In the early 1980s, human insulin produced by recombinant DNA technology came onto the market. It was the first time that this technology had been used in medicine, so hopes were high.

Like many physicians, I used the new human insulin in some patients under the assumption that it was a more physiological alternative to the animal insulins that had been in use for years.

Some of my patients, however, reported a sudden loss of the symptoms that had previously warned them when their blood sugar was low. This development of hypoglycemic unawareness related to human insulin was confirmed in two clinical studies. As a result of these findings, I believe that animal insulin is safer than human insulin for the ten to twenty percent of diabetic patients in whom animal insulin produces more pronounced hypoglycemia symptoms.

Reports of the loss of low blood sugar warning symptoms led insulin manufacturers to acknowledge the potential dangers of human insulin. Nevertheless, they soon began to withdraw bovine (cow) and porcine (pig) insulin from markets all over the world, while promoting the more expensive human insulins as a superior replacement. Diabetics had no option but to switch to the new insulins. This led to an active movement by patients who demanded to keep porcine and bovine insulins available for those who experience a loss of warning symptoms or other side effects from human insulin.

Now, manufacturers are withdrawing the first generation of human insulins and replacing them with even more expensive, patent-protected insulin analogues. Patient organizations such as the International Diabetes Federation have concluded that "there is no overwhelming evidence to prefer one species of insulin over another, and patients should not be changed from one species of insulin to another without reason."

My fifty years of experience as a diabetologist has convinced me that the "one insulin fits all" approach is not working. Alternative treatments - such as bovine and porcine insulin - must remain available.