What To Know About Testosterone Injections


Testosterone injections are used as hormone therapy to treat sexual dysfunction in men and to relieve postmenopausal symptoms in women with testosterone deficiency. In addition, transgender men and non-binary individuals may include testosterone injections in their masculinisation therapy regimens.

Although generally safe for many recipients, testosterone injections can be associated with various side effects, the manifestation of which often correlates with the underlying purpose of the treatment. In particular, although testosterone injections can effectively treat low testosterone levels caused by medical conditions, the Food and Drug Administration (FDA) advises against their use to counteract age-related declines in testosterone due to potential health risks.

For more information about the uses, safety considerations, and potential side effects of testosterone injections, read on.

What Are Testosterone Injections?

What To Know About Testosterone Injections

Testosterone injections refer to the administration of isolated testosterone, a hormone that occurs naturally in both men and women, although typically at higher levels in men.

Increasingly common in the United States, testosterone therapy warrants careful consideration by physicians prior to long-term recommendation to ensure that individuals understand and weigh the risks and benefits involved.

The following sections describe the uses of testosterone injections.

Treating Low Testosterone In Men

In medical practice, doctors may prescribe testosterone injections to treat men with low testosterone levels, a condition called hypogonadism, which is characterised by reduced testosterone production by the testes.

Low testosterone levels can cause adverse effects including reduced sperm count, decreased bone or muscle mass, increased obesity and erectile dysfunction. Typically, healthy adult men have total testosterone concentrations in the bloodstream ranging from 280 to 1,100 nanograms per deciliter (ng/dl).

In treating hypogonadism, testosterone therapy offers several benefits, including improved sexual function, increased lean muscle mass and strength, improved mood, improved cognitive function and potentially reduced risk of osteoporosis.

It's important to recognise that while this therapeutic intervention alleviates the symptoms associated with low testosterone, it does not address the underlying cause.

Individuals who suspect low testosterone levels should seek medical advice for diagnosis. It's important to note, however, that symptoms are non-specific and may be caused by other conditions or lifestyle factors.

It's important to note that not all men with low testosterone need treatment, and there are risks associated with administration. The FDA has only approved testosterone replacement therapy for men with low testosterone due to testicular, cerebral or pituitary disorders, excluding age-related declines.

Testosterone Therapy In Women

In contrast to its use in men, testosterone therapy in women remains controversial.

Typically, healthy adult women have total testosterone levels between 15 and 70 nanograms per deciliter (ng/dl). Reduced testosterone levels in women can lead to fertility complications, menstrual irregularities, vaginal dryness and decreased libido. Despite these manifestations, doctors rarely recommend testosterone injections to treat low testosterone in women because of the potential masculinising effects.

However, doctors may consider testosterone therapy to treat hypoactive sexual desire disorder in postmenopausal women. However, scientific research has yet to prove its effectiveness in treating other postmenopausal symptoms such as anxiety, mood swings, weight gain and reduced bone density.

Currently, the FDA has not approved any products specifically for testosterone therapy in women. In addition, formulations that provide the recommended treatment dose of 300 micrograms per day for women are not readily available in the United States. As a result, women typically require the services of a compounding pharmacy to fulfil such prescriptions.

Masculinising Hormone Therapy

Testosterone therapy serves as a central tool for individuals seeking a more masculine appearance as part of their gender transition journey. Used by transgender men, non-binary individuals and others, testosterone injections are a cornerstone of masculinising hormone therapy.

The administration of testosterone helps to promote male sexual characteristics while reducing female characteristics, ushering in a spectrum of changes that include:

  • Changes in emotional and social functioning
  • Increased facial and body hair
  • Increased incidence of acne
  • Deepening of the voice
  • Onset of male pattern baldness, characterised by a receding hairline
  • Redistribution of body fat
  • Increase in muscle mass
  • Cessation of menstrual periods

These testosterone therapy protocols are similar to those used to treat male hypogonadism. Weekly testosterone injections are often recommended to maintain stable hormone levels.

Types Of Testosterone Injections

Testosterone injections come in several forms, including:

  • Testosterone cypionate (marketed as Depo-Testosterone)
  • Testosterone enanthate (available as Xyosted and its generic iteration)
  • Testosterone undecanoate (marketed as Aveed, known for its extended-release formulation)

How To Use It

A testosterone injection involves the hormone entering the body directly through the muscle. Individuals have two options for administration:

Self-administration at home involves using a home injection kit to inject the hormone into the thigh.
Alternatively, a healthcare professional can administer the injections into the gluteal muscle during a visit to the doctor's surgery.

During the course of testosterone injections, people are usually monitored by visiting their doctor every few months. The length of treatment can vary from a lifelong regimen to short-term interventions, depending on the individual's circumstances.

Are They Safe?

Testosterone injections, when administered under medical supervision such as TRT clinics and following prescribed guidelines, are generally considered safe for many people. However, research has linked testosterone therapy with potential side effects and complications.

Potential adverse effects of testosterone therapy include:

  • Increased risk of cardiovascular complications
  • Worsening of lower urinary tract symptoms
  • Occurrence of polycythemia, a rare form of blood cancer
  • Increased risk of venous thrombosis

Some people may have an allergic reaction to testosterone injections. For example, testosterone undecanoate injections can cause severe allergic reactions or respiratory problems after injection, with symptoms such as difficulty breathing, dizziness and skin rashes.

Other formulations, such as Testosterone enanthate, may increase blood pressure, increasing the risk of stroke or heart attack. Individuals with a history of stroke, heart attack, heart disease or high blood pressure should inform their doctor of these conditions before starting testosterone injections as they may be at an increased risk of complications.

