Testosterone (TRT)
Prescription testosterone treats men with confirmed low testosterone. In large placebo-controlled trials it modestly improved sexual desire and activity, mood and anemia, but it did not improve memory or prevent fractures, did not prevent diabetes in the largest trial, and had small, inconsistent effects on energy. In the 5,246-man TRAVERSE trial, major heart events were no more common than with placebo over about 3 years, but blood clots in the lung, atrial fibrillation and kidney injury were more frequent.
Prescription medication: not a dietary supplement
This is an FDA-approved (or investigational) drug, not a supplement. It requires a prescription and medical supervision. The information below summarizes clinical-trial evidence for education only. It is not a recommendation to obtain or use it without a doctor.
Quick decision guide
May help most
Men with symptoms of low testosterone, confirmed by two low morning blood tests, treated by a prescriber who monitors blood counts, blood pressure and the prostate
Common dosing range
Set and adjusted by a prescriber to blood levels; for example AndroGel 1.62% gel 40.5 mg each morning, or testosterone cypionate 50 to 400 mg injected every 2 to 4 weeks
When to expect effects
Sexual desire and mood: improvement seen by 6 to 12 months in trials; hemoglobin: by 6 to 12 months
Watch out for
Suppresses sperm production; raises red blood cell count and blood pressure; gel can transfer to women and children through skin contact
What is it
Testosterone therapy, often called TRT, is a prescription treatment that replaces testosterone in men whose bodies make too little of it, a condition called hypogonadism. FDA-approved forms include gels rubbed on the skin every day, a skin patch, a buccal system placed on the gum, injections into the muscle (testosterone cypionate, enanthate or undecanoate), a weekly enanthate injection under the skin, pellets placed under the skin every 3 to 6 months, and oral testosterone undecanoate capsules. Testosterone is a Schedule III controlled substance in the United States, so every legitimate product needs a prescription. The labels approve it for low testosterone caused by a problem in the testes, the pituitary gland or the hypothalamus. For years the labels also said that safety and efficacy had not been established for low testosterone due to aging alone; in June 2026 FDA asked manufacturers to remove that statement, so some labels may still carry it while they are updated.
Is it worth it for you?
Use this as a quick fit check, not a diagnosis.
Worth considering if…
Probably skip if…
Evidence at a glance
| Goal | Effect | Best fit | Time |
|---|---|---|---|
sexual desire and sexual activity Good Evidence | Moderate; about 0.5 more sexual acts per day than placebo in TRAVERSE, sustained to 2 years | Men with low libido and two clearly low morning testosterone levels | Seen at 6 months, the first TRAVERSE check, and maintained at 12 to 24 months |
low mood and depressive symptoms Good Evidence | Small | Men with confirmed low testosterone and mild depressive symptoms | Within 1 year in trials |
anemia (low hemoglobin) Good Evidence | About 11 to 14 percentage points more men had anemia corrected than with placebo (TRAVERSE, 6 and 12 months) | Men with confirmed low testosterone and mild anemia | 6 to 12 months |
memory and thinking Good Evidence | None | None identified | No effect at 6 or 12 months |
fracture prevention Good Evidence | No reduction; numerically more fractures (3.50% vs 2.46%) | None identified | No benefit over about 3 years |
diabetes prevention and blood sugar control Good Evidence | No significant difference in progression or glucose control | None identified in TRAVERSE | No benefit over up to 4 years |
erectile function Limited Evidence | Small in one trial (2.64 points on a 0 to 30 erectile function score); none in the larger, longer trial | Unclear; a small benefit appeared only in men 65 and older with low testosterone (below 275 ng/dL) in the Testosterone Trials | Not established |
bone density Limited Evidence | About 6.8 percentage points more spine trabecular bone density than placebo after 1 year | Older men with low testosterone (bone density measure only) | 12 months |
