Testosterone and Heart Health: Why the Right Level Matters

Testosterone and heart health have a more complicated relationship than simply “higher is better.” Testosterone plays an important role in men's health, influencing energy, muscle mass, sexual function and overall well-being. But emerging research suggests that both low and high testosterone levels may be associated with heart-rhythm concerns in some men.

A 2026 review published in the Journal of the Endocrine Society examined testosterone, testosterone replacement therapy (TRT) and atrial fibrillation (AFib). Here's what the latest research may mean for men concerned about testosterone and cardiovascular health.†

How Are Testosterone and Heart Health Connected?

Testosterone can influence more than muscle mass, energy and sexual function. Researchers have also investigated how testosterone levels may relate to cardiovascular health and the electrical activity that regulates heart rhythm.

One area of particular interest is atrial fibrillation, commonly called AFib. AFib is a type of irregular heartbeat in which the heart's upper chambers beat irregularly.

For years, researchers have observed associations between low testosterone and an increased risk of AFib. However, newer research suggests the relationship between testosterone levels and atrial fibrillation may not be as straightforward as previously thought.

Can Low Testosterone Affect Heart Rhythm?

Low testosterone has been associated with an increased risk of AFib in some research.

In one large study involving more than 76,000 U.S. veterans, men whose testosterone levels returned to normal following testosterone replacement therapy had a lower rate of developing AFib than certain comparison groups.†

That finding raised an interesting possibility: for men with genuinely low testosterone, restoring testosterone to an appropriate range could potentially have effects beyond addressing the traditional symptoms of testosterone deficiency.

However, association does not prove cause and effect, and newer research has added important context.

Can Testosterone Replacement Therapy Increase AFib Risk?

The relationship between testosterone replacement therapy and heart health received additional attention following the large TRAVERSE trial.

TRAVERSE studied more than 5,200 men between the ages of 45 and 80 who had low testosterone and either cardiovascular disease or an increased risk of cardiovascular disease.

Researchers found that testosterone therapy did not increase the overall rate of major cardiovascular events such as:

  • Heart attack
  • Stroke
  • Cardiovascular death

However, researchers observed one important difference involving AFib.

Approximately 3.5% of men receiving testosterone developed AFib compared with 2.4% receiving placebo.

This does not establish that TRT causes AFib in everyone. Other research has not consistently found the same increase in risk, making the relationship between TRT and AFib an area that requires additional investigation.

Is There an Ideal Testosterone Level for Heart Health?

One of the more interesting ideas emerging from the research is that testosterone may have a “sweet spot.”

Rather than assuming higher testosterone is always better, some evidence suggests that both very low and high testosterone levels may be associated with greater AFib risk, while levels somewhere in the middle may be associated with lower risk.†

The authors of the 2026 review discuss a total testosterone range of approximately 350–550 ng/dL as a possible mid-range target.

However, this should not be interpreted as a universal recommendation.

An individual's appropriate testosterone level can depend on factors including age, symptoms, overall health, cardiovascular risk and other laboratory findings. More clinical research is needed to determine the testosterone range that provides the optimal balance of benefits and risks.

KEY TAKEAWAY

When it comes to testosterone and heart health, the goal may be restoring appropriate levels rather than simply pushing testosterone as high as possible.†

Why Could High Testosterone Affect Heart Rhythm?

Researchers are investigating several possible mechanisms that could help explain the relationship between testosterone and AFib.

Testosterone can influence the electrical processes that control how the heart beats. At higher levels, testosterone may alter how quickly cardiac cells electrically reset between beats.

In susceptible individuals, these changes could potentially make certain abnormal heart rhythms easier to develop.

Low testosterone may affect cardiac cells differently, including changes involving calcium activity that could also influence electrical signaling.

These mechanisms may help explain why researchers are investigating whether both ends of the testosterone range could be relevant to heart rhythm.

Does This Mean Testosterone Replacement Therapy Is Dangerous?

Not necessarily.

The available evidence is more nuanced.

While the TRAVERSE trial observed more cases of AFib among men receiving testosterone, an analysis of 106 randomized, placebo-controlled trials did not find a statistically significant overall increase in AFib.

