There is a very high chance that tirzepatide bonded to b12 is harmless, but without any actual testing it is not possible to know if this is the case or not. But it is not impossible that it has toxicity that is not immediately apparent, and what is an acceptable risk of that? Injecting compounds with completely unknown properties is intrinsically unsafe. Testing this would require proper in vitro and animal studies at the absolute least, and probably human trials to be actually safe. As well as studies to see how much and how often and under what circumstances this reaction occurred. Compounders are not going to fund that. It certainly appears that they combine when mixed, and this is not a rare one off event. There is no way at all the compounders would know this was happening unless it was tested after compounding with the right tests. I can easily imagine them testing their Chinese sourced peptides at an independent lab before mixing them for sale, but I cannot see why they would do it after mixing with a common molecule that has no known history of reacting like that. Major drug companies do test their formulations very carefully, the last thing they want is something unexpected turning up later making them look bad and potentially costing billions, but compounders are just not operating at that sort of scale. There is zero chance they will continue to use b12 with GLP drugs, the risk and potential for liability is too high.
