Just like any drug, insulin has its activity profile that is measured in three numbers which include onset, peak, and duration. These are also known as the characteristics of insulin and they help to know the differences between fast-acting insulin and slow-acting insulin.

Fast-acting insulin is used due to its fast peak. The insulin acts within a short time to reduce the level of sugar in the blood. Slow-acting insulin, on the other hand, is preferred for its long duration. Its effect in reducing the level of sugar in the blood lasts for several hours.

If you have insulin problems and it needs to be taken frequently, then you will need to go for slow-acting insulin.

Introduction to Insulin Types

When managing diabetes, various types of Insulin help regulate blood sugar levels effectively. Each type has its properties, onset times, peaks, and durations, making them suitable for diabetes management. Here’s a detailed explanation of the main types of Insulin:

1. Rapid-Acting Insulin

Description: Rapid-acting Insulin is designed to work quickly and is typically taken before or after eating. It mimics the body’s natural insulin response to food intake.

Onset: Starts to work within 10-15 minutes.

Peak: Approximately 1-2 hours after injection.

Duration: Last about 3-5 hours.

Examples:

• Humalog (Insulin Lispro)
• NovoLog (Insulin Aspart)
• Apidra (Insulin Glulisine)

Usage: Often used at mealtime to manage spikes in blood glucose levels due to food consumption.

2. Short-Acting Insulin

Description: Short-acting Insulin, also known as regular Insulin, has a slightly slower onset and longer duration than rapid-acting Insulin. It can be taken 30 minutes before meals.

Onset: Starts to work within 30 minutes.

Peak: 2-4 hours after injection.

Duration: Last 5-8 hours.

Examples:

• Humulin R
• Novolin R

Usage: Used similarly to rapid-acting Insulin, but requires precise timing with meals to avoid mismatches between insulin action and food absorption.

3. Intermediate-Acting Insulin

Description: Intermediate-acting Insulin has a slower onset and a prolonged effect. It is generally taken once or twice daily to provide baseline insulin coverage.

Onset: Starts to work within 1-2 hours.

Peak: 4-12 hours after injection.

Duration: Last about 12-18 hours.

Examples:

• Humulin N (NPH)
• Novolin N (NPH)

Usage: Often used in combination with rapid-acting or short-acting insulins to cover basal and mealtime needs.

4. Long-Acting Insulin

Description: Long-acting Insulin provides a consistent insulin level, functioning similarly to the body’s natural basal insulin secretion. It helps maintain stable blood glucose levels throughout the day and night.

Onset: Starts to work within 1-2 hours.

Peak: Minimal to no peak; it provides a steady level.

Duration: Lasts up to 24 hours or more.

Examples:

• Lantus (Insulin Glargine)
• Levemir (Insulin Detemir)
• Tresiba (Insulin Degludec)

Usage: Typically administered once daily (sometimes twice, depending on the formulation and individual needs), providing baseline insulin coverage.

5. Ultra-Long-Acting Insulin

Description: Ultra-long-acting Insulin offers even more extended coverage than long-acting insulins, often lasting beyond 24 hours, reducing the frequency of the required injections.

Onset: Starts to work within 6 hours.

Peak: No significant peak; maintains a steady level.

Duration: Lasts up to 36 hours or more.

Examples:

• Toujeo (Insulin Glargine U-300)
• Tresiba (Insulin Degludec)

Usage: Ideal for those who prefer fewer injections and more stable blood glucose control over an extended period.

6. Pre-Mixed Insulin

Description: Pre-mixed Insulin combines two types of Insulin, usually a rapid-acting or short-acting insulin, with an intermediate-acting insulin in a fixed ratio. This combination simplifies the treatment regimen by reducing the number of injections needed.

Onset: Varies depending on the components.

Peak: Multiple peaks corresponding to the different types of Insulin in the mix.

Duration: Varies generally cover both immediate and prolonged insulin needs.

Examples:

• Humalog Mix 75/25 (75% Insulin Lispro Protamine, 25% Insulin Lispro)
• NovoLog Mix 70/30 (70% Insulin Aspart Protamine, 30% Insulin Aspart)
• Humulin 70/30 (70% NPH, 30% Regular Insulin)

Usage: Commonly used to simplify the treatment plan, providing both mealtime and basal insulin coverage in one injection.

7. Inhaled Insulin

Description: Inhaled Insulin is a rapid-acting insulin administered via inhalation rather than injection, offering an alternative method of administration.

Onset: Starts to work within 12-15 minutes.

Peak: About 30-60 minutes after administration.

Duration: Last approximately 2.5-3 hours.

