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Testosterone, Blood Clots, Strokes and Mini-Strokes


Studies link testosterone therapy to dangerous side effects, including blood clots and strokes. Men who suffered these side effects filed lawsuits against product manufacturers.

Men who are diagnosed with testosterone deficiency (Low T) often are prescribed testosterone therapy, which is FDA approved to treat this condition. However, in recent years, drug companies increasingly marketed hormone therapy drugs like AndroGel to men as a means of maintaining youth and virility or enhancing muscle mass, prompting a five-fold increase in prescriptions of these medications since 2000.

This trend worries many medical professionals, including Dr. Edmund Sabanegh, chairman of the urology department at the Cleveland Clinic.

“The symptoms of low testosterone are kind of what many of us feel when we get older: maybe a little decrease in energy, a little erectile problem, a little drop in libido,” Sabanegh told NBC News. “Often, those are normal [for older men].”

Several recent studies confirm a link to a number of serious side effects, such as an increased risk of potentially fatal blood clots and strokes. These side effects drive men to file lawsuits against the product manufacturers for failing to warn the public.

Blood Clots

Blood clotting is a normal function of the body and helps prevent excessive bleeding after an injury. Normally, these clots are dissolved by the body. Taking testosterone can increase the likelihood of developing blood clots.

Sometimes, clots form when blood cells clump together in veins and arteries without an injury. These thick masses of blood may lodge in veins and arteries, restricting blood flow. When the clot forms in a major vein, it is called deep-vein thrombosis (DVT). DVTs can travel to the lungs (pulmonary embolism) or the brain, causing a stroke. These types of blockages are very dangerous and can be fatal.

Polycythemia, a blood-related disorder that is a common side effect of testosterone therapy, causes an increase in production of hemoglobin, hematocrit and/or red blood cells. This typically leads to thickening of the blood and high blood pressure. Thick blood circulates slower, and slower-moving blood is more likely to form clots.

Additionally, a higher than normal concentration of red blood cells can lead to clumping, promoting clot formation. Testosterone also increases production of thromboxane, a lipid that promotes blood vessel constriction, which further slows blood flow.

A study published in the August 2013 issue of Clinical and Applied Thrombosis/Hemostasis found that blood clots may develop as quickly as one month after beginning hormone therapy drugs.

“Our research found that 1.2 percent of men who landed in the hospital with dangerous and potentially lethal blood clots in the deep veins of the legs or in the lungs developed these clots within three months of starting testosterone therapy,” study author Dr. Charles Glueck of the Jewish Hospital Cholesterol and Metabolism Center told the Cincinnati Business Courier.

According to Glueck, an inherited clotting disorder can make the risk worse. Many people are unaware they should be tested for these genetic mutations as well as hormone levels before beginning Low T therapy.

FDA Requires Testosterone Blood Clot Warning

The U.S. Food and Drug Administration (FDA) is requiring manufacturers of testosterone replacement drugs to include warnings about the increased risk of blood clots that may develop and cause conditions such as deep vein thrombosis and pulmonary embolism.

Product labels already warn of possible clots forming because of a condition called polycythemia, which causes an abnormal increase the size and number of red blood cells. The FDA is demanding more changes because it received reports of “venous blood clots unrelated to polycythemia.”

“We are evaluating the potential risk of these cardiovascular events, which are related to blood clots in the arteries,” the FDA told NBC News.

The agency stressed that testosterone products are only FDA-approved for use by men with medically diagnosed low testosterone levels — called Low T — from “failure of the testicles to produce testosterone for reasons such as genetic problems or chemotherapy.”

The FDA’s move is the latest development in the ongoing controversy that began in January 2014 after a study published in PLoS One showed Low T drugs could more than double the risk of heart attacks in older men in the first 90 days. Earlier studies also link the hormone replacement drugs to increased risk of cardiovascular problems such as stroke and heart attacks.

Popular drugs like AndroGel, Axiron and Testim are used to treat Low T, a condition where men have low testosterone levels – clinically called hypogonadism. The recent surge in prescriptions for the drugs thrust their side effects into the spotlight. In 2013, drug sales topped $1.6 billion.

The agency began scrutinizing the hormone therapy drugs after the PLoS One study. Though, it says this latest addition to the warning label for venous clots is not related to the ongoing investigation.

Strokes and Mini-Strokes

Blood clots caused by androgen replacement drugs can lead to a stroke if they block blood flow to the brain. According to the American Stroke Association, stroke is the fourth leading cause of death in the United States and a leading cause of serious, long-term disability in adults.

A stroke occurs when blood vessels that supply the brain with oxygen and nutrients become blocked by clots (ischemic stroke) or rupture (hemorrhagic stroke), causing brain cells in the affected area to die. Depending upon the area of the brain affected and the amount of damage done, the effects of stroke can range from mild impairments in vision, speech, memory and movement, to major, long-term disabilities in these areas.

Transient ischemic attacks (TIA), commonly called mini-strokes, occur when a blood clot temporarily blocks a blood vessel before dissolving on its own. The majority of these attacks last less than five minutes, with the average length being about one minute. In most cases, they do no permanent damage to the brain, but they are an important warning sign, since about a third of people who experience mini-strokes have a stroke within a year.


Edward Downes filed a lawsuit against Abbott Laboratories and AbbVie after he took AndroGel and suffered a stroke. Other men also filed lawsuits for side effects ranging from heart attacks to blood clots.

“I was in a lot of pain. Dizziness. Confusion,” Downes told CBS Chicago. The 51-year-old continues to struggle to recover and said that he would never have taken the drug if he had known the risks. According to lawsuits, testosterone drug manufacturers encouraged men to take the drugs and failed to properly warn of the risks.