Testosterone Propionate Side Effects: A Complete Review of the Risks

Testosterone propionate is one of the oldest injectable testosterone esters. Its short action made it useful in early endocrinology, but today it is rarely prescribed in the United States and appears mostly in non-medical use. This review from our editorial team summarizes what is known about its adverse effects, from the injection site to the heart.

What testosterone propionate is

Testosterone propionate is testosterone bound to propionic acid, a short three-carbon ester. The ester makes the hormone more fat-soluble so it can be dissolved in oil and injected into muscle, from which it is released gradually into the bloodstream.

Because the propionate ester is short, the compound is cleared faster than longer esters such as cypionate or enanthate. Historically this meant more frequent injections when it was used clinically, which is one reason longer-acting esters largely replaced it in medical practice.

Once the ester is cleaved, the active molecule is ordinary testosterone. That matters for understanding risks: most systemic side effects of testosterone propionate are the side effects of testosterone itself, amplified when blood levels rise above the physiological range.

In the US, all testosterone products are Schedule III controlled substances under the Anabolic Steroid Control Act. Possession without a prescription is illegal, and testosterone is prohibited in sport at all times under the World Anti-Doping Agency (WADA) list.

Local and short-term effects

The most immediate complaints with propionate concern the injection itself. Users and clinicians have long described post-injection pain, soreness, and sometimes swelling or a low-grade fever, often attributed to the ester and the carrier oil.

Any intramuscular injection carries a risk of infection and abscess, especially when sterile technique is not followed. Products from unregulated sources add the possibility of bacterial contamination, wrong concentration, or a different substance altogether, which has been documented in analyses of seized products.

A rare but serious complication of oil-based injections is pulmonary oil microembolism (POME), a reaction that can cause coughing, shortness of breath, and chest tightness shortly after the shot. It is described in prescribing information for some long-acting testosterone products and should be treated as a medical event.

Short-acting esters also produce sharper peaks and troughs in hormone levels. These fluctuations have been associated anecdotally and in some clinical observations with swings in mood, libido, and energy.

• Pain, redness, or swelling at the injection site
• Abscess or infection, particularly with non-sterile technique
• Coughing or breathlessness after injection (possible POME) — seek urgent care
• Allergic reactions to the carrier oil or preservatives

Cardiovascular and blood effects

Testosterone stimulates red blood cell production. Elevated hematocrit (erythrocytosis) is the most common laboratory abnormality in men on testosterone therapy, and it increases blood viscosity, which may raise the risk of clots and stroke. Clinical guidelines from the Endocrine Society recommend monitoring hematocrit for this reason.

At supraphysiological levels, androgens lower HDL ("good") cholesterol and can raise LDL, creating an unfavorable lipid profile. Blood pressure may rise, partly because of fluid retention.

Long-term high-dose anabolic-androgenic steroid use has been linked in imaging studies to left ventricular hypertrophy, reduced heart pumping function, and accelerated coronary artery plaque. A study by Baggish and colleagues found reduced cardiac function and more coronary plaque in long-term steroid users compared with non-users.

Cases of heart attack, arrhythmia, and sudden cardiac death in young steroid users have been reported in the medical literature. While causation in single cases is hard to prove, the overall pattern is consistent enough that cardiologists regard heavy androgen use as a cardiovascular risk factor.

Hormonal, reproductive, and skin effects

External testosterone signals the hypothalamus and pituitary to reduce production of luteinizing hormone (LH) and follicle-stimulating hormone (FSH). As a result, the testes produce less of their own testosterone and fewer sperm. Testicular shrinkage and reduced or absent sperm counts are well documented.

This suppression is the reason testosterone has been studied as a male contraceptive. After stopping, recovery of natural production can take months, and in some men — particularly after prolonged or repeated exposure — it may be incomplete.

Part of testosterone is converted to estradiol by the aromatase enzyme. Elevated estrogen can lead to gynecomastia (breast tissue growth), which may become permanent and sometimes requires surgery. Testosterone is also converted to dihydrotestosterone (DHT), which drives acne, oily skin, and accelerated hair loss in genetically predisposed men.

In women, testosterone causes virilization: voice deepening, facial and body hair growth, clitoral enlargement, and menstrual disruption. Several of these changes, particularly voice changes, may be irreversible.

Liver, mood, and the risks of non-medical use

Unlike oral 17-alpha-alkylated steroids, injectable testosterone esters are not strongly associated with liver toxicity. However, liver enzyme changes and, rarely, more serious liver problems have been reported in heavy users, often in combination with other substances.

Psychiatric effects have been documented in controlled research. In a well-known trial by Pope and colleagues, supraphysiological testosterone produced manic or hypomanic symptoms in a minority of healthy men. Irritability, aggression, and sleep disturbance are commonly reported, and depression can appear after stopping, when hormone levels fall below normal.

Non-medical users often combine testosterone with other drugs, which multiplies risks and makes individual side effects harder to attribute. Shared or reused needles carry a risk of HIV and hepatitis B and C transmission.

A dependence syndrome related to anabolic steroids has been described, with continued use despite harms and difficulty stopping because of withdrawal symptoms such as low mood and fatigue. Professional support from an endocrinologist or addiction specialist can make stopping safer.

Conclusions of the editorial team

Testosterone propionate shares the full side-effect profile of testosterone, with the added local discomfort and hormonal fluctuations typical of a short ester.

The most serious concerns — erythrocytosis, lipid changes, cardiac remodeling, and suppression of fertility — grow with dose and duration and are far more pronounced in non-medical use than in monitored replacement therapy.

Anyone currently using testosterone outside medical supervision should consider regular blood work and an honest conversation with a physician, who can assess cardiovascular risk and plan a safe exit.

For further reading, see our articles on how testosterone cypionate became a medical standard, why natural testosterone sometimes does not recover after a cycle, and how anabolic steroids affect male fertility.

References

1. Bhasin S, Brito JP, Cunningham GR, et al. Testosterone therapy in men with hypogonadism: an Endocrine Society clinical practice guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744.
2. Baggish AL, Weiner RB, Kanayama G, et al. Cardiovascular toxicity of illicit anabolic-androgenic steroid use. Circulation. 2017;135(21):1991–2002.
3. Pope HG Jr, Kouri EM, Hudson JI. Effects of supraphysiologic doses of testosterone on mood and aggression in normal men: a randomized controlled trial. Arch Gen Psychiatry. 2000;57(2):133–140.
4. Pope HG Jr, Wood RI, Rogol A, Nyberg F, Bowers L, Bhasin S. Adverse health consequences of performance-enhancing drugs: an Endocrine Society scientific statement. Endocr Rev. 2014;35(3):341–375.
5. Rasmussen JJ, Selmer C, Østergren PB, et al. Former abusers of anabolic androgenic steroids exhibit decreased testosterone levels and hypogonadal symptoms years after cessation: a case-control study. PLoS One. 2016;11(8):e0161208.
6. Kanayama G, Hudson JI, Pope HG Jr. Illicit anabolic-androgenic steroid use. Horm Behav. 2010;58(1):111–121.