Sven Wombwell
Article by: Sven Wombwell
Estimated 8 minutes read
Quick summary
Testosterone injections (testosterone replacement therapy) are a form of hormone replacement therapy (HRT) used to increase testosterone levels in the body. Taking testosterone injections for muscle-building is so effective because it increases IGF-1, a muscle-building hormone, reduces low testosterone symptoms and promotes overall well-being. Testosterone also has a host of other benefits for long-term health.

Most people know that testosterone injections aid muscle building. But as men age, testosterone levels start declining, and middle-age spread happens. Typically, when you want to get in shape and build lean muscle, you head to the gym and start lifting weights. But what if you were diligent about your diet and didn't miss a workout, and after months of heavy lifting, you still had the same dad bod as when you had started?

Before you blame it on bad genes and throw in the towel, why not evaluate your present situation and health and consider the root cause? Have you felt a little off? Maybe you're noticing more body fat and less muscle mass. And what about your sex drive? Has it also diminished? If you're experiencing those symptoms and others, it could be a sign your testosterone levels have dropped. 

If you've considered testosterone replacement therapy to improve your physique and lose weight, testosterone injections aid muscle building and speed up fat loss, especially when paired with positive lifestyle improvements.

What Is Low Testosterone?

Low testosterone, also known as hypogonadism or low T, refers to a condition in which the body doesn't produce enough testosterone, the primary male sex hormone. Testosterone plays a crucial role in various bodily functions, including the development of male sexual characteristics, increasing muscle mass and bone density, regulation of mood and energy levels, and the production of red blood cells. (1)

Low testosterone can occur due to a variety of reasons. It can result from normal aging, or underlying medical conditions may cause it. Lifestyle factors like obesity, excessive alcohol consumption, and chronic use of certain medications can also contribute to low testosterone levels.

The symptoms of low testosterone can vary but commonly include decreased libido, erectile dysfunction, fatigue, reduced muscle mass, increased body fat, mood changes, decreased concentration, and decreased bone density. 

Treatment for low testosterone may involve testosterone replacement therapy (TRT), administered through gels, patches, injections, or pellets. Remember though, the main goal of TRT should be to restore optimal testosterone levels and alleviate symptoms to protect long-term health. The added bonus for many guys is a better physique.

It is crucial to note that TRT alone may not help you achieve a muscular physique. Diet, exercise, quality sleep and stress all play a factor.

The Effects of Low Testosterone on Building Muscle

So, why is it so difficult to build muscle with low T? Testosterone plays a crucial role in muscle development and growth. It is an anabolic hormone that helps stimulate protein synthesis, which is necessary for muscle growth and repair. When testosterone levels are low, it can be more challenging to build muscle due to several reasons:

  1. Decreased protein synthesis: Testosterone helps stimulate the production of proteins in the body, which are the building blocks of muscle tissue. Low testosterone may reduce protein synthesis, making building and repairing muscle harder. (2
  1. Reduced muscle fiber: Testosterone promotes muscle fiber, and low testosterone levels can inhibit this process, leading to slower muscle growth and development. (3)
  1. Reduced energy and motivation: Testosterone influences energy levels, motivation and overall drive. Low testosterone levels can reduce your energy and motivation for intense workouts, hindering muscle-building efforts. (4)
  1. Higher body fat percentage: Low testosterone levels are often associated with having increased body fat. Excess body fat can affect hormone levels and metabolism, making building muscle and achieving a lean physique more challenging. (5)

While low testosterone can make it more challenging to build muscle, muscle development is influenced by various factors, including genetics, diet, exercise and overall health. 

How Testosterone Injections for Building Muscle Work

Testosterone injections are a form of hormone replacement therapy (HRT) used to increase testosterone levels in the body. Testosterone is a natural hormone produced primarily in the testicles in males and in smaller amounts in the ovaries and adrenal glands in females. Some testosterone is bound to proteins in the body, making it locked and unavailable for the body to use, whereas a small amount called free testosterone remains unbound and can be transported around the body to trigger muscle growth,

When it comes to building muscle, testosterone plays a crucial role. As discussed, it promotes protein synthesis, the process by which your body creates new muscle tissue. Testosterone also enhances nitrogen retention in muscles, increasing muscle mass and strength. (6)

Graphic showing how to keep muscle mass as you age.

Testosterone Injections Are Not Just for Muscle Building.

