Basal insulin (also known as background insulin)
Basal insulins fall into two sub-categories, again based on their duration of action; they are either intermediate-acting (examples include Humulin®-N or NPH) or long-acting (such as Lantus®).
Intermediate-acting insulin starts working 2 to 4 hours after injection, peaks approximately 4 to 12 hours later and continues to work for 12 to 18 hours. It is usually taken twice a day. Since there is a peak of action, it increases the risk of hypoglycemia if not matched appropriately to the consumption of carbohydrates.
Long-acting insulin starts to work several hours after injection and works for approximately 24 hours. There is no peak, so there is a lower risk of hypoglycemia. For type 1 diabetes, long-acting insulin must be used in conjunction with a mealtime insulin. When starting insulin in type 2 diabetes, healthcare professionals usually start patients with this type of insulin, injected once daily.
New generation insulins
Newer formulations of basal insulin have come to market; ultra-long-acting and concentrated forms. Insulin degludec is an example of an ultra-long-acting basal insulin that has a duration of action of longer than 24 hours and lower day-to-day variability than the regular long-acting insulin. Because of this, it has been noted that the ultra-long version has resulted in less frequent symptomatic hypoglycemia.
A promising new treatment has recently been introduced in Canada, an even longer-acting form, a once-weekly insulin injection, offering a more convenient alternative for individuals living with type 1 or type 2 diabetes.
Finally, several concentrated forms of insulin are also available. This format offers lower-volume therapy, predictable and durable glycemic control, and may lower the risk of hypoglycemia compared with the regular insulins of the same origin.
Overall, too much insulin is definitely a cause of low blood glucose. One reason newer insulins are preferred over regular insulin and NPH is that they’re less likely to cause blood sugar lows, particularly overnight. Insulin pumps may also reduce the risk of low blood glucose. Accidentally injecting the wrong insulin type, too much insulin, or injecting directly into the muscle (instead of the just under the skin), can also cause low blood glucose.
With adequate self-management education, appropriate glycemic targets, self-monitoring of blood glucose and support, intensive therapy may result in fewer episodes of hypoglycemia, particularly with use of the newer insulin formulations.