Rather than establishing TRT as universally safe or dangerous, current evidence suggests that its effects and risks may depend considerably on the individual.

Factors that may influence cardiovascular risk include:

  • Age
  • Cardiovascular health
  • Obesity
  • Sleep apnea
  • High blood pressure
  • Diabetes
  • Existing heart-rhythm disorders

For this reason, testosterone replacement therapy should be discussed with an appropriate healthcare professional and individualized according to a person's symptoms, laboratory results and overall health.

Why Total Testosterone Doesn't Tell the Whole Story

A testosterone blood test typically measures total testosterone, but that number doesn't always provide a complete picture.

One reason is sex hormone-binding globulin (SHBG).

SHBG is a protein that binds to testosterone in the bloodstream and affects how much testosterone is available for the body to use. SHBG levels can themselves be influenced by factors such as age, body weight, diabetes, thyroid function and liver health.

For some men—particularly those with abnormal SHBG levels—measuring or calculating free testosterone may provide additional information when a clinician is evaluating possible testosterone deficiency and considering treatment.

This is another reason why focusing on a single testosterone number without considering the individual's overall health can be misleading.

Who Should Be More Careful With TRT?

Men with existing cardiovascular risk factors may require closer evaluation and monitoring before and during testosterone replacement therapy.†

This may be particularly important for men with:

  • Obesity
  • Sleep apnea
  • Poorly controlled high blood pressure
  • Cardiovascular disease
  • Existing heart-rhythm problems
  • A history of AFib

Men who already have AFib may require especially individualized decisions about testosterone therapy.

The 2026 review also cautions against routinely pushing testosterone into the upper-normal range, particularly in men with elevated cardiovascular or heart-rhythm risk.†

Testosterone and Heart Health: Frequently Asked Questions

Can low testosterone affect your heart?

Research has found associations between low testosterone and cardiovascular conditions, including AFib. However, an association does not necessarily mean that low testosterone directly causes a heart-rhythm disorder. Individual cardiovascular health and other risk factors also matter.

Does TRT increase the risk of AFib?

The evidence is mixed. The TRAVERSE trial reported AFib in 3.5% of testosterone-treated participants versus 2.4% receiving placebo. However, an analysis of 106 randomized, placebo-controlled trials did not find a statistically significant overall increase in AFib.

Is higher testosterone always better?

No. Emerging research suggests that when considering testosterone and heart health, higher isn't necessarily better. Both very low and high levels may be associated with increased AFib risk in some populations.

What testosterone level is best?

There is no single ideal testosterone level for every man. The 2026 review discusses approximately 350–550 ng/dL as a potential mid-range target, but this should not be considered a universal clinical recommendation. Age, symptoms, health history and other laboratory findings can influence what's appropriate for an individual.

What should be monitored during testosterone replacement therapy?

Monitoring should be individualized by a healthcare professional. Depending on the patient, this may include testosterone levels, hematocrit, blood pressure and cardiovascular risk factors.†

The Bottom Line on Testosterone and Heart Health

The emerging science around testosterone and heart health points toward an important concept: balance may matter more than maximizing testosterone levels.

Low testosterone has been associated with increased AFib risk, but high testosterone levels may also carry potential risks. For men who have a medical need for testosterone replacement therapy, restoring testosterone toward an appropriate range may therefore be preferable to simply pursuing the highest possible number.†

TRT should be individualized based on symptoms, laboratory findings, medical history and overall health, with appropriate monitoring by a healthcare professional.

Most importantly, the science is still developing. More clinical trials are needed to determine exactly which testosterone ranges provide the best balance between potential benefits and risks.

Reference

Maligireddy AR, et al. Association of testosterone and testosterone replacement therapy with atrial fibrillation: an updated review. Journal of the Endocrine Society. September 1, 2026.

Medical Disclaimer: This article is for informational and educational purposes only and is not medical advice. Testosterone replacement therapy is a medical treatment and should be discussed with a qualified healthcare professional.

† These statements have not been evaluated by the Food and Drug Administration. These statements are not intended to diagnose, treat, cure or prevent disease.