walking and physical function Limited Evidence | Small; about 9 to 14 meters farther in a 6-minute walk in some groups, no change in falls | Older men with low testosterone who already walk at a normal pace | 12 months |
energy and fatigue Limited Evidence | Small; no benefit on the main fatigue measure in one trial, a small gain in energy in the larger trial | Unclear | Not established |
sleep quality Limited Evidence | None | None identified | No benefit seen |
sexual desire and sexual activity
- Effect
- Moderate; about 0.5 more sexual acts per day than placebo in TRAVERSE, sustained to 2 years
- Best fit
- Men with low libido and two clearly low morning testosterone levels
- Time
- Seen at 6 months, the first TRAVERSE check, and maintained at 12 to 24 months
low mood and depressive symptoms
- Effect
- Small
- Best fit
- Men with confirmed low testosterone and mild depressive symptoms
- Time
- Within 1 year in trials
anemia (low hemoglobin)
- Effect
- About 11 to 14 percentage points more men had anemia corrected than with placebo (TRAVERSE, 6 and 12 months)
- Best fit
- Men with confirmed low testosterone and mild anemia
- Time
- 6 to 12 months
memory and thinking
- Effect
- None
- Best fit
- None identified
- Time
- No effect at 6 or 12 months
fracture prevention
- Effect
- No reduction; numerically more fractures (3.50% vs 2.46%)
- Best fit
- None identified
- Time
- No benefit over about 3 years
diabetes prevention and blood sugar control
- Effect
- No significant difference in progression or glucose control
- Best fit
- None identified in TRAVERSE
- Time
- No benefit over up to 4 years
erectile function
- Effect
- Small in one trial (2.64 points on a 0 to 30 erectile function score); none in the larger, longer trial
- Best fit
- Unclear; a small benefit appeared only in men 65 and older with low testosterone (below 275 ng/dL) in the Testosterone Trials
- Time
- Not established
bone density
- Effect
- About 6.8 percentage points more spine trabecular bone density than placebo after 1 year
- Best fit
- Older men with low testosterone (bone density measure only)
- Time
- 12 months
walking and physical function
- Effect
- Small; about 9 to 14 meters farther in a 6-minute walk in some groups, no change in falls
- Best fit
- Older men with low testosterone who already walk at a normal pace
- Time
- 12 months
energy and fatigue
- Effect
- Small; no benefit on the main fatigue measure in one trial, a small gain in energy in the larger trial
- Best fit
- Unclear
- Time
- Not established
sleep quality
- Effect
- None
- Best fit
- None identified
- Time
- No benefit seen
Evidence for 11 uses
AI-assisted evidence assessment. Talk to your doctor before relying on any single supplement.
sexual desire and sexual activity
Disease adjunctIn the Testosterone Trials, 790 men aged 65 or older with testosterone below 275 ng/dL and symptoms used testosterone gel or placebo gel for 1 year. Testosterone raised levels to the mid-normal range for young men and increased sexual activity and sexual desire; in the 470 men with low libido it improved 10 of 12 measures of sexual activity. In the TRAVERSE sexual function study, 1,161 men aged 45 to 80 with low libido and two testosterone levels below 300 ng/dL had about half a sexual act per day more than placebo at 6 and 12 months (0.49 and 0.47), and the effect held at 24 months. Sexual desire also improved. These trials studied men with clearly low levels and low libido; they say nothing about men with normal levels.
Bottom line: The most consistent benefit: more sexual desire and activity in men with truly low testosterone.
low mood and depressive symptoms
Disease adjunctIn TRAVERSE, men on testosterone gel had modest but statistically significant improvements in mood compared with placebo, both among the 2,643 men with significant depressive symptoms and among all 5,204 men. Only 49 men met strict criteria for persistent low-grade depression (formerly called dysthymia), and in that small group testosterone made no significant difference, possibly because the group was too small to tell. The Testosterone Trials in men 65 and older likewise found slightly better mood and less severe depressive symptoms after 1 year. Neither trial was designed to treat major depression, and the Testosterone Trials excluded men with severe depressive symptoms.
