My father is a diabetes patient since 7 years and he is taking insulin since 4 years. I am his son and I am the only one who can give insulin to my dad but now I want my father to take insulin by himself. So I want to get him insulin pen so that he can easily take it. My dad has been prescribed with Human Mixtard 30/70 insulin, so I would like to know which insulin pen would be compatible with it and how to use it. Is all the insulin pen compatible with any insulin liquid?