For anyone arriving from North America, this is usually the first surprise. Melatonin sits beside the vitamins in any US pharmacy. In Korea it’s behind a prescription pad.
The reason isn’t that Korea considers it dangerous. It’s that Korea and the US answered a classification question differently — and everything follows from that one decision.
It’s a hormone
The classification turns on a single fact.
Melatonin is produced by the pineal gland[1]. It acts on melatonin receptors across the brain, retina and circulatory system[1]. Its drug class is melatonin receptor agonist[1].
This isn’t a plant extract or a nutrient. It’s an endogenous hormone — something your body already manufactures on a daily cycle.
Countries that restrict it apply what one analysis calls the precautionary principle: rather than assuming a hormone supplement is safe until proven dangerous, they assume that hormone supplementation warrants medical oversight[2].
The US took the other path. Under DSHEA, melatonin was classified as a dietary supplement — a category with no premarket approval requirement.
Neither approach followed from new safety data. They followed from a prior question: is a hormone taken orally more like a nutrient or more like a drug?
What’s actually licensed in Korea
The prescription product is Circadin prolonged-release tablets, 2 mg[3], with a domestic equivalent also available[4].
The licensed indication is narrow and worth reading exactly:
Short-term treatment of primary insomnia characterised by poor quality of sleep in patients aged 55 or over[5]
Three restrictions in one sentence.
- Aged 55 or over
- Primary insomnia — not insomnia secondary to another condition
- Short-term — the Korean labelling specifies up to 13 weeks[3]
The dose is 2 mg once daily, 1–2 hours before bedtime and after food, swallowed whole[3][5].
Two further points from the label. Safety and efficacy in children aged 0 to 18 has not been established[5]. And Circadin is not recommended in patients with hepatic impairment, because published data show markedly elevated daytime melatonin levels due to decreased clearance in that group[5].
| Korea (prescription) | US (supplement) | |
| Category | Prescription medicine | Dietary supplement |
| Dose | 2 mg | Commonly 3–10 mg |
| Release | Prolonged-release | Usually immediate |
| Indication | Primary insomnia, 55+ | Unrestricted marketing |
| Duration | Up to 13 weeks | Unspecified |
| Premarket review | Required | Not required |
[Table 1] Licensed melatonin in Korea vs typical US supplement · Source: Permits and Regulatory Materials[1][3][5]
The dose difference is the one most people don’t expect. The licensed medicine is 2 mg. Supplement products commonly supply several times that.
Korea isn’t unusual
It’s worth knowing this isn’t a Korean idiosyncrasy.
Melatonin is prescription-only in the UK, Australia and Japan, among others[2]. The UK’s NHS may prescribe the same Circadin 2 mg formulation for adults over 55 with primary insomnia[2], and Circadin is the only licensed melatonin product available in the UK[6].
The regulatory map[1]:
- Australia: Schedule 4, prescription-only
- UK: POM, prescription-only
- Canada: OTC or prescription depending on product
- EU: both, depending on product
- US: OTC
The US is the outlier, not Korea. Most comparable jurisdictions treat oral melatonin as a medicine.
Bringing it in
The rules follow from the classification.
Because melatonin is a prescription medicine here, it falls under the medicines category for customs purposes rather than the health functional food category. As covered in the purchasing comparison post, that means the self-use recognition standard applies — combined value at or under US$150, and a total quantity limit counted across products, not per item.
Products exceeding those limits are held rather than cleared, and releasing them requires approval that isn’t practically obtainable for a personal order.
Two practical notes.
Bringing a personal supply in your luggage is a different situation from ordering online, and treated differently by customs. Small quantities in original packaging with a prescription are the cleanest case.
Rules change. Confirm current requirements with the Korea Customs Service before ordering rather than relying on a description written at any particular time.
The legal alternative
If the reason for interest is sleep, the direct route here is a doctor.
Insomnia is a diagnosable condition with established treatments, and melatonin is one of several options — not necessarily the first. A clinician can distinguish primary insomnia from insomnia secondary to something else, which matters because the licensed indication covers only the former.
And several causes covered elsewhere in this series produce sleep disruption: night sweats during the menopausal transition, thyroid dysfunction, and medication effects among them. Treating the cause works better than treating the symptom.
For sleep-related products sold as health functional foods in Korea, the recognised wording and ingredient list are checkable on the official portal[7]. As covered in the mark post, that wording will be narrower than the marketing around it.
A bit more detail — on one interaction worth knowing. The Korean labelling notes that melatonin has been observed to induce CYP3A at maximum effective doses[3]. The clinical relevance is described as unknown, but induction of that enzyme could reduce plasma concentrations of co-administered medicines[3]. As covered in the interactions post, CYP3A4 handles a large share of prescription drugs — which is a reason to raise melatonin use with a prescriber rather than treat it as inert.
