Diabetes Causes

We still don’t know the causes of Type 1 diabetes. On the other hand, there are clear risk factors, including obesity, ageing, sedentary lifestyle, insulin resistance, family history, and medical history,  that contribute to the onset of Type 2 diabetes.


Diabetes is a serious condition that happens as your blood glucose (sugar) level becomes too high. This is the result of either when your body:

1.    Can’t produce any insulin at all or,

2.    Doesn’t produce enough insulin / produces insulin but it is not effective.

Insulin is a hormone produced in the pancreas, which regulates the amount of glucose in the blood. Insulin helps your body to use blood glucose for energy.

This article aims to explain the main types of diabetes, explore their causes and risk factors, and provide the current diagnosis and treatment for each type of diabetes.

Types of diabetes

There are 2 main types of diabetes: Type 1 diabetes and Type 2 diabetes as shown in Figure 1 below. 

Figure 1: Different types of diabetes (Diabetes UK, 2022) 

There is also gestational diabetes that some women develop during their pregnancy. In addition, there are 8 other types of diabetes, but only 2% of people with diabetes have these types of diabetes.

Type 1 diabetes

About 8 per cent of people with diabetes in the UK have this type of diabetes. Unfortunately, it is a severe and lifelong condition with no cure. Type 1 diabetes results in your blood glucose (sugar) level being too high because insulin is not being produced in the pancreas. The reason is your body attacks the cells that are responsible for making insulin. As such, there is a loss of insulin-producing pancreatic beta cells. 

Type 2 diabetes

More than 90 per cent of people have Type 2 diabetes in the UK. It is a serious condition where either the pancreas can’t make enough insulin or the insulin produced does not work effectively, causing blood glucose levels to continue rising. 

Gestational diabetes

Gestational diabetes is a type of diabetes that can happen during pregnancy. This affects women who have no previous detected or undetected diabetes. This form of diabetes is usually diagnosed from 24 to 28 weeks into a pregnancy.

Causes and risk factors

Type 1 diabetes

Type 1 diabetes is more common in children and young adults. It is even known as a childhood illness. There is currently nothing that can be done to prevent the onset of this type of diabetes. 

As it is often thought of as a childhood disease, some adults with Type 1 diabetes are initially misdiagnosed as having Type 2 diabetes and given the wrong treatment. However, Type 1 diabetes could occur evenly across the first 6 decades of a person’s life.

More than 40 per cent of cases could occur after the age of 30.1 

We still don’t know what causes Type 1 diabetes. Yet, the following factors might contribute to the development of the condition.


There are some genetic risk factors for developing Type 1 diabetes, especially if you have certain variations of the family of genes called the human leukocyte antigen (HLA) complex. Particular HLA combinations are associated with a higher risk of developing Type 1 diabetes.2 

Although the general population carries these HLA variants, only 5% of people will go on to develop this type of diabetes. Furthermore, there is a low concordance rate among identical twins. This means that our risk of Type 1 diabetes is not solely based on our genetic make-up.3

Moreover, the number of people being diagnosed with Type 1 diabetes is rising quickly. 

For these reasons, we can say that Type 1 diabetes is not just down to our genes alone. There must be other factors in play causing it.

Viral infection

The Human Enteroviruses (HEV) have the strongest association with Type 1 diabetes.4 The poliovirus is the most famous HEVs but most HEVs appear as common flu-like infections. 

These viruses enter the gut and usually spread through poor sanitation or hygiene. HEVs are found in pancreas samples of people with Type 1 diabetes. 

However, the exact mechanism of how HEV infection leads to Type 1 diabetes is still unknown. 

Gut microbiota

The gut microbiota refers to the various bacteria, fungi, viruses and microorganisms living within us. Our microbiota can influence our health in different ways. 

Changes in the microbiota could lead to the gut immune system becoming weaker. Thus, there is an increase in gut permeability, small intestinal inflammation and low tolerance to food antigens. We tend to see these symptoms in people with Type 1 diabetes. 

