What is the function of insulin hormone? What type of patients are given insulin injections?

The function of insulin hormone is :-

What is the chemical nature of Insulin hormone?

Why are diabetes patients treated by insulin injections ?

What is the injection administered to diabeteic patients? Why is it given as injection and not as oral pills?

What are the types of recombinant insulin?

Insulin, a hormone, chemically is a

The hormone that acts antagonistically to insulin is