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Insulin Therapy: Types, Side Effects, Tips & More UK (2024)

Written by: Content Team



Time to read 10 min

Our bodies cannot survive without the natural hormone insulin. It controls sugar metabolism and allows the body's cells to use the energy in food.


Unfortunately, people with diabetes either have a hormone shortage or suffer from insulin resistance, which makes their cells unresponsive to its effects.


With over 4.3 million confirmed cases of diabetes in the UK this year, the number of people living with the condition is at an all-time high. 


To many, insulin therapy is one of the few effective diabetes treatments available to control the disease and allow them to live a relatively normal life.


Here's everything you need to know if you or a loved one have recently been diagnosed with diabetes. 


We'll review types of insulin therapy, its side effects, doses, modes of delivery, and tips on how to follow your insulin regimen safely.

Insulin Basics: How Does Insulin Work?

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Insulin injection with a needle

Human digestion is ruled by a complex system of organs that produce enzymes to break down food (exocrine) and hormones that control the body's nutritional needs (endocrine).


The pancreas produces two such hormones: insulin and glucagon.


Insulin, produced by pancreatic beta cells, lowers blood sugar levels by telling the body's tissues to use it, and any excess is stored in the liver as a complex carbohydrate called glycogen.


On the other hand, if blood sugar gets too low, the hormone glucagon, produced by pancreatic alpha cells, signals to the liver to change the glycogen into glucose to raise blood sugar back to normal. This system keeps the body's cells, especially the brain, well-supplied with glucose even when the person hasn't eaten for a while.

How Does Diabetes Affect Natural Insulin?

Diabetes mellitus (diabetes for short) is mainly a disease of the pancreatic cells that produce insulin.


If a person suffers from type 1 diabetes, their body starts attacking these cells due to an autoimmune response. Consequently, their body doesn't make enough or none, which is known as insulin deficiency.


Those who suffer from type 2 diabetes sometimes have insulin deficiency, too. 


However, most of the time, they have other conditions that make their body's cells less responsive to the insulin they naturally produce, known as insulin resistance.


The same happens to some pregnant women who suffer from gestational diabetes. They either become insulin resistant only during pregnancy or develop type 2 diabetes.


In all cases of type 1 diabetes, 25% of the cases of type 2 diabetes, and some cases of gestational diabetes, external insulin therapy is essential to control blood glucose and prevent complications.

Types of Insulin

Insulin vials
Insulin vials

When insulin was discovered in the 1920s and later became the standard for diabetes treatments, it was taken from animals, such as pigs and cows, because of how similar their natural insulin is to human insulin. It's still made and can be prescribed to some patients who don't tolerate synthetic insulin.


Human insulin was later produced using the bacteria E. coli and was made to mimic the natural hormone's properties.


As technology advanced, it allowed for modification of the onset of action and the term of efficacy of the hormone. The resulting types of insulin, called analogue insulin, were classified by the American Diabetes Association to include:

Rapid-Acting Insulin

A rapid-acting insulin is taken 15 minutes before you eat. It reaches the highest concentration about one or two hours after you take it and remains effective for two to four hours.


Example insulins:


  • Insulin Lispro

  • Insulin Aspart

  • Insulin Glulisine

Short-Acting Insulin (Regular Insulin)

Regular insulin is the form of insulin that mimics human-made insulin. You take it about 30 minutes before a meal, reaching its highest concentration in the blood after two or three hours. It remains active for three to six hours.



  • Human Regular Insulin

Intermediate-Acting Insulin

Insulin metabolic pathway
Insulin metabolic pathway

The onset of action for intermediate-acting insulin is usually two to four hours after injection. The highest concentration is between four and 12 hours, and it remains active for 12 to 18 hours.



  • Neutral Protamine Hagedorn (NPH)

Long-Acting Insulin

Longer-acting insulin differs from other types of insulin in that it doesn't have a peak concentration. It takes several hours to start working and can control blood glucose levels for 24 hours.




  • Insulin Detemir

  • Insulin Degludec

  • Insulin Glargine is also marketed as "ultra long-acting insulin" when given in a higher concentration.

