quality:correction, structural:reformatting, information:classification
Society and culture

Melatonin is categorized by the US Food and Drug Administration (FDA) as a dietary supplement, and is sold over-the-counter in both the US and Canada. FDA regulations applying to medications are not applicable to melatonin, though the FDA has found false claims that it cures cancer. As melatonin may cause harm in combination with certain medications or in the case of certain disorders, a doctor or pharmacist should be consulted before making a decision to take melatonin. In many countries, melatonin is recognized as a neurohormone and it cannot be sold over-the-counter. According to Harriet Hall, caution is advisable, since quality control is a documented problem. 71% of products did not contain within 10% of the labelled amount of melatonin, with variations ranging from –83% to +478%, lot-to-lot variability was as high as 465%, and the discrepancies were not correlated to any manufacturer or product type. To make matters worse, 8 out of 31 products were contaminated with the neurotransmitter serotonin.