Bottom line: A small lift in mood, not a substitute for depression care.
anemia (low hemoglobin)
Biomarker supportIn TRAVERSE, 815 men with hypogonadism had anemia (hemoglobin below 12.7 g/dL). Anemia corrected in more men on testosterone gel than on placebo: 41.0% vs 27.5% at 6 months and 45.0% vs 33.9% at 12 months. Among men without anemia, fewer on testosterone developed it. In the Testosterone Trials, in a small group of 62 men 65 and older whose anemia had no known cause, 58.3% were no longer anemic after 12 months of testosterone vs 22.2% on placebo. The same effect has a downside: in that trial 6 of 336 testosterone-treated men who were not anemic at the start reached 17.5 g/dL or higher, which is why prescribers check blood counts. Whether correcting anemia this way improves overall health was not established.
Bottom line: Raises hemoglobin reliably; that helps anemia but is also the main reason for blood-count monitoring.
memory and thinking
No benefit foundThe Cognitive Function Trial followed 493 men aged 65 or older (mean age 72) with low testosterone and age-associated memory impairment for 1 year. Testosterone gel did not improve delayed recall of a story (difference -0.07 points), visual memory, executive function or spatial ability compared with placebo. In TRAVERSE, testosterone also did not improve cognition.
Bottom line: Testosterone did not improve memory or thinking.
fracture prevention
No benefit foundThe TRAVERSE fracture study followed 5,204 men aged 45 to 80 with hypogonadism and heart disease or high heart risk for a median of 3.19 years. A clinical fracture occurred in 3.50% of men on testosterone gel vs 2.46% on placebo (hazard ratio 1.43; 95% CI 1.04 to 1.97). Testosterone did not lower fracture risk, and fractures were numerically more common. This was a subtrial of a heart-safety study, not a trial of men with osteoporosis.
Bottom line: Testosterone did not prevent fractures; it should not replace proven osteoporosis care.
diabetes prevention and blood sugar control
No benefit foundIn TRAVERSE, 1,175 men with hypogonadism and prediabetes were followed for progression to diabetes. Progression did not differ significantly between testosterone and placebo (for example 10.1% vs 14.6% at 24 months; overall P = .49). Among 3,880 men with diabetes, testosterone did not improve blood sugar or HbA1c and did not produce remission more often. The authors concluded that testosterone alone should not be used to prevent or treat diabetes.
Bottom line: Testosterone is not a diabetes treatment.
Evidence is mixed
The Australian T4DM trial (1,007 men aged 50 to 74 with a large waist, testosterone at or below 14.0 nmol/L without pathological hypogonadism, and impaired glucose tolerance or newly diagnosed diabetes, all in a lifestyle program) found fewer men had diabetes on a glucose tolerance test after 2 years with injected testosterone undecanoate than with placebo (12% vs 21%). Hematocrit above 54% occurred in 22% of the testosterone group vs 1% on placebo.
erectile function
Disease adjunctIn the Testosterone Trials, testosterone gel for 1 year improved erectile function in men 65 and older along with desire and activity. However, in the low-libido group, larger rises in testosterone tracked with better desire and activity but not with better erections. In the larger, 2-year TRAVERSE sexual function study of 1,161 men aged 45 to 80, testosterone did not improve erectile function compared with placebo.
Bottom line: Do not expect TRT to fix erections; ask your doctor about other causes and treatments.
Evidence is mixed
The Testosterone Trials found improved erectile function after 1 year; the larger TRAVERSE sexual function study found no improvement over 2 years.
bone density
Biomarker supportIn a Testosterone Trials substudy of 211 men aged 65 or older (mean age 72), 1 year of testosterone gel raised spine trabecular bone density by 7.5% vs 0.8% with placebo and increased estimated bone strength, more in the spine than in the hip. A denser scan did not mean fewer broken bones: in the much larger and longer TRAVERSE fracture study, fractures were not reduced and were numerically more common with testosterone.
Bottom line: Bone density goes up, but fractures did not go down.
walking and physical function
Disease adjunctIn the Testosterone Trials, the Physical Function Trial (390 men 65 and older with limited mobility and slow walking) did not meet its main goal: the share of men who walked at least 50 meters farther in 6 minutes did not differ between testosterone and placebo. Across all 790 men it did (20.5% vs 12.6%), and men on testosterone more often reported that their walking had improved. In men not enrolled in the Physical Function Trial, the gain was about 9 meters in 6 minutes. Falls did not change: 27% in each group had at least one fall.
