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Dangerous Effects of Taking Multiple Diet Pills at One Time

author image Tracii Hanes
Based in Las Vegas, Tracii Hanes is a freelance writer specializing in health and psychology with over seven years of professional experience. She got her start as a news reporter and has since focused exclusively on freelance writing, contributing to websites like Wellsphere, Education Portal and more. She holds a Bachelor of Arts in communication arts from Southwestern Oklahoma State University.
Dangerous Effects of Taking Multiple Diet Pills at One Time
Close-up of diet pills Photo Credit: minoandriani/iStock/Getty Images

The U.S. dietary supplement industry brings in about $26.9 billion per year, according to the Council for Responsible Nutrition. Diet and weight loss aides make up a large portion of this revenue and are sold over the counter in stores across the country. Some diet pills contain ingredients that have not been proven safe or effective. Because diet pills often contain multiple ingredients, taking more than one type at a time could be dangerous. To prevent complications, talk to your physician before trying a new diet supplement.

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Over-the-counter diet pills fall into two basic categories -- fat blockers and appetite suppressants. Stimulants like bitter orange and caffeine are often added to weight loss pills to reduce appetite and increase calorie burning. Orlistat and other fat blockers are another type of supplement that work by decreasing fat absorption from food. Some diet pills contain only one active ingredient while others contain a combination of several vitamins, herbs or medications.

Side Effects and Interactions

All supplements are capable of causing unwanted side effects in some users. According to the Food and Drug Administration, the fat blocker Orlistat may cause severe liver injury in some people. Diet pills that contain multiple ingredients can cause unforeseen interactions when combined with other supplements or drugs. The National Center for Complementary and Alternative Medicine warns that bitter orange has been linked to stroke, heart attack and fainting in healthy users. Combining two supplements with similar effects, such as caffeine and bitter orange, can have an additive effect that increases the risk for serious complications. Hoodia gordonii, an African herb found in some weight loss supplements, does not have sufficient evidence to determine its safety as a diet aid.


The best way to prevent dangerous interactions is to avoid taking multiple diet pills at once. Talk to your doctor before taking a new diet pill, especially if you suffer from a chronic condition like heart disease or hyperthyroidism. Check the FDA website regularly to stay up to date on safety concerns associated with diet pills. Read ingredient labels before taking diet supplements and follow dosing instructions carefully. Stop taking diet pills immediately and seek prompt medical attention if you experience side effects like rapid heartbeat, weakness or chest pains.

Additional Considerations

Over-the-counter diet supplements aren’t regulated as closely as pharmaceutical medications. For this reason, they may contain unsafe ingredients, varying levels of active compounds or unknown contaminants.

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