What Is “Basal” Insulin?

I try hard to make diabetes terms easy to understand, including types of insulin. However, being human, I still fall short! Recently, a person with diabetes I was working with asked me what the heck I was talking about when I mentioned, “basal” insulin. We joked how it was a little different than the basil we cook with, and then I got on to talking in terms he could understand.

Your body’s natural insulin is released in two main phases - a continuous release throughout the day and night and a rapid, larger release in response to food. When replacing or supplementing your natural insulin needs with injections, we try to mimic these patterns.1

What is basal insulin?

Replacing your body’s natural insulin response to food is done with “bolus” dosing. Replacing your body’s natural, continuous insulin release is done with “basal” dosing. You may hear the term “basal/bolus” thrown out at appointments. That’s simply referring to a pattern of insulin injections that replace both of your body’s natural insulin phases.1

Basal dosing can be delivered by an insulin pump, but most often it references long-acting or ultra-long-acting types of insulin. These insulins are usually dosed once a day and provide blood sugar-lowering benefits over a 24-hour period or longer. Examples of basal insulin are Tresiba, Toujeo, Lantus, Levemir, or Basaglar.2

When do people typically start basal insulin?

Basal insulin is usually the first type of insulin you’re introduced to when you have type 2 diabetes (and your body is needing insulin). Starting doses of this type of insulin are usually based on a set dose (for example 10 units) from varying guidelines or a weight-based dose. Either way, the dose you start on, is not the dose you’ll stay on. It’s simply a starting place and from that point on, dosing decisions will be made based on your blood sugar patterns.2

Cap callout

One thing that’s often overlooked in basal insulin dosing is the cap at which doses should stop being increased and bolus insulin should be added. In my experience, the vast majority of people have been pushed beyond their cap (which is a weight-based dose—so it’s different for every person). While this typically is not a “life or death” situation (unless you’re having frequent low blood sugars), it’s a very inefficient way to dose insulin. Once you’re pushed beyond your individual cap, you tend to see less response in your A1c or blood sugar levels and more weight gain.  This is simply because your body needs help replacing the other phase of insulin release - bolus insulin. And no amount of basal insulin can replace the job of bolus insulin.3

Basal insulin experiences

While many folks I help aren’t excited about adding more insulin injections, the significant improvement they see in their blood sugar levels with basal/bolus dosing helps. Once we get both natural insulin phases replaced or supplemented by injections, then dosing adjustments are again based on blood sugar patterns. There really is no “cap” at that point.

At the end of the day, understanding basal insulin, how it works, and what to expect is critical to a successful diabetes management plan.

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