Examples:

• Afrezza

Usage: Used at the beginning of a meal to control postprandial blood glucose levels. It is not suitable for everyone and requires careful usage and monitoring.

Understanding these insulin types, their onset, peak, and duration, and how they are typically used helps individuals with diabetes and healthcare professionals tailor treatment plans that best suit individual needs, improving overall health and quality of life.

Characteristics of Insulin

The three characteristics of insulin include the following:

• Onset: This refers to the length of time it takes insulin to reach the bloodstream and reduce the blood sugar level.
• Peak time: This is the time at which insulin has its maximum strength in terms of reducing the blood sugar level.
• Duration: This refers to how long it takes the insulin to continue lowering blood glucose.

Fast-Acting Insulin

Fast-acting insulin refers to a synthetic (or man-made) form of insulin. This type of insulin is an injectable medication that is prescribed for those that have diabetes to control the level of glucose (or sugar) in their blood.

Fast-acting insulin is absorbed into the bloodstream within a short period, usually within minutes, to act like bolus insulin (i.e. the surge of insulin that the pancreas releases when food is ingested). As a result, this form of insulin is injected just before taking meals or snacks.

Fast-acting insulin can be administered with a needle and syringe, an insulin pump, or a pre-filled pen. There is also a form of fast-acting insulin that the patient can inhale.

Onset, Peak, and Duration of Fast-Acting Insulin

Fast-acting Insulin is known for its rapid onset, with effects typically beginning within 10 to 15 minutes after injection. This type of Insulin reaches its peak concentration in the bloodstream approximately 1 to 2 hours post-administration, ensuring a swift reduction in blood glucose levels. However, The action duration for fast-acting Insulin is relatively short, usually lasting between 3 to 5 hours. Due to this brief duration, it is often paired with other insulin types or multiple daily doses to manage blood sugar effectively.

Uses

Fast-acting insulin is prescribed for those suffering from type 1 diabetes. These people need to take insulin since their pancreas cannot produce it.

A healthy pancreas secretes bolus insulin whenever the level of glucose in the blood increases after ingesting food or beverage. Fast-acting insulin acts like bolus insulin and it is usually administered before taking snacks and meals.

Also, fast-acting insulin is used to reduce high blood glucose to a normal level.

Some patients with type 2 diabetes may need supplemental insulin if they cannot control their blood sugar with exercise, diet, and medications. Although such people need only basal insulin. Basal insulin is bolus insulin’s counterpart and it is the insulin that is usually secreted continuously by the pancreas to keep insulin at a normal level in the bloodstream every time.

Dosage

According to the American Diabetes Association, insulin has a standard U-100 strength. Those that are highly resistant to insulin may require supplemental insulin with a U-500 strength.

Your physician will determine the dosage that you need depending on your weight, dietary needs, sensitivity to insulin, and other factors. However, some general rules are used to calculate the amount of fast-acting insulin an individual needs to take. These rules are determined by the following circumstances:

Taken with meals

If fast-acting insulin needs to be taken with a meal, its dosage usually depends on a ratio of insulin to carbohydrates that are in the meal; usually one unit of insulin per about 12 to 15 grams of carbohydrates.

To lower extremely high glucose levels

Generally, one unit of fast-acting insulin is required to lower the level of sugar in the blood by 50 mg/dl.

Common Brands of Fast-Acting Insulin

Several brands offer fast-acting Insulin, each varying slightly in formulation and effectiveness. These include widely recognized names such as Humalog, NovoLog, and Apidra. These brands are well-regarded for their rapid onset and short duration, making them suitable for managing blood glucose during and after meals.

Humalog, for example, typically begins to work within 15 minutes and peaks around one hour after injection. NovoLog and Apidra have similar profiles, providing quick absorption that aligns well with mealtime requirements. These brands are commonly available in insulin pens, making administration more convenient and reducing the risk of dosing errors.

Pros and Cons of Fast-Acting Insulin

When choosing the appropriate treatment plan, Fast-acting Insulin has several advantages and disadvantages. One of the primary benefits is its ability to quickly reduce blood glucose levels, which is particularly useful during mealtime when blood sugar can spike rapidly. This rapid action helps prevent postprandial hyperglycemia, reducing the risk of long-term complications associated with poor glucose control.

However, there are also downsides to using fast-acting Insulin. Its short duration means it must be administered multiple times daily, which can be cumbersome and increase the risk of missed doses. Additionally, the rapid decrease in blood sugar levels can sometimes lead to hypoglycemia if not carefully monitored and balanced with carbohydrate intake.

