TRT acne: how common it is, why it happens, what to do
TRT hair loss: what's known, what isn't, what to watch
TRT blood pressure: how much it rises and what to do
TRT and sleep apnea: what the evidence shows
TRT heart risk: what TRAVERSE does and doesn't show
Gynecomastia on TRT: breast tenderness, swelling and lumps
What are the side effects of TRT?
The most common TRT side effects are a rise in red blood cells, acne and oily skin, and a small rise in blood pressure. Lower sperm production and smaller testes are common too. Labels also list breast tenderness or growth, fluid retention and worse sleep apnea.
Many of these are mild. Some show up on blood tests before you feel anything, and a few need urgent care.
This page is our hub for TRT side effects. Each section gives you the short version and points to a fuller guide where we have one. It’s general information, not advice about your own treatment.
| Side effect | How common | When it tends to show up | How it’s caught |
|---|---|---|---|
| Higher hematocrit | The most frequent adverse event in trials | From about 3 months, peaking at 9 to 12 | Blood test |
| Higher blood pressure | Small average rises across products | Seen by 12 to 16 weeks in label studies | Blood pressure checks |
| Acne, oily skin | Listed on the labels we checked; among the most common reactions to AndroGel 1% | Variable | You notice it |
| Lower sperm count, smaller testes | Sperm: expected; smaller testes: listed on the DEPO label | Gradually after starting | Semen analysis, exam |
| Breast tenderness or growth | Listed on the DEPO label | Variable | You notice it, exam |
| Fluid retention, ankle swelling | Listed on the labels | Variable | You notice it |
| Worse sleep apnea | Some men, mainly with risk factors | Variable; in one trial, in the first weeks | Snoring, tiredness, sleep study |
| PSA rise | Marginal; larger than placebo in TRAVERSE | Plateaus at about 12 months | Blood test |
Which TRT side effects are most common?
Rising red blood cells top the list. A pooled analysis of trials in men aged 45 and older found this was the most frequent side effect on testosterone. It causes no symptoms early on, so blood tests track it.
Acne and skin changes come next. The AndroGel 1% label names acne among its most common reactions. The DEPO-Testosterone label lists acne, oily skin and male-pattern baldness among reported effects.
Lower sperm production is close to expected, especially with injections. Smaller testes often go with it.
The Endocrine Society tells prescribers to check your symptoms, side effects, testosterone and red blood cells during the first year. For men who choose it, the plan also includes a prostate check.
Does TRT raise your red blood cell count?
Yes, often. The measure is hematocrit, the share of your blood made up of red cells. Men on testosterone were nearly four times as likely as men on placebo to reach a hematocrit above 50%.
The rise usually shows at about 3 months and peaks at 9 to 12 months.
A pooled look at 29 randomized trials found every form of testosterone raised hematocrit. On average it went up about 4 points on cypionate or enanthate injections and about 3 points on gel.
In the Xyosted trials, 4.2% of men reached 55% or more within a year. Some people call this “thick blood”.
The Endocrine Society advises against starting testosterone with an already high hematocrit, and it’s part of the first-year checks. Our TRT blood work guide explains the limits prescribers use and when the test is usually done. Don’t change your treatment because of one result; talk to your prescriber.
Can TRT cause blood clots?
The evidence is mixed. Two pooled analyses, done before the TRAVERSE trial, found no clear link between testosterone and clots in the veins. Both rated the evidence low in certainty, and one said a real increase couldn’t be ruled out.
In the larger one, 13 trials with 5,050 men, clot rates on testosterone and placebo were almost the same.
In TRAVERSE, clots were more common on testosterone in the raw numbers: 1.7% versus 1.2%. That included clots in the lungs (pulmonary embolism) in 0.9% versus 0.5%. Whether a high hematocrit on testosterone causes clots is still debated.
Labels tell prescribers to check men with leg pain, swelling, warmth or redness, or sudden shortness of breath. Those are emergency symptoms, listed at the end of this page.
Does TRT raise blood pressure?
Slightly, on average. In 2025 the FDA reviewed 24-hour blood pressure studies of every testosterone product. It found they all raise blood pressure, and it asked for a warning on every label.
The size of the rise varies by product:
| Product | Average rise (systolic/diastolic, the top and bottom numbers) | When |
|---|---|---|
| Xyosted (weekly injection under the skin) | 3.9/1.5 mm Hg | After 12 weeks |
| AndroGel 1.62% | 1.9/1.3 mm Hg; 3.0/2.2 in men treated for hypertension | After 16 weeks |
| Testosterone gel in TRAVERSE | 1.5 mm Hg more than placebo | At 36 months |
Two other product studies point the same way. In a 26-week study of the Xyosted autoinjector in 133 men, blood pressure measured in the clinic rose by 3.4 points. In a study of 246 men on a testosterone gel, the rise was small on average, but the researchers couldn’t rule out a meaningful rise in men who already had high blood pressure or diabetes.
