Because I have cystic fibrosis along with my type 1 diabetes, I have been told I do not need to limit my calories, etc. I am now taking 30-60 units of Humalog/day. Is this reasonable? If I am not getting lows, is there an upper limit (e.g., 100 U/day) before insulin simply ruins your body, doesn’t work, etc.?

I have a great deal of respect for care providers who work with cystic fibrosis (CF) patients. It is difficult course to navigate with the problems of intermittent infections and problems. However, people with CF are living longer and better lives, so they do develop elevated blood sugars. They are now presenting with the complications we see in people with other kinds of diabetes. Yet, the most common golden rule patients with CF hear is to make sure they keep up their calorie intake to provide the extra energy their body needs. On the surface, it appears contradictory to care for elevated sugars and eat a lot of food.

At our institution, we have been very aggressive about teaching carbohydrate counting to our patients with CF-related diabetes. The goal is to continue to take in appropriate number of calories, and we try to match the calories taken in with an appropriate amount of insulin. This strategy does not limit food but makes sure there is a system in place to make daily adjustments for the amount of food taken in. For instance, if 10 servings of carbohydrate (150 g carbohydrate) are being eaten, and the usual ratio used by the patient is 1 unit per 15 g serving, the patient will administer 15 units of Humalog or Novolog for their meal needs. This same strategy can be used for extra meals.

Unlike patients with other kinds of diabetes, patients with CF tend to have elevated blood sugars more frequently after meals, rather than in the morning. The most important insulin is the amount given with the meal. When successful, the adequate administration of insulin allows your body to utilize the carbohydrates you ingest. If you eat a lot, but have very high sugars, your body cannot utilize the food you take in.

JTL

[Editor’s comment: The bottom line is, with the availability of basal/bolus insulin regimens and the insulin pump, it is now possible to match insulin with food intake. The amount of insulin that is given doesn’t really matter as long as the outcomes are optimal blood glucose control and reasonable body weight.

SS]