The Type 2 Diabetes Guide to Basal Insulin


Insulin is a necessary hormone to stay alive as it helps transport glucose into the cells where it turns into energy. There are two main causes for type 2 diabetes (T2D), which either occur at the same time or one can become a causal effect of the other:

  • A decrease in the quality of insulin
  • A decrease in the amount of insulin produced by the pancreas

A decrease in the quality of insulin causes the pancreas to produce a greater amount of this substance, which causes a progressive deficiency in the amount of insulin available.

And what happens when the amount of insulin is no longer enough to carry out all the activities and functions that our body does during the day? Well, blood glucose levels begin to rise, and sometimes the prescribed oral medication is not enough, so insulin may be required.

You could say that the insulin in our body works in two different ways.

a) Bolus insulin: This is the insulin used to cover the amount of food eaten, mainly carbohydrates, and to lower high blood glucose levels (correction dose).  As you can conclude, this means bolus insulin will lower blood glucose when it is high. Learn more about bolus insulin, here.

b) Basal insulin: This is the insulin that works like a base regardless of the food that is consumed. Our body requires basal insulin to regulate all those glucose variations that are not related to food, but to hormonal, physiological causes, etc. The purpose of this type of insulin is to regulate blood sugar levels.

What basal insulins are available?

The objective of this type of insulin is to cover the insulin requirements in between meals, these can be found in the following forms:

  • Intermediate or NPH
  • Long acting

Basal insulins usually have an onset of action of one to two hours. Basals have a very slight maximum peak that is not considered, except for NPH whose maximum peak is at four to eight hours after its application and its duration ranges from 12 to 42 hours.

When will a doctor prescribe the use of insulin?

According to the American Diabetes Association Standards of Care, physicians are advised to consider prescribing basal insulin for people with type 2 diabetes when:

  • There is ongoing weight loss
  • Symptoms of hyperglycemia are present
  • When A1c levels are greater than 10 percent (86 mmol/mol)
  • When blood glucose levels are very high (greater than 16.6 mmol/L300 mg/dL)

However, if the A1c level remains above the target despite taking basal insulin, a doctor may prescribe bolus insulin to supplement when eating.

Guidelines from Diabetes Canada make similar recommendations.

How to use basal insulin?

Your doctor will tell you which insulin to use as well as the amount of insulin you require. The dose is personalized, and you should not use someone else’s dose. For more information, here are some tips about insulin injection methods.

What are the risks and advantages of taking basal insulin?

The main risk when using insulin is a higher risk of hypoglycemia or low blood sugar, especially if you change the physical activities you are used to, such as walking a little more or doing more intense exercises, or taking more insulin than recommended. However, this can be avoided by using a glucose monitoring device to know how glucose behaves throughout the day. Learn more about hypoglycemia and how to prevent it if it happens. Another risk is skipping or using less insulin than prescribed, which leads to high blood glucose.

The advantage of taking insulin is the several ways in which it can help us achieve better glucose management with higher a time in range delaying or preventing the risk of diabetes complications. The downside is that taking it requires injections.

Key points:

  • Basal insulin is what our body requires to regulate all those glucose variations which are not related to food, but to hormonal, physiological issues, etc.
  • It can take one to four hours to start working.
  • Its maximum peak action goes from four to eight hours or it has a minimum peak action.
  • Its duration ranges from 12 to 42 hours.

Written By Eugenia Araiza, Posted , Updated 09/02/23

Eugenia has a degree in nutrition specializing in diabetes and she is a diabetes educator. She was diagnosed with type 1 diabetes 25 years ago. She is the creator of Healthy Diabetes. She really enjoys studying and helping others in managing their different types of diabetes. She loves studying, managing type 1 diabetes and nutrition. She especially enjoys writing about the impact diabetes has in her life. She lives surrounded by the love of her family, Luis Felipe, who lives with latent autoimmune diabetes in adults (LADA) type diabetes and her teenage son, Indigo.