Some men rise more than these averages. The DEPO-Testosterone label tells prescribers to check blood pressure from time to time, and says testosterone isn’t recommended when high blood pressure is uncontrolled. Our guide to TRT and blood pressure covers home checks and what to ask.
Does TRT raise the risk of heart attack or stroke?
The best evidence so far says no increase in major heart events. The TRAVERSE trial enrolled 5,246 men aged 45 to 80 who had heart disease or a high risk of it. Heart attack, stroke or death from heart disease happened in 7.0% of men on testosterone gel and 7.3% on placebo.
But the trial also found more atrial fibrillation (an irregular heartbeat), acute kidney injury and pulmonary embolism on testosterone. Treatment lasted about 22 months on average, and the trial tested a daily gel, not injections.
In the biggest heart safety trial so far, heart attacks and strokes were no more common on testosterone than on placebo.
After the trial, the FDA removed the heart warning from the boxed warning and added the results to every label.
A 2024 review of 106 placebo-controlled trials also found no difference in major heart events. The extra atrial fibrillation seen in TRAVERSE didn’t show up clearly across the other trials. A pooled analysis of 35 earlier trials also found no difference in the short to medium term, though only 13 reported heart and stroke events.
The Endocrine Society still advises against starting testosterone within 6 months of a heart attack or stroke, or with uncontrolled heart failure. If you have heart disease, ask your prescriber how these results apply to you. Our guide to TRT and heart risk goes through the trials in more detail.
Can TRT make sleep apnea worse?
It can in some men. Sleep apnea is when breathing repeatedly stops and starts during sleep. The Xyosted label says testosterone may worsen it, especially in men with obesity or chronic lung disease.
In a trial of 67 obese men with severe sleep apnea, testosterone worsened breathing measures at 7 weeks. By 18 weeks the difference was small enough to be due to chance, and the authors called the effect mild and time-limited.
A later review agreed that testosterone probably plays a small role. It cited one study where sleep apnea was diagnosed in 16.5% of men on testosterone versus 12.7% of men not on it.
The Endocrine Society advises against starting testosterone with untreated severe sleep apnea. Tell your prescriber if you start snoring loudly, a partner sees pauses in your breathing, or you wake unrefreshed. Our guide to TRT and sleep apnea explains when a sleep study makes sense.
Does TRT cause acne?
Sometimes. Labels report acne in about 1% to 5% of men in their trials, and it usually starts in the first year. It tends to show on the face, chest or back.
Mention it at your next visit rather than treating it with products sold online. Many cases are mild.
On the AndroGel 1% label, acne is among the most commonly reported reactions, along with skin reactions where the gel goes on, abnormal lab tests and prostate problems. Gels can also irritate the skin where you apply them, a separate problem from acne. Our TRT and acne guide, in the cards above, covers what helps and when to see a dermatologist.
Does TRT cause hair loss?
It can speed up hair loss in men who are already prone to it. Male-pattern hair loss affects 30 to 50% of men by age 50, and heredity accounts for about 80% of who is prone to it.
Normal levels of androgens, the male hormones, are enough to cause it in men who are genetically prone. So TRT may speed it up in those men. That is an inference, not a trial finding.
The DEPO-Testosterone label lists male-pattern baldness among reported effects. No study has measured hair loss in men treated for low testosterone. Our TRT and hair loss guide, in the cards above, looks at this in more depth.
Can TRT cause breast tenderness or growth?
Uncommonly. Gynecomastia is the growth of breast gland tissue in men. The DEPO-Testosterone label says it may develop and occasionally lasts, and guidelines say it is rarely reported in trials.
It usually comes from a shift in the balance between estrogen and testosterone, or from a medicine. A European guideline says it isn’t a precancerous condition, and that the first step is to look for the cause. Male breast cancer is rare, which is still why a new lump needs checking.
Don’t treat it yourself. Tell your prescriber about breast pain, enlargement or a lump.
Testosterone can also make the body hold on to salt and water. The label warns that this swelling can be serious in men with heart, kidney or liver disease, and asks patients to report ankle swelling. Our TRT and breast tissue guide, in the cards above, covers this in more depth.
Does TRT affect the prostate and PSA?
PSA, a blood marker made by the prostate, tends to rise a little on testosterone. In TRAVERSE it rose more on testosterone than on placebo, and it tends to level off by about 12 months.
In men screened for prostate risk, high-grade prostate cancer was rare in that trial, and the gap was small enough to be chance: 0.19% versus 0.12%. Rates of urinary retention, biopsies and prostate surgery were also similar.
Prostate checks are part of the first-year plan for men who choose them. The PSA page in our TRT blood work guide explains what prescribers look for.
Does TRT affect mood, fertility or cholesterol?
