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Yaz has been linked to blood clots that can travel to the lungs, heart and brain and lead to serious medical conditions and even death. The blood clots, called deep vein thrombosis (DVT), can cause heart attacks, strokes and pulmonary embolisms. The drug is also linked to gallbladder disease, high cholesterol and high potassium levels that can lead to heart attacks.

*Please seek the advice of a medical professional before discontinuing the use of this drug.

With its chic marketing and catchy name, the Yaz birth control pill was introduced in 2006 and quickly became the most popular and best-selling oral contraceptive in the U.S. But as quickly as the drug’s popularity skyrocketed, it plummeted amid concerns that it raises the risks of deadly side effects more than older contraceptive pills.

Studies from as early as 2006 show the side effects associated with Yaz.

Side effects and risks included in the Yaz drug label include:

  • Thromboembolic disorders
  • Hyperkalemia
  • Carcinoma of the breasts
  • Carcinoma of the reproductive organs
  • Liver disease
  • High blood pressure
  • Gallbladder disease
  • Carbohydrate metabolic effects
  • Lipid metabolic effects
  • depression
  • Headache/migraine
  • Menstrual irregularities
  • Nausea/vomiting
  • Breast pain/tenderness
  • Mood changes
  • Fatigue
  • Irritability
  • Decreased libido
  • Increased weight

Some side effects such as irregular bleeding, nausea, breast tenderness and headache are usually mild and tend to disappear with time. Others such as blood clots, stroke, heart attack and gallbladder disease are more serious and can lead to death.

Blood Clots

Blood Clot Close Up
Microscopic view of a venous thromboembolic event, or blood clot

Drospirenone, an active ingredient in Yaz, significantly increases the chances of developing venous thromboembolic events (VTE), or blood clots, studies show. Blood clots can lead to heart attacks, strokes and pulmonary embolisms, which all can be deadly.

At least five large studies conducted since 2009 have shown that drospirenone not only heightens the risk of blood clots but it does so more than older forms of progesterone. A study by the U.S. Food and Drug Administration (FDA), for example, showed a 74 percent increased risk in Yaz users when compared to users of other oral contraceptives. Bayer, the maker of Yaz, funded the only two major studies that disprove the blood-clot connection.

In 2012, the FDA decided to include an updated warning on the drug’s label. The new label states that some studies show a three-fold increase in blood clot risks for drospirenone users, while other studies find no additional risks. (The other studies the FDA is referring to were funded by Bayer.)

Deep Vein Thrombosis (DVT)

Deep Vein Thrombosis Impedes Blood Flow
DVT is a clot that forms in the body’s deep veins

Specifically, Yaz is linked to deep vein thrombosis (DVT), a blood clot that develops in the deep veins of the body, according to a study published in 2011 in the British Medical Journal (BMJ). Evaluating 1.3 million Danish and Dutch women, the study found a six-fold increase of the risk of blood clots in women using drospirenone compared to women not taking the pill, according to The New York Times.

Long known as the long-haul traveler’s condition, DVT typically forms in the legs, often after long periods of inactivity. It is usually seen in older patients who are sedentary or have heart failure. When the clot forms in the deep veins of the legs, it is often painful and causes the leg to swell. Sometimes there are no symptoms. Once a DVT forms, the clot can easily break off and travel through the body and create numerous dangers.

These Dangers Include:

  • Stroke – If a blood clot travels to the brain, the clot can cut off blood flow and cause a rapid loss of brain functions. The resulting effects could include paralysis and death.
  • Pulmonary embolism – A clot that gets lodged in the narrow arteries in the lungs is called a pulmonary embolism. This type of clot makes it difficult for the lungs to provide the necessary oxygen to the rest of the body.
  • Heart attack – Also called coronary thrombosis, a blood clot in the heart can cause the heart muscle to stop. Yaz tends to increase potassium levels, which also raises the risk of heart attack.

Seemingly healthy women, some as young as 14 and 15, have reportedly died from Yaz-related DVT, and countless others have allegedly been injured. Bayer refutes the claims. It says that the risks of taking Yaz are no different than any other oral contraceptive. A study published in BMJ in 2015, however, looked at nearly 11,000 cases of blood clots in women aged 15 to 49 and found the risks of blood clots associated with birth control pills to be higher for newer birth control drugs like Yaz than for older drugs.


Introduced in the 1960s, birth control pills have long been linked to ischemic strokes, which happen when the blood supply to the brain becomes blocked. Researchers found that the fluctuating estrogen levels in early generations of birth control pills elevate the risk of blood clots, which can lead to stroke. An increasing number of studies now show that Yaz puts women at an even higher risk of having a stroke than first thought because the risk of DVT is significantly higher with Yaz users.

After developing in the deep body veins, blood clots can break off and travel to the brain. When a blood clot fractures from its original location and ends up near the brain, the clot can limit or cut off blood flow to the brain. When this happens, a stroke is imminent. The resulting stroke can leave patients in a vegetative state or dead.

