Eli Lilly identified high levels of a concerning impurity formed by the reaction between tirzepatide and vitamin B12 in compounded versions of the drug, potentially altering toxicity, immunogenicity, and pharmacokinetics.123
The impurity's short- and long-term effects in humans are unknown, posing safety risks to patients using these knockoff products.13
Lilly issued a public warning and open letter on March 12, 2026, urging the FDA to recall compounded tirzepatide products with untested additives like B12.234
Compounded products also showed other issues like bacterial contamination and elevated endotoxins; Lilly has sued compounders amid ongoing legal battles.13
Tirzepatide shortage ended in late 2024, barring routine compounding, yet practices continue under claims of personalization.1
Sources:
1. https://www.biospace.com/business/lilly-flags-concerning-impurities-in-compounded-tirzepatide
2. https://www.finedayradio.com/news/tv-delmarva-channel-33/eli-lilly-discovers-dangerous-impurity-in-copycat-weight-loss-medications/
3. https://intellectia.ai/news/stock/eli-lilly-warns-of-safety-risks-with-compounded-tirzepatide
4. https://www.marketscreener.com/news/eli-lilly-issues-warning-about-potential-safety-risks-of-tirzepatide-compounded-with-vitamin-b12-ce7e5fdddc8df32c