Bottom line: At most a small improvement in walking; no effect on falls.
Evidence is mixed
The trial designed to test walking missed its main goal; benefits appeared only when all participants were pooled and in secondary analyses.
energy and fatigue
Disease adjunctThe Vitality Trial within the Testosterone Trials (men 65 and older with low testosterone and low vitality) found no significant benefit on its main measure, the FACIT-Fatigue scale, after 1 year, although a secondary vitality score improved slightly. In TRAVERSE, men aged 45 to 80 with hypogonadism had a small but statistically significant improvement in energy with testosterone gel compared with placebo. Any effect on tiredness appears small.
Bottom line: Do not count on TRT to fix fatigue; other causes are worth checking with your doctor.
Evidence is mixed
TRAVERSE (5,204 men aged 45 to 80) found a modest, statistically significant improvement in energy, while the Testosterone Trials Vitality Trial found no benefit on fatigue.
sleep quality
No benefit foundIn TRAVERSE, testosterone gel did not improve sleep quality compared with placebo, either in the 2,643 men with significant depressive symptoms or in all 5,204 men aged 45 to 80. Sleep quality was one of several outcomes in this secondary analysis of the trial.
Bottom line: Testosterone did not improve sleep quality, and it can worsen sleep apnea in some men.
How it works
How to take it
What to track
Bottom line: A prescriber sets and adjusts the dose to blood tests; do not change it yourself.
Safety
Know the common side effects, key cautions, and who should avoid it.
Common side effects
Serious risks
High red blood cell count (polycythemia), which may raise the risk of blood clots. The AndroGel label calls for checking hematocrit before starting, at 3 to 6 months and then yearly, and stopping until it falls if it becomes elevated. In the T4DM trial of injected testosterone undecanoate, hematocrit above 54% occurred in 22% of men vs 1% on placebo.
Higher blood pressure. FDA confirmed the increase class-wide in 2025. Measured 24-hour increases in systolic/diastolic pressure were 1.9/1.3 mm Hg with AndroGel 1.62% after 16 weeks, 3.9/1.5 mm Hg with Xyosted after 12 weeks, and 4.9/2.5 mm Hg with Jatenzo after 4 months. Testosterone is not recommended with uncontrolled high blood pressure.
SourceFDA issues class-wide labeling changes for testosterone products (2025) · U.S. Food and Drug AdministrationAndroGel 1.62% (testosterone gel) prescribing information · DailyMed (FDA label)Xyosted (testosterone enanthate) prescribing information · DailyMed (FDA label)Jatenzo (testosterone undecanoate capsules) prescribing information · DailyMed (FDA label)Blood clots in the legs or lungs. In TRAVERSE, venous blood clots occurred in 1.7% of men on testosterone gel vs 1.2% on placebo, including pulmonary embolism in 0.9% vs 0.5%. Sudden shortness of breath, or leg pain, swelling and warmth, need urgent care.
Atrial fibrillation, other heart rhythm problems and acute kidney injury were more common with testosterone in TRAVERSE (atrial fibrillation 3.5% vs 2.4%; rhythm problems needing intervention 5.2% vs 3.3%; acute kidney injury 2.3% vs 1.5%).
Heart attack and stroke: in TRAVERSE (5,246 men aged 45 to 80 with heart disease or high heart risk, mean treatment 21.7 months), major heart events occurred in 7.0% on testosterone gel vs 7.3% on placebo, meeting the test for no meaningful increase. In 2025 FDA then had the boxed-warning language about an increased risk of adverse cardiovascular outcomes removed from all testosterone products. A smaller 1-year Testosterone Trials study of 138 older men did find a greater increase in noncalcified coronary artery plaque with testosterone, whose meaning is unclear.