Bayer claims there is no evidence of increased risk. However, unsealed federal court documents show that Bayer has not been truthful in its safety data concerning Yasmin, the sister drug to Yaz. The documents show that “Bayer presented a selective view of the data and that presentation obscured the potential risks associated with Yasmin.” Yaz and Yasmin are nearly identical drugs, except Yaz contains less estrogen.

Ischemic Stroke Occur in the Thrombus

Pulmonary Embolism

Pulmonary Artery Blocked by an Embolus
A pulmonary embolism is a blood clot that forms in the lungs

Caused by DVT, a pulmonary embolism is a blood clot that settles in the lungs. Typically, these blood clots in the lungs block a coronary artery, which can lead to heart attack, among other serious medical conditions.

When a blood clot travels to the lungs and blocks the pulmonary arteries, the circulation and blood oxygen levels are restricted. This makes it difficult for the lungs to provide oxygen to the body. The results can be debilitating or deadly.

In the Yaz drug insert, the manufacturer warns those who have or have had deep vein thrombosis or pulmonary embolisms not to take the pill. The risk is greatest in the first year of taking the drug but also continues throughout treatment with the pill, the insert says.

Heart Attack

Not only does Yaz’ blood clotting risk increase the chances of a heart attack, but so does the drug’s link to dangerously high potassium levels, called hyperkalemia. Potassium is an important mineral for proper cell functioning and is crucial to heart functioning. It plays a key role in smooth muscle contractions. The average adult needs about 4,700 mg a day for normal functioning.

Drospirenone found in Yaz affects potassium levels by interfering with the normal functioning of the kidney, which monitors and regulates the body’s potassium levels. When the kidney function is stalled, potassium builds in the bloodstream. When blood contains too much potassium, it can cause dangerous heartbeat irregularities and even sudden death. Because hyperkalemia can cause the heart to stop suddenly, medical professionals consider it an extreme emergency. The symptoms are fairly nonspecific, including muscle weakness, malaise and heart palpitations.

Elevated Potassium Buildup in Heart
Potassium buildup in the bloodstream can cause a myriad of issues

Elevated potassium levels from Yaz can cause a host of problems, including:

  • Irregular heart beat
  • Cardiac arrest
  • Changes in muscle control
  • Paralysis
  • Muscle weakness and fatigue

Some drugs, such as ibuprofen, high blood pressure medicine and certain diuretics, can have serious interactions with Yaz and cause hyperkalemia. Yaz should not be taken if you have kidney failure, one kidney, liver disease, adrenal disease or a history of blood clots. Some everyday tasks, such as drinking sports drinks or eating high-potassium foods, coupled with taking Yaz can be dangerous for women.

The risk from a potassium induced heart attack is so great that federal drug regulators demanded that Bayer include the information on the drug packaging and labeling. But many women are saying that was not enough. Young women by the hundreds have reportedly suffered devastating heart attacks after taking Yaz.

Gallbladder Disease

Yaz has also been proven to increase the chances of gallbladder disease and surgical removal of the gallbladder, called cholecystectomy. A study published in the Canadian Medical Association Journal (CMAJ) concluded that drospirenone found in Yaz increased a woman’s risk for developing gallbladder problems by 20 percent. The study called it a “small, statistically significant increase in the risk of gallbladder disease.”

Some studies say drospirenone is linked to gallbladder disease because of its diuretic effect. Other studies say the link between Yaz and gallbladder disease is because the drug increases cholesterol levels, thus creating calcified bits of cholesterol in the gallbladder, known as gallstones. Still others say it is because drospirenone decreases the gallbladder’s movement and impedes bile flow.

Bayer refutes all the research pointing to gallbladder problems, saying they are not clinically significant.

Gallbladder Disease Requires Surgery, Painful Recovery

The gallbladder is a hollow, pear-shaped organ located under the liver. Its primary function is to store and concentrate bile, a digestive liquid formed by the liver. Yaz increases cholesterol levels in bile and decreases gallbladder movement. This could lead to the formation of calcified cholesterol chunks known as gallstones, and the gallbladder could become inflamed.

Conditions associated with gallbladder disease include:

  • Gallstones (cholelithiasis) – crystallized bile can form hardened stones that can cause pain and inflammation
  • Cholecystitis – inflammation of the gallbladder due to gallstones
  • Gallbladder cancer – symptoms are known to resemble gallstones
  • Gallstone pancreatitis – when gallstones block the duct to the pancreas, the pancreas can become inflamed

Even though gallbladder disease is not normally fatal, treatment entails a painful and costly surgery. Typically, removing the gallbladder is done through laparoscopy or an abdominal incision. Removal of the gallbladder can cause fat malabsorption and diarrhea that could last for years after the surgery. There is also a risk of postcholecystectomy syndrome, which is persistent pain, gas, bloating and vomiting following gallbladder-removal surgery.


Emily Miller is an award-winning journalist who has held writing and editorial positions with numerous print and online publications around the U.S. She draws on her background as both a patient and a journalist to help readers understand complex health topics. Her most recent experience is in writing about litigation involving medicines that cause life-altering side effects.

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