Benefits, risks, fertility and monitoring

Everything below applies to men with confirmed low testosterone. None of it has been shown in men whose testosterone is normal. In short: treatment helps some things and not others, has known risks that are checked for on a schedule, and affects fertility. If you have not yet read how assessment works, start there; if you are choosing where to get care, the providers table and the costs page show what each service charges for follow-up.

What treatment has been shown to do

Sexual function is the most consistent benefit. Lean mass and muscle strength increase, with a larger effect from injections than from gels. Bone density rises. Anemia corrects more often than on placebo. Effects on energy and mood are smaller and less consistent than the marketing around testosterone suggests, and the effect sizes with their confidence intervals are set out in the evidence guides, starting with what testosterone therapy does.

What the safety evidence shows

TRAVERSE, published in the New England Journal of Medicine in June 2023, randomized 5,246 men aged 45 to 80 who had hypogonadal symptoms and two fasting testosterone levels below 300 ng/dL. Major adverse cardiac events occurred in 7 percent of men on testosterone and 7.3 percent on placebo. The same trial found a higher incidence of atrial fibrillation, acute kidney injury and pulmonary embolism in the treated group. Snyder's 2024 fracture substudy found clinical fractures in 91 treated men (3.50 percent) against 64 on placebo (2.46 percent), a hazard ratio of 1.43 (95% CI 1.04 to 1.97).

Hematocrit rises on treatment, sometimes sharply. In the T4DM trial a hematocrit above 54 percent occurred in 106 of 491 treated men, against 6 of 484 on placebo. The European Association of Urology lists a hematocrit of 54 percent or above among its contraindications. Blood pressure also rises: the United States regulator stated on 28 February 2025 that ambulatory monitoring studies confirmed an increase across the whole class.

Canada has published nothing on testosterone since 15 July 2014, and the Canadian product monograph authorized 12 December 2025 still states that safety and efficacy for age-related hypogonadism are not established. That gap between Canadian labelling and the current trial evidence is real, and it is covered in how Canada's rules compare.

Fertility and testicle size

How replacement therapy differs from non-medical steroid use, in dose, monitoring and harms, is on the TRT compared with anabolic steroid use page.

Can TRT affect testicle size or fertility?

Yes. Testosterone taken as treatment signals the pituitary to lower its output of LH and FSH, the hormones that drive the testicles. Testosterone made inside the testicles falls, and sperm production falls with it. The Canadian Urological Association notes that testosterone can act as a contraceptive, and the American Urological Association that it can reduce sperm counts to very low levels or to none. The testicles can become smaller: the CMAJ 2015 guideline lists atrophy and impaired sperm production among the harms. How much size changes at prescribed doses has not been well measured; the studies that measured it were in anabolic steroid users taking much higher doses.

The guidelines agree on men who want children. The American Urological Association says testosterone should not be prescribed to men currently trying to conceive. The Endocrine Society recommends against it for men planning fertility in the near term, and says men who are unsure may want to bank sperm. The Canadian Urological Association recommends caution and referral to a male fertility specialist, and the European Association of Urology says not to use it in men wishing to be fathers. Anyone who may want children should raise this before the first prescription, not after.

Sperm production often returns after stopping, but timing varies and recovery is not guaranteed. In a pooled analysis of 1,549 healthy men who took hormonal contraception (Liu 2006), the median time to recover was 3.4 months, and 90% had recovered within 12 months. The American Urological Association cautions that these results may not apply to men with testosterone deficiency, and that some men may never recover.

What happens if I stop TRT?

Symptoms that improved on treatment can come back, and the body's own production has to restart, which takes time. The Canadian Urological Association says treatment should be stopped if it causes significant side effects, if a new reason not to use it appears, or if symptoms have not improved after an adequate trial of about three months. How long the body's own testosterone takes to recover after prescribed treatment has not been well studied. In the one prospective study of former anabolic steroid users (Smit 2021), who took far higher doses, testosterone returned to normal within three months in most men and sperm counts took about a year; at one year, 11% still had low testosterone. The Endocrine Society notes that recovery after long, high-dose use can take months or years and may be incomplete. Stopping is a decision to make with the prescriber, who can plan the follow-up blood work.

When treatment is not appropriate

Published contraindications and cautions include breast or prostate cancer, a palpable prostate nodule or an unexplained raised PSA, a hematocrit above the threshold above, untreated severe obstructive sleep apnea, uncontrolled heart failure, a recent myocardial infarction or stroke, thrombophilia, and an active desire to father children. This is a short summary of published lists. The decision belongs to a clinician who knows the person.

The monitoring schedule

The schedule above is the guideline schedule. Each provider also publishes its own follow-up interval and follow-up charges, which are recorded in the providers table and on the costs page. A provider's interval is its published service schedule, not a medical recommendation, and the two are kept separate on this site. Monitoring is a practical question when choosing how to get treated: ask any service who orders the repeat blood work, who reads it, who acts on an abnormal result, what each follow-up costs, and what happens if you move province. The full picture is in the guide on monitoring during testosterone therapy in Canada. If a product you are prescribed is reported short, the shortages page sets out what to ask.

Questions to ask before starting

• What specifically are we treating, and how will we know in six months whether it worked?
• What is my hematocrit and my blood pressure now?
• Do I want children, now or later?
• Who arranges and reviews the follow-up blood work, and what does it cost me?
• What happens if I stop after a year? (See stopping TRT above.)