Testosterone injection is one of the most frequently used forms of testosterone replacement therapy. Many men consciously choose it because it is reliable, effective, and relatively cost-efficient. At the same time, questions often arise: How is testosterone injected correctly? How often should it be injected? Which is better, subcutaneous or intramuscular? And how should the medication be stored correctly?
The following article summarizes the most important basics of testosterone injections and shows you what is important for safe and effective use. The information presented is for general medical information purposes only and does not constitute individual treatment advice. Decisions regarding testosterone therapy should always be made based on a personal consultation with a doctor.
If you have questions about your hormone levels, symptoms, or possible treatment options, please consult a qualified doctor. Alternatively, you can schedule a consultation with a doctor directly here .
Why is testosterone injected?
In cases of medically confirmed testosterone deficiency, testosterone replacement therapy may be beneficial ( Wang & Swerdloff, 2022 ). The aim is to bring hormone levels into a physiological range and alleviate typical symptoms such as fatigue, loss of libido, loss of strength, or concentration problems ( Sizar et al., 2023 ).
You can learn more about testosterone deficiency in our article " Testosterone deficiency in men: causes, symptoms and solutions ".
Testosterone injections, often in the form of testosterone enanthate or testosterone undecanoate, allow for reliable absorption of the hormone into the body. Compared to gels or patches, injections offer more stable bioavailability ( Al-Zoubi et al., 2021 ).
What testosterone preparations are available?
Various testosterone esters are available worldwide for injection therapy . However, not all preparations are approved in Germany. In everyday medical practice, two testosterone preparations are primarily used.
Approved testosterone preparations in Germany
Testosterone Enanthate
Testosterone enanthate is the most commonly used injectable preparation. It is a medium-acting ester that is usually administered every two weeks, or split into once-a-week or 3.5-day doses.
This flexible dosing allows for more consistent testosterone levels. This can help reduce hormonal fluctuations and potential side effects. Enanthate is particularly well-suited for individually tailored therapy, as dosages can be adjusted relatively easily ( Pastuszak et al., 2021 ).
Testosterone undecanoate
Testosterone undecanoate is a long-acting depot preparation. After an initial phase, injections are usually only required every 10 to 14 weeks.
The advantage lies in the infrequent injections and the consistent long-term effect. However, the dosage is less flexible. If side effects occur or adjustments are needed, the therapy can only be changed with a delay, as the hormone remains in the body for many weeks.
Unapproved testosterone preparations in Germany
Testosterone Cypionate
Cypionate is widely used in countries like the USA, but is not approved in Germany. Its duration of action is similar to that of enanthate, but slightly longer.
Testosterone Propionate
Propionate is a short-acting ester with very rapid release. Due to its short half-life, injections would be required every one to two days. This drug is also not approved in Germany and is not routinely used here.
Why injections are often preferred
Testosterone injections allow for direct and reliable absorption of the hormone into the bloodstream. This enables precise control of hormone levels and their maintenance within the desired physiological range ( Dobs & Campbell, 2022 ). Compared to transdermal applications with gels, injections are significantly less dependent on external factors. Sweat, skin condition, incorrect application, or incomplete absorption do not play a role when injecting testosterone ( Pastuszak et al., 2021 ).
Testosterone gels also carry the risk of unintentional transmission to other people, for example through skin contact with partners, children, or pets. While this risk is low with proper use, it should not be underestimated. Consistent hand hygiene, covering the application site, and observing waiting times before skin-to-skin contact are crucial.
Injections completely eliminate this risk of transmission, as the testosterone is introduced directly into the body and not released through the skin. For many men, this represents an additional safety feature, especially within their families.
How is testosterone injected?
There are two main methods for injecting testosterone: intramuscular (IM) and subcutaneous (SC). Both methods differ in terms of technique, tolerability, and legal classification.
Intramuscular (in)
In intramuscular injection, testosterone is injected directly into a muscle, usually the shoulder muscle (enanthate), the gluteal muscle (undecanoate), or the outer thigh. This method has been established for decades and corresponds to the approved use of testosterone preparations available in Germany.
Advantages:
-
rapid and reliable absorption into the bloodstream
-
medically well-researched and standardized
-
suitable for larger injection volumes
Disadvantages:
-
The injection may be more painful.
-
higher demands on the technology
-
possible risk of muscle irritation or hardening
Intramuscular injection is the officially approved route of administration for testosterone enanthate and testosterone undecanoate in Germany. It is therefore generally recommended by a physician. While an injection into the shoulder muscle (enanthate) can be performed by patients themselves after proper training, the injection into the gluteal muscle (undecanoate) should always be administered by a doctor, as important nerves can be damaged if the injection is administered incorrectly.
