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Why Free Testosterone Levels Shouldn't Be Ignored


taylor picture

By: Taylor Ford
Executive Editor



  • The chart below is probably what you are looking for.
  • Men's testosterone levels start gradually declining by about 1% beginning in their 30s.
  • Testosterone is crucial for overall men's health, we have the guide to help you know the importance of your T levels and the signs of potentially low levels. 


free testosterone levels by age chart

I just hit 35, and I'm fully aware I am just getting started on this journey. Starting at age 30, the average decline in testosterone in men is 1% per year. Most people know that testosterone plays a huge role in men's health and wellness. Still, many don't understand the science or difference between free and total testosterone.  Every guy can benefit from learning more about testosterone and how it affects the body. Free testosterone levels are especially worth knowing more about.

Table Of Contents

What Is Total Testosterone?

Free testosterone is the testosterone in the blood that is bioavailable. It is 'free' because it is unattached to any protein. Most testosterone is attached to one of two proteins: albumin and sex hormone-binding globulin.

While overall testosterone levels are important, a man's free testosterone range is also key because free testosterone is the type of testosterone that is easily usable by the body.

Testosterone that is attached, or bound, to proteins is not available to androgen receptors. Only free testosterone can interact with androgen receptors. Androgen receptors are a kind of hormone that plays a hugely important role in many aspects of bodily function. The reproductive, cardiovascular, neural, immune, and musculoskeletal systems all rely on androgen receptors and, thus, on free testosterone.

What Is Free Testosterone?

When it comes to measuring testosterone levels, there are two types of testosterone that are typically assessed: free testosterone and total testosterone. Total testosterone is the overall amount of testosterone in the bloodstream, including both bound and unbound testosterone. Bound testosterone is not available for use by the body.

The healthy level of testosterone in men can vary depending on factors such as age, overall health, and individual variations. However, generally speaking, a normal total testosterone level for adult men is typically considered to be somewhere between 300 to 1,000 nanograms per deciliter (ng/dL).

What Is the Difference Between Total Testosterone and Free Testosterone?

In summary, the main difference between free testosterone and total testosterone is that free testosterone refers to the unbound and biologically active form of testosterone, while total testosterone refers to the overall amount of testosterone in the bloodstream, both bound and unbound.

The Function of Free Testosterone

While bound testosterone plays a vital role in the body, many bodily functions can only be stimulated by free testosterone.

The functions of free testosterone include:

  • enhancing sleep quality and duration
  • improving sexual functioning
  • increasing energy and endurance
  • and raising red blood cell production.

Other functions are to balance cholesterol and high blood pressure levels, support bone strength, support muscle strength, promote a healthy weight by stimulating metabolic function, and enhance memory and focus.

man in start position before running

Free Testosterone Levels by Age

Normal levels of free testosterone levels in the blood are affected by aging. As a man gets older, his levels of both free testosterone and overall testosterone naturally drop. Normal free testosterone levels are determined by a man's age. The same goes for overall testosterone levels.

Testosterone peaks in a man's late teens, and starts to gradually decline after the age of 30. At this stage, testosterone levels will decline by about 1% each year. Testosterone is measured by nanograms per deciliter.

free testosterone levels by age chart

Puberty onset (transition from Tanner stage I to Tanner stage II) occurs for boys at a median age of 11.5 (+/-2) years and for girls at a median age of 10.5 (+/-2) years. There is evidence that it may occur up to 1 year earlier in obese girls and in African American girls. For boys, there is no definite proven relationship between puberty onset and body weight or ethnic origin. Progression through Tanner stages is variable. Tanner stage V (young adult) should be reached by age 18.

Average Free Testosterone Levels by Age Chart

So we've discussed that once you turn 30 your testosterone levels begin to decline. The general understanding of measuring free testosterone is that it is around 1-2% of total testosterone. Free testosterone levels in men vary by age, ranging from:

Age Range Reference Range (ng/dL)
20-<25 years 5.25-20.7
25-<30 years 5.05-19.8
30-<35 years 4.85-19.0
35-<40 years 4.65-18.1
40-<45 years 4.46-17.1
45-<50 years 4.26-16.4
50-<55 years 4.06-15.6
55-<60 years 3.87-14.7
60-<65 years 3.67-13.9
65-<70 years 3.47-13.0
70-<75 years 3.28-12.2
75-<80 years 3.08-11.3
80-<85 years 2.88-10.5
85-<90 years 2.69-9.61
90-<95 years 2.49-8.76
95-100+ years 2.29-7.91
Mayo Clinic Labs


Free Testosterone Calculator

Free Testosterone Range:


Low Testosterone Levels

While normal free testosterone levels do naturally drop over the years, not all decreases in testosterone are non-problematic. Low testosterone is a medical condition, occurring when the amount of testosterone in the blood drops below the normal range. Testosterone deficiency, also known as hypogonadism, is a condition in which the body produces insufficient amounts of testosterone.

