If you watched sports or other shows that were geared towards men in the late 2000’s, you probably saw at least one ad for low testosterone, e.g. “Is it Low T”, which pairs nicely with the ads for Viagra, trucks, and beer. This direct-to-consumer-advertising to “raise awareness” about low testosterone was very effective for the pharmaceutical industry, as both testing and treatment for “low T” skyrocketed. In the US for example, prescription use of testosterone increased nearly 10-fold between 2000 to 2011, yet:
- 1 in 4 patients have no testosterone level measured prior to starting therapy
- 1 in 3 patients who are treated don’t meet diagnostic criteria for low testosterone
- 1 in 2 patients don’t have blood levels rechecked after starting testosterone therapy
To avoid falling into this trap, this guide will provide an abbreviated primer to ensure an accurate diagnosis, and an initial action plan if you are concerned that you may have low testosterone, which we will refer to as testosterone deficiency.
For a more detailed discussion of the physiology of testosterone, its impact on health and performance, consequences of testosterone deficiency, and strategies for managing testosterone deficiency, check out the full Barbell Medicine Testosterone Course.
What Is Low Testosterone (Male Hypogonadism)?
Low testosterone or male hypogonadism is a clinical syndrome that results from a failure of the testes to produce enough testosterone and/or sperm due to disease at one or more areas in the hypothalamic–pituitary–testicular axis. Some medical guidelines prefer the term “testosterone deficiency” over male hypogonadism, which is what we’ll use for the remainder of this article.
How is Low Testosterone Diagnosed?
A proper diagnosis of testosterone deficiency requires the presence of both:
- Signs or symptoms of testosterone deficiency
- Low blood levels of testosterone
Testosterone deficiency is not simply a laboratory finding of “low T”, as an individual must also have accompanying symptoms.
What Are the Symptoms of Low Testosterone?
The symptoms of testosterone deficiency are numerous and can be categorized as specific, suggestive, or non-specific, depending on how well they correlate to testosterone levels.
Specific symptoms are most closely related to testosterone deficiency. If a person has one or more of these symptoms, suspicion for testosterone deficiency increases the most:
- Incomplete or delayed sexual development
- Loss of body hair (axillary or pubic)
- Small testes (normal volume 15-35 mL)
Suggestive symptoms often occur due to testosterone deficiency, but can also be explained by other causes too. People with these should be evaluated for both testosterone deficiency and other causes at the same time:
- Decreased libido (from previously normal libido)
- Gynecomastia (breast tissue enlargement)
- Infertility
- Erectile dysfunction
- Hot flashes
- Decreased spontaneous erections
- Decreased genital sensation or orgasm
Non-specific symptoms can be seen in association with testosterone deficiency, but they are so common that they’re more often unrelated to testosterone levels, especially when the person does not have the more specific or suggestive symptoms listed above. For example, a person who has poor sleep and an increase in body fat, but who still has normal libido and erectile function, is highly unlikely to have testosterone deficiency. This person needs a broader evaluation rather than fixating on testosterone levels alone as the most likely cause. Some examples of non-specific symptoms:
- Depressed mood
- Impaired concentration
- Low bone density
- Unexplained anemia
- Sleep disturbance
- Loss of muscle mass
- Increase in body fat
- Decreased energy or motivation
To summarize, there are many different symptoms of testosterone deficiency, many of which can also be caused by other medical conditions. While checking testosterone levels can be useful, it is often necessary to investigate other causes as well.
What Does Testosterone Do?
Testosterone is a steroid hormone with many functions across the body. The term “steroid” describes its chemical structure, and a “hormone” regulates functions in tissues throughout the body.
In men, testosterone is primarily made (95%) in the Leydig cells of the testes, whereas 5% is made in the adrenal glands that sit on top of the kidneys. Testosterone is released into the bloodstream and mostly circulates bound to proteins known as sex hormone binding globulin (SHBG) and albumin. About 1 to 4% of circulating testosterone is unbound, or “free”.
