Dangerous Effects of Taking Multiple Diet Pills at One Time

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.

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 have 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.

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.