease as you age and can lead to age-related testosterone deficiency. Going back to our Amazon truck analogy, Sometimes, even if you have a lot of trucks (total testosterone), only a few might be working (free testosterone). The rest could be tied up or parked, not helping as much.
So, even if your total testosterone looks fine, you could feel tired or weak if your free testosterone is low because not enough of it is getting the job done!
If your doctor suspects that you may have low testosterone, you will most likely first be given a simple blood test for your total testosterone. Suppose your total testosterone levels come back as low. In that case, your doctor may follow up with a test for your free testosterone, as this will give your healthcare provider a more accurate picture of your ability to produce adequate amounts of testosterone.
Total testosterone (total T) is measured via a simple blood test. Based on the results of your total T-test, your doctor may follow up with a free testosterone test.
It could be more important for your doctor to know your free testosterone level than your total testosterone level. Sometimes, men could be suffering from “low testosterone” even if their levels of “total testosterone” appear in the normal range.
If your standard blood test for total testosterone shows up as normal and yet you are exhibiting symptoms of low testosterone, getting your free testosterone level can shed light on why you may be experiencing signs of testosterone deficiency. In many ways, free testosterone levels better predict testosterone deficiency symptoms than your total testosterone levels.
Testing free testosterone is also important in patients who may be suffering from metabolic conditions such as diabetes or obesity, which can artificially lower total testosterone levels.
If you seem to be experiencing the symptoms of low testosterone, usually doctors will test your total testosterone. However, in some cases, for a more exacting diagnoses, and treatment plan, doctors may want to see your free (unbound) testosterone level.
The following table illustrates the range of normal “free” testosterone for men and women by age.
| GENDER / AGE (Y) | RANGE (PG/ML) |
|---|---|
| MALE | |
| 0 to 19 | Not established |
| 20 to 29 | 9.3−26.5 |
| 30 to 39 | 8.7−25.1 |
| 40 to 49 | 6.8−21.5 |
| 50 to 59 | 7.2−24.0 |
| >59 | 6.6−18.1 |
| FEMALE | |
| 0 to 19 | Not established |
| >19 | 0.0−4.2 |
Source: LabCorp (FREE T)
Total testosterone (total T) is measured via a simple blood test. Based upon the results of your total T tests, your doctor may follow up with a free testosterone test.
The following chart illustrates the normal total testosterone levels for men and women by “Tanner Stage” and age. The Tanner Scale breaks down the observable signs of puberty into 5 stages, running from Stage I from about age 10 to Stage V at 15 for boys, and about age 8 to 15 for girls.
| TANNER STAGE | MALE | FEMALE |
|---|---|---|
| TESTOSTERONE (NG/DL) | TESTOSTERONE (NG/DL) | |
| I | <3 | <3−6 |
| II | <3−432 | <3−10 |
| III | 65−778 | <3−24 |
| IV | 180−763 | <3−27 |
| V | 188−882 | 5−38 |
| ADULT MALE | ADULT FEMALE | |
| >18 y: 264−916 | 20 to 49 y: 8−48 | |
| >49 y: 3−41 |
Source: LabCorp
To compare so that you can better understand how variable that “so-called” normal levels of testosterone can be, the following chart gives the “normal” testosterone levels from Quest Diagnostics, another respected testing lab. Quest does not use the Tanner Scale but rather indicates the normal ranges for males and females by age.
| 1–5 Years | ≤5 | ≤8 |
| 6–7 Years | ≤25 | ≤20 |
| 8–10 Years | ≤42 | ≤35 |
| 11 Years | ≤260 | ≤40 |
| 12–13 Years | ≤420 | ≤40 |
| 14–17.9 Years | ≤1000 | ≤40 |
| ≥18 Years | 250–1100 | 2–45 |
Source: Quest Diagnostics
If you compare this chart, to the first chart from LabCorp, you can see how the “normal” ranges differ. These two charts come from two of the most respected testing labs in the country, and yet they have differences. That should help you to understand why it is very hard to pinpoint what is the “normal” total testosterone level for any given person, of any given age. This is precisely why our doctors try to bring every patient to a “target level” that we have found to be optimal for most patients, regardless of age or gender.
