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Are You on the Right Kind of Insulin

Learn about the different forms of insulin and how to choose the best types for you.

Insulin is a critical hormone in the body. A hormone is a substance produced by one of the glands of the body that is carried in the blood to cause a change in a distant tissue or organ. Insulin is produced by the beta-cells of the pancreas and travels to the liver, muscles, and fat cells to cause those cells to take up glucose (or sugar) to use as energy. The pancreas releases insulin when blood glucose levels rise, which often occurs after absorbing sugar (or carbohydrates) from our food. When the liver, muscle and fat cells absorb glucose, blood glucose levels return to a normal range. For people without diabetes, natural insulin brings their glucose levels back down after a meal.

People with type 1 diabetes and some people with type 2 diabetes need to take insulin because their bodies either cannot produce enough insulin (insulin deficiency) or cannot respond well to their own insulin (called insulin resistance). The goal of taking insulin by injection, pen, pump, or inhalation is keep blood glucose levels as near to the non-diabetes range as possible. Click to learn more about type 1 diabetes and type 2 diabetes.

Were you recently diagnosed with diabetes? Check out our diagnosis article series

Characteristics of Insulin 

The main types of insulin used today are human insulin preparations and insulin analogs – we’ll get into the differences between the two types. These types are further differentiated by a few characteristics:

  • Onset of Action– How long it takes insulin to begin lowering blood glucose after being administered. 

  • Peak Action – The length of time that insulin works at its maximum strength and is most effective at lowering blood glucose.

  • Duration of Action – The total length of time that insulin is able to lower blood glucose and then completely leave the body. 

The most common insulin regimens are those that combine insulins with different onsets of action, peak action times, and durations of action depending on the time of day and meal schedules. This enables people to cover both their meals and have insulin action between meals and throughout the night.   

Basal vs. Prandial (“bolus”) Insulin

Some people taking insulin need to use both a basal and a prandial insulin each day, while others may only need to use basal insulin.

  • Basal (long-acting) insulins are designed to be injected once or twice daily to provide a constant background level of insulin throughout the day. Basal insulins help keep blood sugars at a consistent level when you are not eating and through the night but cannot cover carbs eaten for meals or snacks or glucose spikes after meals.

    • Some people use other medications, like GLP-1 agonists, to help cover mealtimes. GLP-1/basal treatments for people with type 2 diabetes combine basal insulin with GLP-1 agonist medication in one daily injection. This combination can effectively lower glucose levels while reducing weight gain and risk of hypoglycemia (low blood sugar). Learn more here.

  • Prandial (rapid-acting or “mealtime”) insulins are taken before, during, or after mealtime and act rapidly, serving to cover carbohydrates eaten and bring down the high sugar levels following meals. They are also taken to correct a high glucose level; ultra-rapid-acting prandial insulin can act even more quickly in the body to bring down glucose levels.

Analog vs. Human Insulin

  • Human insulins were developed first and are essentially identical in structure to the insulin produced in the human body. These are generally cheaper than analog insulins and can be bought without a prescription at places like Walmart and CVS Pharmacy, but they come with a greater risk of hypoglycemia, diabetic ketoacidosis (DKA), and weight gain.

  • Analog insulins are similar in structure but have minor modifications to give them certain functions and characteristics. While analog insulins cost more, they generally lead to less hypoglycemia, DKA, and weight gain. Prandial analog insulins tend to act faster than human insulin, so they can be injected closer toward mealtime (15-20 minutes), whereas human insulins need to be administered about 30 minutes before eating and thus require more advance planning. 

Because human insulins work differently from analog insulins, be sure to discuss with your healthcare professional if you choose to transition between analog and human insulins. 

Insulin Concentrations

Insulin can come in four concentrations: U-100, U-200, U-300, and U-500.

Most insulin used in the United States is U-100, which means that there are 100 units of insulin per milliliter of liquid. U-200 and U-300 concentrated insulins are mainly basal insulins, though there is one U-200 prandial insulin available in a pen. U-500 insulins are the most concentrated and are typically used by people with type 2 diabetes who have extreme insulin resistance. 

Types of Insulin 

Both analog insulins and human insulins have long-acting (basal) and rapid-acting (prandial) versions. 

  • Analog insulins are categorized by rapid-acting, long-acting, and ultra-long-acting. 

  • Human insulins are categorized by regular/short-acting and intermediate-acting. You may also hear human insulins categorized as R or NPH, which is the same as regular or intermediate-acting, respectively.

Analog insulin types:





Onset: 12-20 min after injection

Peak: 30 min - 2 hours

Duration: 2-7 hours

Insulin aspart (Fiasp)

Insulin lispro (Lyumjev)

Insulin human inhalation (Afrezza)


Onset: 30 min after injection

Peak: 1-2 hours after injection

Duration: 3-5 hours

Insulin aspart (NovoLog, Lispro) 

Insulin glulisine (Apidra)

Insulin lispro (Admelog, Humalog)


Onset: 1-2 hours after injection

Peak: none

Duration: 12-24 hours

Detemir (Levemir)

Glargine (Basaglar, Lantus, Semglee)


Onset: 1-6 hours after injection

Peak: none

Duration: 36-42 hours

Degludec (Tresiba)

Glargine u-300 (Toujeo)

Human insulin types:




Regular or short-acting

Onset: 30 min after injection

Peak: 2-3 hours after injection

Duration: 3-6 hours

Human Regular (Humulin R, Novolin R)


Onset: 2-4 hours after injection

Peak: 4-12 hours after injection

Duration: 12-18 hours

NPH (Humulin N, Novolin N)

To learn more about the types of insulin and which might be best for you, talk with your healthcare team. Feel free to share this article with them, to make sure you discuss all of your options. Check out diaTribe’s Access Series to learn how to navigate the healthcare insurance system when you need insulin.