The primary job of basal insulin is to keep your blood glucose levels stable during periods of fasting, such as while you’re sleeping. Without this insulin, your glucose levels would rise at an alarming rate.

While fasting, your liver continuously secretes glucose into the bloodstream. Basal insulin keeps these glucose levels under control.

It ensures that your cells are fed with a constant stream of glucose to burn for energy throughout the day.

Here’s what you need to know about basal insulin medication and its importance for managing diabetes.

There are three main types of basal insulin.

Intermediate-acting insulin, NPH

Brand-name versions include Humulin and Novolin. This insulin is administered once or twice daily. It’s usually mixed with mealtime insulin in the morning, before your evening meal, or both. It works hardest in the 4 to 8 hours after injection, and the effects start waning after about 16 hours.

Long-acting insulin

Two types of this insulin currently on the market are detemir (Levemir) and glargine (Toujeo, Lantus, and Basaglar). This basal insulin begins working 90 minutes to 4 hours after injection and remains in your bloodstream for up to 24 hours. It may start weakening a few hours earlier for some people or last a few hours longer for others. There isn’t a peak time for this type of insulin. It works at a steady rate throughout the day.

Ultra-long acting insulin

In January 2016, another basal insulin called degludec (Tresiba) was released. This basal insulin begins working within 30 to 90 minutes and remains in your bloodstream for up to 42 hours. As with the long-acting insulins detemir and glargine, there isn’t a peak time for this insulin. It works at a steady rate throughout the day.

Insulin degludec is available in two strengths, 100 U/mL and 200 U/mL, so you must be sure to read the label and follow instructions carefully. Unlike detemir and glargine, it may be mixed with other rapid-acting insulin that may reach the market soon.


When deciding between intermediate- and long-acting basal insulins, there are many factors to consider. These include your lifestyle and willingness to inject.

For example, you can mix NPH with mealtime insulin, while long-acting basal insulin must be injected separately. Factors that can affect your insulin dosage include your body size, hormone levels, diet, and how much internal insulin your pancreas still produces, if any.

Many people with diabetes like basal insulin because it helps them better manage blood sugar levels between meals, and it allows for a more flexible lifestyle.

For example, if you use long-acting insulin, you don’t have to worry about peak times of insulin activity. This means that meal timing can be more flexible. It may also reduce your risk of low blood sugar levels.

If you struggle to maintain your target blood sugar levels in the morning, adding basal insulin to your dinnertime or bedtime regimen may help solve this problem.

With basal insulin, you have three dosage options. Each option has pros and cons. Everyone’s basal insulin needs are different, so your doctor or endocrinologist can help you decide which dosage is right for you.

Taking NPH at bedtime, in the morning, or both

This approach can be valuable because the insulin peaks during the predawn and afternoon hours, when it’s needed most. But that peak can be unpredictable depending on your meals, meal timing, and activity level. This may result in low blood sugar levels while you’re sleeping or low or high blood glucose levels during daytime hours.

Taking detemir, glargine, or degludec at bedtime

The continuous flow of these long-acting insulins is one of their main advantages. But, some people find that the detemir and glargine insulin wears off sooner than 24 hours after injection. This can mean higher blood glucose levels at your next scheduled injection. Degludec should last until your next scheduled injection.

Using an insulin pump

With an insulin pump, you can adjust the rate of basal insulin to coincide with your liver function. One drawback to pump therapy is the risk of diabetic ketoacidosis due to pump malfunction. Any slight mechanical problem with the pump can result in you not receiving the correct amount of insulin.

Some potential side effects associated with basal insulin include hypoglycemia and possible weight gain, though to a lesser degree compared with other types of insulin.

Certain drugs, including beta-blockers, diuretics, clonidine, and lithium salts, can weaken the effects of basal insulin. Talk to your doctor and endocrinologist about the medications you currently take and any dangerous drug interactions.

Basal insulin is a crucial component in your diabetes management. Work with your doctor or endocrinologist to determine which type is best for you and your needs.