5 testosterone side effects you must be aware of

Testosterone replacement can boost strength, mood, and sex drive, but it also shifts blood pressure, blood thickness, fertility, skin, and sleep. Here’s how to recognize testosterone side effects early and work with your doctor to keep therapy safe and effective.

The relationship

Testosterone replacement therapy (TRT) is prescribed when the body’s own testosterone is low and causing symptoms like fatigue, low libido, and loss of muscle. Large analyses suggest that men with clear symptoms and total testosterone below 350 ng/dL, or free testosterone below 100 pg/mL, are most likely to benefit from TRT.^[1]

The same hormone shifts that improve energy and sex drive also drive testosterone side effects. As testosterone rises, the body makes more red blood cells, oil glands become more active, sperm production may shut down, and fluid balance shifts. These changes can raise blood pressure, thicken the blood, worsen acne, suppress fertility, and aggravate sleep apnea.^[2]

Modern randomized trials show that, in carefully selected men without major uncontrolled heart disease, TRT does not clearly raise the rate of heart attacks or strokes compared with placebo. But more subtle effects such as a 2–5 mmHg rise in blood pressure and a steady climb in hematocrit, the percentage of blood made up of red cells, are common enough that they must be tracked and managed.^[2],[3]

How it works

To understand testosterone side effects, it helps to see what testosterone does in different tissues and how TRT changes normal hormone loops. Here are the main pathways.

Testosterone and red blood cell production

Testosterone stimulates the kidneys to make more erythropoietin, a hormone that signals the bone marrow to produce red blood cells. This can raise hemoglobin and hematocrit, a condition called erythrocytosis, which means “too many red blood cells.”^[3]

Meta-analyses show that up to 15–20% of men on TRT develop a hematocrit of 54% or higher, a common safety threshold where guidelines advise lowering the dose, switching formulations, or using therapeutic phlebotomy, which is a controlled blood draw to reduce blood thickness.^[3],[4]

Most expert groups recommend checking hematocrit at baseline, 3–6 months after starting TRT, and at least yearly. A hematocrit above 54% should trigger action, and many clinicians start adjusting therapy once levels creep above 50–52%, especially in men with cardiovascular risk.^[4]

Fluid balance and blood pressure

Testosterone affects the kidneys’ handling of sodium and water, and it may increase vascular tone, which is the tightness of blood vessel walls. These shifts can raise blood pressure by a few points and may unmask previously controlled hypertension.^[2],[5]

In randomized trials, men on TRT often have small but measurable increases in systolic blood pressure compared with placebo. For someone starting with borderline readings, this can be enough to cross into the hypertensive range, defined as 130/80 mmHg or higher in many guidelines.^[5]

Skin, oil glands, and acne

Testosterone is converted in the skin to dihydrotestosterone (DHT), a more potent androgen that strongly stimulates sebaceous glands. Sebaceous glands are small skin structures that make oil, or sebum. When sebum production rises, pores clog more easily and can lead to acne and oily skin.

Topical gels and higher-dose injectable TRT, which cause faster hormone swings, are more likely to cause noticeable skin-related testosterone side effects. Dermatology data suggest that more stable testosterone levels may reduce acne risk compared with peak-and-trough dosing patterns.

Fertility and the brain–testicle loop

The hypothalamus–pituitary–gonadal (HPG) axis is the hormone feedback loop that controls testosterone and sperm. The hypothalamus and pituitary are brain regions that release signals to the testes. When you take external testosterone, the brain senses high levels and reduces luteinizing hormone (LH) and follicle-stimulating hormone (FSH), which are signals that tell the testes to make testosterone and sperm.

This shutdown can sharply lower sperm counts and even cause azoospermia, which means no sperm in the semen. Studies show that many men on TRT for several months see sperm counts drop below levels needed for reliable fertility, and recovery after stopping TRT can take 6–12 months or more.^[6]

Prostate growth and urinary symptoms

The prostate is a small gland below the bladder that helps produce semen. It is sensitive to DHT, which is made from testosterone inside the gland. TRT usually causes a modest rise in prostate size and prostate-specific antigen (PSA), a protein measured in blood as a prostate marker.^[7]

Large reviews have not shown a clear increase in prostate cancer rates with TRT in men who are properly screened, but TRT can worsen lower urinary tract symptoms in some men with existing benign prostatic hyperplasia, or BPH, which is noncancerous prostate enlargement that makes urination harder.^[7]

Conditions linked to it

Most testosterone side effects are manageable when therapy is tailored and monitored. Still, several clinical conditions are linked to TRT and deserve clear discussion before starting.

