Insulin Types: Their Peak Times and Durations

Insulin is a hormone every living mammal needs in order to stay alive. In those of us with diabetes, insulin is either something we don’t produce at all or something we struggle to produce enough of.

Without adequate insulin — whether it’s from your pancreas, a syringe, a pen, or an insulin pump — your blood sugar will rise to dangerously high levels. Without enough insulin, you will get very sick.

Let’s take a closer look at insulin, how it works, and the many options available today for people with diabetes.

What is insulin and how does it work?

Insulin is a peptide hormone produced by the beta cells of the pancreas. It’s secreted when the “GLUT2 transporter” detects a change in the “serum glucose level.”

In a non-diabetic body

In a non-diabetic body, the pancreas produces insulin in response to the food you eat. As your body breaks down your meal and converts some of it to glucose, insulin is responsible for making it possible to use that glucose as energy for the body.

The pancreas also releases a constant small drip of insulin, because the human body requires a constant presence of insulin in order to function properly.

In a person with type 1 diabetes or type 2 diabetes

In a person with type 1 diabetes: the pancreas constantly tries to produce beta cells in order to make insulin, but the immune system continues to attack and destroy most or all of those beta cells.

For those with type 1 diabetes, the evolution of the disease and the attack on the beta cells occur very quickly, which means people get sick very quickly. Often mistaken at first for the lingering flu, a simple blood test and urine test can determine and diagnose type 1 diabetes.

Immediately upon diagnosis, patients should begin taking pharmaceutical insulin via pump, pen, or syringe.

In a person with type 2 diabetes: the body is either struggling to produce a normal amount of insulin (for reasons still unknown), or the body is struggling with severe insulin resistance which makes it difficult to manage healthy blood sugar levels with the available amount of insulin.

For those with type 2, the struggle to properly produce or make use of their own insulin is usually a slower process, sometimes taking years before you show strong enough symptoms to warrant an HbA1c test, a diagnosis, and eventual treatment.

Basal and Bolus insulin

Regardless of the type of diabetes, those needing multiple daily injections will need background insulin (basal) as well as insulin to cover meals and corrections (bolus).

Depending on which delivery mechanism is used, the basal can be a long-acting insulin or a rapid-acting insulin while boluses will always be rapid-acting or short-acting insulin (more about the different insulins in the next section).

Types of insulin

Let’s look at each type of insulin and all the pertinent information that goes along with it, including onset (how fast it starts to work in the body), peak times (when the insulin works the strongest), and duration (how long it is active in the body), and more.

Finding the ideal combination and regimen for your body can take a great deal of time. It’s important to approach any changes in your insulin regimen with patience, and additional blood sugar tests for safety.

Rapid-acting insulin

Chemically, there is a slight difference between the amino acid structures of each insulin.

Fiasp is almost chemically identical to Novolog, except it has the addition of vitamin B3 (niacinimide) which enables it to start working in your bloodstream slightly more quickly than other injected insulins.

It also contains the amino acid L-arginine, which is supposed to make it more stable in the few hours after dosing. 

When comparing Novolog to Humalog, some patients report a noticeable difference between the two but research hasn’t determined any significant difference in their efficacy.

Apidra is only approved for 48 hours in an insulin pump before requiring a site change; Novolog, Humalog, and Fiasp are approved for 72 hours.

Inhaled Insulin (Afrezza)

Afrezza is the fastest rapid-acting insulin on the market, but switching to it from an injected rapid-acting insulin requires training, as it’s an inhaled mealtime insulin.

A newer technology, this type of insulin is used in a similar manner to an inhaler and is only available in a rapid-acting form. However, inhaled insulin cannot replace pumps, pods, pens, or syringes for people with type 1 diabetes.

Today’s current inhaled insulin technology is limited to doses of 4, 8 or 12 units at a time (not a one-to-one comparison to 1 IU of other rapid-acting insulins), and is only intended to cover your needs during a meal or correction.

