Low testosterone · Telehealth for men · Canada & USA
What are the side effects of TRT?
The most common side effect of testosterone replacement therapy is a rise in red blood cells (hematocrit). Acne, oily skin, a small PSA rise and lower sperm production also have a clear link, while breast swelling, balding and worse sleep apnea are uncommon, according to the Endocrine Society. In the large TRAVERSE trial, testosterone gel did not raise the rate of heart attack or stroke. Most side effects show up on labs early. We help men in Canada and the USA look at causes first, plan the right labs and track hematocrit, PSA, estradiol, lipids and blood pressure by telehealth.
Part of our low testosterone and andropause guide for men in Canada and the USA.
Which TRT side effects are real, and how common are they?
The Endocrine Society’s 2018 guideline sorts the risks of TRT into three groups. A clear link: erythrocytosis (too many red blood cells), acne and oily skin, finding a hidden prostate cancer, growth of an existing metastatic prostate cancer, and lower sperm production. Uncommon, with weak evidence: breast enlargement (gynecomastia), male pattern balding in men with a family tendency, and new or worse obstructive sleep apnea. Tied to the form: injections can bring swings in mood or libido and injection-site pain, gels can pass to a partner or child through skin contact, and patches often irritate the skin. How often? In a 2005 meta-analysis of 19 randomized trials in men 45 and older (Calof and colleagues), men on testosterone were nearly four times as likely as men on placebo to reach a hematocrit above 50 percent (odds ratio 3.69), and prostate events of any kind were found more often (odds ratio 1.78). Rates of heart events, sleep apnea and death did not differ. If you are still sorting out whether your symptoms point to low T, start with low testosterone symptoms.
TRT and hematocrit: the red blood cell effect
Testosterone raises hemoglobin and hematocrit, and the Endocrine Society notes the rise grows with the dose and blood level and is larger in older men. In a 2010 meta-analysis of 51 studies (Fernández-Balsells and colleagues), hematocrit rose by about 3 points on average. Erythrocytosis (hematocrit above 54 percent) is the most frequent adverse event in testosterone trials, and in the guideline’s own meta-analysis it was about eight times more likely than on placebo (relative risk 8.14). The form matters: in a 2023 randomized trial (Rivero and colleagues), hematocrit climbed from 42.7 to 46.6 percent after four months of cypionate injections but did not change significantly on nasal gel. Why it matters: in a large health-records study (Ory and colleagues, 2022), men on testosterone whose hematocrit reached 52 percent or more had more heart attacks, strokes and blood clots in the first year than men whose hematocrit stayed normal (5.15 versus 3.87 percent). The guideline’s rule: check hematocrit before starting, at three to six months, then yearly; take extra care if it starts above 48 percent (50 percent at high altitude); if it passes 54 percent, pause until it is back in range, check for low oxygen and sleep apnea, and restart at a lower dose. Blood donation (phlebotomy) also works, and the Canadian Urological Association lists a lower dose, a break, a different form or blood donation when hematocrit stays at 55 percent or higher. Hematocrit belongs on the labs to ask for list before you start.
Does TRT cause acne, hair loss or breast changes?
Acne and oily skin have a clear link with testosterone, and together with breast tenderness they are among the most common drug-related complaints, says the Endocrine Society. Hair loss is less certain: the guideline lists male pattern balding as uncommon, with weak evidence, mostly in men with a family tendency. Breast enlargement is also uncommon. Breast symptoms tie back to estradiol, because part of your testosterone is converted to estradiol (more so in body fat, the Canadian Urological Association notes), and the CUA advises measuring estradiol before treatment in men with breast symptoms or gynecomastia. The form makes a difference here too: in the 2023 Rivero trial, estradiol rose with injections but not with nasal gel. If a breakout, thinning or breast tenderness shows up, your estradiol, the dose, its timing and the form are the first things to review.
TRT, fertility and testicle size
Testosterone from outside the body tells the pituitary to cut LH and FSH, the two signals that drive the testes. In a 2005 study in healthy men (Coviello and colleagues), weekly injections pushed LH and FSH down to 5 and 3 percent of baseline and cut testosterone inside the testes by 94 percent within three weeks. With less of their own testosterone, the testes make fewer sperm and get smaller: in a 1981 study (Palacios and colleagues), testicular volume fell by about 16 to 19 percent after four months of injections and returned to normal size after they stopped. In a World Health Organization contraceptive trial (Lancet, 1990), 65 percent of 271 healthy men had no sperm in their semen by six months of weekly injections; after stopping, sperm counts took a median of just under four months to recover to 20 million per mL. That is why the Endocrine Society advises against TRT for men who want a child in the next six to twelve months, and the Canadian Urological Association points men who want to keep their fertility toward options that raise their own testosterone, such as hCG or clomiphene. For recovery and options in depth, read TRT and fertility.