• Erythrocytosis and clot risk: Elevated hematocrit above 54% is the most consistent lab side effect of TRT. Very high levels may increase the risk of blood clots, particularly in men with other risk factors such as smoking, obesity, or inherited clotting disorders.^[3],[4]
• Hypertension and cardiovascular strain: Small average rises in blood pressure are common. In men with pre-existing heart disease, these changes could add up, which is why guidelines stress careful selection and follow-up for anyone with recent heart attack, stroke, or uncontrolled heart failure.^[2],[5]
• Reduced fertility: TRT is effectively a male contraceptive for many men. Long-term use can suppress sperm counts to near zero. Recovery is often possible but not guaranteed, and it may take many months after stopping therapy.^[6]
• Worsening sleep apnea: Obstructive sleep apnea is a condition where breathing repeatedly stops during sleep. TRT can worsen apnea severity in predisposed men, possibly by affecting upper-airway muscles and central breathing control.^[8]
• Acne, hair loss, and gynecomastia: Skin changes, male pattern baldness in genetically prone men, and breast tissue growth called gynecomastia can all appear or accelerate with TRT through shifts in DHT and estradiol, which is estrogen made from testosterone.^,[7]

Limitations note: Evidence on long-term cardiovascular and prostate cancer risk with TRT is still evolving. Many trials are short, involve selected lower-risk men, and use different TRT doses and formulations. That means current data are reassuring for properly selected patients but cannot guarantee safety for every man or every regimen.

Symptoms and signals

Knowing what to watch for makes it easier to catch testosterone side effects early. Bring any of the following changes to your clinician’s attention.

• Blood pressure and circulation:
  • New or worsening headaches, especially in the morning
  • Shortness of breath with light activity or climbing stairs
  • Facial flushing or a sense of “pressure” in the head
  • Home blood pressure readings creeping above 130/80 mmHg
• Blood thickness:
  • Unusual fatigue or sluggishness despite good sleep
  • Reddened or “ruddy” complexion
  • Dizziness or visual changes when exerting yourself
• Skin and hair:
  • New acne on face, chest, or back
  • Noticeably oilier skin or scalp
  • Faster recession of the hairline or thinning at the crown
• Fertility and sexual function:
  • Difficulty conceiving after 6–12 months of trying
  • Changes in testicle size or firmness
  • Breast tenderness or swelling around the nipples
• Prostate and urinary tract:
  • Weak urinary stream or trouble starting urination
  • Needing to urinate more often, especially at night
  • Burning, blood in urine, or pain should be evaluated urgently
• Sleep and breathing:
  • Loud snoring noticed by a partner
  • Pauses in breathing during sleep
  • Waking unrefreshed or with morning headaches
• Mood and energy:
  • New irritability, aggression, or anxiety
  • Energy crashing between injections if dosing intervals are long

What to do about it

Testosterone side effects are not a reason to panic, but they are a reason to have a clear plan. A structured approach helps you and your clinician stay ahead of problems.

1. Step 1: Get the right testing before and during TRT

   Before you start TRT, confirm true hypogonadism, which means low testosterone with consistent symptoms. This requires at least two early-morning total testosterone tests on different days, and often a free testosterone level when total testosterone is borderline but symptoms are strong.^[1]

   A thorough baseline panel usually includes:

   • Total and free testosterone
   • LH and FSH to evaluate the HPG axis
   • Hematocrit and hemoglobin
   • PSA and digital rectal exam for men over 40–45 or with risk factors
   • Lipid panel, fasting glucose, and liver function tests
   • Blood pressure and body mass index

   Once on TRT, most guidelines recommend checking testosterone, hematocrit, and PSA at 3 months, 6 months, and then every 6–12 months, with more frequent checks if values are borderline or doses change.^[4],[7]

2. Step 2: Combine lifestyle, dosage, and formulation choices

   Many testosterone side effects can be reduced by how you dose and what you do outside the clinic.

   • Use the lowest effective dose: Aim for testosterone levels in the mid-normal range, not the high-athlete range. Overshooting your dose increases erythrocytosis, acne, and mood swings without proven extra benefit.^[2],[3]
   • Pick a steady formulation: Smaller, more frequent injections or transdermal gels can smooth hormone ups and downs. This may ease mood swings and some cardiovascular strain compared with large, infrequent injections that cause peaks and troughs.
   • Protect your blood pressure: Limit sodium, moderate alcohol, maintain a healthy weight, and keep up regular exercise. These habits lower baseline blood pressure and help buffer TRT-related increases.^[5]
   • Preserve fertility when needed: If you want children in the near future, discuss alternatives such as selective estrogen receptor modulators or human chorionic gonadotropin (hCG), which can raise testosterone without shutting down sperm production in some men.^[6]
   • Treat sleep apnea: If you snore loudly or have known sleep apnea, make sure it is evaluated and treated, often with continuous positive airway pressure (CPAP), before and during TRT.
   • Target skin side effects: Mild acne often responds to over-the-counter washes with benzoyl peroxide. More serious cases may need prescription creams or oral medications from a dermatologist.
3. Step 3: Adjust early if warning signs appear

   Testosterone side effects are usually reversible when caught early. Do not wait for them to “fix themselves” if you see clear patterns.

