" It is reassuring that as far as we can determine, no testosterone associated thromboembolic events have been reported to date."
Rhoden EL, Morgentaler A. Risks of testosterone-replacement therapy and recommendations for monitoring. The New England journal of medicine. 2004;350(5):482-492.
There is a lot of discussion regarding whether testosterone thickens your blood and can cause blood clots. This myth comes from a confusion between a physiologic state called erythrocytosis and a genetic disease called polycythemia vera. When you take testosterone, there is a possibility it will increase your red blood cells. In many cases, it may increase them above what we would consider normal. However, there is no evidence that testosterone causes blood clots (venous thromboembolism) in those without an underlying condition, and no studies proving otherwise. In fact the American Urologic Association (AUA) has made the following guideline statement.
Guideline Statement 19. "Patient should be informed that there is no definitive evidence linking testosterone therapy to a higher incidence of VTE."
There is a Huge Difference in Thrombosis Risk Between TRT and Steroid Abuse!
You often find guys taking testosterone in large doses (usually bodybuilders) will have high red cell count, increasing the risk of blood clots. In this situation, the standard advice given to guys is to give blood to lower their blood counts; this is called therapeutic phlebotomy. However, this practice does not apply to men who are on testosterone replacement therapy (TRT) to maintain their optimum levels.
When undertaking TRT under a reputable doctor's guidance, there is no risk of developing blood clots unless you already have that risk due to underlying conditions. So you run the same chance of thrombosis as a guy traveling by airplane or climbing a mountain!
Per Gonzales et al, in their study rightly state: this happens because testosterone directly affects a red blood cell precursor cell in the bone marrow and causes it to increase red blood cell production. Interestingly, in this study, they also show when people are at altitude, their testosterone increases slightly and causes this same process so that the body can compensate for the low oxygen environment.
"Testosterone stimulates erythropoiesis through the production of haematopoietic growth factors and … testosterone is suggested to act directly on bone marrow, and specifically, the polychromatophilic erythroblast."
"Serum testosterone levels are increased after acute exposure to high altitude. Therefore, testosterone may play a role in high-altitude tolerance."
Gonzales GF. Serum testosterone levels and excessive erythrocytosis during the process of adaptation to high altitudes. Asian J Androl. 2013;15(3):368-374.
So why are we not concerned about people in higher altitudes forming clots?
- Because they are not at an increased risk for clots in the first place unless they already have a clotting disorder (thrombophilia).
- If doctors made these people give blood (Like with steroid abusers) because of "thickened blood," they would be guilty of malpractice. This comparison may sound extreme, but in this case, it could potentially kill that patient by decreasing their oxygen-carrying capacity, which you need to acclimate to higher altitudes.
Smoking and Red Blood Cell Volume
Chronic smokers are also a group of people who typically have an elevated red blood cell volume because smoking decreases oxygenation due to lung damage. If we made those people give blood because we were afraid of them having a clot, then again, doctors would be committing malpractice. By the way, chronic smokers are at increased risk of clots simply by being smokers.
Cancer Testosterone and Blood Clots
Another study conducted on cancer patients tried to look at the effects of testosterone on them. The funny thing about this study, not one single patient developed a blood clot while on testosterone. Why is this funny? People with cancer are more than likely to develop clots over cancer-free counterparts because cancer is a hypercoagulable state.
It is common for people with cancer to get blood clots, yet when placed on testosterone therapy, they did not see any increase in risk.
As a result, while on TRT and achieving your 'optimal' levels, you are highly unlikely to develop a blood clot. If you do, the likely cause will be unrelated to TRT and likely due to reduced testosterone or lifestyle symptoms such as:
- Heart conditions
- High blood pressure
- High cholesterol
There are plenty of studies (1) dispelling the myths about testosterone causing blood clots. One study which pretty much puts the nail in the coffin of the 'blood clot myth' is the following. This Study of 71,407 men on TRT discovered absolutely no increase in the likelihood of blood clots. They state:
"This study did not detect a significant association between testosterone replacement therapy and risk of DVT/PE in adult men with low sTT (serum total testosterone levels) who were at low to moderate baseline risk of DVT/PE."
By now, you can clearly see plenty of evidence to back up that TRT for optimum levels will not cause blood clots. One of the most compelling facts is: If a man uses TRT to reach their optimum levels that mimic their prime years, why did they not suffer blood clots when they were younger?