TRT and heart risk: what the TRAVERSE trial found
TRAVERSE (Lincoff and colleagues, New England Journal of Medicine, 2023) was built to settle the heart question. It enrolled 5,246 men aged 45 to 80 with low-T symptoms, two fasting testosterone levels under 300 ng/dL, and existing heart disease or high heart risk, and gave them testosterone gel or a placebo gel. Over close to three years of follow-up on average, a heart attack, stroke or cardiovascular death occurred in 7.0 percent of the testosterone group and 7.3 percent of the placebo group (hazard ratio 0.96), so testosterone was noninferior. The trial did find more atrial fibrillation, acute kidney injury and pulmonary embolism with testosterone, and a TRAVERSE fracture study (Snyder and colleagues, 2024) found more fractures, not fewer (3.50 versus 2.46 percent). In February 2025 the US FDA removed the boxed-warning language about heart outcomes and added the TRAVERSE results to every testosterone label, and it added a blood pressure warning because ambulatory monitoring studies showed blood pressure rising with all testosterone products. In June 2026 it asked for further label updates, including revised prostate safety information. On cholesterol, the 2010 meta-analysis found a small drop in HDL. How this fits the bigger choice is covered in TRT or fix the causes first.
TRT and the prostate: PSA and cancer risk
Testosterone raises PSA a little. In a systematic review cited by the Endocrine Society, PSA rose by about 0.3 ng/mL in young men with low T and 0.44 ng/mL in older men; in the Testosterone Trials, a rise of more than 1.4 ng/mL happened in 2.4 percent of treated men at three months and 4.7 percent at one year, against 1.6 and 0.6 percent on placebo. Does TRT cause prostate cancer? In the TRAVERSE prostate analysis (Bhasin and colleagues, JAMA Network Open, 2023) of 5,204 men screened to exclude high prostate risk, high-grade prostate cancer occurred in 0.19 percent on testosterone and 0.12 percent on placebo, a difference that was not statistically significant, and rates of any prostate cancer, urinary retention, biopsies and procedures did not differ. The Canadian Urological Association cites a meta-analysis of 22 randomized trials with 2,351 men that found no higher prostate cancer risk. The caution is for cancer that is already there: the Endocrine Society says testosterone can bring a hidden cancer to light and helps metastatic prostate cancer grow, so it advises against starting with a PSA above 4 ng/mL (above 3 for higher-risk men, such as African American men or men with a first-degree relative with prostate cancer) until it has been checked, and calls for a closer prostate work-up if PSA rises by more than 1.4 ng/mL in the first year, passes 4 ng/mL, or the prostate exam changes.
TRT, sleep apnea and blood pressure
The Endocrine Society lists new or worse obstructive sleep apnea as uncommon, with weak evidence, and the 2005 Calof meta-analysis found no significant difference in sleep apnea between testosterone and placebo. Even so, the guideline advises against starting testosterone while severe sleep apnea is untreated, and it pairs a high hematocrit with a check for sleep apnea and low oxygen. Sleep apnea can also lower testosterone on its own (the Canadian Urological Association lists it among causes that can be corrected), so it is one of the first things we look at. Blood pressure is the newer item: the FDA now says testosterone raises blood pressure across all products, so a home or pharmacy reading belongs in every check-in. More on sleep in low testosterone and sleep.
What gets monitored on TRT, and when
The Endocrine Society sets a standard plan: review symptoms and side effects, and check testosterone and hematocrit at three to six months, at one year and then yearly. Testosterone should sit in the mid-normal range; with cypionate or enanthate injections it is measured midway between shots, and a result above 600 or below 350 ng/dL means the dose or interval needs adjusting. Men 55 to 69, and men 40 to 69 at higher risk, who choose prostate monitoring have a PSA and prostate exam before starting and again at three to twelve months, then follow normal screening. Men with osteoporosis get a bone density scan after one to two years. The Canadian Urological Association’s schedule is close: baseline, three months, six months, then yearly. To that list we add what this page shows matters: estradiol, lipids, blood pressure and a sleep apnea screen. When total T is borderline, free T and SHBG help read the numbers, explained in free vs total testosterone.
