The chart titled “Basal Insulin Action” illustrates the approximate level of insulin in the bloodstream using various types of basal insulin programs.
Basal option 1: NPH or Lente at bedtime. The advantage of this program is the peak that occurs during the predawn hours—for those who need it. The disadvantages include the unpredictability of the peak and the potential for a blood glucose rise in the daytime and evening as the insulin action falls to very low levels at these times.
Basal option 2: Ultralente at dinner. The advantage of this program is the gradual peak during the night, along with a constant presence of basal insulin throughout the 24-hour time period. The disadvantages include absorption inconsistencies, potential blood glucose rises during the night (due to the lack of a substantial peak), and the potential for blood glucose rises during the evening as the insulin wears off. Because Ultralente usually lasts for more than 24 hours, there is also the possibility of overlapping doses when taking injections 24 hours apart.
Basal option 3: Glargine or detemir once daily at bedtime. The main advantage of this program is the relatively unwavering flow of basal insulin (a very slight peak may occur 6–10 hours after injection) and consistent absorption pattern that is unaffected by exercise and skin temperature. The disadvantages include the potential for blood glucose rises during the night (due to the lack of a predawn peak) and the potential for blood glucose drops in the afternoon and evening (if meals are delayed), if the basal insulin level exceeds the liver’s production of glucose. In some people, glargine begins to wear off in less than 24 hours, resulting in a blood glucose rise prior to the next injection.
Basal option 4: Insulin pump therapy. Pump therapy offers the greatest degree of flexibility in terms of matching basal insulin to the body’s needs. Because small pulses of rapid-acting insulin analogs—either lispro (Humalog), aspart (Novolog), or glulisine (Apidra)—are used to deliver basal insulin, the “basal rate” can be adjusted hourly, if needed, to match the liver’s normal, 24-hour pattern. Pumps also permit temporary changes to basal insulin rates to accommodate short-term changes in basal insulin needs (for situations such as illness, high or low activity levels, stress, and menstrual cycles).
Perhaps the greatest drawback to pump therapy is the risk of ketoacidosis. Any mechanical problem resulting in stoppage of insulin delivery can cause a severe insulin deficiency and production of ketones in just a few hours.
Starting doses
Once you have selected a strategy for supplying basal insulin, the next step is to determine the proper dose. Ideally, this should be done in cooperation with a physician who is experienced at setting and adjusting insulin doses.
In most cases, the daily dose of basal insulin is not very different from the total daily dose of bolus insulin. The daily basal insulin requirement generally depends on a person’s body weight and sensitivity to insulin, which is affected greatly by physical activity and hormone levels. For those with Type 2 diabetes, the daily basal insulin requirement can vary considerably: Some people who still produce their own insulin may require only a few units daily, while people who are obese and highly insulin resistant may require hundreds of units daily.
For people who produce virtually no insulin on their own (including those with Type 1 diabetes), insulin requirements are somewhat more predictable. The chart “Typical Basal Requirements” provides typical ranges for daily basal insulin needs.
