If the fasting blood sugar is elevated and consistently equal to or greater than the bedtime blood sugar, giving NPH at bedtime will address this dawn phenomenon. In this case, NPH is best administered around 10 or 11 pm to maximize its glucose-lowering effects in the dawn hours (~ 3 to 8 am), when there is a natural increase in the hormones (growth hormone, cortisol, and glucagon) that increase blood sugars. Caution should be exercised to avoid giving NPH at suppertime or too early before bed, as this will increase the risk for nocturnal hypoglycemia.
Another factor to keep in mind is that patients may snack immediately before or right after they take their bedtime blood sugar (ie, not accurately reflecting the actual peak in blood sugar at night). If this is the case, you may mistakenly think they have the dawn phenomenon. Regarding risk for nocturnal hypoglycemia, it is not recommended to routinely give prandial insulin for hyperglycemia at bedtime. The proper approach to glucose management should be proactive (treat to prevent), not reactive (treat to fix).
Q: Can you provide some brief examples of which insulin to use and why?
1. If the bedtime and daytime blood sugars are on goal but the fasting is high, fix the dawn phenomenon with NPH insulin at bedtime. In this case, fixing fasting hyperglycemia may increase the risk for daytime hypoglycemia if the patient is on a secretagogue (sulfonylurea, glinide), so you may need to decrease the dose of the secretagogue accordingly.
2. If blood sugar is high only after a meal (or meals), use prandial insulin only for that meal.
3. If blood sugars are mild to moderately high “around the clock,” the addition of once-daily basal insulin generally works very well.
Note: Although there are other insulin treatment regimens (basal + prandial and premixed once or twice daily,) it is not possible to fully discuss these more complex regimens in a single column. This article is intended for the “when, why, and how” to add once-daily insulin to the regimen of a patient whose A1C is in the 7% range on maximal doses of metformin plus a secretagogue.