Last updated on July 26th, 2026 at 08:10 am
Low testosterone isn’t one condition with one cause; it splits into two distinct clinical categories, and knowing which one applies to you changes how a doctor actually treats it.
Low testosterone means testosterone has dropped below a healthy range, and it rarely comes from a single cause.
Doctors classify it into two distinct types depending on where the problem originates: the testes themselves or the signaling system in the brain that controls them.
This guide covers both classifications, how common low testosterone actually is, the full range of causes, and what happens if it goes unaddressed.
For a complete picture of testosterone in general, see our main testosterone guide.
Table of Contents
What is Low Testosterone?
Low testosterone is testosterone that has dropped below the normal healthy range for an adult man, typically below 300 ng/dL, confirmed through at least two separate morning blood tests rather than a single reading, according to the Endocrine Society.
A single low result isn’t enough to diagnose it on its own, since levels can dip temporarily from illness, poor sleep, or overtraining, which is why medical guidelines call for confirmation before treatment decisions get made.
Primary vs. Secondary Low Testosterone
Primary Low Testosterone
Primary low testosterone originates in the testes themselves.
Genetic conditions, physical injury, infection, or certain medical treatments can prevent the testes from producing adequate testosterone, regardless of how strong the signal from the brain is.
Secondary Low Testosterone
Secondary low testosterone originates upstream, in the pituitary gland and hypothalamus.
These structures send the signals that tell the testes how much testosterone to produce, and conditions like obesity, diabetes, chronic stress, or certain medications can weaken that signal.
In this case, the testes function normally; they’re simply receiving fewer instructions.
Knowing which category applies matters, since treatment for each differs meaningfully.
A doctor typically determines this through additional hormone testing beyond a basic testosterone panel.
How Common Is Low Testosterone?
Low testosterone is far from rare. Roughly 35 percent of men over 45 meet the clinical criteria for low testosterone, according to the Endocrine Society, and the rate climbs with age from there.
Despite that, it remains widely underdiagnosed, since many of its symptoms overlap with normal aging, depression, or simple fatigue, and get dismissed without ever being tested.
Signs and Symptoms, Briefly
Low testosterone typically shows up through a mix of physical and emotional changes: persistent fatigue, reduced muscle mass, increased body fat, lower sex drive, and mood changes like irritability or low motivation.
None of these symptoms alone confirms low testosterone, since each overlaps with several other conditions.
Our full guide to signs of low testosterone breaks down the complete symptom picture and how it differs by age.
Causes of Low Testosterone in Men
Age-Related Decline
One primary cause of low testosterone in men is age.
Testosterone production slows gradually as the cells in the testes become less responsive to signals from the pituitary gland.
This process typically begins around age 30 and becomes more noticeable for many men after 50.
Two additional factors often compound this natural decline: DHEA, a hormone that supports testosterone production, drops with age too, and rising body fat increases aromatase activity, an enzyme that converts testosterone into estrogen.
Lifestyle and Environmental Causes
Another cause of low testosterone in men is lifestyle and environemental.
A sedentary lifestyle slows metabolism and shifts hormone balance in the wrong direction.
A diet heavy in processed food and sugar contributes to weight gain and metabolic issues that lower testosterone over time.
Heavy alcohol use interferes with testicular function directly, and smoking introduces toxins that disrupt hormone production.
Everyday exposure to endocrine-disrupting chemicals, found in some plastics and personal care products, can also interfere with hormone signaling.
Recreational drug use, including marijuana, may interfere with the same hormonal pathways.
Chronic Health Conditions
Chronic health conditions also cause low testosterone in men.
Obesity, particularly excess abdominal fat, increases insulin resistance and aromatase activity together, both of which push testosterone lower.
Type 2 diabetes and metabolic syndrome follow a similar pattern, since insulin dysregulation disrupts hormone production directly.
Hypertension and cardiovascular conditions are associated with reduced testosterone, likely tied to reduced blood flow affecting hormone transport.
Sleep apnea disrupts the deep sleep cycles where testosterone release primarily occurs.
Thyroid dysfunction slows multiple body systems at once, testosterone production among them.
Medications Worth Knowing About
Long-term opioid use suppresses testosterone by disrupting the hypothalamic-pituitary-gonadal axis, a condition specifically named opioid-induced androgen deficiency.
Depending on the population studied, this affects between 20 and 80 percent of chronic opioid users, according to a 2025 review published in Andrology.
Corticosteroids used for arthritis, asthma, or inflammation can slow hormone activity in the adrenal glands.
Certain antidepressants and beta blockers may affect testosterone with long-term use.
Anabolic steroid use suppresses the body’s own natural production once use stops.
Statins and some cancer therapies have also been linked to changes in testosterone in some men.
Psychological and Emotional Factors
Chronic stress raises cortisol, and elevated cortisol works directly against healthy testosterone production.
Depression and anxiety can lower testosterone too, creating a cycle where low energy and low mood reinforce each other.
The Risks of Leaving It Unaddressed
Untreated low testosterone doesn’t just affect energy and mood in the short term.
Over time, it’s linked to reduced bone density, increased body fat, loss of muscle mass, and a higher long-term risk of conditions like metabolic syndrome.
The post on dangers of low testosterone covers these long-term consequences in depth.
What to Do Next
If you’re experiencing symptoms of low testosterone, the right next step is a real conversation with a doctor, not a guess based on how you feel.
Read the post on testing and interpretation for what an actual diagnosis involves.
If low testosterone is confirmed, treatment ranges from lifestyle changes to medical intervention depending on severity.
This post on natural ways to boost testosterone covers the first line of approach, and our guide to medical treatment for low testosterone covers replacement therapy and its real risks.
Frequently Asked Questions
What is the difference between primary and secondary low testosterone?
Primary originates in the testes themselves. Secondary originates in the brain’s signaling system, the pituitary gland and hypothalamus, which tells the testes how much to produce.
How common is low testosterone in men?
Roughly 35 percent of men over 45 meet the clinical criteria for low testosterone, though it remains widely underdiagnosed due to overlapping symptoms.
What are the most common causes of low testosterone?
Natural age-related decline, obesity, chronic stress, poor sleep, and certain medications like opioids and corticosteroids are among the most common contributing factors.
What happens if low testosterone goes untreated?
Long-term risks include reduced bone density, increased body fat, loss of muscle mass, and a higher risk of related metabolic conditions over time.
Conclusion
Low testosterone splits into two distinct clinical pictures, affects roughly a third of men over 45, and rarely comes from a single cause.
Left unaddressed, it carries real long-term risks beyond just low energy and mood.
Start with the symptom and testing guides linked above if you suspect this applies to you, rather than assuming based on age alone.
Pyo Merez is a 45-yeard old husband, father, and a chemical engineer by profession and the founder of Gentsways, a men’s lifestyle site built in honour of his father, Dee Clement. He has been writing about men’s development, style, and character through his father’s lens since 2021, drawing on lived experience, his father’s example, and research from reputable publications. He is not a certified trainer or therapist; where fitness or health topics require it, articles are reviewed by qualified contributors.