My dad has diabetes and has been diagnosed with “lipid necrosis at injection sites”. He takes Mixtard, 25 units before breakfast and 15 units before dinner. He has recently changed from animal to human Mixtard. Why does lipid necrosis occur? Does it have something to do with the type of anti-diabetic drug being injected?

The term you use “lipid necrosis at injection sites” indicates to me that you are probably referring to a condition known as lipoatrophy which can occur at and around insulin injection sites. Lipoatrophy is characterized by a depressed area of the skin around the injection site which occurs due to a loss of fat in that area. Lipoatrophy is likely to be an immune reaction to the insulin.

This condition is usually associated with the use of less purified animal-origin insulins that have far greater immunogenic properties than the human insulins. The use of highly purified human insulins is associated with a much smaller incidence of lipoatrophy. Also, large doses of insulin at one site may lead to lipoatrophy.

I think that the switch to human insulin may be very helpful for your father. Additionally, it is very important for him to frequently rotate injection sites.

CF