Human Insulin for Diabetes: Why Doctors Are Revisiting Regular R Insulin

What Is Regular Human Insulin and Why Is It Back in the Spotlight?

Regular human insulin, commonly referred to as R insulin or Humulin R, is a short-acting insulin that is structurally identical to the insulin produced by the human pancreas. First made widely available through recombinant DNA technology in the early 1980s, it was the standard of care for diabetes management for years before the introduction of rapid-acting analog insulins like lispro, aspart, and glulisine in the late 1990s and 2000s.

The renewed interest in human insulin stems from several converging factors. The cost of analog insulins has risen dramatically, with some patients in the United States paying hundreds of dollars per month out of pocket. Meanwhile, human insulin is available at a fraction of the cost — in some cases, over-the-counter at major pharmacies for approximately $25 per vial. Prominent diabetes clinicians, including the late Dr. Richard K. Bernstein, long advocated for the use of regular insulin as part of a carefully managed low-carbohydrate diabetes regimen, arguing that its pharmacokinetic profile can be well-matched to controlled meal plans.

How Does R Insulin Compare to Modern Analog Insulins?

The primary pharmacological difference between regular human insulin and rapid-acting analogs lies in their onset and duration of action. Regular insulin typically begins working within 30 minutes of injection, peaks at 2 to 3 hours, and has a total duration of approximately 6 to 8 hours. By contrast, rapid-acting analogs begin working in about 15 minutes, peak within 1 hour, and last 3 to 5 hours. This means patients using R insulin need to inject approximately 30 minutes before meals to align the insulin peak with postprandial glucose rise.

According to the American Diabetes Association (ADA), both human insulin and analog insulins are considered appropriate for diabetes management. A 2018 analysis published in BMJ Global Health found that human insulin and analog insulins produced similar improvements in hemoglobin A1c levels, though analogs were associated with modestly lower rates of hypoglycemia. For patients who follow structured meal plans with predictable carbohydrate intake, regular insulin can be highly effective. The World Health Organization includes human insulin on its Model List of Essential Medicines, underscoring its continued importance in global diabetes care.

What Should Patients Know About Managing Low Blood Sugar?

Hypoglycemia, or low blood sugar, is the most common acute complication of insulin therapy regardless of the type used. Symptoms include shakiness, sweating, confusion, rapid heartbeat, and in severe cases, loss of consciousness. The ADA recommends the "rule of 15" for treating mild to moderate hypoglycemia: consume 15 grams of fast-acting glucose (such as glucose tablets, juice, or regular soda), wait 15 minutes, and recheck blood glucose. If levels remain below 70 mg/dL, the treatment should be repeated.

Because regular human insulin has a longer duration of action than rapid-acting analogs, some clinicians note that the risk window for hypoglycemia can be extended, particularly if meals are delayed or skipped. This makes blood glucose monitoring especially important for patients using R insulin. Continuous glucose monitors (CGMs) have made this process considerably easier and safer. Patients considering a switch to or addition of human insulin should work closely with their healthcare provider to adjust dosing, timing, and dietary patterns to minimize hypoglycemic episodes while maintaining good glycemic control.