Testosterone injections can provide a range of benefits for individuals with symptoms of low T. They can include: (7)

  • Increased muscle mass: Testosterone is a natural anabolic hormone crucial for developing and maintaining muscle tissue. Around the age of 35, testosterone levels start to decline, coinciding with a 3-5 percent loss of muscle mass each decade. Testosterone injections enhance muscle protein synthesis, increasing muscle mass and strength. To age healthily, building and maintaining muscle is crucial. Moreover, TRT can help you keep or develop new muscles well into old age. 
  • Strengthen bone density: Testosterone plays a significant role in maintaining bone density and strength. Low testosterone can contribute to decreased bone mineral density and an increased risk of osteoporosis. Testosterone injections can help improve bone density and reduce the risk of fractures.
  • Enhanced libido and sexual function: Testosterone is crucial for sexual health and function. Low testosterone levels can lead to a decrease in libido and sexual dysfunction. Testosterone injections can improve sex drive, enhance erectile function and overall sexual satisfaction.
  • Increased energy and vitality: Testosterone plays a role in energy levels, mood and overall well-being. Individuals with low testosterone often experience fatigue, low energy, and decreased vitality. Testosterone injections help boost energy levels and improve mood, leading to an overall increase in quality of life. As a result, you'll likely have the energy to work harder in the gym. 
  • Enhanced cognitive function: Testosterone may positively impact cognitive function, including memory and attention. Testosterone injections may help improve mental performance. Above all, there is evidence that TRT can help you avoid dementia and Alzheimer's.
  • Decreased body fat: Sadly, obesity and type 2 diabetes rates are soaring in the USA. One of the most significant benefits of testosterone is how they help you burn fat. Testosterone promotes the breakdown of visceral fat and inhibits fat storage, improving body composition. TRT, combined with lifestyle improvements, could help millions of men keep a healthy body weight, avoid metabolic disorders and live longer.
  • Increased red blood cell production: Testosterone injections can stimulate the production of red blood cells, increasing hematocrit and hemoglobin levels. This can be beneficial for individuals with conditions such as anemia.

Lifestyle, Exercise and Testosterone for Building Muscle

As discussed, testosterone plays a critical role in building muscle but is less effective than combined with exercise, and proper nutrition, allowing for recovery and sleep.

According to Peter Fotinos, MD.

Firstly, while on testosterone, as your levels become optimized, resistance weight training is your best friend. Heavy weights following the progressive overload method promote muscle growth and fat loss.

Progressive overload is progressively raising the weight, frequency, or repetitions within your strength training regimen. By doing so, this process pushes your body and enables your musculoskeletal system to develop greater strength over time.

Secondly, you must feed the machine by eating the right foods. Protein is the muscle's building block, so try increasing your protein intake to about 200 grams daily. Include lots of leafy greens, and try an eat as many different colored vegetables as possible. Eat the rainbow, as they say.

Finally, avoid refined carbohydrates and processed foods. These include sugary desserts, white bread, rice, pasta, and snack foods like chips, crackers, and pretzels. These refined carbs have undergone processing that removes the outer grain, which contains fiber and some protein. As a result, consuming them leads to a rapid increase in glucose (sugar) levels.

TRT is Not the Same as Illegal Steroids

It is essential to highlight the difference between testosterone replacement therapy (TRT) and illegal steroids, as they are very different. TRT is a medically supervised treatment that aims to optimize testosterone levels in individuals with symptoms of low T. It involves using prescription medications, such as testosterone injections or gels, to bring hormone levels back to optimal. Under the supervision of a healthcare professional, TRT is perfectly safe and can benefit long-term health, so you age better. 

On the other hand, illegal steroid use involves using non-medical, unsupervised anabolic steroids for purposes such as athletic performance enhancement or bodybuilding. These substances often come from the black market, bypassing medical guidelines and pose significant health risks. Many have questionable sources and are for use on animals like cattle to increase meat production. Understanding the differences and adhering to proper medical guidance when considering hormone replacement therapy is crucial.


Around the age of 35, testosterone levels begin to decrease. While it's a natural part of getting older, you don't have to live with the negative symptoms. If you suspect your testosterone levels are low and feel the effects, you can get a simple blood test to check your levels. You may find that testosterone injections could be a good option if you're ready to alleviate the symptoms and start feeling like yourself again.

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