Insulin is the hormone that makes sure that glucose in the blood gets into cells and provides them with energy to function. Without insulin, glucose stays in the bloodstream, causing chronically high blood sugar levels and serious diabetes-related health complications.
Insulin therapy is the only treatment for people with type 1 diabetes and sometimes a necessary option for people with type 2 diabetes.
But taking insulin is not as easy as taking tablets . First, it is a liquid medication that must be injected subcutaneously, sometimes several times a day. Second, it requires precise dosing and careful blood sugar control. Third, it is a very unstable medication that must be handled and stored with care. And fourth, there are more than 20 different types of insulin !
The two main types of insulin are basal and bolus insulin . While basal insulin acts as a slow background insulin, injecting bolus insulin helps control blood sugar after a meal.
Diabetics are often prescribed both basal and bolus insulin. Understanding the difference between the two and how they work together is important for good diabetes management .
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What is basal insulin?
Basal insulin, also called background insulin or long-acting insulin , is a slow-acting insulin used to keep blood sugar levels under control during fasting periods, such as between meals or overnight . Therefore, basal insulin is given at night.
The body, or more specifically the liver, constantly secretes glucose to enter the bloodstream and provide energy to cells. This process, called glycogenolysis , is essential for the functioning of our body.
If you don't have diabetes, your pancreas naturally releases background insulin to move glucose produced by the liver from the bloodstream into cells. But in insulin-dependent diabetes, the pancreas doesn't produce enough (or any) insulin . This causes blood sugar to rise to alarming levels, even when you don't eat carbohydrates or sugar.
Basal insulin mimics natural insulin . It works slowly, releasing microdoses of pure crystalline insulin into the bloodstream throughout the day and night (generally over 12 to 24 hours, depending on the type of insulin). It is usually injected once or twice daily .
These long-acting insulins play an important role in the treatment of type 1 diabetes and are sometimes also necessary for people with type 2 diabetes.
There are three main types of basal insulin with different onset times (how quickly the effect starts), durations of action (how long the effect lasts), and peak times (when the effect reaches its peak).
Medium-acting insulin (basal)
Intermediate-acting insulin is the most commonly prescribed basal insulin . It enters the bloodstream about one to four hours after injection, reaches its peak level four to 12 hours later, and lasts for about 12 to 18 hours.
It is given once or twice daily and can sometimes be mixed with bolus insulin (fast-acting insulin).
Intermediate-acting insulin is also called NPH insulin (neutral protamine Hagedorn insulin) or isophane insulin. It is sold under the brand names Humulin-N, Novolin-N and ReliOn and is available in the form of injection pens, ampoules and cartridges for insulin pumps.
Unlike most other insulins, NPH basal insulin does not look clear but cloudy .
Long-acting insulin (basal)
Long-acting insulin stays in the bloodstream longer than intermediate-acting insulin . There are two types of long-acting basal insulin available in the U.S. market, including detemir (sold under the name Levemir ) and glargine (sold under the names Lantus , Toujeo, and Basaglar ).
In contrast to intermediate NPH insulins, long-acting insulins do not have a peak time of action. Instead, they work evenly throughout the day, with an onset of action 1 to 4 hours after injection and a duration of action of up to 24 hours.
These insulins are clear in appearance . They are usually given once a day and cannot be mixed with other insulins.
Very long-acting insulin (basal)
Very long-acting insulins are relatively new products. They stay in the bloodstream for 36 to 42 hours and have no peak period.
Degludec basal insulin (marketed as Tresiba ) was launched in 2016 and can stay in the bloodstream for up to 42 hours. It is available in two strengths (100 U/ml and 200 U/ml). Also, Toujeo U-300 is referred to by some as an ultra-long-acting insulin, while others place it in the long-acting insulin category.
Which basal insulin is good for you?
Deciding on a type of basal insulin ultimately depends on your lifestyle and diabetes management. There are many factors to consider , including your weight, diet, your average HbA1c level, how much insulin your pancreas is still producing, how well you cope with injections, and more.