Reduced fertility. Testosterone suppresses sperm production; the AndroGel 1.62% label states that reduced fertility is observed in some men on therapy, and the Xyosted label adds that the impact on fertility may be irreversible. In a World Health Organization trial of healthy men given 200 mg testosterone enanthate weekly, sperm disappeared from the semen in an average of 120 days in the men who reached zero; after stopping, sperm counts took a median of 3.7 months to reach 20 million per mL.
Prostate effects: testosterone can worsen benign prostate enlargement and raises PSA. In TRAVERSE, which excluded men with PSA above 3.0 ng/mL or severe urinary symptoms, high-grade prostate cancer occurred in 0.19% on testosterone vs 0.12% on placebo, not a significant difference. Testosterone is contraindicated in men with known or suspected prostate cancer.
Boxed warning for gels: secondary exposure. Children have developed signs of early puberty (genital enlargement, pubic hair, aggressive behavior, advanced bone age) after contact with a gel user's skin, and some changes did not fully reverse. Women can also be affected.
Boxed warning for Aveed (testosterone undecanoate injection): pulmonary oil microembolism reactions (urge to cough, shortness of breath, throat tightening, chest pain, fainting) and anaphylaxis, during or right after any injection. It is given only through a restricted program, with 30 minutes of observation after each shot.
Abuse and dependence. Testosterone is a Schedule III controlled substance. Abuse at higher-than-labeled doses, often with other anabolic steroids, has been linked to cardiac arrest, heart attack, heart muscle disease, stroke, liver damage and severe psychiatric effects, and stopping high doses can cause withdrawal with depression, fatigue and craving.
Worsening sleep apnea, especially with obesity or chronic lung disease, and fluid retention that can lead to heart failure in men with existing heart, kidney or liver disease.
Who should avoid it
- Men with breast cancer or known or suspected prostate cancer (contraindicated in the labels)
- Pregnant women (contraindicated), and women and children who could touch a gel user's application site
- Men planning to father a child in the near term (the Endocrine Society recommends against starting testosterone)
- Men with an elevated hematocrit, untreated severe obstructive sleep apnea, severe urinary symptoms, uncontrolled heart failure, a heart attack or stroke within the past 6 months, or an inherited clotting disorder (thrombophilia)
- Men with a prostate nodule, PSA above 4 ng/mL, or PSA above 3 ng/mL with higher prostate cancer risk (for example African American men or men with a father or brother with prostate cancer), unless a urologist has evaluated them first
- Men with uncontrolled high blood pressure (not recommended in the labels)
- Men whose low testosterone has not been confirmed with symptoms and morning blood tests on at least two separate days
Pregnancy & breastfeeding
Testosterone is contraindicated in pregnancy because it can masculinize a female fetus. A pregnant partner can absorb testosterone gel through skin contact, so gel users should wash their hands, let the gel dry, cover the site with clothing and wash it before skin-to-skin contact, as the label directs. For men, testosterone suppresses sperm production and can reduce fertility, possibly permanently, so a couple trying to conceive should discuss this with a doctor before treatment.
Interactions
Androgens can increase sensitivity to oral anticoagulants, and the Depo-Testosterone label lists bleeding in men also taking anticoagulants. The labels recommend more frequent INR and prothrombin time checks, especially when testosterone is started or stopped; the anticoagulant dose may need to be lowered by your prescriber.
In men with diabetes, testosterone can lower blood sugar and change insulin sensitivity, so insulin needs may fall. Watch for low blood sugar and let the prescriber who manages your diabetes know you started testosterone.
Taken together with testosterone they can increase fluid retention, which needs careful monitoring, particularly in men with heart, kidney or liver disease.
Choosing a product
What to look for on the label, and what to be skeptical of.
Look for…
Be skeptical of…
Frequently asked questions
Is testosterone therapy safe for my heart?⌄
The best evidence is the TRAVERSE trial of 5,246 men aged 45 to 80 with heart disease or high heart risk. Over about 3 years, heart attacks, strokes and heart deaths occurred in 7.0% of men on testosterone gel and 7.3% on placebo, and FDA removed the boxed-warning language about increased heart risk in 2025. The same trial found more blood clots in the lungs, atrial fibrillation and kidney injury with testosterone, and testosterone raises blood pressure slightly, so your prescriber should check your blood pressure and blood count regularly.