Testosterone acts on tissues in the body primarily by binding to the Androgen Receptor and subsequently regulating the function of that tissue. Androgen receptors are spread throughout the body, including the muscles, bones, brain, liver, skin, and more. Here are a few examples of what testosterone does in the human body:
- Muscle: muscle remodeling, growth, and function
- Bone: maintaining bone mass and density
- Brain: affects mood, libido, and cognitive function
- Other: Stimulates hair growth, sperm production, and red blood cell production
Testosterone plays an important role in many processes in the body, which highlights the importance of appropriately identifying and treating those with testosterone deficiency.
What Causes Low Testosterone?
Low testosterone or testosterone deficiency is caused by disease at one or more areas in the hypothalamic–pituitary–testicular axis and classified as primary or secondary.
- Primary testosterone deficiency is when the testes are functionally unable to produce testosterone, which essentially always requires testosterone therapy.
- Secondary testosterone deficiency is when there is a problem in the signal being sent from the brain to the testes. It does not always require testosterone therapy, because there are many reversible causes of secondary testosterone deficiency.
Secondary testosterone deficiency is much more common in practice. It is often associated with things like excess body fat, insulin resistance, diabetes, fatty liver, and the use of certain medications like opioids, corticosteroids, or after stopping anabolic steroid use. Excessive exercise and extreme leanness can also contribute to this phenomenon.
Potential underlying causes of these conditions, and how they can be differentiated, is discussed in greater detail in the full course.
Preventing Low Testosterone
Preventing low testosterone or testosterone deficiency in men is complicated, as testosterone levels tend to reflect the overall health status of an individual. Testosterone deficiency is estimated to affect 2-12% of middle-aged and older men, but a person’s overall health is more predictive of their risk of developing low testosterone.
For example, among aging men who remain lean and healthy, testosterone deficiency is very rare (well below 0.5%), suggesting that testosterone deficiency is not an inevitable consequence of aging. In contrast, testosterone deficiency affects about 30-50% of men with obesity and diabetes. Obesity increases the risk of testosterone deficiency by approximately 13-fold.
Therefore, prevention of testosterone deficiency requires a holistic approach that focuses on overall health through achieving and maintaining a healthy body weight and composition, getting enough exercise, eating a healthy dietary pattern, adequate sleep, as well as management of other health conditions.
Diagnosis and Testing
The diagnosis of testosterone deficiency in men requires both signs and symptoms and laboratory evidence showing low testosterone levels. Correctly measuring and interpreting blood tests is complex, and is more error-prone than many people realize. When measuring blood testosterone levels, there are several different types of tests available, each with different interpretations and uses.
Laboratory Tests For Low Testosterone
The most common lab tests used when assessing an individual for low testosterone are total testosterone, free testosterone, luteinizing hormone (LH), follicle stimulating hormone (FSH), and steroid hormone binding globulin (SHBG). Importantly, not all of these tests are performed initially, as a step-wise approach is preferred to avoid unnecessary testing and improve diagnostic accuracy.
Total Testosterone
A Total Testosterone level measures testosterone in all of its circulating forms. The details of these forms are outside the scope of this primer and are explained in greater detail in the full course. Total testosterone is typically measured in units of nanograms per deciliter (ng/dL) or nanomoles per liter (nmol/L). To convert values, divide a level in ng/dL by 28.8 to get the measurement in nmol/L.
In order to minimize test variation and error, blood draws should ideally be performed in a fasted state between 8:00-10:00 AM time frame assuming a normal sleep-wake schedule; otherwise, within 3 hours of waking. Avoid testing during illness or while taking a limited course of medications known to lower testosterone levels, such as glucocorticoids. Finally, testing should ideally be performed using a CDC Certified Lab Assay.
Despite following these steps, there will still be an element of natural variation and lab error involved with repeated measurements. As a result, it can be challenging to confidently determine when a “real” change in testosterone levels has occurred, versus simple “noise” from test variation. In order to be more confident that repeated testosterone measurements are sufficiently different that any change between them is “real”, use the BMJ “Your Results May Vary” tool. This can help differentiate natural variation and lab error from meaningful changes in blood testosterone levels in response to lifestyle or treatment interventions.
What is a Low Testosterone Level?
Most clinical practice guidelines use a level of 300-350 ng/dL as the lower limit of normal for total testosterone, regardless of age. There is no consensus on the lower limit of normal total or free testosterone. No studies have shown a single cutoff that reliably separates those who will improve from treatment from those who won’t.
