Short answer: It has been reported, and every US testosterone label carries a warning. Clots in the deep veins (DVT) and lungs (pulmonary embolism) have been reported after approval. In the TRAVERSE trial of 5,198 men, clots were numerically more common on testosterone gel than placebo: 1.7% versus 1.2%, including lung clots in 0.9% versus 0.5%. The labels also say a rise in red blood cells may raise clot risk.
Depo-Testosterone, testosterone enanthate, Xyosted, Aveed, AndroGel 1.62% and Kyzatrex all have a venous thromboembolism warning. It says there have been reports after approval of deep vein thrombosis (DVT, a clot in a deep vein, usually in the leg) and pulmonary embolism (PE, a clot that travels to the lungs) in people using testosterone products.
For prescribers, the labels say to check for DVT in anyone reporting pain, swelling, warmth or redness in the lower leg, and for PE in anyone with sudden shortness of breath. If a clot is suspected, the labels say to stop testosterone and start appropriate workup and treatment. The Kyzatrex label lists lower limb pain, swelling or redness, and shortness of breath or chest pain as signs to report promptly.
TRAVERSE randomly assigned men aged 45 to 80 with low testosterone and heart disease or several heart risk factors to daily testosterone gel or placebo gel. Its main finding was that testosterone was not worse than placebo for heart attacks, strokes and heart-related deaths (7.0% versus 7.3%). The published paper notes a higher rate of pulmonary embolism, atrial fibrillation and acute kidney injury in the testosterone group.
| Event | Testosterone gel | Placebo |
|---|---|---|
| Any venous clot (VTE) | 1.7% | 1.2% |
| Deep vein thrombosis | 0.6% | 0.5% |
| Pulmonary embolism | 0.9% | 0.5% |
The labels call the difference "numerically higher", meaning the numbers were higher but the comparison was not built to prove a difference. TRAVERSE used a gel, so it does not show whether injections carry more, less or the same clot risk.
Testosterone can raise hemoglobin and hematocrit, the share of blood made up of red cells. The Xyosted, Aveed, AndroGel and Kyzatrex labels say an increase in red blood cell mass may increase the risk of clots, and ask for hematocrit to be checked before starting and during treatment: about every 3 months on Xyosted, and at 3 to 6 months and then yearly on Aveed and AndroGel. See TRT hematocrit monitoring.
MedlinePlus lists other things that raise DVT risk, including long periods sitting such as plane or car travel, recent surgery, obesity, smoking, a family history of clots, age over 60, and making too many blood cells.
MedlinePlus describes DVT as usually affecting one leg, with redness, warmth, swelling, and pain or tenderness. A clot that breaks off can lodge in the lungs, which the labels describe as sudden shortness of breath. Chest pain or sudden breathlessness needs emergency care.
Testosterone can also change how blood thinners work. The Xyosted and AndroGel labels say changes in anticoagulant activity may be seen with androgens and recommend more frequent INR and prothrombin time checks in people taking warfarin, especially when starting and stopping testosterone.
Keeping hematocrit results, dose dates and any leg or breathing symptoms in one place makes a prescriber's check faster. Dose Track stores lab results next to your dose log.
Read more on Dose Track: TRT hematocrit monitoring · Hematocrit (glossary) · Low testosterone and TRT · Xyosted side effects · Depo-Testosterone side effects