Insulin

Insulin production

Since it was discovered and first used to treat people with diabetes in 1922, insulin production has evolved along with diabetes treatment and management. The first type of insulin was animal insulin extracted from beef and pork pancreas. Some people with diabetes still use this type of insulin because they find purified (cleaned) animal insulin works best for them.

In the early 1980s, technological advances made it possible to produce human insulin synthetically in a laboratory – biosynthetic human insulin (BHI) – to resemble insulin made by the body.

A decade later, analogue insulin was introduced. Analogue insulin is also a synthetic insulin made in a laboratory but altered to create genetically engineered insulin known as analogues. Human and analogue insulins are available for insulin replacement therapy.

Most recently, the development of biosimilar insulins (BI) has emerged. Biosimilar insulins are not generic because they are developed using a different process and may have slight differences in their molecular structure, making them distinct from the original products.

Insulin types

There are four main categories of insulin, each with unique characteristics and uses. Some are taken once daily, some twice daily before breakfast and bedtime, and some before each meal.

• Basal insulins—also called long-acting or background insulins—are taken once or twice a day, usually in the morning or at bedtime. They work slowly to maintain stable blood glucose levels overnight or between meals.
• Bolus insulins, usually taken before meals, work quickly to help manage the rapid rise in glucose levels after eating. Some insulins are a mixture of slow-acting background and rapid-acting mealtime insulin.
• Mixed insulins are taken before meals without basal insulin at a different time. They can be a combination of short-acting and intermediate-acting insulin or rapid-acting and intermediate-acting insulin. The insulin is premixed and is cloudy instead of clear.

Insulins are also classified by the timing of their action in the body, specifically, how quickly they start to act, when they have a maximal effect, and how long they act – onset, peak effect and duration.

Matching insulin to diabetes type

Different types of diabetes may require different insulin regimens. There are many different insulin regimens, starting with intensive therapies that attempt to replicate the body’s normal pattern of insulin secretion using basal and bolus insulin. These therapies require more injections and calculations but provide greater freedom and flexibility with insulin doses adjusted to fit daily lifestyle changes.

Sliding scale therapy involves progressively increasing pre-meal or nighttime insulin doses based on pre-defined blood glucose ranges. These are more approximate doses. Food intake and activity levels should be as consistent as possible for this treatment to work effectively.

People with type 1 diabetes typically use a combination of rapid-acting or short-acting insulin before meals and long-acting or ultra-long-acting insulin for basal coverage.

Insulin can be prescribed in many ways for people with type 2 diabetes, depending on the individual’s needs. It can be taken once a day, many times a day, or even through an insulin pump. It may be given as a single treatment or with other medications and can include long-acting or even rapid-acting insulin.

Women with gestational diabetes typically use rapid-acting insulin before meals and sometimes long-acting insulin.

How to take insulin

People with diabetes can take insulin by injection or infusion. As insulin types have advanced, insulin injection methods have also evolved. When insulin was first administered, people used glass syringes and vials. Today, disposable plastic syringes are widely available.

In the 1980s, insulin pens became an alternative to syringes and vials. These devices enable more accurate dosing, better adherence and less pain in the injection site. They have also benefited from improved technology, using digital displays and memory to record recent insulin doses.

Insulin pumps are the most advanced form of insulin delivery. They are small, computerised devices programmed to deliver insulin under the skin. Insulin pumps can be used with continuous glucose monitoring (CGM) devices that check blood glucose levels.

For people with type 1 diabetes, insulin infusions — when insulin is taken using intravenous (IV) therapy — may be necessary to treat hyperglycaemia. This is usually done for diabetic ketoacidosis (DKA) or for diabetes management during surgery or a hospital stay.

Choosing the right insulin

The choice of insulin can depend on various factors:

• Individual lifestyle: Work schedule, meal patterns and physical activity levels.
• Blood glucose patterns: Fasting and post-meal glucose levels.
• Risk of hypoglycaemia: Some insulins carry a lower risk of causing low blood glucose.
• Age and overall health: Certain insulins may be more suitable for older adults or those with other health conditions.
• Personal preferences: Some people may prefer insulin pens over vials or fewer daily injections.

What works for one person may not work for another. Understanding the different types of insulin is a crucial step in managing diabetes effectively. By working with a team of healthcare professionals and staying informed, you can manage your diabetes and lead a healthy life.

Side effects and risks

While insulin is a lifesaver for many, there are also potential side effects:

• Hypoglycaemia (low blood sugar): The most common and severe side effect. Symptoms include shakiness, sweating, confusion, and, in severe cases, loss of consciousness.
• Weight gain: Insulin can lead to weight gain, which may be managed through diet and exercise.
• Injection site reactions: Redness, swelling or itching at the injection site.
• Insulin resistance: In some cases, the body may become less responsive to insulin over time.
• Allergic reactions: Rare but can occur. Symptoms may include rash, difficulty breathing or swelling.
• Lipodystrophy: Changes in fat tissue at injection sites can affect insulin absorption.