It all started with a question from a student.

He was a good one: sharp, engaged, the kind who stayed after to ask follow-up questions. He was also a dad, and one afternoon after our nursing lecture about circadian rhythms, he lingered by my desk and asked the question: “Hey, is it OK to give my little ones melatonin gummies every night? They won’t go to sleep without them.”

I paused before answering, adjusting myself to the realization of how many well-meaning people (including healthcare professionals) were probably doing the exact same thing without understanding what they were actually giving their children.

Melatonin isn't a supplement, silly, it’s a hormone.

Serotonin and melatonin aren't two separate systems, they're one continuous biochemical pathway. Your body takes tryptophan from food, converts it into serotonin (which runs the daytime show—metabolism, mood, body temperature), and then when it's time for sleep, your pineal gland converts that serotonin into melatonin.

Serotonin handles the days, melatonin handles the nights. One molecule; one gland; one light-driven schedule.

When you comprehend that, you understand why flooding your body with a synthetic version of one half of this system might not be as harmless as the packaging suggests.

The Myth of Melatonin

Melatonin doesn't even begin releasing until about one to two hours after light stops hitting your retinas. So if you're lying in bed at 10 PM scrolling your phone, the blue light from that screen is telling your brain: It's still daytime. Don't release the melatonin yet.

Then you pop a gummy and wonder why it doesn't work.

Sleep hygiene is the single most important thing you can do for your sleep; it's what the biology requires. Despite the predilections of the lazier segments of society, the bed is only for two things: sleep and sex.

That is all.

Alas, Americans love their pills. And there is a vast supplement industry that is happy to oblige.

Melatonin is classified as a dietary supplement, which means the FDA does not approve it for safety, effectiveness or labeling accuracy before it hits the shelf. A 2023 study in the Journal of the American Medical Association analyzed 25 melatonin gummy products. Of those, 22 (approximately 88%) were inaccurately labeled. Actual melatonin content ranged from 74% to 347% of what the bottle claimed.

Dr. Pieter Cohen points out that just one-tenth of a milligram of melatonin raises a healthy adult's blood levels to normal nighttime values. Over-the-counter supplements contain five to ten milligrams per dose (fifty to one hundred times what the body needs). If someone told you they were taking a hundred times the recommended dose of any hormone (testosterone, insulin, thyroid), wouldn't you be alarmed?

Yet, because melatonin sits on a shelf next to the vitamin C, people treat it like it's harmless. Like any hormone, too much of it can be harmful.

And the (over)dosing makes the poison.

Most of the developed world recognizes this. In the United Kingdom, melatonin is prescription-only. In Japan, the manufacture and sale of melatonin supplements is prohibited entirely. Across the EU, it's classified as a pharmaceutical.

The United States is the global outlier: anyone can walk into a drugstore and buy a teeming bottle of 10 mg gummy for their toddler.

No prescription. No oversight. No guarantee that the bottle contains what it claims to.

The Unwitting Poisoning of Children

This next part of the research was exceedingly troubling.

Parents across America are giving their children a hormone that has never undergone the formal safety testing required for a new drug in pediatric populations. The evidence supporting melatonin use in otherwise healthy American children is, as one review put it, "non-existent."

Despite there being almost no studies on the use of melatonin in kids, between 2012 and 2021, poison control calls for pediatric melatonin ingestion increased by 530%. Nearly 28,000 emergency department visits. Over 4,000 hospitalizations. Two deaths. Many involved young children who mistook the little bear-shaped gummies for candy.

Even when parents are giving melatonin as directed (not overdoses, but intentional nightly use), the long-term picture is troubling. As a child approaches puberty, the body naturally decreases its melatonin production; that decline is part of the biological cascade that triggers puberty itself. Flood a child's system with supplemental melatonin for years, and you may be telling its body, "It's not time yet; don’t evolve into the pubescent state."

This isn't just theoretical. A 2023 systematic review observed delayed pubertal timing after an average of 7.1 years of treatment. A 2025 study in the American Journal of Epidemiology confirmed it.

A Matter of the Heart

A study presented at the AHA's 2025 Scientific Sessions reviewed over 130,000 adults with insomnia and found long-term melatonin users had approximately 90% higher rates of heart failure diagnosis and almost 3.5 times the hospitalization rate. The researchers call this association, not causation. That said, the study has real limitations, like a paucity of details on insomnia severity or on the intensity of the mental health of subjects.

But the absence of definitive proof is not the same as the presence of safety. Millions of Americans are taking this hormone nightly, but we didn't have a study this large until 2025, only last year. This is not reassuring.

That should make all of us—clinicians and consumers—deeply uncomfortable.

And in case you were wondering: melatonin's intended clinical use is short-term and small-dosage (one to three milligrams for up to three nights), to help reset the body’s circadian rhythms after jet lag or shift work.

If you can't sleep, the answer is almost never a pill. It's your environment, your habits, and your relationship with light. And if your children won't sleep, before you reach for that gummy bottle, try the behavioral approach first. Cool, dark, quiet room. Same routine. Same bedtime. Same wake time.

Most pediatric sleep problems will resolve with consistency, not chemistry.