Testosterone is a hormone that plays a primary role in the development of male characteristics. Produced mainly in the testicles, it is responsible for regulating sex drive, bone mass, fat distribution, muscle mass, and the production of red blood cells and sperm. While considered a male sex hormone, females also produce testosterone in much smaller quantities. The brain’s hypothalamus and pituitary gland control testosterone production.
The Lifecycle of Male Testosterone
Testosterone production is not constant and follows a distinct lifecycle. Levels surge during puberty, driving the development of secondary sexual characteristics like a deepening voice, growth of facial and body hair, and increased muscle mass. This period leads to peak testosterone levels during adolescence and early adulthood.
Following this peak in the late teens and 20s, testosterone levels begin a gradual decline. This reduction often starts around age 30, and it is estimated that levels can drop by about 1% to 2% per year. This age-related decline is a natural process connected to changes in testicular function and the brain’s regulatory signals.
Defining a “normal” testosterone level is complex because ranges can vary significantly between individuals and laboratories. However, medical guidelines provide a general framework based on age. These levels are measured in nanograms per deciliter (ng/dL). It is important to view these ranges as population averages rather than a strict diagnostic tool for any single person.
| Age Group | Average Total Testosterone Range (ng/dL) |
| :— | :— |
| Adolescence (16-17) | 102–1,010 ng/dL |
| Early Adulthood (20-39) | 352–1,000 ng/dL |
| Middle Age (40-59) | 215–916 ng/dL |
| Senior Years (60+) | 156–859 ng/dL |
Recognizing the Signs of Low Testosterone
When testosterone levels fall below a healthy range, a condition known as hypogonadism, it can manifest through physical, sexual, and emotional changes. A single sign is not enough for a diagnosis, but a consistent pattern of several symptoms often prompts a medical consultation.
Physical changes are frequently associated with low testosterone. Men may experience persistent fatigue or a lack of energy, a decrease in muscle mass and strength, and an increase in body fat. Other indicators include the development of enlarged breast tissue (gynecomastia) or reduced body and facial hair growth.
Changes related to sexual function are common indicators. A reduced sex drive, or libido, is a primary symptom. This may be accompanied by difficulty achieving or maintaining an erection and a reduction in spontaneous erections. Infertility can also be a consequence, as testosterone is involved in the development of mature sperm.
The effects of low testosterone can extend to emotional and cognitive well-being. Men may experience mood swings, feelings of irritability, or a depressed mood. Cognitive issues such as difficulty concentrating and memory problems have also been linked to the condition. These symptoms, combined with the physical and sexual changes, can have a noticeable impact on a person’s quality of life.
Factors That Influence Testosterone Levels
While age is a primary driver of the natural decline in testosterone, it is not the only factor. A variety of lifestyle choices and underlying medical conditions can also influence hormone levels. Understanding these contributors provides context for why an individual’s testosterone might be lower than expected.
Chronic health conditions can play a role. Obesity and type 2 diabetes are strongly linked to lower testosterone, as excess body fat can increase the conversion of testosterone into estrogen. Other conditions that can interfere with production include:
- Problems with the testicles
- Pituitary gland disorders
- HIV/AIDS
- Liver or kidney disease
Lifestyle habits also have a direct impact. Poor sleep quality is a contributor, as the body produces testosterone during sleep. High levels of chronic stress can elevate the hormone cortisol, which can suppress testosterone production. Substance use, including chronic alcohol consumption and drugs like opioids and anabolic steroids, can interfere with hormonal signaling pathways.
How Testosterone Levels Are Medically Evaluated
Diagnosing low testosterone begins with a consultation with a healthcare provider to discuss any symptoms being experienced. If signs suggest a potential issue, the primary tool for diagnosis is a blood test to measure testosterone in the bloodstream, which confirms a suspected case of hypogonadism.
The timing of the blood test is specific. Testosterone levels fluctuate throughout the day, peaking in the morning. For this reason, healthcare providers schedule the blood draw for the early morning, before 10 a.m., to get the most accurate reading. An acute illness can temporarily lower levels, so it’s important to be healthy at the time of the test.
A single low reading is often not enough for a definitive diagnosis. Because levels can vary, a provider will require at least two separate blood tests on different days to confirm the level is consistently low. This approach helps to rule out temporary fluctuations and ensures an accurate baseline measurement.