Once we determine what your unique optimal level is, we can tailor treatments that will get you in that zone, so you can perform at your personal best, regardless of your age.
Your free or bioavailable testosterone influences the use and production of other critical hormones, which, in turn, can impact your total testosterone level.
Free Testosterone Levels and HGH – Men with low free testosterone often also have low levels of human growth hormone (HGH). Several studies have concluded that when testosterone replacement therapy is prescribed for older men in combination with HGH therapy, greater overall improvements in strength and energy are achieved than when given either therapy alone.
One study concluded, “Supplemental testosterone produced significant gains in total and appendicular lean mass, muscle strength, and aerobic endurance with significant reductions in whole-body and trunk fat. Outcomes appeared to be further enhanced with HGH supplementation.”
Free Testosterone Levels and Thyroid Hormones – Sub-normal levels of thyroid hormones (hypothyroidism) have been associated with low levels of free testosterone in men. This type of low-free testosterone (hypogonadism) is reversible with thyroid hormone replacement therapy.
Free Testosterone Levels and Insulin – Medical researchers have found that low free testosterone levels are common in men with type 2 diabetes and, therefore, may be associated with insulin resistance. Such studies have concluded that free testosterone deficiency is common in men with diabetes, regardless of the type. This has led to an avenue of research that testosterone replacement may be a possible way to treat or prevent adult-onset diabetes in men.
Just as in males, there is a clear difference between total and free testosterone in women. We have learned that testosterone in the male body travel either as “bound” or “unbound.” The same holds true in women.
Total testosterone measures all the testosterone found in a woman’s blood. This includes testosterone that is attached, or bound, to proteins and testosterone that is circulating freely. Most testosterone is attached to proteins called sex hormone-binding globulin, or SHBG, and albumin. Only a small amount remains unbound as free testosterone.
Free testosterone is the form that is most readily available for the body to use. Even though women have much lower testosterone levels than men, this active portion may still affect sexual desire, energy, muscle strength, mood, motivation, and general well-being. Because the amount of free testosterone is so small, changes in SHBG can have a major effect on how much active testosterone is available.
This is why a total testosterone result may not always tell the whole story. A woman may have a total testosterone level that appears to be within the laboratory’s normal range but still have a low amount of free or available testosterone. In other cases, total testosterone may appear low because less testosterone is attached to SHBG, while the amount of free testosterone remains adequate. Certain health conditions, medications, and changes in estrogen levels can affect SHBG and alter the relationship between total and free testosterone.
Just as in her male counterpart, doctors may begin with a total testosterone blood test when a woman has symptoms that could be linked to low testosterone. Depending on her symptoms and initial results, the doctor may also test free testosterone, bioavailable testosterone, SHBG, or albumin. Bioavailable testosterone includes free testosterone plus testosterone that is loosely attached to albumin and can be released for the body to use.
Testing may be considered when a woman reports a persistent loss of sexual desire, unexplained fatigue, reduced strength, changes in body composition, or other symptoms that may be related to a broader hormone imbalance. Doctors may also measure total and free testosterone when looking for signs of excess testosterone, such as unusual facial or body hair growth, severe acne, irregular menstrual cycles, or other possible signs of polycystic ovary syndrome.
A high total or free testosterone result may point toward excess androgen production and may lead to further testing. A low result may suggest reduced testosterone production, but the number should never be judged by itself. Testosterone levels in women can be affected by age, menopause, ovarian or adrenal function, medications, hormone treatments, and the amount of SHBG in the blood.
Doctors must also take care when measuring testosterone in women because female levels are naturally much lower than male levels.