If you experience any of the following symptoms after a testosterone injection, you should seek immediate medical attention:

  • Shortness of breath
  • Slow or slurred speech
  • Chest pain
  • Weakness or numbness in your limbs
  • Pain in your arms, neck, back or jaw
  • Dizziness or lightheadedness

In cases where a doctor prescribes male testosterone injections for adolescents to treat a constitutional delay in growth and puberty, the aim is to facilitate an accelerated growth spurt during puberty. It's important to note that this therapy should not interfere with the adolescent reaching their final adult height.

Side Effects

People who receive testosterone injections may experience mild side effects, including:

  • Breast enlargement or tenderness
  • Acne
  • Deepening of the voice
  • Tiredness
  • Hoarseness
  • Back pain
  • Redness, bruising, pain, bleeding or hardness at the injection site
  • Difficulty falling asleep or staying asleep
  • Weight gain
  • Joint pain
  • Mood changes
  • Headache

If you experience more serious side effects, seek immediate medical advice.

These serious side effects may include:

  • Nausea or vomiting
  • Pain, redness, or warmth in the lower legs
  • Swelling of the hands, ankles, feet, or legs
  • Difficulty breathing
  • Jaundice (yellowing of the eyes or skin)
  • Prolonged erections
  • Changes in urination, such as difficulty passing urine, increased frequency, weak stream, urgency, or blood in the urine
  • Severe pain in the right upper abdomen
  • Mood changes, including depression, anxiety, or thoughts of suicide

What Other Types Of Testosterone Replacement Therapy Are Available?

There are several forms of testosterone replacement therapy other than injections. Testosterone and other hormones can be given in capsules, depots, creams and gels.

  • Gels: A relatively new approach involves applying testosterone gel once a day to areas such as the shoulders, upper arms, inner thighs, back of the calves or abdomen.
  • Patches: Transdermal patches adhere directly to the skin on the back, upper arms, thighs or abdomen. However, skin irritation is a common side effect.
  • Depots: Typically consisting of crystalline testosterone, depots involve the implantation of crystals under the skin. A disadvantage is that they disrupt the natural daily testosterone rhythm, which typically peaks in the morning.
  • Capsules: Taken several times a day, depending on the severity of symptoms, capsules aim to maintain a constant level of testosterone. However, testosterone absorbed through the gastrointestinal tract is rapidly metabolised in the liver, which can reduce its effectiveness.

Frequently Asked Questions

What are testosterone injections and why are they prescribed?

Testosterone injections are a form of hormone therapy used to replace low levels of testosterone in the body. They are usually prescribed to people with conditions such as hypogonadism, where the body doesn't produce enough testosterone naturally. In addition, transgender men may use testosterone injections as part of their hormone replacement therapy to masculinise their bodies.

How are testosterone injections given?

Testosterone injections are usually given into the muscle, usually the gluteus maximus (buttock) or the deltoid (shoulder). The injection is given deep into the muscle tissue to ensure proper absorption and distribution of the hormone into the bloodstream. It's important to follow the correct injection techniques and guidelines given by a healthcare professional to minimise the risk of complications.

What are the possible benefits of testosterone injections?

Testosterone injections can help relieve symptoms associated with low testosterone levels, such as low libido, fatigue, muscle weakness and mood changes. They can also promote the development of male characteristics, including increased muscle mass, facial hair growth and deepening of the voice. For transgender men, testosterone injections can help align physical characteristics with their gender identity.

What are the possible risks and side effects of testosterone injections?

Although testosterone injections are generally safe when administered correctly under medical supervision, they can carry risks and side effects. These can include acne, fluid retention, increased red blood cell count, mood swings and changes in cholesterol levels. In some cases, testosterone therapy can worsen underlying conditions such as sleep apnoea or benign prostatic hyperplasia (BPH). It's important for people who receive testosterone injections to be monitored regularly by a healthcare professional so that any potential risks can be effectively managed.

Are there any considerations or precautions I should take before starting testosterone injections?

Before starting testosterone therapy, it's important to undergo a full assessment by a healthcare provider, including blood tests to assess testosterone levels and any underlying health conditions. People with a history of certain medical conditions, such as prostate cancer or cardiovascular disease, may need to proceed with caution or avoid testosterone therapy altogether. In addition, it is important to discuss the potential benefits and risks of testosterone injections with a healthcare provider and to follow the prescribed dosage and monitoring schedule to ensure safe and effective treatment.


In summary, testosterone injections are prescribed by doctors to treat low testosterone levels caused by certain medical conditions in men. While these injections will not cure the underlying condition, they can help to relieve the symptoms associated with it. In addition, testosterone injections can be used to treat sexual dysfunction resulting from post-menopausal changes or as part of masculinising hormone therapy.

However, individuals need to be aware of the potentially serious complications associated with testosterone use, both in the short and long term. Before prescribing testosterone replacement therapy, doctors should carry out a full assessment and have a detailed discussion with the individual about the benefits and risks involved.

Following the doctor's instructions is essential to minimise any potential risks associated with testosterone therapy.


  • National Center for Biotechnology Information. “Testosterone Therapy Improves the First Year Height Velocity in Adolescent Boys with Constitutional Delay of Growth and Puberty.” PubMed Central, PMC5556315. Link.
  • National Center for Biotechnology Information. “An update on the role of testosterone replacement therapy in the management of hypogonadism.” PubMed Central, PMC4772354. Link.
  • National Center for Biotechnology Information. “Hormone therapy for transgender patients.” PubMed Central, PMC5182227. Link.
  • National Center for Biotechnology Information. “Treatment of Hypogonadism: Current and Future Therapies.” PubMed Central, PMC5265703. Link.
Mario Basler ist Experte für Diabetologie und Ernährungsmedizin. Er hat mehrere Bücher zum Thema Diabetes und Ernährung geschrieben und lehrt zu diesen Themen national und international an Universitäten und auf Kongressen.


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