Low testosterone levels can make you feel, well, not like yourself. Low testosterone causes a wide variety of health issues. Among the problems that low testosterone can cause are: low sex drive, increased body fat, loss of muscle mass, fatigue, hair growth or loss, and decreased bone mass. How do you tell if you have low testosterone? Keep reading below:

Signs/Symptoms of Testosterone Deficiency (TD)

The signs and symptoms' of testosterone deficiency can vary, but they often include:

Low sex drive:

Testosterone is a primary factor in sex drive and libido. Low testosterone can lead to a decrease in sexual desire and function.

Erectile dysfunction:

Testosterone plays a critical role in the production of nitric oxide, a molecule that helps relax blood vessels and promote blood flow. Insufficient levels of testosterone can cause erectile dysfunction or difficulty achieving or maintaining an erection.

Fatigue and decreased energy:

Testosterone also plays a role in energy levels and vitality. Men with low testosterone levels may feel fatigued, lack motivation, and experience decreased energy levels.

Decreased muscle mass and strength:

Testosterone is essential for building and maintaining muscle mass and strength. Men with low testosterone may experience a decrease in muscle mass, strength, and endurance.

Increased body fat:

Testosterone helps regulate body fat distribution, and low testosterone levels can lead to an increase in body fat, particularly in the abdominal area.

Mood changes:

Testosterone plays a role in mood regulation, and low testosterone levels can lead to irritability, depression, and anxiety.

Decreased bone density:

Testosterone is essential for bone health and density. Men with low testosterone levels may be at a higher risk of developing osteoporosis or bone fractures.

How to Diagnose Low Testosterone?

There are a lot of different routes to check your levels and see if you have low testosterone. Laboratory testing: Blood tests are commonly used to measure t levels. Total t, free t, and SHBG levels may be measured by blood test to assess an individual's hormonal status. These tests are usually done in the morning when your t levels are typically at their highest. There are also at home saliva tests available to check your testosterone production and levels from home.

How to Increase Testosterone Levels

We have a complete guide on how to increase free testosterone levels that is worth checking out. Eating a nutritious diet, losing weight, reducing stress, getting good sleep, and practicing strength training are some of the ways to counteract the signs of low testosterone and fight against the nasty symptoms described above.

Another key step is taking a quality supplement. Mdrive will help increase your strength while boosting your energy and drive. Contact us for more information, or check out our line of supplements for men here.


Can I raise my testosterone naturally?

In a 2007 research study, men who did strength training 3 days a week for a month did show an increase in t levels.

Another study showed that HIIT (high intensity interval training) can increase testosterone levels in men.

There are also foods that have been shown to boost your testosterone levels as well as some foods to avoid. Simply put, avoid soy-based foods, processed foods, nuts, and alcohol. Stick with Tuna, Salmon, egg yolk, beans, beef, and avocados.



What is Testosterone Replacement Therapy? (TRT)

Testosterone replacement therapy (TRT) is a medical treatment designed to help men with low levels of testosterone.

Testosterone replacement therapy is typically prescribed to men who have been diagnosed with low testosterone levels, also known as hypogonadism. This condition can be caused by a variety of factors, including aging, injury or infection to the testicles, or certain medications.

TRT works by supplementing the body with testosterone, which can be administered in several forms, including injections, patches, gels, and pellets. The goal of TRT is to restore testosterone levels to a healthy range and alleviate symptoms associated with low testosterone, such as decreased sex drive, fatigue, depression, and muscle weakness.

It's important to note that TRT is not a cure for low testosterone. Rather, it is a long-term treatment that requires ongoing monitoring and adjustment by a healthcare provider. TRT may also have side effects, such as acne, breast enlargement, sleep apnea, and an increased risk of blood clots and prostate cancer.

TRT is not recommended for men with a history of prostate or breast cancer or those with high levels of red blood cells or a history of blood clots. Additionally, TRT should only be prescribed by a healthcare provider with expertise in treating symptoms of low testosterone levels.

What is a normal testosterone level?

"Normal testosterone levels" can be difficult to define and can vary depending on factors such as age, sex, and individual characteristics. In adult men the typical range of normal testosterone is In adult men, a normal total testosterone level is somewhere between 300 to 1,000 nanograms per deciliter (ng/dL). However, it's important to note that optimal or healthy testosterone levels may differ for each individual and can depend on various factors.


2 comments on Why Free Testosterone Levels Shouldn't Be Ignored
  • Guang lu
    Guang luJanuary 04, 2024

    Good to know

  • Reynold Lupo
    Reynold LupoApril 20, 2022

    In the middle of a quandary, though my testosterone levels are consistently high (783ng/dl), my “free testosterone” levels are consistently low. The last blood test I did showed a level of zero! I’m old, 77, workout and have always been on the stocky side. I have a high percentage of body fat.
    my doctor claimed that "free testosterone " levels are variable and you can get different readings. Not sure I believe this.
    Are there any supplements specific to this condition ?

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