November 2, 2026, 12:49 pm | Read time: 3 minutes
Testosterone is considered the hormone for strength, muscles, and male vitality. But more isn’t necessarily better: High testosterone levels could be linked to an increased risk of heart arrhythmias. But when is testosterone actually too high? An endocrinologist explains the potential health consequences of an excess and what men should watch out for.
In men, testosterone is primarily produced in the testes. The hormone plays an important role in muscle building, bone health, libido, and sperm production. Its impact on heart health, however, is not yet fully understood. A recent review examines whether both low and high testosterone levels could increase the risk of atrial fibrillation.1 In this heart rhythm disorder, electrical signals in the atria become disordered, which can increase the risk of stroke. The authors suspect a U-shaped relationship: At both ends of the testosterone distribution, the risk could be elevated. However, this connection has not been proven.
How an Endocrinologist Assesses the Possible Connection
An important basis of the review is the TRAVERSE study with more than 5,000 men who had proven testosterone deficiency and increased cardiovascular risk. Under testosterone therapy, atrial fibrillation occurred slightly more often than under placebo. Severe cardiovascular events such as heart attack, stroke, or cardiovascular death were not more frequent overall.
“This U-curve is not really supported by the data so far,” says Dr. Tim Hollstein, senior physician and specialist in internal medicine, endocrinology, and diabetology at the University Hospital Schleswig-Holstein in Kiel. The previous studies differed, among other things, in terms of the age and health status of the participants.
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When Is Testosterone Too High?
There is no universally valid threshold. The upper limit of the reference range depends, among other things, on the laboratory and the measurement method. “A repeatedly higher value should be clarified,” explains Hollstein. It is also important how much testosterone is freely available: Transport proteins in the blood can increase the total value, even though free testosterone is normal.
Possible causes of elevated levels include the intake of testosterone supplements or anabolic steroids. Rarely, hormone-producing tumors or congenital disorders may be behind it. Slightly elevated natural levels often cause no symptoms in men. With a significant excess, acne, oily skin, or increased hair loss can occur. “The testosterone level cannot be reliably determined by appearance, sexual desire, or behavior,” emphasizes the expert.
It’s different with additionally taken hormones: They can suppress the body’s own hormone production and sperm formation. Smaller testes, reduced fertility, high blood pressure, and an increased number of red blood cells are possible consequences. Long-term anabolic steroid use can also affect blood lipids; certain anabolic tablets can damage the liver.
When Is Treatment Sensible?
In cases of proven testosterone deficiency and appropriate symptoms, a medically supervised replacement therapy can be sensible. Men with normal levels should not independently take additional testosterone. Those already undergoing treatment should not discontinue therapy without consulting a doctor.
For men with naturally high values within the normal range, Hollstein currently sees no reason to lower them as a precaution. Whether testosterone itself increases the risk of atrial fibrillation and whether lowering it would help is not clarified. An unusual value should be medically examined. In testosterone therapy, regular monitoring of blood pressure, blood count, and hormone levels is important.