New warnings on popular birth control, Yaz

Julie Bromberg


(For the 2014 update, click here.)

With all the different brands of birth control pills out there, most women have no idea which ones they should choose. When taken correctly, all birth control pills are similarly effective at preventing pregnancy, so it makes sense to pick the birth control with the least likelihood of serious side effects.1 One of the most serious side effects of birth control pills is blood clots, which can prevent normal blood flow and cause stroke, heart attack, and death.

In August 2009, two independent studies found that the type of hormone used in Yaz and Yasmin birth control pills put women at higher risk of blood clots than other birth control pills. All birth control pills contain the female hormone progestin, but different pills have different types of progestin. Yaz contains a newer type called drospirenone, which, like other newer types of progestin, has a greater risk of blood clots than older versions.2, 3 In addition to increased risk of blood clots, Yaz can increase the level of potassium in your blood which can cause life-threatening health problems.4

While several independent studies agree that Yaz can increase a woman’s risk of blood clots, one major study, funded by Bayer HealthCare, reported that the risks of Yaz are the same as other birth control pills.5 Bayer HealthCare makes Yaz, and research funded by the companies that produce a drug tend to have more favorable results than studies funded by independent sources6 (see Industry Ties Report “Rosier” Results for more information).

By the end of 2008, Yaz was the number-one selling birth control pill in the United States. Higher risk of blood clots and complications from potassium are not the only concerns surrounding Yaz birth control. In 2008, the Food and Drug Administration (FDA) warned Bayer that their advertisements for Yaz were misleading, because they understated the risks of Yaz, and exaggerated the benefits, suggesting that Yaz could cure acne and mood problems. The FDA became so concerned about the deceptive nature of these ads that in February 2009, the FDA required Bayer to spend $20 million on ads to correct the company’s earlier misleading advertisements, a penalty that is very rare for the FDA.7 Bayer has complied and is currently airing their corrective ads, but some public health advocates have pointed out that distracting noises and activity in the commercials detract from the correction.

Bottom Line:

To reduce your risk of the greatest dangers from birth control pills, avoid taking pills that contain drospirenone, such as Yaz, since they increase your risk of blood clots more than other birth control pills. Although all birth control pills can increase your risk of blood clots, some types of pills have lower risk:

  • progestin-only birth control (Yaz is not progestin-only),
  • pills that contain levonorgestrel (a different type of progestin hormone that has been used in birth control pills since the 1970s).

If you are taking birth control pills or thinking about taking them, talk with your doctor about which kind has lower risks.

All articles on our website have been approved by Dr. Diana Zuckerman and other senior staff.

To read more about the dangers of birth control pills containing drospirenone, click here.


1. Dunn N. (August 2009) Oral Contraceptives and Venous Thromboembolism. British Medical Journal, 339: b3164.

2. Van Hylckama Vlieg A, Helmerhorst FM, Vandenbroucke JP, Doggen CJM, and Rosendaal FR. (2009) Effects of Oestrogen Dose and Progestogen Type on Venous Thrombotic Risk Associated with Oral Contraceptives: Results of the MEGA Case-Control Study. British Medical Journal, 339: b2921.

3. Lidegaard Ø, Løkkegaard E, Svendsen AL, and Agger C. (August 2009) Hormonal Contraception and Risk of Venous Thromboembolism: National Follow-up Study. British Medical Journal, 339: b2890.

4. Hopkins Tanne J. (February 2009) Bayer to Spend $20 Million to Correct Misleading Advertising for Oral Contraceptive Yaz. British Medical Journal, 338: b674.

5. Dinger JC, Heinemann LA, and Kuhl-Habich D. (2007) The Safety of a Drospirenone-Containing Oral Contraceptive: Final Results from the European Active Surveillance Study on Oral Contraceptives Based on 142,475 Women-Years of Observation. Contraception, 75: 344- 354.

6. Lexchin J, Bero LA, Djulbegovic B, and Clark O. Pharmaceutical Industry Sponsorship and Research Outcome and Quality: Systematic Review. British Medical Journal, May 2003; 326:1167-1170. doi:10.1136/bmj.326.7400.1167

7. Hopkins Tanne J. (February 2009) Bayer to Spend $20 Million to Correct Misleading Advertising for Oral Contraceptive Yaz. British Medical Journal, 338: b674.