Most TRT side effects are manageable
Most of these effects depend on dose and blood level, and they show up on labs before they cause trouble. The guideline tools are simple: lower the dose or change the interval, switch the form (the CUA notes nasal gel may suppress sperm production less, and in the Rivero trial it left hematocrit and estradiol unchanged), take a break until hematocrit settles, or donate blood. A man who wants children plans differently from the start. And the American Urological Association (2018, reviewed 2024) says a man is a candidate for testosterone therapy only when low levels come with symptoms, so for many men the best way to avoid side effects is to fix what is lowering testosterone first: weight, sleep, alcohol, medications and stress. That path is laid out step by step in TRT or fix the causes first.
How Odin helps
Odin Health Labs is telehealth for men in Canada and the USA with andropause and low testosterone symptoms. On a free call we go through your symptoms, history, medications and any labs you already have. We help you plan a full baseline: two morning testosterone tests, SHBG and free T, hematocrit, PSA, estradiol and lipids, plus blood pressure and a sleep check. Then we build a written plan that looks at causes first: weight, sleep, training, nutrition, alcohol and stress. If you start TRT or are already on it, we track your hematocrit, PSA, estradiol, lipids and blood pressure with you at each check-in, explain every result in plain language and flag changes early, before they become problems. Our health coaching keeps the plan on track, functional health looks at the whole picture, and our supplements page shows where they fit.
Telehealth consults
Video or phone, anywhere in Canada or the USA, at a time that fits your week.
A full baseline
Testosterone, hematocrit, PSA, estradiol and lipids before any decision.
Causes first
A written nutrition, training, sleep and stress plan aimed at what is lowering your T.
Side effects tracked
Regular check-ins and repeat labs, so changes are caught early.
From worry about side effects to a plan
Here is how we work with you, start to finish.
- Step 1
Talk through symptoms and goals
On a free call we go through your energy, drive, sleep, weight, medications and any plans for children.
- Step 2
Get a full baseline
Two morning testosterone tests plus hematocrit, PSA, estradiol, lipids and blood pressure.
- Step 3
Fix the causes first
A written nutrition, training, sleep and stress plan, and a clear look at whether TRT fits.
- Step 4
Track side effects early
Check-ins and repeat labs on the guideline schedule, and we adjust the plan with you.
Sources
- 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. doi.org/10.1210/jc.2018-00229
- Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular Safety of Testosterone-Replacement Therapy (TRAVERSE). N Engl J Med 2023;389(2):107–117. doi.org/10.1056/NEJMoa2215025
- Bhasin S, Travison TG, Pencina KM, et al. Prostate Safety Events During Testosterone Replacement Therapy in Men With Hypogonadism. JAMA Netw Open 2023;6(12):e2348692. doi.org/10.1001/jamanetworkopen.2023.48692
- Snyder PJ, Bauer DC, Ellenberg SS, et al. Testosterone Treatment and Fractures in Men with Hypogonadism. N Engl J Med 2024;390(3):203–211. doi.org/10.1056/NEJMoa2308836
- Calof OM, Singh AB, Lee ML, et al. Adverse events associated with testosterone replacement in middle-aged and older men: a meta-analysis of randomized, placebo-controlled trials. J Gerontol A Biol Sci Med Sci 2005;60(11):1451–1457. doi.org/10.1093/gerona/60.11.1451
- Fernández-Balsells MM, Murad MH, Lane M, et al. Adverse effects of testosterone therapy in adult men: a systematic review and meta-analysis. J Clin Endocrinol Metab 2010;95(6):2560–2575. doi.org/10.1210/jc.2009-2575
- Ory J, Nackeeran S, Balaji NC, et al. Secondary Polycythemia in Men Receiving Testosterone Therapy Increases Risk of Major Adverse Cardiovascular Events and Venous Thromboembolism in the First Year of Therapy. J Urol 2022;207(6):1295–1301. doi.org/10.1097/JU.0000000000002437
- Rivero MJ, Ory J, Diaz P, et al. Comparison of Hematocrit Change in Testosterone-deficient Men Treated With Intranasal Testosterone Gel vs Intramuscular Testosterone Cypionate. J Urol 2023;210(1):162–170. doi.org/10.1097/JU.0000000000003487
- Coviello AD, Matsumoto AM, Bremner WJ, et al. Low-dose human chorionic gonadotropin maintains intratesticular testosterone in normal men with testosterone-induced gonadotropin suppression. J Clin Endocrinol Metab 2005;90(5):2595–2602. doi.org/10.1210/jc.2004-0802