Individual needs and preferences should determine the choice between fast-acting and slow-acting Insulin. In some cases, combining different insulin types, such as pairing a long-acting insulin with a fast-acting one, can provide a more balanced approach to diabetes management.

For more detailed information about Insulin and its various types, consult healthcare professionals or reliable medical sources. They can provide personalized advice and explore different treatment options to find the most effective regimen for managing your diabetes.

How long does it take fast-acting insulin to start working?

How long it takes for fast-acting insulin to begin working depends on the specific products, but can start working within 5 minutes. It could also take as long as 30 minutes depending on the specific type of fast-acting insulin used.

The following are the various fast-acting insulin products and the time it takes for each of them to start working:

• Humalog: The onset of action time is between 10 and 20 minutes.
• Novolog:  Its onset of action time is between 10 and 20 minutes.

• Apidra: It takes between 10 and 20 minutes to start working.
• Afrezza:  It starts working within 3 to 7 minutes.

Slow-Acting Insulin

Slow-acting insulin helps to create a healthy baseline blood sugar level. In other words, when food gets into the body, the blood sugar increases from a lower point, thereby making it easier to manage.

Most people use an electronic insulin pump to administer slow-acting insulin thereby eliminating the need for manual injections. However, those that don’t have access to pumps or decide not to use a pump due to their lifestyles may go for injections.

The three types of slow-acting insulin that are on the market include detemir, glargine, and degludec.

Onset, Peak, and Duration of Slow-Acting Insulin

Its gradual onset and prolonged effect characterize slow-acting or long-acting Insulin. Typically, the onset of slow-acting Insulin occurs within 1 to 2 hours after injection, with no distinct peak as it maintains a steady insulin release over time. This treatment method ensures a consistent background insulin level, often lasting up to 24 hours or more. This slow and sustained action makes it ideal for maintaining baseline insulin levels and preventing fluctuations in blood sugar throughout the day and night.

Uses

Slow-acting insulin is usually injected once a day to keep the level of blood sugar steady. The insulin is injected by using a needle or pen device. Ensure that you inject your slow-acting insulin at the same time daily to avoid stacking the doses. Stacking refers to the process of taking your doses very close together, thereby making the activity of the insulin overlap.

Dosage

Each of the slow-acting insulin has its required dose. These dosages differ based on the type of diabetes the patent has and if there’s a history of insulin use.

When someone starts using new insulin, the doctor usually recommends that they start with a smaller portion of the target dose so that the body can have time to adapt to the additional insulin. Once the body has adapted to the extra dose, the doctor will then gradually increase the dosage to give a full dose.

An insulin regimen may be adjusted if there’s a change to the person’s diet, levels of physical activity, or if the person falls ill. The insulin dosage may also be changed by any factor that can affect the blood sugar and negative reactions to the hormone (for instance, weight).

A trial and error process is usually involved when trying to find the ideal dosage of slow-acting insulin. Thus, it requires carefully monitoring the levels of blood sugar.

Recommended Usage of Slow-Acting Insulin

Slow-acting Insulin plays a critical role in comprehensive diabetes management, particularly for those who require a consistent insulin supply to regulate blood glucose levels. It is commonly used in combination therapy with other insulin types, such as fast-acting or short-acting Insulin, to cover basal and mealtime insulin needs. Administered once or twice daily, slow-acting Insulin offers a straightforward method to manage diabetes with fewer injections than fast-acting options.

Healthcare providers recommend slow-acting Insulin for individuals who need steady insulin coverage, particularly those with Type 1 diabetes or advanced Type 2 diabetes. It is essential to follow healthcare advice and regularly monitor blood glucose levels to adjust dosages appropriately and minimize side effects.

Pros and Cons of Slow-Acting Insulin

Slow-acting Insulin has several advantages that contribute to its widespread use. One significant benefit is the reduced number of daily injections required, which can simplify the treatment regimen and improve adherence. Its steady and predictable release profile reduces the risk of blood sugar fluctuations, enhancing overall health by maintaining more stable glucose levels.

However, there are also potential drawbacks. Slow-acting Insulin may not provide sufficient coverage for mealtime blood sugar spikes, necessitating additional fast-acting or short-acting Insulin. This can complicate the treatment plan and require careful coordination to avoid hypoglycemia. Additionally, achieving the optimal dosage may take time and adjustments, requiring close monitoring and communication with healthcare providers.

Fast-acting and slow-acting insulins have unique characteristics that make them valuable in diabetes management. Understanding their onset, peak, and duration differences, as well as their pros and cons, can help individuals tailor their treatment plans to their specific needs and improve their overall health outcomes.

