Testosterone has received a lot of attention lately. This hormone is found naturally in humans and animals. In humans, it is most concentrated in men, causing them to, well, be men. Women’s ovaries also make testosterone but in much smaller amounts. 

However, when we talk about testosterone, most people mean free testosterone. This is a bit different from total testosterone. 

Free Testosterone vs. Total Testosterone 

The male body’s majority of testosterone is bound to one of two receptors: albumin or sex-hormone binding globulin (SHBG). This testosterone is called “bound testosterone.” The testosterone that isn’t bound is called “free testosterone.” Of course, your total testosterone is both of these totals added together. 

Free testosterone is what connects to testosterone-specific cells within the body. Bound testosterone cannot do this, as it is already bound to specific receptors. Therefore, free testosterone affects most of the cells in your body. Many of the effects associated with testosterone are caused by free testosterone, specifically.

Usually, 98% of testosterone is bound, but this number can vary. For example, some men may have normal levels of total testosterone while having low levels of free testosterone. Therefore, regular testosterone tests may show that their levels are normal. As you might imagine, this can make diagnosis confusing. Often, this occurs when the man has excessive levels of chemicals that convert free testosterone to bound testosterone. 

For this reason, it’s essential to consider your free testosterone – not just your total levels. Today, tests often check for total and free testosterone levels to cover both of these cases. 

The Role of Free Testosterone

Free testosterone can react to the testosterone receptors in your cells. Therefore, it is the most dynamic form of testosterone responsible for changes in your body. 

Often, this also means that your total testosterone will be low. However, this isn’t always the case. I

Free testosterone does a lot in the body. It affects muscle growth and bone mass, for instance. Someone with low free testosterone may have difficulty maintaining muscle mass. 

Furthermore, testosterone affects mood. Those with low testosterone may experience depression or other mood problems. Fatigue may also occur, which is linked to further mood problems. 

Of course, low sex drive and fertility can also occur due to low testosterone. 

How Do Doctors Test for It?

The role of free testosterone is becoming more paramount in the medical community today. However, many testosterone tests still only check total testosterone. Therefore, these tests may miss instances where just free testosterone is low. So, if you’re worried about your testosterone, it’s important to have your doctor check both parameters. 

Often, these tests are done through the testing of a blood sample. You’ll need to provide one in the morning, usually between 7 and 10 AM. However, there are exceptions to this time, so be sure to talk with your doctor about your lifestyle. Often, your testosterone will be highest at this time, though this isn’t always the case. 

Getting blood for a testosterone test is like getting it for any other test. The doctor will draw a small amount of blood through a small needle and into a vial or test tube. Then, the blood will be tested. Often, this testing can be done on-site. 

What Benefits Does Free Testosterone Bring?

Most of the benefits linked to testosterone are linked to free testosterone. Bound testosterone affects our bodies much less than free testosterone. 

Free testosterone may help with cardiovascular health; however, studies show mixed results. There does seem to be more complexity to the relationship between the heart and testosterone than we originally thought. One study did link normal testosterone levels with lower heart attack chances

This testosterone also increases muscle mass while lowering fat. Treatment for low testosterone is linked with a decrease in fat which is why TRT is so commonly abused by both people trying to lose weight and athletes trying to improve performance. 

Testosterone also improves bone density. Low testosterone is directly linked with osteoporosis

Furthermore, testosterone also plays a major role in sex and libido. Men with low testosterone may have a low sex drive and poor erectile function. 

Free testosterone also affects mood. Men with deficient testosterone have a higher chance of depression and irritability. However, this isn’t linked to normal decreases in testosterone. 

How Do I Increase Free Testosterone?

There are many ways to increase overall testosterone, which often leads to an increase in free testosterone. 

Weightlifting and HIIT are types of exercises that can increase testosterone. At the same time, excessive cardio may lower testosterone, so try to steer clever of that. However, because obesity can also lower testosterone, it can be tricky to balance things out. 

Eating a healthy diet is also vital. After all, we need different vitamins and minerals in our food to make testosterone. Dieting and overeating can both cause issues with testosterone levels. Too much bad food and not enough food both cause distributions in hormonal production.

Chronic stress can lower testosterone and affect your health in other ways. For instance, stressed people are more likely to gain weight and less likely to eat a healthy diet (factors that also affect testosterone). 

Consider taking a vitamin D supplement, especially if you live further away from the equator. Low vitamin D is linked to lower testosterone levels. Studies have shown that vitamin D supplementation may help treat low testosterone

The Downsides of Low Free Testosterone

Testosterone has a strong impact on sex drive and sexual function. People who have low testosterone often have a low sex drive and erectile dysfunction. Furthermore, testosterone can sometimes affect sperm count, causing male infertility. (Testosterone treatment will not “cure” this fertility issue, as testosterone treatments often negatively impact fertility).

Furthermore, males may experience a decrease in masculine features. For instance, facial, armpit, and pubic hair may decrease. Testosterone doesn’t necessarily affect the hair on your head but the relationship is still unclear here. 

Some men also have hot flashes. Because testosterone affects mood, men may become depressed or anxious if their testosterone levels are not normal. High testosterone can also affect mood. Increased body fat paired with decreased muscle mass and endurance may also occur. 


Free testosterone is not bound to receptors, allowing it to affect cells in your body. Therefore, it’s what causes most of the benefits of testosterone. For instance, free testosterone controls muscle mass, mood, male sexual health, bone density, and many other health factors. 

Often, someone with low testosterone will also have low total testosterone as their body isn’t making enough testosterone. 

Usually, this occurs when too much testosterone becomes bound for one reason or another. 


Does free testosterone do anything?

Free testosterone does most of the things that are contributed to testosterone. Because this testosterone isn’t bound, it can affect many cells in the body. Therefore, it’s the cause behind many biological changes caused by testosterone. It affects a male’s sexual health, including libido, erectile function, and sperm health. It also causes male hair growth on the face, armpits, and pubic area. 

This testosterone is also linked to mood regulation, cardiovascular health, muscle mass, and bone density. 

In other words, it does a lot. 

What should my free testosterone percentage be?

Free testosterone only makes up around 2% of the testosterone in the body. The large majority of testosterone your body makes is bound to the sex hormone-binding globulin or albumin. 

Is free or total testosterone more important?

Both types of testosterones are necessary. However, when talking about low testosterone, free testosterone is more important. 

Therefore, when getting your testosterone checked by your doctor, we recommend getting your free testosterone checked specifically. 

About the Author Tim Rockwell

Tim Rockwell is a highly skilled and knowledgeable fitness expert. With a background in exercise science and years of experience in the fitness industry, Tim is passionate about sharing his expertise with others through his writing. He currently contributes articles to Eurasc, where he shares practical tips and strategies for leading a healthy, active lifestyle.

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