- Palacios A, McClure RD, Campfield A, Swerdloff RS. Effect of testosterone enanthate on testis size. J Urol 1981;126(1):46–48. doi.org/10.1016/s0022-5347(17)54372-4
- World Health Organization Task Force on Methods for the Regulation of Male Fertility. Contraceptive efficacy of testosterone-induced azoospermia in normal men. Lancet 1990;336(8721):955–959. pubmed.ncbi.nlm.nih.gov/1977002
- Grober ED, Krakowsky Y, Khera M, et al. Canadian Urological Association guideline on testosterone deficiency in men: Evidence-based Q&A. Can Urol Assoc J 2021;15(5):E234–E243. doi.org/10.5489/cuaj.7252
- Mulhall JP, Trost LW, Brannigan RE, et al. Evaluation and Management of Testosterone Deficiency: AUA Guideline (2018, reviewed 2024). American Urological Association. auanet.org testosterone deficiency guideline
- US Food and Drug Administration. FDA issues class-wide labeling changes for testosterone products (February 28, 2025) and Testosterone Information (June 2026 update). fda.gov labeling changes
Frequently asked questions
What are the most common side effects of TRT?
A rise in red blood cells (hematocrit) is the most frequent side effect in testosterone trials, according to the Endocrine Society’s 2018 guideline. Acne and oily skin, breast tenderness, a small rise in PSA and lower sperm production are also linked to testosterone. Breast enlargement, male pattern balding and new or worse sleep apnea are uncommon. Each form adds its own, such as injection-site pain, skin irritation from patches or gel rubbing off onto a partner. Regular labs catch most of these early, and we track them with you.
Does TRT raise hematocrit, and when is it too high?
Yes. Testosterone raises hemoglobin and hematocrit, more in older men and at higher doses. The Endocrine Society advises checking hematocrit before starting, at three to six months and then yearly, taking extra care if it starts above 48 percent, and pausing treatment if it passes 54 percent until it settles, then restarting at a lower dose. In a 2022 study of men on testosterone, those whose hematocrit reached 52 percent or more had more heart attacks, strokes and blood clots in the first year. We follow your hematocrit with you at every check-in.
Does TRT shrink your testicles or affect fertility?
It can. Testosterone from outside the body switches off the LH and FSH signals that drive the testes, so they make less of their own testosterone and fewer sperm. In a 1981 study, testicular volume fell by about 16 to 19 percent after four months of injections and returned to normal after they stopped. In a World Health Organization trial, 65 percent of healthy men on weekly injections had no sperm by six months. If you may want children, plan that before you start. See our TRT and fertility guide.
Does TRT cause hair loss or acne?
Acne and oily skin have a clear link with testosterone. Hair loss is less certain: the Endocrine Society lists male pattern balding as an uncommon side effect with weak evidence, mostly in men with a family tendency toward it. If acne or thinning shows up, your levels, the dose, its timing and the form you use are worth reviewing, and we go through them with you.
Is TRT bad for your heart or prostate?
In the TRAVERSE trial of 5,246 men aged 45 to 80 with heart disease or high heart risk, a heart attack, stroke or cardiovascular death occurred in 7.0 percent of men on testosterone gel and 7.3 percent on placebo. Atrial fibrillation, acute kidney injury and pulmonary embolism were more common with testosterone, and the FDA added a blood pressure warning in 2025. High-grade prostate cancer occurred in 0.19 versus 0.12 percent, not a significant difference. Testosterone does raise PSA a little and can speed up an existing prostate cancer, so PSA is checked before starting and during the first year.
How does Odin Health Labs work with my doctor?
Odin Health Labs is a telehealth service for men in Canada and the USA with low testosterone (andropause) symptoms. We work alongside your own doctor: we go through your symptoms, history and lab results with you, help you prepare questions about TRT side effects and monitoring, build your nutrition, training, sleep and stress plan, and track hematocrit, PSA, estradiol, lipids and blood pressure with you at follow-up check-ins, using the Endocrine Society’s monitoring plan as the checklist. We can share your plan and results with your doctor if you choose. See our low testosterone overview and our Privacy Policy.
Want TRT side effects caught early, or avoided?
A free call is the first step: we go through your symptoms and results, plan the right baseline labs and set up a causes-first plan with regular check-ins.