Moreover, children who develop Type 1 diabetes are prone to HEV virus infections and do not develop tolerance to cow milk antigens. A possible reason is the lack of butyrate-producing bacteria in the gut of these children.5

Butyrate has anti-inflammatory properties to induce mucin synthesis and increase the gut’s barrier mechanism. 


There is various research investigating  whether our diet, especially during childhood, could influence the risk of Type 1 diabetes. However, the evidence is not yet conclusive.

Nonetheless, Type 1 diabetes people have a higher prevalence of vitamin D deficiency.3

As vitamin D promotes pancreatic beta-cell function through various mechanisms, it could be involved in either the development of Type 1 diabetes or insulin sensitivity.

Other factors

Many other factors such as pollutants, vaccines, hygiene, maternal age, psychological stress and seasonal factors have been suggested as possible environmental factors that could cause Type 1 diabetes.

Yet, there are no definitive conclusions made thus far.

Type 2 diabetes

Type 2 diabetes is a serious condition that can turn into a lifelong disease. Unlike Type 1 diabetes, this form of diabetes can be prevented through a combination of lifestyle interventions. 

Furthermore, people who have Type 2 diabetes may go into diabetes remission. Remission is when your HbA1c  -  a measure of your long-term blood glucose (sugar) levels -  remains below 48 mmmol/mol (6.5%) for at least 6 months.6 

Type 2 diabetes can come slowly, usually over the age of 40. Nevertheless, the following risk factors may accelerate the onset of this type of diabetes.


Your risk increases with age. Yet it varies significantly among different ethnic groups. 

If you are from a Black African, African Caribbean and South Asian (Indian, Pakistani, Bangladeshi, Sri Lankan) background, you will be at a higher risk of developing Type 2 diabetes from a younger age (over 25).


Obesity is the single greatest risk factor. It is responsible for 80% to 85% of someone’s risk of developing Type 2 diabetes.7

You are more at risk if you have extra weight around your tummy as you increase the chances of fat building around vital organs like the liver and pancreas.

This might cause insulin resistance as the insulin is not able to get through the fat layer. Therefore, the insulin that your body produces doesn’t work properly.

Physical inactivity / sedentary lifestyle

Being physically inactive means that you are not doing the recommended levels of physical activity in a week. The UK Chief Medical Officer’s Guidelines recommend that you do every week:

  •  At least 150 minutes of moderate-intensity activity, or
  • 75 minutes of vigorous activity

 Regular physical activity could reduce your risk of developing Type 2 diabetes by up to 40%.8 

Nevertheless, you might be doing the recommended amount of exercise per week but spend long periods sitting or lying down (not including sleeping). This is known as a sedentary lifestyle and includes the following:

  • Working at a desk for long periods
  • Studying at school or home for long periods
  • Sedentary screen time
  • Driving or travelling for long hours daily 

If you lead a sedentary life despite carrying out the recommended physical activities, you still have an increased risk of type 2 diabetes. 

Insulin resistance

Insulin resistance happens when the insulin that your body produces doesn’t work properly. As mentioned above, having too much fat around your stomach can cause it. However, there might be other factors that are completely unrelated to your weight. 

If you are from a South Asian background, you are more likely to experience insulin resistance at a younger age. This could be linked to how the visceral fat (fat around the middle) is stored in the body.

Family history

By having close relatives (parents, siblings or children) with diabetes, you are 2 to 6 times more likely to get type 2 diabetes as well.9 

Medical history

If you have a history of high blood pressure, cardiovascular diseases, gestational diabetes, or severe mental illness, you are more at risk of developing Type 2 diabetes.

Gestational diabetes

Gestational diabetes affects at least 5 in every 100 women during pregnancy.10

It is caused by hormone changes during pregnancy, making it harder for you to use insulin properly. As a result, you are at an increased risk of insulin resistance. 

