ASK THE DOCTOR

by Wesley W. Wilson, MD

NOTE: If you have any questions for "Ask the Doctor," please send them to the VOICE editorial office. The only questions Dr. Wilson will be able to answer are the ones used in this column.

Wesley Wilson, MD is an Internal Medicine practitioner at the Western Montana Clinic in Missoula, Montana. Dr. Wilson was diagnosed with type 1 diabetes in 1956, during his second year of medical school.

Q. I am 70 years old, female, slightly overweight, and insulin-dependent. I inject twice a day, 70/30 premix. My problem is night-time lows. I have had several bad reactions in my sleep, in the early hours of the morning (4 to 6 a.m.). They are getting more frequent in the past few months. At the same time, I am having an increasing number of daytime reactions. However, neither my diet, dosage, nor my exercise level have changed in recent years. What should I do differently?

A: Hypoglycemic episodes are always troublesome, but particularly troublesome if they occur at night. My first question to you is: When do you take your insulin? 70/30 insulin is a mixture consisting of 70% human N and 30% human R insulin. The convenience of a premixed combination of rapid and intermediate duration insulin is attractive, but the 70/30 mixture may not be best for all persons, as it lacks some degree of flexibility. It is often helpful to adjust the amount of either the rapid or the intermediate acting insulin to change the time of insulin effect. This can be done easily if the insulin user mixes her own N and R insulin (or Humalog insulin, which has a much quicker and shorter duration of action—not available in a premixed solution at this time), and there are advantages for persons using rapid insulins in this manner.

Probably the most frequently used insulin program for persons with type 1 diabetes consists of a mixture of N and R insulin or human N and Humalog insulin given before breakfast. A dose of human R or Humalog given before dinner to cover the carbohydrate in that meal, and a separate dose of human N taken at bedtime (about 10 p.m.) provide insulin effect during the seven or eight hours of sleep. 70/30 insulin taken with dinner may lead to low blood sugars six hours later—caused by the human N, and 70/30 insulin taken at bedtime may cause low sugars after several hours, due to the action of the R insulin. Most individuals with diabetes need a rapid rise in insulin level at mealtime, such as that seen with human R, or especially with Humalog taken before a meal—but they also need a lower, longer-acting insulin level spread over a long period of time, such as provided by human N or U, to keep sugar level under control between meals, and especially at night. Insulin need, other than at mealtimes, is often highest in the early morning hours (from 3 to 4 a.m.) and a dose of human N taken at 10 p.m. often provides the added insulin needed to cover that time. It is conceivable that you might do better not with premixed, but with an especially tailored mixture of insulin, and you may need to switch the time of your bedtime insulin, or the time of your daytime insulin, to a different hour.

Since you are having increasingly frequent insulin reactions in the day as well, I would be concerned about the possibility of kidney disease, since kidney disease is an unfortunate but frequent problem for persons living with diabetes. The gradual development of kidney disease may cause no symptoms, but may cause a sizeable reduction in insulin need! Persons who are having deterioration in kidney function can become more and more sensitive to their standard dose of insulin, and can have recurrent episodes of hypoglycemia. Fairly simple blood tests can be performed to see if there is any impairment of kidney function, and that certainly seems reasonable.

My third question to you: Has your weight changed? Reduction in weight certainly can cause increased insulin sensitivity, and may require a change in insulin dose.

If your kidneys are OK and your weight has not changed, I think it is important for you to discuss the insulin reactions you are having with your physician, and consider changing the time of your insulin administration, the mixture of insulins you are using, or perhaps both.

Hypoglycemia, in addition to being uncomfortable and unpleasant, can be dangerous—leading to falls, confusion, and emergency room visits. It is important to try and avoid that problem.