Warning issued over counterfeit weight-loss drugs smuggled into South Korea

Consumers are being urged to exercise extra caution as the domestic influx of counterfeit versions of well-known weight-loss drugs — including Mounjaro and Wegovy — has risen sharply in recent months.

The Korea Customs Service announced Thursday that it has tightened customs inspections across major entry channels — including traveler baggage, express courier shipments and international mail — to block the import of harmful counterfeit obesity drugs and prevent illegal smuggling.

Customs seizures of weight-loss drugs surged from 4 cases in 2024 to 1,189 in 2025, and have already reached 5,030 cases through August this year — 4.2 times last year's full-year total.

Over the past three years, customs authorities have seized a combined 6,223 cases of weight-loss drugs. By entry channel, international mail accounted for 4,961 cases, traveler baggage for 1,232 and express courier for 30.

Seizures of illegal pharmaceuticals brought in from abroad extend well beyond weight-loss drugs. The Korea Customs Service has intercepted about 60,000 cases of illegal medicines over the past three years, including roughly 21,000 cases through August this year.

The Korea Customs Service works with the Ministry of Food and Drug Safety to manage customs clearance for pharmaceuticals entering the country from abroad, in order to protect public health.

Under current rules, harmful drugs that the Ministry of Food and Drug Safety has flagged to the Korea Customs Service may only clear customs if they meet designated import requirements, such as holding an exemption recommendation for import-requirement verification.

Mounjaro and Wegovy imported from overseas also fall under the category of harmful drugs flagged by the ministry. Customs officers screen such items through X-ray scanning and physical inspection; products that fail to meet the required import conditions are held from clearance and then returned or destroyed.

When violations go beyond a simple failure to meet import requirements — such as confirmed smuggling — the agency pursues investigation and punishment in accordance with relevant laws.

The Korea Customs Service operates a border-level interception system that links on-site customs inspections with scientific analysis conducted by the Central Customs Laboratory, responding to the growing variety of narcotics and other public-safety hazards entering the country.

The Central Customs Laboratory scientifically analyzes the composition and characteristics of items seized or held by customs, supporting clearance decisions, enforcement operations and criminal investigations.

As part of that analytical work, the Central Customs Laboratory teamed up with researchers at Chung-Ang University's College of Pharmacy to analyze Mounjaro products originating from India that had been intercepted at the border — examining active-ingredient content, impurities and other product characteristics.

The laboratory used an analytical method established by the Ministry of Food and Drug Safety's National Institute of Food and Drug Safety Evaluation to measure the content of tirzepatide, Mounjaro's active ingredient. A Chung-Ang University research team — Kim Su-hyeon, Choi Jong-woo and Byeon Su-bin — focused on impurities, a critical aspect of pharmaceutical quality control, and conducted a detailed analysis.

Inconsistent active-ingredient levels, unidentified impurities detected; rights holder confirms products are counterfeit

The analysis found wide variation in active-ingredient content across products, and multiple unidentified impurities were detected in some. Taken together, the findings indicate that the Mounjaro products examined cannot be considered to reliably meet pharmaceutical quality and safety standards.

The products were also found to have been transported without a cold-chain distribution system — the refrigerated logistics required to maintain drug quality during distribution.

Mounjaro must in principle be refrigerated at 2 to 8 degrees Celsius, making proper quality management essential not only during manufacturing but also throughout transport and storage.

Na Dong-hee, a professor at Chung-Ang University's College of Pharmacy, said the analysis found inconsistent active-ingredient levels across products as well as unidentified impurities. "Injectable drugs in particular require strict manufacturing and quality controls — not only for active ingredients and impurities but also for sterility assurance," Na said. "Purchasing and using products of unverified origin and quality on one's own can be dangerous."

Lee Jin-hee, director general of the Korea Customs Service's Customs Clearance Bureau, said the agency would strengthen inspections across all entry channels — traveler baggage, international mail and express courier — as illegal import attempts involving weight-loss drugs and other pharmaceuticals continue to increase, and would respond firmly to smuggling and other illegal activities.

"We will also work more closely to link on-site customs inspections with the specialized analysis of the Central Customs Laboratory, so that narcotics, illegal pharmaceuticals and other items that threaten public health and safety are thoroughly blocked at the border before they can enter the country," Lee said.