As a result, there is some room for clinical judgment when interpreting test results in the context of a patient’s signs and symptoms, such that a single universal cutoff does not need to be applied rigidly for treatment purposes. Some clinicians may still offer a trial of treatment to individuals with blood levels slightly above these cutoffs in scenarios where their signs and symptoms are very suggestive of testosterone deficiency.
Free Testosterone
Recent evidence has shown that low free testosterone levels are more closely correlated to the signs and symptoms of testosterone deficiency when compared with total testosterone levels, primarily due to the effects of Sex Hormone Binding Globulin. These details are discussed in greater detail in the full course.
Free testosterone levels can be measured using a variety of methods, some more reliable than others. Below are suggested reference ranges for free testosterone measurements, depending on the measurement method used:
- Lab-Calculated Free Testosterone (most practical method): 65-100 pg/mL
- Equilibrium Dialysis (ideal method): 65-100 pg/mL
- Analog/RIA (less preferred method): 1.0-1.5 ng/dL or 10-15 pg/mL
A related test called “Bioavailable Testosterone” combines free testosterone and albumin-bound testosterone, but this test is generally less useful than the above measures.
Other Testing
Many other tests can be obtained when evaluating a person with signs and symptoms of testosterone deficiency. This is because there is so much overlap in the symptoms of testosterone deficiency with other conditions, such as anemia, thyroid disorders, sleep apnea, and many others. These tests are not all required in all situations, but can be used selectively based on the clinical presentation. The details of these tests and how they should be used are beyond the scope of this primer.
Treatment
Once a diagnosis of testosterone deficiency has been established based on signs and symptoms, as well as low blood levels of testosterone, we can discuss treatment. Treatment depends on the type of testosterone deficiency, and whether an underlying cause for the condition can be identified. It does not always require immediate testosterone replacement therapy in all cases.
Lifestyle Changes For Low Testosterone
For cases of potentially reversible testosterone deficiency, let’s discuss the most important aspects of an action plan built around normalizing testosterone levels through lifestyle and, when appropriate, testosterone therapy.
Dietary Interventions For Low Testosterone
The most important aspect of diet as it relates to testosterone levels involves achieving and maintaining energy balance at a healthy body composition. As mentioned above, excess body fat and its metabolic consequences like diabetes and fatty liver dramatically increase the risk of testosterone deficiency. At the other end of the spectrum, extreme leanness and low levels of body fat due to low calorie intake can also cause low testosterone levels.
Achieving a healthy level of body fat from either extreme can significantly increase blood testosterone levels. The amount testosterone increases, as well as many of the other improvements in mental and physical well-being people experience, is most closely related to the overall amount of excess fat lost, or when normalizing body fat levels from extremely low ranges. A good initial target is to achieve a waist circumference below current ethnic-specific cutoffs.
Beyond achieving a healthy body composition, there are also specific nutrients of concern relating to blood testosterone levels. These are discussed in greater detail in the full course, but we will summarize a few points here.
Total Fat & Cholesterol: Current evidence suggests a small effect of low-fat diets (< 25% calories from fat) versus high fat (35-40% calories from fat) on lowering testosterone levels. People consuming severely fat-restricted diets (despite appropriate overall calorie intake) may consider increasing their total fat intake, however in most cases the expected effect of this on testosterone levels is modest.
Current evidence is inconsistent on the effects of specific types of fat (e.g., saturated vs. unsaturated) on testosterone levels. Our current recommendations follow those for a generally health-promoting diet: saturated fat intake should be maintained at around 10% of calories, mostly biased away from animal-derived sources. The remainder of unsaturated fat intake can be derived from fish (e.g. salmon), dairy, and plant sources (e.g. avocado, nuts, olives/olive oil, etc.).
Deliberately increasing dietary cholesterol intake is often claimed to increase testosterone levels, since testosterone is synthesized from cholesterol. However, we don’t have strong evidence of a large effect from this practice. This may be due to mechanisms that regulate how much cholesterol is produced in the body with varying amounts of dietary intake. When the overall diet is relatively low in saturated fats compared with unsaturated fats (as in the dietary pattern recommended above), dietary cholesterol has minimal impact on blood cholesterol levels. As a result, regularly eating foods like eggs can be part of a healthy diet — but as with dietary fat above, the expected effect of this on blood testosterone levels is modest.
