Melatonin: Over-the-Counter and More Than a Sleep Aid

Ninety. That is the number of adverse-event reports analyzed by Anses among people who used melatonin-based dietary supplements. Headaches, dizziness, nightmares, tremors: the list is striking, especially for a product as readily available as herbal tea, sold in pharmacies and supermarkets. For years, melatonin has been marketed as the gentle, natural solution to insomnia, but it is far from just a simple plant extract. It is indeed a hormone produced by the body itself, and its action extends well beyond the regulation of sleep. This should prompt a more serious look at this small tablet.

A Hormone that Goes Beyond Sleep

In the body, melatonin is naturally produced at night and plays a central role in initiating sleep. This function has earned it the reputation of a “natural sleep aid,” widely sold over the counter in many dietary supplements. Yet reducing melatonin to that single role would be a mistake. This hormone also affects mood, the immune system, the regulation of body temperature, and even intestinal motility. It possesses vasodilatory, vasoconstrictive, and pro-inflammatory properties, which means, in practical terms, it can influence the diameter of blood vessels and participate in certain inflammatory processes. All of these subtle but real mechanisms help explain why this small molecule deserves more consideration than a mere “boost” for better sleep.

Adverse Effects Reported by Anses

It is precisely because melatonin acts on so many functions of the body that adverse effects can occur. The national nutrivigilance system, led by Anses, analyzed 90 cases of adverse effects reported after consuming dietary supplements containing this hormone. The symptoms listed include headaches, dizziness, sleepiness, nightmares, or irritability. Other reports describe more specific issues, such as tremors or migraines, as well as digestive problems like nausea, vomiting, or abdominal pain. Each case was studied individually by the agency, which then shared its conclusions with the individuals concerned and the manufacturers. These effects occur depending on the consumption context or in interaction with other substances, underscoring that melatonin, even when sold as a dietary supplement, is not without consequences for everyone.

Populations Who Should Abstain Completely

In light of these findings, Anses has identified profiles for whom melatonin-containing supplements are strongly discouraged, or should be avoided entirely. This includes pregnant or breastfeeding women, children and adolescents, but also people with inflammatory or autoimmune diseases. The agency also urges great caution for anyone who must perform activities requiring sustained vigilance, since the sedative effects of melatonin can affect concentration or reflexes. These recommendations are not merely precautionary—they are grounded in retrospective analysis of reported cases and a review of the available scientific literature.

When Medical Advice Becomes Essential

Beyond the populations that must abstain entirely, there are other situations that require consulting a physician before taking melatonin. This is the case for people with epilepsy, asthma, or mood, behavior, or personality disorders. Yet the most important caution concerns individuals who are on medication. Indeed, melatonin can interact with other substances, and its effects on the immune system, blood vessels, or inflammation can modify the effectiveness or tolerability of certain drugs. A detail that often goes unnoticed when the product is purchased over the counter, almost reflexively, as one would grab a bottle of vitamin C.

Dietary Supplements and Medicines: An Essential Distinction

In France there are several forms of melatonin use: medicines, magistral preparations, and dietary supplements. These statuses are not equivalent. Dietary supplements, sold over the counter, follow a regulation different from that of melatonin-based medicines, which are prescribed by a health professional for specific medical indications and controlled dosages. This distinction is far from trivial: it explains why the same active ingredient can be seen as completely harmless when in a supplement, while it is tightly regulated when dispensed as a medicine. It is precisely this ambiguity that led Anses to clarify matters and to remind that melatonin, in any form, remains an active substance.

Recommendations for Prudent Use

On the basis of this risk assessment, Anses has issued recommendations for three audiences: consumers, manufacturers, and healthcare professionals. The guiding principle is simple: favor occasional use of melatonin rather than prolonged use, given the lack of sufficient data on long-term effects. To summarize the key cautions to consider before taking melatonin, the following points should be kept in mind:

• Completely avoid supplements in cases of pregnancy, lactation, in children and adolescents, or in inflammatory or autoimmune diseases
• Seek medical advice in cases of epilepsy, asthma, mood disorders, or personality disorders
• Be particularly vigilant if you are on ongoing medication, due to the risk of interactions
• Favor short-term use over prolonged use in the absence of sufficient long-term data

What to Remember Before Taking It

Melatonin is not merely a comforting gesture to sleep better. It is a full-fledged hormone, with a broader influence on the body than one might think, and dietary supplements should not be used without careful forethought. For individuals with a health condition, those undergoing treatment, or simply those with doubts, consulting a health professional remains the best precaution before slipping this little tablet into one’s nightly routine.