Premixed Insulin

Some diabetes patients require a mixture of human insulin or rapid-acting and long-acting insulin analogues to control their condition. Premixed insulin can be prescribed to avoid dose confusion and potential risks.




  • Premixed human insulin: Made of short and intermediate-acting insulins, like Humulin M2, M3, and M5 & Insuman Comb 15, 25, and 50.

  • Premixed analogue insulin: Made of rapid and long-acting insulins, like Humalog Mix 25 & Humalog Mix 50 & NovoMix 30.

Modes of Delivering Insulin Therapy

Depending on the type of diabetes the patient has, they can be better candidates for different insulin regimens. Each regimen requires a different insulin delivery method and can vary highly regarding the extent of patient participation.


There are two main modes of insulin delivery: continuous subcutaneous insulin infusion (insulin pump) and multiple daily injection therapy. There's also a new technology for inhaled insulin on the market. Let's go over each one in more detail.

Continuous Subcutaneous Insulin Infusion (Insulin Pump Therapy)

Glucose monitor around a man
Glucose monitor around a man's stomach

Patients with type 1 diabetes need to continuously monitor their blood sugar levels to administer the necessary insulin dose at the right time. This usually requires using a bolus dose of rapid or short-acting insulin at mealtime and a basal dose of longer-acting insulin at bedtime to control their blood glucose overnight.


Forgetting or missing a dose of insulin could have serious repercussions, which requires a certain amount of vigilance that not all patients have, especially younger ones.


Insulin pumps are a form of continuous subcutaneous insulin infusion that doesn't require a new insulin shot every time. They mimic the natural way the body releases insulin, allowing people with type 1 diabetes to have better control over their blood sugar, use less insulin per dose, and feel less restrained by their condition.




  • Controls the 'Dawn phenomenon', where patients experience high blood sugar levels in the morning.

  • Improves HbA1C test results when used for a longer period (more than three months).

  • Instead of multiple daily injections, the patient experiences the needle only once a week when the injection site is changed.




  • Needs constant monitoring to inject insulin in case the pump malfunctions. This should prevent diabetic ketoacidosis (DKA) from developing.

  • Is a constant reminder of having diabetes since the patient needs to feed it information about meals, exercise, snacks and basal insulin doses throughout the day.

  • Can cause weight gain in some patients.

Insulin Injections

Insulin injection into the stomach area
Insulin injection into the stomach area

The oldest insulin treatment method for diabetes is injection, which makes it a more well-studied mode of therapy than other diabetes treatments


The insulin regimen for daily injections varies among patients; those with type 2 diabetes usually require two daily injections, while those with type 1 might require more.


Injecting insulin can be done via a:


  • Syringe and Vial: The insulin dose is measured and injected into the stomach's skin, front or side of the leg, back of the upper arm, or the upper buttocks.

  • Insulin Pen: It's a similar system to a syringe. A pen can be pre-loaded with insulin or fitted with ready-to-use cartridges with different insulin types.

  • Needle-Free Insulin Jet Injector: For young patients or those who fear needles, a jet injector with a needle-free nozzle delivers the same results without dealing with a sharp needle.


The goal here is to deliver the insulin to the subcutaneous tissue, which allows it to disperse through the fat layer and be absorbed by the body's cells to control blood sugar levels.




  • Syringes are cheaper and more available than other insulin delivery methods.

  • Pens have comfortable needles that are shorter and thinner than syringes.

  • Needle-free injectors are fast, easy, and painless.




  • Not changing the injection site can cause hard lumps or fatty tissue to appear under the skin.

  • Aren't as discreet as insulin pumps.

  • Frequent syringe or cartridge changes can be bothersome to some patients.

Inhaled Insulin

A new technology for inhaled insulin, which was patented less than 20 years ago, created quite a stir in insulin therapy discussions.


Instead of injecting liquid insulin into the bloodstream, a fine, aerosolised powder of ultra-rapid-acting insulin reaches the blood via the superfine blood capillaries around the lungs through inhalation. This allows for fast absorption of insulin and, consequently, better control over blood sugar.




  • A decent alternative to the bolus dose of insulin right before meals.

  • Doesn't require learning any injection or measuring techniques.

  • More discreet to use.




