Hello Well, the interaction is more with the person than the drugs. They are often used together. Here s the problem. Lisinopril is not a very good drug. How much of it gets in Lisinopril bioavailability (approximately 25%) is not significantly affected by food, age, or co-administration of Hydrochlorothiazide (HCTZ), is small and often is half of that and sometimes a bit more. This varies day to day. If someone has kidney trouble then Lisinopril both lowers the work the kidney does and also lowers the Work The Kidney does--meaning the kidneys do less and are less effective, but protected from wear and tear. Metformin goes out by the kidneys and if the kidneys are somewhat bad, the metformin will build up. This can rarely then make the kidneys shut down and produce a fatal response to the liver and kidneys. Generally, this does not happen. Generally people have normal liver and kidneys and then the drugs are fine. Then, lots of diabetic drugs can lower the sugar too much. This is checked by fingerstick. Metformin is one of the LEAST likely to do this. Jardiance is the next least likely. Neither is likely to do that by itself. but if you add Glimepiride which directly lowers sugar with other drugs, then there can be sugar level that goes too low. fixable by adjusting medicines or taking sugar. Mostly, the problem is the sugar never getting low enough. Hope I have answered your query. Let me know if I can assist you further.