WASHINGTON, March 12 - Eli Lilly said it discovered an impurity in compounded weight-loss products that include vitamin B12 together with tirzepatide, the active ingredient in its branded treatments Zepbound and Mounjaro. In a public letter describing laboratory testing of samples obtained from compounding pharmacies, medspas and telehealth networks, the company reported that a chemical reaction between tirzepatide and vitamin B12 produced a previously unrecognized impurity.
Lilly said it found the impurity in all ten samples it tested. The company noted that nothing is known about the impurity's short- or long-term effects in humans, its potential influence on how the drug interacts with GLP-1 and GIP receptors, or risks related to toxicity, immune response, and the compound's absorption, distribution, metabolism, and elimination.
In the letter, Lilly's chief medical officer, David Hyman, warned about the broader risks of compounded products. He said the U.S. Food and Drug Administration has cautioned that compounded medications can pose safety, effectiveness, and quality concerns because they are not reviewed by the agency. According to Hyman, adding a reactive substance such as vitamin B12 without clinical testing or FDA review introduces additional unknown risks.
Lilly said it has informed the FDA of its laboratory findings and urged a nationwide recall of products that contain both tirzepatide and vitamin B12. The disclosure follows the company's ongoing efforts to challenge what it describes as illegal copies of its branded medicines; Lilly has filed lawsuits against compounding pharmacies, wellness centers and other companies that, it says, market products claiming to contain tirzepatide.
Compounders have defended their practices by citing a limited provision of federal law permitting compounding when patients require individualized formulations for medical reasons, such as adding vitamins or creating dosages not available in branded products.
The issue of compounded weight-loss drugs sold through telehealth channels has drawn regulatory scrutiny. The FDA issued warning letters in September to 30 telehealth companies over false or misleading claims about compounded versions of weight-loss medicines. The agency also has said it could take action against so-called illegal copycat drugs.
In February, telehealth company Hims & Hers Health announced plans to offer a compounded version of Novo Nordisk's Wegovy pill but subsequently withdrew that plan. The company instead announced this week that it will sell Novo Nordisk's branded Wegovy and Ozempic on its platform.
Lilly's testing and its public letter emphasize uncertainties around compounded preparations that mix tirzepatide with vitamin B12. The company said the impurity appears to result from a chemical interaction between the active pharmaceutical ingredient and the added vitamin, but identified no clinical data about the impurity's effects. Lilly's call for a nationwide recall and notification to the FDA signal escalation in the company's response to compounded products it considers unauthorized.
Separately, promotional material referenced in the original reporting noted that an AI-based stock evaluation product reviews Lilly among many companies using numerous financial metrics and identifies stocks based on risk-reward assessments. That product cited past winners as examples and offered to indicate whether Lilly is featured in any current strategies. The statements about the evaluation product were presented as information in the source material.
Summary
Eli Lilly reported that compounded weight-loss products that combine tirzepatide with vitamin B12 contain an impurity formed by a chemical reaction between the two ingredients. The impurity was present in all ten samples Lilly tested, and its effects on humans and on the drug's pharmacology are unknown. Lilly notified the FDA and recommended a nationwide recall, while continuing legal action against compounders and noting the prior FDA warnings to telehealth companies.
Key points
- Lilly identified a previously unknown impurity resulting from a reaction between tirzepatide and vitamin B12 in compounded products; the impurity appeared in all ten samples tested.
- The company has alerted the FDA and called for a nationwide recall of products containing both ingredients while pursuing legal action against compounders and sellers of alleged copycat tirzepatide products.
- Sectors potentially affected include pharmaceutical manufacturers, compounding pharmacies, telehealth providers, and the broader supply chain for weight-loss therapeutics.
Risks and uncertainties
- Unknown clinical impact of the detected impurity - the safety, toxicity, immune response, and pharmacokinetics in humans have not been established. This creates potential patient safety risks in compounded medicine use, affecting health care providers and patients.
- Regulatory and legal exposure for compounders and telehealth companies - prior FDA warnings and Lilly's calls for recall and litigation increase uncertainty for firms marketing compounded tirzepatide products, with implications for telehealth business models and compounding pharmacies.
- Market and supply implications for branded manufacturers and distributors - heightened scrutiny may affect distribution channels for weight-loss therapies and influence demand management decisions by retailers and telehealth platforms.