What is basal insulin?

Basal insulin is sometimes called background insulin. It is an intermediate or long-acting insulin that is absorbed slowly and gives the body a steady, low level of insulin to manage blood glucose. This mimics the body’s natural low-level steady release of insulin. It is also used to describe the low-level steady trickle of insulin delivered by an insulin pump.

Dr. Jack Merendino, MD
Endocrinology Diabetes & Metabolism
The term “basal” insulin applies to insulin that is long-acting and provides a base or background of insulin throughout 24 hours. Long-acting or basal insulins include insulin glargine, sold as brand-name Lantus and Toujeo, and insulin detemir, sold as brand-name Levemir.

We all need insulin in our body at all times. The amount of insulin rises and falls with meals. During prolong intervals between meals and especially overnight, insulin production returns to its background or “basal” level. But it turns out that many people have their biggest problem with blood sugar control during these times. This is because the liver releases glucose into the bloodstream to provide energy between meals. This glucose release should be accompanied by insulin from the pancreas, but in those with type 2 diabetes often the amount of insulin the body makes is much less than what is needed. These people typically awaken with high glucose levels. Normal fasting glucose levels, as measured after going at least 8 hours overnight without eating, should be less than 100. Many people who have type 2 diabetes have fasting sugars that are as high as 200 or sometimes even higher.  

Here is a “quick and dirty” test that I apply when deciding on what form of insulin to start: if a person has a fasting sugar that is significantly higher (i.e., 25 to 40 mg/dl) than his or her pre-dinner sugar, basal insulin is probably the right choice. If the reverse pattern is seen, basal insulin may still be appropriate, but other approaches might also be effective.  

Most patients with type 2 diabetes should probably be treated with basal insulin as their starting form of insulin, and often basal insulin in combination with other medications will often work for a patient over the long-term.  
Remember that for patients with type 1 diabetes, both “basal” and “bolus” (the short-acting insulin given with meals) are necessary, and that in any individual determining what kind of insulin and how much insulin to give are complex decisions that must be made by your doctor considering multiple factors.  

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Important: This content reflects information from various individuals and organizations and may offer alternative or opposing points of view. It should not be used for medical advice, diagnosis or treatment. As always, you should consult with your healthcare provider about your specific health needs.