<b>All uses except jet lag: </b>Consult a physician if sleeplessness persists for more than 4 weeks (chronic insomnia). <b>All uses: </b>Some people may experience drowsiness. Do not drive or use machinery for 5 hours after taking melatonin. Avoid taking with alcohol or products that increase drowsiness. 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, if you are taking steroids or blood thinners, medications for seizure or blood pressure, medications to suppress the immune system (immunosuppressive medications), to affect mental state or to increase sedation, or 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/or cold medications containing dextromethorphan, antinausea and anti-migraine medications. Discontinue use and consult a physician if you show signs of weakness, oral ulcers, or abdominal pain accompanied by severe muscle pain, or if you experience skin changes. Stop use if allergy occurs or if you experience headache, confusion, or nausea. Do not use if you have scleroderma or if you are pregnant or breastfeeding. Some people may experience diarrhea, nausea, vomiting, and abdominal pain. Keep out of reach of children.