Total Carbohydrates: severe carbohydrate restriction (< 5% of total energy) decreases testosterone levels, whereas moderate carbohydrate restriction has no consistent effect on testosterone levels. As a result, if a person chooses to consume a low-carbohydrate diet, avoiding severe restriction to very low levels of intake is recommended. Carbohydrate sources that can be part of a healthy dietary pattern include fruits, fibrous and starchy vegetables, whole grains, oats, and legumes. Sugar-sweetened beverages and common ultra-processed snack foods high in sugars and other refined carbohydrates should be minimized.
Total Protein: there is no consistent effect of protein on testosterone within usual ranges of intake. Three small, short-term studies have found that extremely high protein diets (greater than 3.4 g protein per kg bodyweight per day) decreased testosterone levels. However, for most individuals aiming for a minimum of 1.2 g per kilogram body weight per day, with upwards of 2.2 g per kilogram per day is appropriate.
Specific concerns are often raised regarding soy-derived protein. This is because soy contains isoflavones, a type of phytoestrogen that is often claimed to lower testosterone levels or interfere with testosterone signaling. This has been studied extensively, with a meta-analysis of 41 studies and over 1000 men concluding:
“Regardless of the statistical model, no significant effects of soy protein or isoflavone intake on any of the outcomes measured were found. Sub-analysis of the data according to isoflavone dose and study duration also showed no effect.”
Regular consumption of soy protein has shown numerous health benefits, including reductions in cardiovascular risk. While no clear detrimental effects have been shown in humans at usual levels of intake, incorporating it into one’s diet in the context of testosterone-related concerns can be a matter of personal preference.
Improving Sleep For Low Testosterone Levels
Testosterone production is dependent on adequate sleep. While testosterone levels typically follow a daily rhythm, peaking in the morning and dipping in the evening, testosterone production does not inherently follow a circadian rhythm. Rather, it is more related to when an individual sleeps.
Production of testosterone requires at least 3 hours of initial uninterrupted sleep, and levels remain elevated until wakening, when peak levels occur. It then declines throughout the period of wakefulness.
Morning testosterone levels are independently predicted by the overall measured sleep duration. As a result, aiming for at least the first 3 hours of deep, uninterrupted sleep, and an appropriate overall sleep duration of 7.5-8 hours is a useful strategy for improving testosterone levels.
This can be challenging for many reasons, including poor sleep hygiene, sleep-disordered breathing (such as obstructive sleep apnea) or other sleep disorders, and also because testosterone deficiency itself can cause disrupted sleep.
Working to improve sleep hygiene, undergoing evaluation for sleep disorders such as obstructive sleep apnea, and consulting with a physician for other sleep-related concerns can be important steps in this process. Certain supplements and medications can be useful to improve sleep rhythms and quality.
Exercise Training To Improve Testosterone Levels
Exercise has little direct impact on testosterone levels, as it does not produce a sustained increase in resting testosterone levels in most individuals regardless of the type of training they’re doing, whether lifting weights, sprints, or aerobic exercise.
However, exercise has numerous beneficial effects on factors that can impact testosterone levels indirectly. For example, exercise has beneficial impacts on appetite regulation, which can facilitate healthier body composition. Long-term exercise can also help sustain weight loss. It also improves sleep quality, metabolic function, fatty liver disease, and many other conditions. In general, interventions that improve general health will tend to lead to improvements in testosterone levels.
Exercise can improve the effectiveness of testosterone therapy versus testosterone therapy alone. If testosterone therapy is stopped, continuing exercise improves the durability of effects well after this discontinuation. Based on these observations, we recommend all individuals aim to meet and/or exceed the current Physical Activity Guidelines for Adults.
The effects of exercise on testosterone, as well as the effects of testosterone on performance, are complex. We discuss these in much greater detail in the full course.
Supplements For Increasing Testosterone
The vast majority of dietary supplements have little to no clinical effect. Marketing can be dubious and misleading, often based on anecdotes, or comparing testosterone levels that might appear to show an improvement, but actually fall within the range of natural variation or lab error as mentioned above.
