Testosterone is an integral part of men’s sexual wellness. Testosterone helps makes a man a man. Unfortunately, some men have no choice but to rely on testosterone therapy to get enough of this essential hormone. Testosterone therapy comes with a few concerns, including the potential connection between testosterone replacement and blood clots. Our own Dr Rand McClain weighs in on the question, “can testosterone cause blood clots?”
The short answer is “no.” Most of the scientific evidence out there shows that, when taken properly, testosterone doesn’t cause blood clots. However, some studies do indicate there is a potential increased risk for those who have underlying genetic clotting disorders. That’s why it’s important that your doctor understands your medical history.
Testosterone also increases the number of red blood cells. This increase could, in theory, thicken your blood and lead to clots. There’s no proof that this is what happens, however.
Testosterone signals the body that it’s time to produce more red blood cells. These are the cells that carry oxygen around the body. Most people on testosterone replacement therapy (TRT) will see increased red blood cell count. The more of these cells we have, the thicker blood becomes. Some people think thicker blood leads to increased blood clot risk. However, there are no studies that show a connection between red blood cell count and blood clot risk.
Some people attribute the increased red blood cell count from TRT with polycythemia. This is a condition that affects bone marrow, which produces red and white blood cells. Those with polycythemia often produce too many red blood cells. They also produce an abundance of white blood cells and platelets. As you might know, platelets are partly responsible for blood clotting. Too many platelets leads to blood clot issues. Some clinicians believe testosterone can cause polycythemia, but that’s not true. Testosterone only increases red blood cell count and doesn’t affect white blood cell or platelet production.
Several studies have shown that men with underlying clotting disorders are at risk of blood clots when taking testosterone. The clots develop within the first six months of treatment. The CDC estimates roughly 5-8% of Americans have at least one genetic risk factor for a clotting disorder. The results show how important it is that you obtain your family medical history and share it with your care provider before starting testosterone therapy.
Several studies have looked into the potential connection of testosterone replacement therapy and blood clot risk. Two large studies looked at large groups of men taking testosterone to get a clear answer. One study didn’t find a link but the other one showed a potential increased risk. Here’s a breakdown of the studies, the results, and what they all mean.
This particular study looked at 30,572 men over the age of 40. Researchers compared the rate of blood clots on men taking testosterone compared to men that weren’t. The research showed that testosterone therapy didn’t increase the risk of VTE (the medical term for blood clots.) While this study failed to show a connection, another study questioned those findings.
This second study appears to contradict the first. This study seems to show there was an increased risk of blood clots while taking TRT. The study looked at 19,215 men with confirmed blood clots, comparing them to 909,530 people without blood clots. They then examined whether or not men taking TRT were more at risk of developing clots compared to the men who weren’t taking hormones. The research showed that, overall, testosterone therapy doesn’t increase blood clot risk.
However, when the researchers changed their approach and looked at just the first six months of taking testosterone, they reported there was increased risk of blood clots. Put another way, this would mean that men were more likely to develop blood clots during the first six months of TRT. There was no increased risk after six months.
As worrying as the results of the second study might sound, they should be taken with a grain of salt. The study found an increase of ten additional clots (for the first six months) per 10,000 person years. This means that if a physician had 1,000 men on testosterone therapy, only one of those men would develop a blood clot per year compared to men not taking TRT. The average rate of blood clots in the general population is around 1-2 per 1,000 people. Ultimately, physicians would see two or three people with blood clots instead of one or two per thousand men.
Most people understand that taking testosterone therapy, especially with injections, increases total red blood cell count in the blood stream. Theoretically, that increase could make blood thicker. This thicker blood would have more difficulty going through blood vessels smoothly. Every doctor knows that blood is more likely to clot when it stops moving. When taken together, this information suggests that increases in red blood cell count from testosterone could increase the chances of developing a blood clot.
However, many studies have looked at the issue and found that this isn’t the case. Study after study shows there is no straight connection between TRT and blood clot risk. We know this because men with naturally high testosterone levels aren’t at increased risk, nor are people with other health conditions that increase red blood cell count such as lung disease.
You can rest assured that testosterone replacement and blood clots are not as connected as some would have you believe.