While some type 2s who only require mealtime insulin may find that inhaled insulin covers their needs, anyone with type 1 diabetes would also need a long-acting basal insulin and potentially also another short or rapid-acting insulin.

Short-acting insulin

Name	Generic Name	Manufacturer	Onset (min)	Peak (hrs)	Duration (hrs)
Humilin R / Novolin R	Regular	Lilly / Novo	30 – 60	2 – 4	6 – 8

Unlike rapid-acting insulin, short-acting insulin is delivered only via injection and requires more planning for meals because it doesn’t begin working for nearly an hour, and doesn’t peak until more than two hours after injection.

This short-acting insulin is not commonly used today since rapid-acting insulin provides much better insulin coverage for meals.

Using short-acting insulin also means you must eat according to its peak, requiring you to plan ahead for every meal, leaving little room for flexibility.

It is making a bit of a comeback for those who follow strict low-carb diets because high-protein and high-fat meals digest slowly. A rapid-acting insulin may then be used for corrections or higher-carb meals.

In hospitals, patients will find that when receiving insulin via IV, short-acting insulin is still commonly used based on traditional “sliding scale” insulin dosing protocols.

Note: Regular insulin is still relevant in the United States because it can be purchased at a low price in Walmart and therefore is an option for people who don’t have health insurance.

Intermediate-acting insulin

Name	Generic Name	Manufacturer	Onset (hrs)	Peak (hrs)	Duration (hrs)
NPH	Isophane	Lilly / Novo	1 – 3	4 – 6	10 – 16

NPH is commonly used as a basal insulin due to the lengthy amount of time it stays in your system. However, because it only lasts 10 to 16 hours, it’s usually given twice per day — once in the morning, and once at night.

With its peak taking longer to occur, there is a greater fluctuation in blood sugars throughout the day as opposed to longer-acting insulin varieties. To manage this, patients using this insulin must follow a strict eating schedule, and eat a very precise amount of carbohydrates at precise times of day.

NPH is commonly mixed with the rapid or shorter-acting insulins mentioned above but is being used less and less these days. Thankfully, better long-acting options are available today!

Note: While NPH insulin is not commonly used in the US, it is another insulin that can be purchased at a low price in Walmart.

Long-acting basal insulin

Name	Generic Name	Manufacturer	Onset (hrs)	Peak (hrs)	Duration (hrs)
Lantus/Basaglar	Insulin glargine	Sanofi / Lilly	1 – 2	6	24
Levemir	Insulin detemir	Novo Nordisk	1 – 3	8 – 10	24
Tresiba	Insulin degludec	Novo Nordisk	1 – 2	none	Up to 42

The long-acting insulin varieties are used in a similar fashion to the basal insulin in the pump, providing a constant presence of background insulin just like the pancreas would drip, drip, drip.

For Lantus and Levemir, some patients will find it beneficial to cut their total dose in half, taking one injection in the morning and another at night, 12 hours later.

Some studies have demonstrated a lower risk of nocturnal hypoglycemia and major hypoglycemia in Levemir than Lantus.

Most patients seem to report in forums and online discussions that their body responds more favorably to one type of insulin over the other.

Lantus is also much more acidic than Levemir, which can cause a mild-to-moderate burning sensation during injection for some people.

Tresiba is the new kid on the block, having come to the market in 2016, but also has demonstrated to cause fewer hypoglycemic events than Lantus or Levemir. Tresiba also works in the body for up to 42 hours. While it’s still taken once per day, Tresiba is said to provide a much more stable and constant action compared to Lantus because Lantus has a half-life of only 12 hours which means its efficacy peters out much sooner than Tresiba.

Toujeo is a newer but not nearly as popular form of insulin glargine, like Lantus, but is a more concentrated version with triple the potency. It is only approved for patients aged 18 and older. While some patients like it, many have reported in the comments on this article that they’ve experienced very unpredictable fluctuations in their blood sugar levels after the first few weeks of taking it.

