Heart palpitations can occur for many reasons. Common causes include stress, anxiety, panic attacks, vigorous physical activity, and the use of stimulants like caffeine, nicotine, or certain drugs. Other causes could be hormonal changes, fever, dehydration, electrolyte imbalances, and certain medical conditions including arrhythmias, thyroid problems, anemia, or heart disease. Some medications and nutritional supplements can also cause palpitations. In some cases, palpitations are harmless, but if they are accompanied by chest pain, dizziness, or difficulty breathing, medical attention should be sought urgently.