Testosterone Enanthate Year-1 Outcomes: What Real Users Actually Experience

What the Year-One Data Actually Cover

Testosterone enanthate injections are labeled for replacement therapy in men with primary hypogonadism (testicular failure) or hypogonadotropic hypogonadism (a pituitary or hypothalamic cause) [4]. The label says to confirm the diagnosis with morning serum testosterone measured on at least two separate days, both below the normal range [4]. FDA says none of the approved testosterone products are approved for men with low testosterone who lack an associated medical condition [8]. FDA requested removal of the age-related limitation in June 2026 [8], and the intramuscular testosterone enanthate label still says its safety and efficacy for age-related hypogonadism have not been established [4].

The one-year sexual-function and vitality results come from a testosterone gel trial, not an injection trial [3]. The large cardiovascular outcome trial, TRAVERSE, also used a topical gel [9], and a controlled dose-response study of weekly enanthate injections ran 20 weeks [10].

Sexual Function, Mood and Energy at One Year

The one-year symptom data come from a trial of 790 men aged 65 and older with serum testosterone below 275 ng/dL, randomized to testosterone gel or placebo gel for one year [3]. Testosterone increased sexual activity on the Psychosexual Daily Questionnaire (P<0.001) and increased sexual desire and erectile function [3]. The investigators concluded that treatment produced a moderate benefit for sexual function, some benefit for mood and depressive symptoms, and no benefit for vitality or walking distance [3]. On a fatigue scale, testosterone had no significant benefit for vitality [3]. Rates of adverse events were similar between the groups, but the number of participants was too small to draw conclusions about the risks of treatment [3].

Body Composition: 20-Week Enanthate Data, Not Year-One Data

Sixty-one healthy men aged 18 to 35 with normal testosterone were given a GnRH agonist to suppress their own testosterone production, then weekly enanthate injections of 25, 50, 125, 300 or 600 mg for 20 weeks [10]. Fat-free mass rose with dose: 3.4 kg at 125 mg, 5.2 kg at 300 mg and 7.9 kg at 600 mg weekly [10]. Changes in fat mass and HDL cholesterol were negatively correlated with testosterone concentrations [10]. Sexual function, mood and PSA did not change significantly at any dose [10].

Nadir testosterone concentrations were 542 ng/dL at 125 mg weekly and 1,345 ng/dL at 300 mg weekly [10]. The 125, 300 and 600 mg weekly doses all exceed the label's statement that total doses above 400 mg per month are generally not required; the label dose is 50 to 400 mg every 2 to 4 weeks, and injections more often than every two weeks are rarely indicated [4].

Hematocrit: The Most Predictable Change

A network meta-analysis of 29 placebo-controlled randomized trials covering 3,393 men found that every testosterone formulation raised mean hematocrit [1]. Intramuscular enanthate or cypionate raised mean hematocrit by 4.0% versus placebo (95% CI 2.9 to 5.1) [1]. The increase was significantly greater than with a patch; differences from the other formulations were not statistically significant [1]. Gel raised it 3.0%, patch 1.4%, oral testosterone undecanoate 4.3% and intramuscular testosterone undecanoate 1.6% [1].

In a retrospective single-center review of 178 men treated for three years, erythrocytosis (hematocrit >50%) occurred in 66.7% of men on injectable testosterone, 12.8% on gels and 35.1% on pellets [5]. The injection group was younger (mean 42.5 years versus about 54) and started with a higher hematocrit, and the study was not randomized [5].

One review of the erythrocytosis literature concluded that men on testosterone replacement had a 315% greater risk of erythrocytosis, defined as hematocrit above 0.52, than controls, that all formulations raise hemoglobin and hematocrit, and that injectables do so the most [11]. A separate review found short-acting injectables carried the highest incidence and that a link between erythrocytosis and thromboembolic events remains unclear [12].

Polycythemia is listed among the enanthate label's hematologic adverse reactions, and venous thromboembolism including deep vein thrombosis and pulmonary embolism has been reported with testosterone products; the label directs evaluation of leg pain, edema, warmth and erythema for DVT and acute shortness of breath for PE, and discontinuation if an event is suspected [4].

