Testosterone injections deliver testosterone into the muscle. The testosterone is then absorbed directly into the bloodstream over time. The absorption period depends on the type of testosterone injected. Injections usually take place in the thighs, glutes or deltoid muscles.
Read on to learn about the most common forms of injectable testosterone, therapeutic dosages, pros and cons of testosterone injections, and injection demonstration resources.
Two Most Common Types of Injectable Testosterone
The most common forms of injectable testosterone for testosterone replacement therapy (TRT) include testosterone enanthate (TE) and testosterone cypionate (TC). Testosterone enanthate and testosterone cypionate are modified forms of testosterone. Specifically, a carboxylic acid ester has been added to the 17-beta-hydroxyl group. This attachment makes TE and TC less polar than free T. As a result, they have longer half-lives and are absorbed more slowly from the injection area. Once in the bloodstream, the ester is removed to yield free (active) T. Due to their long half-lives, both TE and TC provide a sustained release of testosterone into the bloodstream for one to two weeks. As a result, testosterone injections of TE or TC need only be administered every week or every other week.
Half-Lives of TE and TC
Testosterone enanthate possesses a half-life of roughly 8-10 days. Testosterone cypionate possesses a half-life of roughly 10-12 days. [Half-lives depend on a person’s own rate of metabolism, so they may vary.] Therefore, it takes approximately 8 to 10 days for the body to metabolize and clear half the concentration of the testosterone enanthate following an injection. As a result, users need only inject every week or every other week.
Dosing Regimens for TRT
The recommended dosing regimen of testosterone enanthate or testosterone cypionate for testosterone therapy is 100 to 200 mg every week or 150 to 400 mg every other week. Weekly injections are preferred because more frequent injections lower fluctuations in serum testosterone. About 30% of men treated for low testosterone use testosterone injections.
Pros of Testosterone Injections
Injectable testosterone can be self-administered. The two most common forms (testosterone enanthate and testosterone cypionate) are both brand name and generic medications in the United States. They both can also be compounded at a compounding pharmacy.
Dosages can be changed with each injection, if necessary, to achieve optimal concentrations. Often the testosterone injections can be given twice a week in a split dose to reach optimal blood levels without too much fluctuation between injections.
Testosterone enanthate and testosterone cypionate only need to be injected every week or every other week. Also, a longer lasting version, testosterone undecanoate, is now available in the US. The FDA approved injectable testosterone undecanoate in 2014. It will extend the period between injections to ten weeks after an initial ramp-up period.
Cons of Testosterone Injections
Testosterone injections do not mimic physiologic dosing. As a result, T levels can fluctuate in between doses. Fluctuations in testosterone are not ideal. These fluctuations can affect mood, emotional stability, and sexual activity. Shortening the interval between injections and lowering the dosage proportionally can minimize this cyclical nature of highs and lows. The longer lasting version of injectable testosterone, testosterone undecanoate, maintains T levels in normal ranges.
Following injection of testosterone enanthate or testosterone cypionate, T levels exceed normal physiological levels for the first two to three days. Levels then steadily decline to levels below normal just prior to the next injection. Shortening the interval between testosterone injections and lowering the dose can minimize this cyclical nature of highs and lows, which is why weekly injections of 100 to 200 mg are preferred to every other week injections of 150 to 400 mg.
Of note, another testosterone ester, testosterone undecanoate, has been approved that maintains T levels in normal ranges.
- Testosterone injections are more likely to cause an increased red blood cell count than other forms.
Men using injectable testosterone should be vigilant with their physician in monitoring for this particular problem. A simple measure of your red blood cell count can alert your physician of this problem, which can then be treated. Lowering the injectable dosage and shortening the time between injections may potentially reduce the possibility of this side effect.
Injection site pain is relatively common in the beginning although injection site pain rarely indicates a problem.
You need to visit a physician for testosterone injections if you're unable to self-administer at home.
For injection information, the University of Michigan provides a detailed PDF primer on how to give a Testosterone Intramuscular (IM) Injection. A Intramuscular Injection Video demonstration can also be found at LowTestosterone.com. Ask a physician to explain and demonstrate the technique.