You are at a greater risk of gestational diabetes if you have the following risk factors:

  • Overweight or obese
  • Previous history of this diabetes
  • Previous pregnancy with a very large baby - 4.5 kg / 10lb or more
  • Family history of diabetes
  •  African Caribbean, Middle Eastern or South Asian background 

Having gestational diabetes increases your risk of developing it in future pregnancies as well as having Type 2 diabetes. 

Furthermore, you also risk your child becoming overweight and developing Type 2 diabetes as an adult.

Diagnosis and Treatment

The common diabetes symptoms for all types of diabetes (a child or an adult) are: 

  •  Going to the toilet often at night
  • Feeling really thirsty
  • Feeling more tired than usual
  • Losing weight rapidly
  •  Blurred eyesight
  •  Increased hunger
  • Longer time for cuts and wounds to heal
  • Genital itching or thrush 

If you feel that you have the symptoms of diabetes or you are at a greater risk of getting it, you can see your GP for a blood test.

Type 1

Symptoms tend to appear quickly, sometimes over just a few days or weeks. This is usually the case in children and young adults. Therefore, it is harder to ignore these symptoms. 

Although Type 1 diabetes is usually diagnosed in childhood, it can occur at any age. The symptoms are the same at any age.

However, adults with Type 1 diabetes may not recognise their symptoms as quickly as children. This can lead  to late  diagnosis and treatment being delayed. 



You will need to take insulin to manage your blood glucose (sugar) levels. This can be done by injection (using an insulin pen) or by using a pump. 

Islet cell transplant

You may be able to get a transplant if you experience hypoglycaemia (or hypos) often. A hypo happens when your blood glucose level becomes too low, falling below 4 mmol/l. Severe hypos tend to happen in people who:

  • Have had diabetes for more than 15 years,
  •  Are not able to recognise when their blood glucose level is low (known as impaired hypoglycaemic awareness).

For these people, an islet transplant can be life-saving. The procedure extracts islet cells from the pancreas of a deceased donor and implants them in the recipient’s liver.  

Type 2

This form of diabetes can be easily missed as it develops more slowly, sometimes over 10 years. Hence, it can be difficult to spot the symptoms. In fact, 6 out of 10 people have no symptoms when they are diagnosed with Type 2 diabetes.11 

Therefore, it is better to understand your risk level using the risk tool from Diabetes UK.12

There are 4 different levels of being at risk of Type 2 diabetes.

Figure 2: Different risk levels for Type 2 diabetes (Diabetes UK, 2022)

Risk levels

The higher your risk, the more likely you’ll develop Type 2 diabetes in the next 10 years. Understanding your risk factors can help you prevent or delay this form of diabetes. 

For example, if you fall under the high-risk category, there is a one out of four chance that you will get Type 2 diabetes in the next 10 years.



You may need some medication to help manage your blood glucose levels. The most widely used tablet is metformin.

In addition, other medications stimulate the pancreatic beta cells to release insulin, such as sulphonylureas. 

Diet and exercise

By changing your diet and activity levels, you may not need any medication for Type 2 diabetes. A low-calorie diet (800 to 1200 calories a day) has been shown to reduce the amount of fat in the liver and pancreas. As such, the amount of insulin produced during mealtimes can return to normal.13 

In addition, weight management treatment which includes a low-calorie diet can help you put your Type 2 diabetes into remission.14

Weight loss surgery

There is a weight loss surgery (also called bariatric surgery) that can be effective in managing your diabetes and losing weight at the same time.

This surgery helps your body produce and utilise insulin more effectively. Most people who undergo the surgery have to stop their medications soon afterwards.15


Some people with Type 2 diabetes may need to use insulin as a treatment. You might need to be on insulin if you have the following:

  •  Very high blood glucose levels when you are first diagnosed
  • Other medications are not able to manage your blood sugar levels


High blood sugar levels can seriously damage many parts of your body including your blood vessels. These are called diabetes complications. 

