There is definitely no problem mixing. Some people say don't mix oil based and water based in the same syringe but that's a wives tale. The rational for not mixing is that oil and water don't mix but in the case of an injection, why would thay have to mix? They don't they will stay seperated for the most part and your body will absorb all the same. This works well when combinind winny with an oil based that needs to be injected often.