Blood Pressure

FDA's February 2025 class-wide labeling action followed ambulatory blood pressure monitoring studies that confirmed an increase in blood pressure with all testosterone products, and it required a blood pressure warning for products that did not already have one [2]. The enanthate label states that testosterone can increase blood pressure, which can increase cardiovascular risk over time, that blood pressure should be monitored periodically, especially in men with hypertension, and that testosterone products are not recommended for men with uncontrolled hypertension [4].

Cardiovascular Safety: What Applies to Injections

TRAVERSE randomized 5,246 men aged 45 to 80 with symptoms of hypogonadism, two fasting testosterone levels below 300 ng/dL and existing or high cardiovascular risk to daily 1.62% testosterone gel or placebo gel [9]. Mean treatment duration was 21.7 months and mean follow-up 33 months; the primary composite of cardiovascular death, nonfatal myocardial infarction or nonfatal stroke occurred in 7.0% of the testosterone group and 7.3% of the placebo group, hazard ratio 0.96 (95% CI 0.78 to 1.17), meeting noninferiority [9]. Doses were adjusted to keep testosterone between 350 and 750 ng/dL [9].

TRAVERSE tested a gel, not injections [9]. The enanthate label states that long-term clinical safety trials have not been conducted to assess cardiovascular outcomes, that epidemiologic studies and randomized trials have been inconclusive for major adverse cardiovascular events, that some studies but not all have reported an increased risk, and that patients should be informed of this possible risk [4].

FDA reviewed TRAVERSE and said it did not demonstrate a new safety signal or trend in adverse cardiovascular outcomes, and in June 2026 the agency requested further label updates, including removing the age-related hypogonadism limitation and revising prostate cancer and benign prostatic hyperplasia safety information [8].

Fertility and Testicular Changes

The enanthate label notes that during exogenous androgen administration the body's own testosterone release is inhibited through feedback inhibition of pituitary luteinizing hormone [4]. The label lists oligospermia at high dosages among male adverse reactions, and its abuse section lists testicular atrophy, subfertility and infertility among reactions reported in men using anabolic androgenic steroids [4].

Recovery figures come from men who were not hypogonadal at baseline or from men treated for testosterone-associated infertility. An integrated analysis of 30 studies of 1,549 healthy eugonadal men on hormonal contraception found a median of 3.4 months for sperm concentration to return to 20 million/mL, with recovery probabilities of 67% by 6 months, 90% by 12 months, 96% by 16 months and 100% by 24 months; recovery was faster with shorter-acting testosterone, shorter treatment, older age and higher baseline sperm counts [6].

Among 66 men with infertility after testosterone use who stopped testosterone and received high-dose hCG plus a selective estrogen receptor modulator, 46 (70%) reached a total motile count above 5 million within 12 months [13]. Older age and longer testosterone use predicted slower recovery, and 64.8% of azoospermic men reached the threshold versus 91.7% of cryptozoospermic men [13]. A separate series of 49 men with azoospermia or severe oligospermia on testosterone, treated with hCG 3,000 units subcutaneously every other day plus clomiphene, tamoxifen, anastrozole or recombinant FSH, reported return or improvement of spermatogenesis in 47 men (95.9%), with an average time of 4.6 months and a mean first density of 22.6 million/mL, and no difference by type of testosterone [14].

The Endocrine Society guideline recommends against starting testosterone therapy in men planning fertility in the near term [7].

Breast Tissue, Skin and Injection Sites

The enanthate label states that gynecomastia frequently develops and occasionally persists in patients treated for hypogonadism, and lists acne, male pattern baldness, hirsutism, increased or decreased libido, headache, anxiety and depression among adverse reactions [4]. Testosterone is converted to estradiol by the enzyme aromatase [15], and most gynecomastia results from deficient androgen action or excessive estrogen action in breast tissue, where estrogens stimulate growth and androgens inhibit it [16]. Pain and inflammation at the injection site are also listed [4].

What First-Year Monitoring Covers

The Endocrine Society guideline recommends monitoring symptoms, serum testosterone, hematocrit and prostate cancer risk during the first year of therapy [7]. It also recommends against starting testosterone in men with breast or prostate cancer, elevated hematocrit, untreated severe sleep apnea, uncontrolled heart failure, or a heart attack or stroke within the previous six months [7]. The enanthate label contraindicates the drug in men with carcinoma of the breast or known or suspected carcinoma of the prostate, in women who are or may become pregnant because androgens can virilize a female fetus, and in anyone with hypersensitivity to a component [4]. Periodic blood pressure monitoring is part of the label's warnings [4].