Low Testosterone in Men: Know the Symptoms, Understand the Risks

Author: Quyen Johnson, APRN, FNP-C

1. Introduction about Low Testosterone or Low T

The symptoms of low testosterone are wide-ranging and can affect nearly every aspect of a man’s health and daily functioning. They are typically grouped into four categories: sexual, physical, psychological, cognitive and other general symptoms. Understanding the whole spectrum is essential, as some signs may be subtle or mistaken for different conditions.

Low testosterone, or hypogonadism, is a common but often underdiagnosed condition that affects a significant number of men, especially as they age. Research shows that around 35% of men over the age of 45 have clinically low testosterone levels.¹

In addition to age, certain health conditions are strongly linked to testosterone deficiency. Studies report that 30–50% of men with obesity and up to 50% of men with type 2 diabetes also have low testosterone.^2-4 These overlapping health concerns can compound symptoms and increase the risk of long-term complications.

Despite its prevalence, many men are unaware that their symptoms, such as fatigue, reduced libido, or mental fog, may be related to hormone imbalance. In this post, we’ll focus on low testosterone’s key symptoms and associated health risks, helping you better understand when it may be time to get evaluated.

2. Symptoms of Low Testosterone

• Sexual changes are often the most noticeable and specific signs of testosterone deficiency. These may include:
  • Decreased libido (sex drive) ^5-7,15
  • Erectile dysfunction, including difficulty achieving or maintaining an erection ^5-7
  • Reduced frequency of spontaneous erections, especially morning erections ^5-7
  • Decreased sperm production, which may contribute to infertility ^5-7
  • Fewer sexual thoughts or fantasies ^5-7

  These symptoms are among the most predictive of low testosterone and are often the first to prompt men to seek medical evaluation.

Low testosterone can have a significant impact on physical performance and appearance. Common physical manifestations include:

• Persistent fatigue or lack of energy: Reduced energy and fatigue are commonly reported symptoms.^5,15
• Loss of muscle mass and strength (sarcopenia): Testosterone is crucial for muscle maintenance, and its deficiency is associated with sarcopenia.^{8, 9}
• Increased body fat, particularly in the abdominal area: Low testosterone is linked with increased adiposity and metabolic syndrome.¹⁰
• Decreased body or facial hair growth: Reduced virilization, including decreased body and facial hair, is a sign of low testosterone.⁵
• Reduced bone density, increasing risk of osteoporosis and fractures: Low testosterone is associated with decreased bone mineral density and increased fracture risk.¹¹
• Mild Anemia (low red blood cell count): Testosterone deficiency can lead to unexplained anemia.⁵
• Hot flashes or night sweats: These symptoms can occur in more severe or prolonged testosterone deficiency.⁵

Mental and cognitive health are also affected by low testosterone. These symptoms may appear gradually:

• Irritability, mood swings, or feelings of sadness ^5,14
• Depressed mood or emotional flatness ^12-13
• Difficulty concentrating or remembering things (“brain fog”) ⁵
• Reduced motivation or drive⁵
• Anxiety, low self-esteem, or general dissatisfaction ^12-13
• Sleep disturbances, such as insomnia or unrestful sleep ^12-13

These changes can affect personal and professional life, often leading to reduced overall well-being.

• Decline in physical or work performance ⁹
• A general feeling of being unwell or loss of vitality ⁹

Together, these varied symptoms highlight the wide-ranging impact of testosterone on the male body beyond just reproductive health and the importance of early recognition and evaluation.

3. Health Risks of Untreated Low Testosterone

Low testosterone levels have been linked to an increased risk of high blood pressure, atherosclerosis (hardening of the arteries), and overall cardiovascular disease.^{16, 19} Some studies suggest that men with low T may have higher rates of heart attacks and strokes, particularly when testosterone deficiency is combined with other risk factors such as obesity or diabetes.^{17, 19} A meta-analysis of observational studies confirmed that low endogenous testosterone levels predict overall and cardiovascular mortality, as well as cardiovascular morbidity.¹⁸

Testosterone deficiency is strongly linked to metabolic dysfunction, particularly in the form of insulin resistance, visceral obesity, and metabolic syndrome. This isn’t a one-way relationship; it’s bidirectional. Low testosterone can contribute to increased fat storage around the abdomen and worsening insulin sensitivity, and these metabolic changes can, in turn, further suppress testosterone production.

