On June 19, 2014, the U.S. Food and Drug Administration (FDA) announced that it was requiring manufacturers of all testosterone products (also known as “low-T” products) to include a general warning in labels about the risk of blood clots in the veins. Venous blood clots can develop into deep vein thrombosis (DVT) and pulmonary embolism (PE). Deep vein thrombosis clots usually occur in the legs, whereas pulmonary embolisms travel from one part of the body and end up in a lung. If untreated, both of these clots can result in death.

The FDA's new mandate comes only months after it announced that it was evaluating the possible risk of heart attack, stroke, and death in testosterone therapy and “low-T” users due to blood clots in the arteries. The FDA’s investigation into clots in the arteries is still ongoing.