There are two types of diabetes complications: Chronic and Acute complications. Chronic complications are long-term problems that build up gradually over many years. In contrast, acute complications can happen at any time and cause chronic complications.16

Table 1: Major complications of diabetes 

Eye problemsHypoglycaemia (or hypos)
Foot problemsHyperglycaemia (or hyper)
Heart disease and strokeHyperosmolar Hyperglycaemic State (HHS)
Kidney diseaseDiabetic Ketoacidosis (DKA)
Nerve damage 
Gum disease 
Sexual problems 
Related conditions, like cancer 


Diabetes is a serious condition that is on the rise in the UK. The 2 major types of diabetes account for 98% of all diabetes patients. While the causes of Type 1 diabetes are not clear, there are clear risk factors for Type 2 diabetes. Moreover, the single greatest risk factor is obesity.   

Although there is no cure for Type 1 diabetes, you can make lifestyle changes to prevent, or delay Type 2 diabetes. Furthermore, you can even go into diabetes remission.


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  2. Genetic and Rare Diseases Information Centre [Internet]. Gaithersburg: GARD; 2014. Diabetes mellitus type 1; 2014 Apr 25 [cited 2022 Apr 10].
  3. Savastio S, Cadario F, Beux S, Giorgis A, Bagnati M, Bellomo G, et al. Vitamin D and type 1 diabetes. J Rheumatol [Internet]. 2018 Dec [cited 2022 Apr 10]; 12(Supp-1,M8): 289-299.
  4. Christen U, Bender C, von Herrath MG. Infection as a cause of type 1 diabetes. Curr   Opin Rheumatol [Internet]. 2012 Jul [cited 2022 Apr 10]; 24(4): 417-423.
  5.   Vaarala O. Gut microbiota and type 1 diabetes. Rev Diab Stud [Internet]. 2013 Feb [cited 2022 Apr 10]; 9(4): 251-259.
  6. Diabetes UK [Internet]. London: Diabetes UK. Diabetes Remission [cited 2022 Apr 10].
  7. Diabetes UK [Internet]. London: Diabetes UK; 2017. Number of people with diabetes reaches 4.8 million; 2017 Nov 10 [cited 2022 Apr 10].
  8. GOV.UK [Internet]. Crown: GOV.UK; 2022. Physical activity: applying all our health; 2022 Mar 10 [cited 2022 Apr 10].
  9. Diabetes UK [Internet]. London: Diabetes UK. Diabetes risk factors [cited 2022 Apr 10].
  10. Diabetes UK [Internet]. London: Diabetes UK. What is gestational diabetes [cited 2022 Apr 10].
  11. Diabetes UK [Internet]. London: Diabetes UK. What are the signs and symptoms of diabetes [cited 2022 Apr 10].
  12. Diabetes UK [Internet]. London: Diabetes UK. Type 2 diabetes – know your risk [cited 2022 Apr 10].
  13. Diabetes UK [Internet]. London: Diabetes UK. The direct route to type 2 remission [cited 2022 Apr 10].
  14. Diabetes UK [Internet]. London: Diabetes UK. Research spotlight – putting type 2 diabetes into remission [cited 2022 Apr 10].
  15. Diabetes UK [Internet]. London: Diabetes UK. Weight loss surgery for type 2 diabetes [cited 2022 Apr 10].
  16. Diabetes UK [Internet]. London: Diabetes UK. Complications of diabetes [cited 2022 Apr 10].

Vijendran Santhirasegaran

Master's degree - Instructional Design and Technology, Nanyang Technological University, Singapore
Santhirasegaran has 9 years of experience in the private equity industry. As such, he has worked with others to raise capital for seed and start-up investments such as health tech start-ups.
He is passionate about health and fitness. Moreover, he is intrigued by preventive healthcare and longevity studies. Santhirasegaran is a Chartered Financial Analyst (CFA Charterholder), and a fellow member of the Association of Chartered Certified Accountants (FCCA).https://www.linkedin.com/in/v-santhirasegaran-72b24921a/

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