   • If hematocrit climbs toward or above 54%: Your clinician may lower the dose, lengthen the dosing interval, switch from injections to gel, or prescribe therapeutic phlebotomy until levels normalize.^[3],[4]
   • If blood pressure rises: Tighten lifestyle measures, review all supplements and medications, and consider dose reduction. Some men need adjustment of blood pressure medications when starting TRT.
   • If PSA rises quickly or urinary symptoms worsen: Urologic evaluation is essential. Sometimes TRT is paused while prostate issues are clarified.
   • If mood becomes unstable: Switching to a steadier formulation or adjusting the dose often helps. In some, testosterone levels that are too high can feel as uncomfortable as levels that are too low.
   • If fertility is a priority: Stopping TRT and starting medications to restart the HPG axis may be necessary. A reproductive endocrinologist or male fertility specialist can help.

Myth vs Fact: Clearing up common beliefs about testosterone side effects

• Myth: “Testosterone always causes heart attacks.”
  
  Fact: In men carefully screened for heart disease and monitored regularly, large trials have not shown a clear increase in major heart attacks or strokes compared with placebo, though small changes in blood pressure and blood counts still matter.^[2],[5]
• Myth: “TRT will definitely give you prostate cancer.”
  
  Fact: Current evidence does not show higher prostate cancer rates in men on TRT who were properly screened and followed. TRT is avoided in known prostate cancer but is not automatically a cause of cancer on its own.^[7]
• Myth: “If side effects show up, you have to stop TRT forever.”
  
  Fact: Many testosterone side effects respond to dose changes, schedule adjustments, or switching formulations. Some men do pause therapy, but many continue safely with a revised plan.
• Myth: “Testosterone therapy and steroids are the same thing as bodybuilding abuse.”
  
  Fact: Clinical TRT aims to restore normal physiological levels in men with deficiency. Supraphysiologic dosing used in some bodybuilding circles is much higher and brings a different, higher risk profile.
• Myth: “If a little testosterone feels good, more will feel better.”
  
  Fact: Benefits often plateau once levels are mid-normal, while side effects rise with higher doses. The goal is balance, not maximum numbers.

Bottom line

Testosterone replacement therapy can be life-changing for men with true deficiency, but it is not a simple “set and forget” prescription. The same biology that restores energy, libido, and muscle can raise blood pressure, thicken the blood, suppress fertility, and aggravate skin and sleep problems. Well-run TRT programs use clear diagnostic thresholds, choose the lowest effective dose, and track hematocrit, PSA, and blood pressure from the start. With that structure in place, most testosterone side effects can be predicted, detected early, and managed before they threaten long-term health.

References

1. Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. The Journal of clinical endocrinology and metabolism. 2018;103:1715-1744. PMID: 29562364
2. Fernández-Balsells MM, Murad MH, Lane M, et al. Clinical review 1: Adverse effects of testosterone therapy in adult men: a systematic review and meta-analysis. The Journal of clinical endocrinology and metabolism. 2010;95:2560-75. PMID: 20525906
3. Coviello AD, Kaplan B, Lakshman KM, et al. Effects of graded doses of testosterone on erythropoiesis in healthy young and older men. The Journal of clinical endocrinology and metabolism. 2008;93:914-9. PMID: 18160461
4. Corona G, Maseroli E, Rastrelli G, et al. Cardiovascular risk associated with testosterone-boosting medications: a systematic review and meta-analysis. Expert opinion on drug safety. 2014;13:1327-51. PMID: 25139126
5. Snyder PJ, Bhasin S, Cunningham GR, et al. Effects of Testosterone Treatment in Older Men. The New England journal of medicine. 2016;374:611-24. PMID: 26886521
6. Liu PY, Handelsman DJ. The present and future state of hormonal treatment for male infertility. Human reproduction update. 2003;9:9-23. PMID: 12638778
7. Twitchell DK, Pastuszak AW, Khera M. Controversies in Testosterone Therapy. Sexual medicine reviews. 2021;9:149-159. PMID: 33309270
8. Hoyos CM, Yee BJ, Phillips CL, et al. Body compositional and cardiometabolic effects of testosterone therapy in obese men with severe obstructive sleep apnoea: a randomised placebo-controlled trial. European journal of endocrinology. 2012;167:531-41. PMID: 22848006