  • Contraindicated for patients who smoke or have asthma, chronic obstructive pulmonary disease (COPD), or other respiratory diseases.

  • Inhaled insulin has several drug interactions.

  • Type 1 diabetes patients still require longer-acting insulin to control their basal insulin levels.

Side Effects of Insulin Therapy

Even though it's a natural hormone, just like any other drug, taking insulin for diabetes can have some side effects. But, of course, they're less dangerous than the health problems that arise from having diabetes and not getting treated for it.


The most common side effects of insulin therapy are hypoglycemia and weight gain. Here's more on each:

Hypoglycemia (Hypos)

Woman experiencing low blood sugar
Woman experiencing low blood sugar

Our body organs, especially the brain, require a specific amount of blood sugar in the form of glucose to function normally.


This glucose is obtained from the food we eat, and the rest is stored in different body areas as fat thanks to the effect of insulin.


When insulin levels are too high, the body cells store away too much blood sugar, and the amount left in the blood is too low for the body to fuel itself properly. 


This can cause hypos symptoms, like:


  • Dizziness

  • Headache

  • Sweating

  • Heart palpitations

  • Hunger

  • Irritation

  • Nausea

  • Abdominal pain

  • Blurry vision


These signals tell the body needs food to elevate glucose levels to normal. However, some people ignore these signals for too long, leading to severe hypoglycemia, whose symptoms can include loss of consciousness (fainting), seizures, coma, and even death. If a person is going through severe hypoglycemia, they need immediate medical care.


To prevent hypos, make sure you're calculating your insulin doses correctly, not skipping meals, and avoiding drinking alcohol without eating a proper meal first. Physical activity can also naturally lower blood sugar levels, so adjust your insulin dose if you exercise.


If you experience hypos more often than usual, then the insulin dose you're on should be lower. 


Could you speak with your physician about your symptoms and ask for a dose adjustment?

Weight Gain

Person measuring their waist
Person measuring their waist

Insulin is considered an anabolic or growth hormone. That means it signals the bones and muscles to build themselves and increases their protein and glycogen concentration. 


It also stimulates the storage of excess blood sugar as fat in the body, which can lead to noticeable weight gain after initiating insulin therapy. This is a common side effect that many patients notice right away.


The weight you gain depends on how much insulin you take, the type of insulin you're using, and other factors like diet and the amount of physical activity you engage in.


Taking insulin doses much higher than you need can make you feel excessively hungry. It can also cause hypos, which signals your body to want more food. And if you take insulin from an animal source or human (regular) insulin, you're likely to experience more hunger than someone using an insulin analogue.


Since insulin helps reduce blood sugar right after a meal, if you consume a lot of simple carbohydrates that get absorbed easily through your digestive system, you might feel hungry shortly after eating.


If you need help adjusting your insulin dose or diet, please feel free to talk to your healthcare team about your concerns.

Tips for Successful Insulin Therapy

Insulin therapy is a means to an end: to keep your blood sugar levels within the healthy range so you can enjoy a normal life. To make the most of your insulin treatment, try the following tips:


  • Keep your blood sugar levels in check by investing in a blood glucose monitoring device. You should be able to spot spikes and avoid things that trigger them.

  • Carbohydrate counting is your friend. It allows you to adjust your insulin dose and give your body the right amount for your meal.

  • Keep unopened insulin vials refrigerated between 2–7 degrees Celsius.

  • Discard opened vials after one month.

  • If you use an insulin pen or jet injector, they need to be taken out of the fridge before use.

  • Only inject insulin at room temperature to avoid pain.

  • Change the insulin injection site frequently to avoid hard or fatty lumps under your skin.

  • If you fear needles that prevent you from adhering to your insulin regimen, consider using a needle-free injector or an insulin pump.

Wrapping Up

For some people with diabetes, the only way to live a normal life is through insulin therapy. UK doctors prescribed almost 8 million insulin items in the years 2020/21, which signals a constant rise that likely won't stop.


Understanding the difference between insulin formulas and how much insulin you need is a wonderful first step toward being your healthiest. 


There are also different modes of delivering insulin therapy that work for each type of diabetes, so you should always check with your healthcare team for which method suits your condition.

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