How long does slow-acting insulin last?

The duration differs and it is determined by the specific type of slow-acting insulin used. However, it should last between 22 and 24 hours. Highlighted below are the types of slow-acting insulin and the duration it takes for each product to last:

• Lantus: It lasts between 22 and 24 hours.
• Basaglar: It lasts between 22 and 24 hours.
• Levemir: Its action lasts for about 24 hours.

Summary

So, how is fast-acting insulin different from slow-acting insulin?

Fast-acting insulin becomes effective and wears off within a shorter period than slow-acting insulin. Fast-acting insulin is usually used about 30 minutes before taking a meal so that it can have enough time to work. This type of insulin is clear and does not settle out when the vial sits for some time.

According to the American Diabetes Association, there are three main differences between fast-acting insulin and slow-acting insulin:

Onset

Fast-acting insulin lowers the levels of sugar in the blood within 15 to 30 minutes while it takes several hours after injection for the effect of slow-acting insulin to be felt.

Peak time

Fast-acting insulin has a peak time of about 1 to 3 hours after it is injected. Slow-acting insulin, on the other hand, does not have a peak time. It helps to regulate the sugar levels in the blood at a fairly stable rate.

Duration

Fast-acting insulin can control the level of sugar in the blood for a few hours. Slow-acting insulin, on the other hand, can remain effective for about 24 hours or more (depending on the specific type of slow-acting insulin product injected).

FAQs: The Difference Between Fast-Acting and Slow-Acting Insulin

1. What are the main types of insulin, and how do they differ?
Insulin is categorized by its speed of action and duration. The main types include rapid-acting, short-acting, intermediate-acting, long-acting, ultra-long-acting, pre-mixed, and inhaled insulins. Each type has specific onset times, peak effectiveness, and durations, which make them suited to different aspects of blood sugar management.

2. How quickly does rapid-acting insulin begin working?
Rapid-acting insulin typically starts working within 10 to 15 minutes after administration, making it ideal for use around mealtimes to manage spikes in blood glucose. It reaches peak effectiveness in about 1-2 hours and usually lasts 3-5 hours.

3. What is the purpose of long-acting insulin?
Long-acting insulin provides a steady release over a prolonged period, usually up to 24 hours or more. It helps maintain stable blood glucose levels by stimulating the body’s basal insulin needs throughout the day and night, allowing for consistent control.

4. Is inhaled insulin a viable alternative to injectable insulin?
Yes, inhaled insulin, such as Afrezza, is a rapid-acting insulin administered through the mouth rather than injection. It is particularly effective for managing blood glucose at mealtimes but may only suit some. Patients considering inhaled insulin should consult their healthcare provider.

5. What does “pre-mixed” insulin mean?
Pre-mixed insulin combines two types of insulin—typically a rapid-acting or short-acting insulin with an intermediate-acting insulin—in a fixed ratio. This combination provides immediate and longer-term blood sugar control in one injection, simplifying the treatment regimen for many individuals.

6. How does insulin help regulate blood sugar?
Insulin aids glucose absorption into cells for energy. Different types of insulin are used to either address immediate glucose spikes after meals or provide ongoing baseline coverage, mimicking how the body would naturally release insulin.

7. How should people manage insulin dosages based on their meals?
When taking insulin with meals, fast-acting insulin doses often depend on the carbohydrate content in the meal. Many follow a ratio guideline, such as one unit of insulin for every 12-15 grams of carbohydrates. Still, the specific dosage varies by individual needs and should be determined by a healthcare provider.

8. Which insulin products last longer than slow-acting insulin?

Toujeo and Tresiba are referred to as ultra-slow-acting insulin products because they last longer than slow-acting insulin. Toujeo was approved in February 2015 by the FDA. It starts working within 6 hours and lasts for 36 hours without any peak.

Tresiba was approved in September 2015 by the FDA. It starts working within 1 hour and lasts for at least 42 hours. Just like Toujeo, it also has no peak.

9. Do I have to inject all insulin?

No. Not all insulins need to be injected. Afrezza is a fast-acting insulin that is inhaled via the mouth.

10. Do I need to be administered with more than one insulin?

Your doctor is in the best position to determine if you need more than one insulin.

Some type 2 patients may be required to use slow-acting insulin to put their blood sugar level under control, while others may need both meal-time and slow-acting insulin to effectively control their blood sugar level.

Patients using an insulin pump will need to use fast-acting insulin. The pump can give a slow and steady dosage of insulin to take you through the day the same way slow-acting insulin would do. It is, however, advisable to have slow-acting insulin as a backup in case the pump fails.