Multiple studies confirm this pattern. For example, Pivonello et al. (2019) highlight how low testosterone promotes visceral fat accumulation and insulin resistance, which further lowers testosterone.²⁰ Similarly, Bianchi and Locatelli (2018) emphasize the strong association between testosterone deficiency and central obesity, insulin resistance, and the broader metabolic syndrome.²¹ They also note that testosterone therapy in hypogonadal men can help reverse some of these issues.²¹

Additional research by Kelly and Jones (2013) and Grossmann (2014) supports the same connection—linking low testosterone with increased fat mass, reduced insulin sensitivity, and impaired glucose regulation, all key components of type 2 diabetes risk.^{22, 23}

In short, this is a vicious cycle: low testosterone leads to metabolic dysfunction, and metabolic dysfunction worsens testosterone levels. Left unaddressed, this can make weight management, energy levels, and overall health progressively harder to maintain.

Testosterone plays a central role in maintaining bone density and skeletal strength, not just through surface-level support but at a cellular level.^{8, 24} It promotes bone formation and helps inhibit bone resorption, ensuring a healthy balance between building and breakdown. ^{8, 24}

Its effects are mediated directly by binding to androgen receptors in bone tissue and indirectly through its conversion to estradiol, a form of estrogen critical for preserving trabecular (spongy) bone, commonly found at the end of long bones such as the spine and hips. ^{8, 24}

When testosterone levels drop, this balance shifts. Men with untreated low T are at higher risk for osteopenia, osteoporosis, and fragility fractures, especially as they age. ^{8, 11, 24, 25, 26} This risk may go unnoticed because bone loss is often silent until a fracture occurs. Because bone loss happens silently, many don’t recognize the issue until after an injury occurs.

Testosterone plays a significant role in erythropoiesis, the red blood cell production process. Low testosterone levels are associated with anemia, as evidenced by several studies. For instance, a study published in JAMA Internal Medicine demonstrated that testosterone treatment in older men with low testosterone levels and unexplained anemia significantly increased hemoglobin levels compared to placebo. ²⁷ A randomized clinical trial published in JAMA Network Open found that testosterone therapy was more effective than placebo in correcting anemia and preventing its development in men with hypogonadism. ²⁸

Low testosterone can lead to anemia, which in turn can exacerbate symptoms such as fatigue, reduced stamina, and impaired cognitive performance. 

Beyond mood swings or irritability, long-term testosterone deficiency may increase the risk of clinical depression and generalized anxiety. ^{12, 13} Some men report a diminished sense of purpose or vitality over time, impacting relationships, work performance, and overall quality of life. ⁵

Several studies have demonstrated a relationship between declining testosterone levels and cognitive decline. For instance, epidemiological studies have shown that lower testosterone concentrations are linked with higher prevalence and incidence of cognitive decline and dementia, including Alzheimer’s disease.²⁹ Additionally, longitudinal studies have indicated that changes in testosterone levels over time are associated with cognitive decline.³⁰

Mechanistically, androgens, including testosterone, have neuroprotective effects. Testosterone deficiency may impair cognitive function by increasing oxidative stress and decreasing synaptic plasticity.³¹ Furthermore, lower levels of testosterone have been associated with an increased risk of all-cause dementia and Alzheimer’s disease.^{32, 33}

Persistent low testosterone may lead to infertility, erectile dysfunction, and low libido that does not respond to other treatments.⁵ The relationship between low testosterone and sexual dysfunction is complex and influenced by various factors, including psychological and relational aspects.³⁴

While these symptoms may start as minor frustrations, they can significantly affect emotional connection and relationship satisfaction.

Summary

 Recognizing and treating low testosterone early is not just about symptom relief; it’s about protecting long-term health. Low testosterone is associated with reduced longevity and increased risk of chronic diseases such as obesity, sarcopenia, osteoporosis, and cognitive impairment. ³⁴ Ignoring the underlying hormonal imbalance can allow these risks to progress quietly, increasing the burden of disease later in life.

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