Commonly used insulins in dogs with diabetes include Vetsulin and Novolin NPH (among others). Your veterinarian will discuss in greater detail the type of insulin being used.
Insulin should be refrigerated. Insulin suspensions (e.g. NPH, Vetsulin) need to be mixed completely by rolling the insulin between your palms or inverting it gently. Vetsulin needs to be shaken until uniformly milky and then allowing foam to disperse.
Insulin solutions (e.g. Levemir) are clear and do not need mixing prior to administration. Do not allow insulin to be frozen
Do not expose insulin to direct heat or light
Provided insulin is refrigerated, it does not need to be discarded after one month provided it is working and is not discolored.
Be sure to understand the dose of insulin you are to use. Do not change the dose without consulting your veterinarian.
Insulin overdose can be deadly.