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Basal insulin

Lets talk about Insulin! There are many types of insulin available for multiple daily injection (MDI) use. The most commonly used and most effective MDI therapies for T2DM are basal insulin + orals/GLP-1 (will explain in future posts) or basal insulin + rapid acting insulin. For T1DM we always must use both basal and rapid acting insulin to control glucose levels.

Today, I will focus on basal insulins. A successful dose of basal insulin should allow you to skip meals without fearing hypoglycemia, eat later than usual without hypoglycemia, and allow accurate carb coverage with rapid acting insulin. Pictured below are some of the many basal insulins currently available including; Levemir, Lantus, Basaglar (generic of Lantus), Tresiba, and Toujeo. If you are taking long acting insulin, you are more than likely taking one of these.

But how do they work and why do we take them the way that we do? Levemir, Lantus, and Basaglar are made up of different components, but act very similarly. All can be taken between 1-2x/day. Levemir begins working within 1 hr, peaks in 5hrs, and has a duration of 18-24hrs. Lantus/Basaglar begins working in 1-2hrs, peaks at 6hrs (less peak than Levemir), and has a duration of 18-24 hrs.

These three insulins are often given at night to ward off “dawn phenomenon”, an increase in glucose levels occurring ~3am when the liver kicks out glucose to get your day started. When given at the correct time, the peak of these insulins will counteract “dawn phenomenon”. A large nighttime dose can make it difficult to time this while still preventing nocturnal hypoglycemia before the peak. A peak of your insulin ~2am for instance may be the cause of your nighttime lows. Also keep in mind, not everyone has a “dawn phenomenon”.

For someone who frequently suffers from nocturnal hypoglycemia, it is best to inject basal insulin in the mornings causing the peak to occur during the day (which is safer). This person may reduce their lunchtime dose of rapid acting insulin if low BGs occur around peak time. Whatever time you give these basal insulins it is important to take them at the same time every day to prevent a gap in coverage or doubling of insulin. Additionally; Lantus, Basaglar, and Levemir can be split into two doses if they are not lasting a full 24hrs (this is very common). For instance, Lantus given at bedtime may lose its efficacy around dinner the next day. The prandial (mealtime) insulin given for dinner will work for 4-5hrs after that but since Lantus takes 1-2hrs to kick in, there would be a gap in coverage leading to elevated morning glucose levels. People who experience this should try splitting their doses (with your clinician's approval, of course).

The newest basal insulins available include Toujeo and Tresiba, both of which require 1 injection/day and have no true peak. This leads to very stable blood glucose levels. Toujeo begins working after 6hrs and has a duration of 24-36hrs. Tresiba begins working after 1hr and has a duration of >42hrs. Because of this, Tresiba can be injected at different times of the day (>8hrs from previous dose). Tresiba is therefore great for people with hectic schedules or who sometimes miss their dosages.

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