How to Understand and Use Insulin – Part 2

This is the second part of a six part series on “How to Understand and Use Insulin.” The goal of this series is to promote a better understanding of insulin for those readers who already take insulin, including the many people with Type 2 diabetes who have switched from pills to insulin to treat their diabetes. The first and second parts of the series discuss the technical factors involved in minimizing variations in insulin absorption. Parts three and four will focus on adjusting insulin, and parts five and six will focus on insulin research.

Dr. Barry H Ginsberg, MD, PhD, and Endocrinologist, is currently the Medical Director for Becton-Dickinson, the largest manufacturer of syringes in the United States. Becton-Dickinson provides 95% of the syringes used in this country.




A similar effect is seen with exercise, although the full effect of exercise is much more complex than just its effect on insulin absorption (this will be discussed in subsequent articles). Exercising a region will lead to a dramatic increase in the rate of absorption of insulin and the amount absorbed, similar to that seen when warming the region. Although the clinical implications are complex, as a simple rule, people with diabetes should generally avoid injecting into an area that will be heavily exercised in the next 4 hours and should check their blood glucose before exercise. If their blood glucose is less than 150 mg/dl, they should eat some simple carbohydrate, such as glucose tablets before exercising (the amount will vary with the type and duration of the exercise and the initial blood glucose). If it is above 300 mg/dl they should probably postpone the exercise.

Injection technique can make a major difference in the rate and amount of insulin absorbed. As seen in Figure 1, we normally inject insulin into the subcutaneous fat. Under varying conditions, however, insulin might be injected into the subdermal space (between the skin and the subcutaneous fat), the subcutaneous fat, the epimuscular space (between the subcutaneous fat and the muscle) or intramuscularly (into the muscle). Absorption of insulin from each of these sites is different and all are faster than absorption from the subcutaneous tissue.

Injection of insulin into the sub-dermal space is an unusual event. It can occur if you go at too great an angle or use a very short needle. Insulin absorption from this area is not very well-studied, but seems to be very fast. It is difficult to reproducibly inject into this space and few try.



The type of device may alter insulin absorption. Although most people with diabetes use syringes to deliver insulin, there are the alternatives of jet injectors, insulin pens and insulin pumps. In addition, there are some experimental techniques such as the use of “sprinkler” needles. Insulin injected by syringes or pens is deposited as a single large drop (Figure 2). Since this minimizes the area for absorption of insulin, movement of insulin to the blood is slow. In contrast, the insulin delivered from a jet injector disperses upon hitting the skin and forms multiple small droplets. Since the surface area of these multiple droplets is much larger, insulin is absorbed about 15 minutes earlier after jet injection than after a syringe or pen. One type of experimental needle delivers insulin through minute holes in the wall. Insulin is also absorbed faster from this “sprinkler” needle.



Next Issue: Part 3-Adjusting Insulin.

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