Even among those which do have some evidence of effect, it is typically inconsistent, modest (often clinically insignificant), and far less than the effect of general health improvements or, if appropriate, prescription testosterone therapy. In addition, a large proportion of “testosterone boosting” supplements are mislabeled, contain contaminants (sometimes including actual anabolic steroids), and contain ingredients lacking evidence of benefit on testosterone levels.
So, while there are many claims on the internet about improvements in testosterone levels from various forms of supplements, we feel that the potential benefit from these supplements is outweighed by their potential risks. Further discussion of specific supplements, including vitamin D, zinc, selenium, and others is included in the full course.
If the other lifestyle measures described above are insufficient to improve a person’s testosterone deficiency, we recommend proceeding to medical therapy, as below.
Medical Treatment of Low Testosterone
While many cases of testosterone deficiency are reversible through many of the lifestyle interventions described above, not everyone will be able to resolve symptoms and normalize blood levels through those methods alone.
There are different methods available to treat testosterone deficiency. These include testosterone therapy, or non-testosterone agents aimed at increasing the body’s own production of testosterone. Each of these have their own set of potential benefits, risks, costs, and unique considerations for each individual patient. These specific considerations are outlined in greater detail in the full course, and should always be discussed in collaboration with the prescribing physician.
Testosterone Replacement Therapy (TRT) Monitoring
There is no evidence to support aiming for specific blood level targets. Rather, it is often best to aim for somewhere in the middle of the reference range of 300 to 800 ng/dL, and adjust based on symptoms and/or any undesirable side effects that emerge, often related to excessively high peak levels.
Side Effects of Testosterone Replacement Therapy (TRT)
The most important, and often under-recognized side effect of testosterone therapy is suppression of fertility. Sperm production can be fully suppressed in as little as 10 weeks of testosterone therapy. Recovery of sperm production varies between men after stopping testosterone therapy; up to 4-10% of men never fully recover and require advanced fertility treatments.
Testosterone deficiency is correlated with a higher risk of cardiovascular disease than people with normal testosterone levels. Individual risk varies, but appropriately treating individuals with true testosterone deficiency does not increase risk of heart disease, and may actually lower it.
Prostate cancer is another oft-touted risk of testosterone therapy, though current evidence has not shown an increased risk of prostate cancer in those with appropriately treated testosterone deficiency.
These and other side effects concerning sexual function, elevated blood counts, gynecomastia, and so on are discussed in greater detail in the full course.
Prognosis
The prognosis for individuals with testosterone deficiency varies based on the cause, the chosen intervention, and response to treatment.
In primary testosterone deficiency where the testes are functionally unable to produce testosterone, medical intervention with testosterone therapy is essentially always required. In contrast, those with secondary testosterone deficiency caused by obesity, diabetes, or medications may be able to manage testosterone deficiency with lifestyle change alone.
When should I see my doctor about low testosterone?
Individuals should discuss with their physician if they are concerned about testosterone deficiency based on symptoms they are experiencing. “Just checking” testosterone levels without any symptoms or concerns is unlikely to provide benefit or useful information.
As mentioned above, specific signs like incomplete sexual development are highly suggestive of testosterone deficiency, whereas non-specific symptoms like fatigue or loss of muscle mass are more often caused by other issues unrelated to testosterone levels.
What should I expect if I have low testosterone (male hypogonadism)?
Generally speaking, those with testosterone deficiency are likely to see improved health and function when treated appropriately, whereas those who have been improperly diagnosed, started on treatment without adequate workup, and/or are improperly managed may experience harm.
As mentioned above, treatments include both lifestyle and medical interventions that work together to improve a person’s health and quality of life.
Wrap-Up
Despite receiving a glut of advertising and influencer attention to testosterone deficiency, the condition itself is relatively rare among lean, healthy men – even at older ages. Still, many would likely benefit from accurate sources of information and discussing any concerns relating to testosterone with a trained health care professional.
In this article, we’ve provided an overview for what testosterone deficiency is, its diagnostic criteria, causes, treatments, and more. For those interested in a testosterone action plan, we’ve developed a free 10-step action plan. If you’re interested in learning more about testosterone, we go into far greater depth on its physiology, function, testing, treatment, and impacts on both health and performance in our full course.
Thanks for reading!