Will TRT affect my fertility?⌄
Yes, it can. Testosterone from outside the body signals the brain to stop the hormones that drive sperm production, and the labels state that reduced fertility occurs in some men, and at least one label (Xyosted) says the impact on fertility may be irreversible. In a World Health Organization contraception study of healthy men, weekly testosterone injections stopped sperm production in about two thirds of them within 6 months; in that study, sperm counts usually recovered within months after the injections stopped. The Endocrine Society recommends against starting testosterone if you plan to father a child soon. Talk to your doctor before starting if fertility matters to you.
How is low testosterone diagnosed?⌄
The Endocrine Society recommends diagnosing low testosterone only in men who have symptoms and signs of deficiency plus clearly and consistently low levels, measured on fasting morning blood samples and confirmed with a repeat test. The FDA labels likewise require morning measurements on at least two separate days below the normal range before treatment starts. The TRAVERSE trial, for example, enrolled men with two fasting levels below 300 ng/dL and symptoms. A single afternoon test is not enough.
Does TRT raise the risk of prostate cancer?⌄
In TRAVERSE, men screened to exclude high prostate risk (PSA above 3.0 ng/mL or severe urinary symptoms) had similar rates of high-grade prostate cancer on testosterone and placebo (0.19% vs 0.12%), and similar rates of any prostate cancer and urinary retention. PSA did rise more with testosterone. The labels contraindicate testosterone in men with breast cancer or known or suspected prostate cancer and call for prostate evaluation before and during treatment. In June 2026 FDA asked manufacturers to revise the prostate cancer and enlarged-prostate safety information in the labels.
Is TRT approved for low testosterone that comes with aging?⌄
The products are approved for low testosterone caused by a testicular, pituitary or hypothalamic problem. Their labels have said that safety and efficacy in men with age-related low testosterone have not been established. In June 2026 FDA asked manufacturers to remove that statement, so some labels may still carry it while they are updated. In the Testosterone Trials of men 65 and older, testosterone helped sexual function, mood and anemia, but not memory, energy or the main walking test.
Can a testosterone booster supplement replace TRT, or should I add one?⌄
Over-the-counter testosterone boosters are not prescription testosterone. A review of 50 of them found that most claimed to boost testosterone, but published evidence of a testosterone increase existed for only 27 of their 109 ingredients (24.8%), and some exceeded upper intake limits for zinc, niacin or magnesium. FDA has also found products sold as bodybuilding supplements that illegally contain hidden steroids. If you are on TRT, tell your doctor or pharmacist about every supplement you take.
References by claim
sexual desire and sexual activity
low mood and depressive symptoms
Bhasin et al., 2024 · PubMed (2024) link
walking and physical function
Bhasin et al., 2018 · PMC (2018) link
memory and thinking
Resnick et al., 2017 · PMC (2017) link
diabetes prevention and blood sugar control
Safety
AndroGel 1.62% (testosterone gel) prescribing information · DailyMed (FDA label) link
FDA issues class-wide labeling changes for testosterone products (2025) · U.S. Food and Drug Administration link
Xyosted (testosterone enanthate) prescribing information · DailyMed (FDA label) link
Jatenzo (testosterone undecanoate capsules) prescribing information · DailyMed (FDA label) link
Lincoff et al., 2023 · PubMed (2023) link
Budoff et al., 2017 · PMC (2017) link
PMID 1977002 · PubMed (1990) link
Bhasin et al., 2023 · PMC (2023) link
Aveed (testosterone undecanoate injection) prescribing information · DailyMed (FDA label) link
Depo-Testosterone (testosterone cypionate injection) prescribing information · DailyMed (FDA label) link
Bhasin et al., 2018 · PubMed (2018) link
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Disclaimer: This page summarizes published clinical-trial data for educational purposes and is not medical advice or a recommendation to use this prescription medication. Dosing, eligibility, and monitoring must be decided by a licensed prescriber.