Insulin delivery options for people with diabetes

Once you are diagnosed with type 1 diabetes, and for some diagnosed with type 2 diabetes, it’s critical that you begin taking insulin to bring your blood sugar levels back to a healthier, safer range.

Only a few decades ago, there was only one option: sharpening and boiling the same syringe over and over and over to then take injections with insulin that dictated exactly when and how much you could eat. These insulins were first derived from pigs and cows.

Today, thankfully, we have a slew of options for both the type of insulin we want to take and how we want to take it.

Injections via pen or syringe

This method has been around the longest, since the discovery of insulin in 1921 by Frederick Banting and Charles Best.

Insulin is injected subcutaneously in one of many injection sites on the body: abdomen, thighs, upper arms, or butt. This can be done with a pre-filled insulin pen or by using a syringe to draw up the desired amount of insulin from a traditional vial. Typically, users will need a long-acting basal insulin paired with a rapid-acting insulin for mealtimes.

While insulin pens and syringes cannot offer the extremely precise measured doses a pump or pod can administer, they are certainly the most affordable method of insulin delivery. For those who don’t like the bulk of wearing a pump or pod, using a pen or syringe can be just as an effective way of managing blood sugars.

Pump or pod

An insulin pump is a small, electronic device that contains a battery, insulin reservoir, pump, and tubing that ends in a needle or cannula to deliver insulin into the body.

The device is worn on your belt or in your pocket while the tubing connects the insulin reservoir to an “infusion site” in your subcutaneous flesh (your body fat), where the insulin is delivered.

Insulin pods are more compact and sit directly on the body without any additional exterior tubing. A separate hand-held device is used to tell the pod when to deliver insulin.

Both a pump and pod are programmed to deliver rapid-acting insulin 24 hours a day based on each person’s individual needs. For insulin needs during meals or to make corrections to high blood sugar levels, the user would simply use the buttons on the pump or on the handheld device for the pod to give precise doses of insulin.  

The three greatest benefits of delivering insulin via pump or pod, compared to a syringe or pen, are:

1. The ability to deliver extremely precise dosing options, down to 0.025 units.
2. The ability to suspend or quickly reduce insulin delivery to compensate for variables like exercise, or for a picky toddler who decided halfway through dinner to stop eating.
3. The freedom to eat something, take insulin, and then eat more just a bit later all with the push of a button rather than another injection.

While an insulin pump is the most advanced insulin delivery option available today, it isn’t necessarily the best fit for everyone.

Insulin pumps and pods do come with a few flaws, including:

1. The supplies for pumps and pods are far more expensive than syringes and pens.
2. A mechanical or physical error that results in severe high blood sugars and requires a new infusion site set-up.
3. Every 3 to 4 days, the user must take time to remove the current infusion site and set-up a new one.

If you’re curious about insulin pump therapy, talk with your doctor about the best options for you! It’s certainly worth a try, and if you don’t like it, you can always go back to injections via pen or syringe.

For a more in-depth look at the difference between insulin pumps and manual injections, you can read my post on why I choose manual injections over an insulin pump.

Determining the right insulin doses for you

The most challenging part of living with diabetes and requiring insulin via syringe, pen, pump, or pod is determining just how much insulin your body needs at certain times of day, and for certain types and amounts of food.

This is a never-ending process of fine-tuning, adjusting, testing, and experimenting. Simply losing 5 pounds or gaining 5 pounds can have a significant impact on the amount of insulin you need.

Making changes in how you eat can mean you suddenly (or gradually) need more or less insulin. A stressful day or an entire stressful year can have a tremendous impact on your insulin needs.

The variables are endless.

For assistance in adjusting your insulin doses to meet your body’s current needs and prevent frequent high and low blood sugars, it’s imperative that you work with your medical team.

Living with diabetes is no simple task, and the medical technology and pharmaceutical drugs we require in order to stay alive are complicated and expensive. Above all else, remember that no one does diabetes perfectly. Perfect blood sugars are something we might strive for, but without a healthy pancreas and immune system, no one should expect perfection.

Do the best you can, and never give up.