All uses except jet lag: Consult your physician if sleeplessness persists for more than 4 weeks (chronic insomnia). All uses: Avoid taking with alcohol or products that cause drowsiness. Consult a physician prior to use if you are taking steroids or blood thinners, medications for seizure or blood pressure, or medications to suppress the immune system (immunosuppressive medications), to affect mental state, or to increase sedation. Consult a physician prior to use if you have cardiovascular, immune, liver, or chronic kidney disease, hormonal or seizure disorders, asthma, depression, diabetes, low blood sugar, or migraine. Consult a physician prior to use if you are taking carbidopa or drugs/supplements with serotonergic activity. These may include, but are not limited to, L-tryptophan, S-adenosylmethionine (SAMe), St. John’s wort, antidepressants, pain killers, over-the-counter cough and cold medication containing dextromethorphan, anti-nausea medication, and anti-migraine medication. Do not use this product if you are pregnant or breastfeeding, or if you have scleroderma. Stop use and consult a physician if you show signs of weakness, oral ulcers, abdominal pain accompanied by severe muscle pain, or if you experience skin changes. Some people may experience drowsiness, diarrhea, vomiting, and abdominal pain. Do not drive or use machinery for 5 hours after taking melatonin. Stop use if allergy occurs or if you experience headache, confusion, or nausea. Keep out of reach of children.