Subcutaneous (sc)
In subcutaneous injection, testosterone is injected into the subcutaneous fat tissue, often in the abdominal area. This method is increasingly used by patients because it is perceived as less painful and easier to perform.
Advantages:
-
reduced pain sensitivity
-
easier everyday use
-
Well suited for more frequent, low-dose injections
Disadvantages:
-
limited injection volume
-
slower absorption of the active ingredient
It is important to know that testosterone preparations are currently only approved for intramuscular use in Germany. Subcutaneous injection therefore constitutes an off-label use.
Nevertheless, current studies show that subcutaneous testosterone injections, when dosed correctly, have comparable efficacy and good tolerability ( Figueiredo et al., 2021 ). The side effect profile also does not differ significantly from intramuscular administration. Many patients also report improved ability to manage daily life and less injection pain ( Kaminetsky et al., 2015 ).
Off-label use should always be medically supervised. Correct technique, sterile procedures, and regular monitoring of hormone levels are essential to ensure safety and therapeutic success. It should be noted that subcutaneous injection is particularly suitable for shorter injection intervals, such as once a week or every 3.5 days. With longer intervals and correspondingly larger individual doses, the injection volume can often be too large for the subcutaneous fat tissue, potentially impairing tolerability.
How often should testosterone be injected (injection intervals)?
The frequency of testosterone application has a crucial influence on the stability of the hormone level and the occurrence of possible side effects.
In Germany, the standard dosage of testosterone enanthate is 250 mg every 14 days. This dosage is officially approved and corresponds to the product information. However, many modern treatment approaches rely on shorter injection intervals with adjusted doses to achieve more consistent testosterone levels, e.g., every 7 days or every 3.5 days ( Pastuszak et al., 2021 ). The goal is to consistently reach 250 mg within two weeks. With injections every 14 days, a sharp rise in testosterone levels often occurs shortly after administration, sometimes reaching the supraphysiological range. During this phase, aromatase activity is elevated, which can lead to increased conversion of testosterone to estrogen and promote corresponding side effects. Towards the end of the interval, however, testosterone levels often drop significantly, so deficiency symptoms can reappear.
Many experts now recommend split dosing to avoid strong fluctuations in hormone levels and to reduce side effects.
Hygienic aspects of frequent injections
An important point in Germany is the availability of the preparations. Testosterone enanthate is generally only available here as a 1 ml breakable ampoule containing 250 mg . These ampoules are intended for single use.
Those who use shorter injection intervals face two options:
Either only part of the ampoule is drawn up and the rest discarded. This is hygienically safe, but leads to medication loss.
Or the remaining contents are stored for later injection. This can increase the risk of contamination, even with careful handling.
Generally speaking, more frequent injections are associated with a slightly higher risk of hygiene issues. However, with correct technique, sterile procedures, and proper storage, this risk is low. Many patients report good tolerability and stable treatment results. Specific handling and storage should always be discussed individually with the treating physician. Generally, however, many doctors report positive experiences when the drawn-up testosterone is stored at room temperature, protected from light, and not refrigerated, ideally already in the used syringe and with a freshly changed, unused injection needle before the next use.
Individual decision and medical supervision
Shorter injection intervals can lead to better hormone levels and fewer side effects. However, they are performed outside the standard dosage range and should always be medically supervised.
The following are important:
-
clean injection technique
-
sterile materials
-
regular laboratory tests
-
individual dose adjustment
Any adjustments are made at your own risk and should be medically supervised.
What injection equipment is needed?
The right injection equipment is crucial for a safe and hygienic injection. In addition to the appropriate needles, other materials are needed to minimize the risk of infection and ensure clean application.
Basic equipment for injection
A complete set of equipment includes:
-
Disposable syringes, usually 1 ml volume
-
Drawing-up cannula, usually 20 gauge
-
Injection needle, usually 25 to 27 gauge
-
Disinfectant for skin and ampoule
-
Alcohol swabs or sterile compresses
-
Disposable gloves
-
Plaster or sterile swab for use after the injection
Testosterone buildup
Testosterone solutions are oil-based and relatively viscous. Therefore, a larger needle, usually a 20G drawing-up needle , is used to draw up the medication .
Advantages of the larger cannula:
-
faster oil absorption
-
less effort required
-
reduced strain on the syringe
The neck of the ampoule should be thoroughly disinfected before drawing up the solution.
