Side Effects of Thermogenic Pills

Thermogenics are drugs or supplements designed to facilitate weight loss by simulating exercise. Most thermogenic products generally contain strong stimulants that enable weight loss by boosting energy levels and increasing blood flow. The most common herbs used as thermogenics include caffeine-containing herbs like kola nut, guarana and green tea. Other thermogenic herbs include bitter orange and ma huang (ephedra). Unfortunately, even over-the-counter thermogenic supplements are associated with significant side effects, many of which can be life-threatening.

A woman is putting a supplement pill in her mouth. (Image: Alliance/iStock/Getty Images)


Renowned naturopath Dr. Andrew Weil warns that stimulant thermogenics are addictive and frequently abused. Symptoms of stimulant addiction include fatigue, headache, dizziness, flu-like symptoms, apathy, depression and irritability. Even mild stimulants like green tea may cause addiction after only a few uses.


People with anxiety disorders should avoid all thermogenics, including caffeine. Caffeine notoriously triggers episodes of mild nervousness. Stronger stimulants like ephedrine and synephrine may generate a severe panic response. The U.S. Food and Drug Administration warns that the thermogenic herb ephedra may cause intense feelings of anxiety. Psychosis has also been reported.


Restlessness and insomnia are common side effects associated with thermogenics.

Gastrointestinal Problems

Stimulant thermogenics tend to irritate the colon, leading to abdominal pain and diarrhea. Avoid all thermogenics if you have irritable bowel syndrome or inflammatory bowel disease.

Changes in Heart Rate

The U.S. Food and Drug Administration warns that thermogenic herbs can elevate heart rate and blood pressure. Additionally, Dr. Andrew Weil notes that these products may cause palpitations or cardiac arrhythmia.

Severe Reactions

The Food and Drug Administration links thermogenics to severe adverse events, including heart attack, seizures, coma and death. While some of these events have occurred in otherwise-healthy individuals, many have had pre-existing conditions that increase the likelihood of these complications.

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