Mood: on average, slightly for the better. A pooled analysis of 27 randomized trials with 1,890 men found a small drop in depression symptoms. The Testosterone Trials in older men found slightly better mood but no gain in vitality.
Averages hide individual experiences. Labels list anxiety, depression and changes in libido among reported reactions, and some men describe irritability. A weekly mood rating helps you and your prescriber see whether a change is real.
Fertility: testosterone from outside the body makes your brain turn down LH, the signal that tells the testes to make their own testosterone. At higher exposure it also turns down FSH, which supports sperm production. Sperm counts can fall, sometimes to zero, and labels list smaller testes (testicular atrophy), subfertility and infertility.
In studies of healthy men on hormonal male birth control (testosterone alone or with a progestin), sperm counts were predicted to recover to 20 million per mL in 67% of men within 6 months of stopping, 90% within 12 months, and all by 24 months. Men on long-term TRT may recover more slowly. The Endocrine Society advises against starting testosterone if you’re planning children soon.
Cholesterol: the DEPO-Testosterone label says cholesterol may increase. One clinic comparison found only short-lived changes, and a large review found no harmful effect on lipids, the fats in your blood.
Do injections and gels cause different side effects?
Yes, in a few important ways. This isn’t a recommendation for one form over another; that’s your prescriber’s call.
- Hematocrit: short-acting injections carry the highest risk of erythrocytosis, an abnormally high red cell count. In one clinic review of past records, hematocrit above 50% occurred in 66.7% of men on injections, 12.8% on gels and 35.1% on pellets. The injection group was younger and started higher, so the gap may be overstated.
- Skin: gels can irritate the skin where you apply them. Injections can cause pain and inflammation where you inject.
- Partners and children: testosterone gel carries a boxed warning. Children who touched skin where gel was applied have shown virilization, which means early male-type development. The label says children should avoid contact with unwashed or uncovered application sites.
Who is more likely to get TRT side effects?
Some men carry more risk for particular effects. That doesn’t rule out treatment; your prescriber may just watch some things more closely.
- Higher starting hematocrit or a higher BMI (a weight-for-height measure): in a Swiss clinic study of 247 men (92 with follow-up hematocrit data), mostly on long-acting injections, these predicted who developed a high hematocrit. 23% went above 50%. The product used there is less common in the US.
- Injections rather than gel: linked to bigger hematocrit rises, as above.
- High blood pressure: on AndroGel 1.62%, men already treated for hypertension had a larger average rise, 3.0/2.2 mm Hg.
- Obesity or chronic lung disease: more likely to see sleep apnea get worse.
- Heart, kidney or liver disease: fluid retention can be more serious.
Tell your prescriber about these before you start.
Are there long-term TRT side effects we don’t know about yet?
Some questions are still open. The largest safety trial followed men for about 33 months on average. Many men take testosterone for decades, and effects that build over 10 or 20 years haven’t been tested in a randomized trial.
Earlier studies were more worrying. The TOM trial, in 209 older men with limited mobility, stopped early after more heart-related events on testosterone gel. Its authors said the small size and unusual group limited what it could show.
Later and larger studies didn’t confirm that signal. That uncertainty is why both main US guidelines, from the Endocrine Society and the American Urological Association, put so much weight on regular monitoring.
When should you call your prescriber or get emergency help?
Sort new symptoms into three groups. When in doubt, call.
Call 911 or go to the emergency room for:
- Chest pain or pressure, a possible sign of a heart attack.
- Sudden shortness of breath, a possible clot in the lungs. Labels say to seek urgent care.
- A painful, swollen, warm or red leg, a possible clot in the leg.
- Signs of a stroke: face drooping, arm weakness, slurred or strange speech.
- An erection that doesn’t go away. MedlinePlus calls this a medical emergency.
- Thoughts of harming yourself. In the US, call or text 988, or go to the emergency room. The Xyosted label reports suicidal thoughts in clinical trials.
Call your prescriber promptly for:
- Erections that are too frequent.
- Ankle swelling, nausea, vomiting, or changes in skin color.
- Breast pain or enlargement.
- New loud snoring, breathing pauses, or daytime sleepiness.
- New or worsening depression, anxiety or a big change in mood.
Mention at your next visit: acne, oily skin, hair thinning, mild soreness where you inject, and gradual changes you’ve noticed in your log.
How can you keep track of TRT side effects?
Some side effects you can feel, and some only a test can show.
- Things you can log: skin, sleep and snoring, mood, energy, libido, ankle swelling, soreness where you inject. A quick weekly rating shows patterns that are easy to miss from memory.
- Things only labs and checks show: hematocrit, PSA, estradiol, cholesterol and blood pressure. The Endocrine Society plan checks hematocrit at the start, at 3 to 6 months and then yearly. The draw-date planner helps you time draws around your injections, so results are comparable.
One record of both gives a clear picture at each visit. Bring it to your appointments, and ask your prescriber which changes are worth a call between visits.