Injection needles depending on the application
Intramuscular
Longer needles are usually needed for injection into the muscle to safely reach the muscle tissue.
Typical specifications:
-
25G to 27G
-
Length usually 16 to 25 mm
-
Suitable for the shoulder muscle (significantly longer needles are sometimes required for undecanoate and injection into the gluteal muscle)
These needle lengths are generally sufficient to safely deliver testosterone into the muscle tissue without injecting unnecessarily deeply. This helps reduce pain, bruising, and local irritation.
Especially with oil-based preparations like testosterone enanthate, a clean technique is important, as the volume in the shoulder muscle is limited and excessive amounts can cause local discomfort.
Subcutaneous
For injection into subcutaneous fat tissue, significantly shorter and finer cannulas are often sufficient.
Typical specifications:
-
27G to 30G
-
Length approximately 8 to 13 mm
-
often available as insulin cannulas
They are particularly well suited for more frequent injections because they are less painful.
Needle length and comfort
The choice of needle length affects not only safety but also comfort.
Needles that are too short for intramuscular use can prevent the testosterone from reaching the muscle correctly. Needles that are too long for subcutaneous use are unnecessarily painful.
A suitable selection reduced:
-
Pains
-
Tissue irritation
-
Bruises
-
Inflammation risks
Hygiene and safety
New sterile syringes and needles should be used for each injection . Reuse increases the risk of infection and tissue irritation.
Important hygiene steps:
-
Wash or disinfect your hands thoroughly.
-
Disinfect the skin at the injection site.
-
Clean the ampoule before opening.
-
Use sterile materials
-
Cover the injection site after the injection.
Disposable gloves are not strictly necessary, but they do increase hygiene and safety.
Disposal
Used needles and syringes should be disposed of in a puncture-proof container. This protects against injuries and meets hygiene standards.
Where should testosterone (enanthate) be stored?
Testosterone preparations should be stored correctly to maintain their effectiveness and safety.
Recommended storage conditions:
-
at room temperature, ideally between 15 and 25 degrees
-
protected from direct sunlight
-
Do not store in the refrigerator
-
Store in a dry place, protected from light.
-
safely out of reach of children and pets
Why refrigeration is not advisable: Oily testosterone solutions can crystallize at low temperatures. This makes drawing up the solution more difficult and the injection more uncomfortable. In most cases, these crystals dissolve again when the preparation is slowly warmed to room temperature.
Further important information:
-
Store testosterone in its original packaging if possible.
-
Check expiry dates regularly.
-
Do not store opened ampoules for unnecessarily long periods.
-
Do not use if visible changes to the solution are present.
Proper storage is essential to maintaining the quality of the medication and ensuring its safe use.
Typical beginner mistakes when administering a testosterone injection
Inadequate hygiene: Those who do not thoroughly disinfect their hands, skin, or ampoules increase the risk of infections and inflammation.
Reuse of needles or syringes: Single-use materials must not be reused, as blunt needles and germs can cause pain and tissue damage.
Incorrect injection technique: An injection that is too shallow or too deep can impair the effect and cause local irritation.
Excessive injection volumes: High volumes in one area, especially in the shoulder muscle, can cause pain, pressure, and hardening.
Irregular injection intervals: Fluctuating intervals lead to unstable testosterone levels and promote side effects.
Unauthorized dose increases: Excessive doses increase the risk of acne, water retention, and hormonal side effects.
Improper storage: Cold, heat or light can impair the quality of the product.
Lack of medical check-ups: Without regular blood tests, potential risks such as elevated hematocrit levels remain undetected.
Relationship between injection method and side effects
The type and frequency of testosterone injections influence how stable the hormone level remains in the body. Longer intervals between injections more frequently lead to significant fluctuations, which can increase the risk of certain side effects ( Wang & Swerdloff, 2022 ).
These include, among others:
-
acne
-
Mood swings
-
elevated estrogen levels
-
Water retention
Shorter injection intervals with lower individual doses can often reduce these fluctuations, which can improve the tolerability of the therapy. However, any adjustments should always be made under medical supervision and never independently.
Our conclusion, your knowledge
Testosterone injections are an effective and proven treatment for testosterone deficiency. Crucial to success are the correct injection technique, a sensible dosage strategy, and regular medical monitoring.
Whether subcutaneous or intramuscular, weekly or every 3.5 days, the optimal solution is individual and should always be determined in consultation with a doctor.