Only your diabetes doctor can determine which type of basal insulin is best for you. Never use an insulin that has not been prescribed for you.
In addition to basal insulin, you may also be prescribed bolus insulin.
What is bolus insulin?
In contrast to basal insulin, bolus insulin, also called rapid-acting insulin, short-acting insulin or mealtime insulin, has a short duration of action and acts on blood sugar after a meal (also called postprandial blood sugar).
The carbohydrates you eat (rice, bread, pasta, fruit, etc.) contain sugar that is digested in the stomach and absorbed into the bloodstream as glucose. In people without diabetes, the pancreas responds immediately and starts producing insulin to keep blood sugar levels within a normal range. However, if the pancreas does not produce enough insulin or any insulin at all, the glucose stays in the blood and causes a rise in blood sugar (hyperglycemia).
Therefore, a bolus dose of insulin is needed to regulate blood sugar after meals. However, not all diabetics need bolus insulin. Diabetics whose pancreas still produces insulin can correct their blood sugar after meals with other medications, such as metformin or other tablets.
Bolus insulin must be fast-acting and is injected before, during or immediately after meals. It can be given using a pen, syringe or insulin pump every time a person eats carbohydrates (unless it is to correct hypoglycemia).
As with basal insulins, there are different types of bolus insulins, including rapid-acting and short-acting insulins.
Fast-acting insulin (bolus)
Rapid-acting insulin, also called regular insulin, provides insulin for meals eaten within 20 to 60 minutes of injection . It begins to work within about 30 minutes, reaches its peak in 2 to 3 hours, and stays in the bloodstream for 3 to 6 hours. It must be injected 30 minutes before each meal or carbohydrate intake (including snacks).
Novolin-R, Humulin-R and Velosulin (for insulin pumps) are short-acting, regular bolus insulins. Their liquid looks clear.
Fast-acting insulin is newer than regular insulin and works even faster . It covers the insulin requirement for meals taken at the same time as the injection. The onset of action is 10 to 15 minutes, the peak effect is 30-90 minutes and the total duration is 2 to 4 hours.
There are several types of rapid-acting bolus insulins, including aspart (marketed as Novolog and Fiasp ), lispro (marketed as Humalog and Admelog ), and glulisine (marketed as Apidra ). These are also clear insulins.
Depending on the type of diabetes, blood sugar management plan, lifestyle, and other factors , a person may be prescribed basal insulin, bolus insulin, or a combination of both .
Basal insulin vs. bolus insulin: The bottom line
The most important points about the difference between basal and bolus insulins are:
- They both lower blood sugar levels.
- They target different "types" of blood sugar: basal insulin acts on fasting blood sugar, while bolus insulin acts on blood sugar after eating.
- They have different start times, peak times and durations.
- Basal insulin is a slow-acting background insulin, while bolus insulin is a fast-acting insulin.
- Diabetics may be prescribed basal insulin, bolus insulin, or both.
- Sometimes they can also be mixed to reduce the number of injections.
The basal-bolus concept
The basal-bolus concept is an intensive insulin therapy that involves injecting both basal and bolus insulin . It is mainly used for people with type 1 diabetes. Like any medical treatment, it has some advantages and inconveniences.
Advantages :
- It allows more flexibility in mealtimes
- It lowers A1C more than other diabetes treatments
Disadvantages :
- It includes up to 4 insulin injections per day
- Patients must keep a supply of both types of insulin
- There is a risk of confusing one insulin with another
With new technologies for diabetes care and modern insulin pumps that eliminate the need for daily injections, the basal-bolus concept is performed less and less than before . Instead, doctors now prefer automated insulin delivery solutions that are close to an artificial pancreas and allow for optimized blood sugar control and a better quality of life.
Do you receive basal-bolus insulin therapy? What do you think about it? Do you find it convenient and efficient? Or would you use a smart insulin pump instead?