As a general guide, commonly used reference ranges for adult females may include:
Low testosterone in men can sometimes be related to an injury or disease condition. However, most often, low testosterone in men is caused by the steady drop of testosterone as you age. This “age-related” testosterone deficiency is also known as andropause. It is similar to menopause in women. However, unlike menopause, which occurs at a specific time in a woman’s life, the symptoms of andropause develop gradually over time. Most men between the ages of 40 and 65 are likely to be feeling some of the symptoms of low testosterone or andropause.
The signs and symptoms of low testosterone or andropause include:
There can be a number of causes of low testosterone. Any disease, injury, or condition that negatively affects the testes could result in low testosterone. However, the most common cause of low testosterone, particularly in men over 40, is the normal decline in testosterone levels that occurs as men age.
Testosterone production starts in the womb. It continues through adolescence until it reaches its highest level at about eighteen. In most men, their testosterone levels will stay at or pretty close to that maximum level through their 20s. Then, once you are over 30, your testosterone level will start on a steady downward slope. By the time you are over 40, most men will be feeling the negative impacts of low testosterone.
Testosterone replacement therapy, or TRT, delivers prescription testosterone directly into your body, increasing the level of the free testosterone in your blood. TRT is the safest and most effective treatment there is for patients diagnosed with low testosterone.
Testosterone replacement therapy can take several different forms. Our doctors have found that testosterone injections tend to be the most effective form of testosterone therapy for most patients. Testosterone injections are intramuscular, which means that they are given into the muscles. The very vascular muscles of your arm, your thigh, or the “glutes” are the most common injection sites. The needles used to deliver low testosterone treatments are very thin, much like the ones diabetics use to deliver insulin. Once you learn how to give yourself your testosterone injections, you will find them easy to do and quite painless.
There are many benefits to testosterone therapy for men. One of the first benefits most men see after starting testosterone therapy is an increased sex drive and improved sexual performance.
Besides improving your sex life, some of the other benefits of testosterone therapy for men include:
Some of the other benefits of TRT include:
TRT will be tailored to your unique needs and lifestyle, so the length of time you need to be taking testosterone will vary from patient to patient. Typically, however, low testosterone treatments last from about six months to a year for your first round of Low-T treatment. After that, you will be evaluated for the need to continue your low testosterone treatment.
Low testosterone symptoms can be frustrating, but finding the right answers should not be.
Nexel Medical provides adults with personalized hormone evaluations designed to look beyond a single laboratory result. Our experienced medical providers consider your symptoms, health history, lifestyle, current medications, and complete hormone test results before recommending treatment. When appropriate, testing may include total testosterone, free testosterone, SHBG, and other hormones that can affect how you feel.
You do not have to accept ongoing fatigue, loss of strength, reduced sexual desire, mood changes, or declining performance as an unavoidable part of getting older. Contact Nexel Medical today to schedule your consultation, complete your hormone evaluation, and take the first step toward a treatment plan designed around your individual needs.
Yes. This can happen when too much testosterone is attached to proteins in the blood, especially sex hormone-binding globulin, or SHBG. In that case, the total amount may appear normal, but less testosterone is available for the body to use. Doctors may test SHBG and free testosterone when symptoms do not match the total testosterone result.
Both results can be important. Total testosterone shows the full amount of testosterone in the blood, while free testosterone shows the small portion that is not attached to proteins. Doctors often review both numbers together because either result alone may not provide a complete picture of a person’s hormone health.
Age, body weight, sleep, stress, certain medical conditions, and some medications can affect testosterone levels. Changes in SHBG can also alter how much testosterone is bound or free. Because several factors can influence the results, doctors compare blood tests with symptoms, health history, and other hormone levels before making a diagnosis.
In many cases, yes. Testosterone levels can change from one day to another and may also vary based on the time of testing. A doctor may repeat the test when a result is unusually high or low, does not match the person’s symptoms, or needs to be confirmed before treatment is considered.
Neither test is always more important. Total testosterone shows the full amount of testosterone in the blood, while free testosterone shows the small amount that is not attached to proteins. Doctors often use both results, along with SHBG levels, symptoms, age, and menopause status, to get a more complete picture.
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