What the classification difference means
Three things follow that are worth carrying.
A US label’s dose isn’t a benchmark. The licensed medicine is 2 mg prolonged-release. A 10 mg immediate-release supplement isn’t a stronger version of the same thing — it’s a different exposure profile that no regulator here reviewed.
“Available without prescription elsewhere” isn’t a safety finding. As covered in the classification post, the category a product sits in reflects a regulatory decision, not a measurement of risk.
And the restriction cuts both ways. Prescription status means a clinician assesses whether it’s appropriate — which is the oversight the US model doesn’t provide, and the reason the precautionary jurisdictions chose it.
Whether that’s worth the inconvenience is a reasonable thing to have views about. But it’s a different question from whether melatonin is dangerous.
Closing
The question this post started with has a simpler answer than it appears.
Melatonin requires a prescription in Korea because Korea classified an endogenous hormone as a medicine. The UK, Australia and Japan reached the same conclusion. The US, under a 1994 framework that created the dietary supplement category, reached a different one.
What makes the comparison instructive is the dose. The licensed product here is 2 mg, prolonged-release, for adults over 55, for up to 13 weeks — narrow enough that most people buying 10 mg gummies abroad would fall outside every one of those parameters.
That’s not an argument that supplement melatonin is harmful. It’s that the two regulatory systems produced products that barely resemble each other, and the availability difference is the visible part of a much larger divergence.
Key Terms
- Pineal gland — the small brain structure that produces melatonin on a daily cycle.
- Receptor agonist — a substance that activates a receptor, as the body’s own signalling molecule would.
- Primary insomnia — insomnia not caused by another medical or psychiatric condition.
- Prolonged-release — a formulation designed to release the active ingredient gradually.
- Precautionary principle — a regulatory approach that assumes caution in the absence of proof of safety.
- CYP3A — a liver enzyme family responsible for metabolising a large share of prescription medicines.
At a Glance
- Melatonin is a hormone produced by the pineal gland, classed as a melatonin receptor agonist
- Korea’s licensed product is Circadin 2 mg prolonged-release, or a domestic equivalent
- Indication: primary insomnia in patients aged 55 or over, short-term, up to 13 weeks
- Dose: 2 mg once daily, 1–2 hours before bed, after food, swallowed whole
- Safety and efficacy in ages 0–18 not established; not recommended in hepatic impairment
- Prescription-only also in the UK, Australia and Japan — the US is the outlier
- US supplements commonly supply several times the licensed 2 mg dose, usually immediate-release
- Korean labelling notes melatonin induces CYP3A at maximum effective doses
※ This article describes regulatory classification and licensed product information for general information only. It does not replace medical advice, diagnosis or treatment, and is not guidance on obtaining or using melatonin. Persistent sleep difficulty warrants medical assessment — insomnia has many causes, several treatable. Do not import prescription medicines outside applicable rules, and confirm current customs requirements before ordering from abroad.
References
- “Melatonin as a medication and supplement”, Wikipedia (pineal origin, drug class, receptor targets, and legal status by jurisdiction), https://en.wikipedia.org/wiki/Melatonin_as_a_medication_and_supplement
- “Is Melatonin Banned in Other Countries? OTC Restrictions Reviewed” (precautionary principle framing; UK NHS prescribing; Australian customs practice), https://premiumgrounding.com/blogs/news/melatonin-banned-other-countries
- Pharmaceutical Information Center, 「서카딘서방정2mg」 Drug Information — Korean licensed indication, dosing, 13-week limit and CYP3A induction note, https://www.health.kr/searchDrug/result_drug.asp?drug_cd=2014062500015
- Pharmaceutical Information Center, 「제일멜라토닌서방정2mg」 Drug Information — domestic equivalent product information, https://health.kr/searchDrug/result_drug.asp?drug_cd=2025042200003
- European Medicines Agency, “Circadin — Summary of Product Characteristics” (indication wording, posology, paediatric and hepatic impairment statements), https://www.ema.europa.eu/en/documents/product-information/circadin-epar-product-information_en.pdf
- “Dissolution of Intact, Divided and Crushed Circadin Tablets”, MDPI (Circadin as the only licensed melatonin product in the UK), https://oalib-perpustakaan.upi.edu/Record/doaj_50a695050b364da487da8c921e4d2d6c/Similar
- Food Safety Korea (MFDS), recognised functional ingredient and approved wording lookup, https://www.foodsafetykorea.go.kr/