Many Individuals are among a growing number of sleep-deprived consumers turning to a once-little-known hormone, often referred to as the “sleep hormone,” for relief for insomnia.

In all, U.S. consumers are expected to spend more than $425 million on melatonin supplements in 2018, up from $259 million in 2012, according to Nutrition Business Journal. More than 3 million adults and close to a half-million children take it, and that number is expected to grow as more sleep-deprived families clamor for cheap “natural” remedies and companies roll out everything from melatonin teas to mouth sprays to animal-shaped gummies.

But with such growth have come concerns that consumers have a view of the potent, complex hormone that’s too simple. The growing use, or misuse, is showing up in other ways. Calls to poison control centers about melatonin have skyrocketed. People think of it as a vitamin, but in reality, melatonin is a hormone

Taken at the right time, in the right dose, melatonin can, indeed, repair a sleep schedule thrown off kilter by jet lag, a long weekend filled with late nights, or certain circadian rhythm disorders. And for some people, it can have a mild hypnotic effect.

But as a remedy for general sleeplessness, it has its limits. And when it comes to its use in children, concerns abound. Melatonin supplements appear to be safe when used short-term; less is known about long-term safety.