Causes of Type 2 Diabetes

What is Type 2 Diabetes?

Type 2 diabetes is the most common type of diabetes affecting society. It happens when blood sugar (glucose) is high and uncontrolled due to an impairment in the way body regulates glucose levels.1,2

This is a chronic disease, which means it is lifelong and sometimes does not present with any symptoms, but can lead to problems in the blood vessels, nerves and even the immune system of the body.1

In this type of diabetes, the body's cells do not respond well to insulin, a hormone responsible for facilitating the entry of glucose into the body's cells. In addition, the pancreas might also produce lower levels of this hormone and therefore, there is a lack of glucose inside the cell and high levels of sugar in the bloodstream.1,2

Type 2 diabetes is more common in older adults, however, the number of children with this disease has been increasing, possibly due to the high rate of obesity among the younger generations.1

Symptoms of type 2 diabetes

Type 2 diabetes develops more slowly than type 1 diabetes and can take several years to show. Most people will not notice any changes, but some of the signs can be:

  • Feeling thirsty even when drinking a great amount of water.
  • Passing out a lot of urine, especially overnight.
  • Feeling hungry all the time.
  • Losing weight even without trying and eating a lot.
  • Feeling tired.
  • Frequent infections, especially thrush.
  • Healing of wounds can take longer.
  • Blurred vision.
  • Pin and needles sensation or numbness on extremities (hands and feet).
  • Areas of dark skin, mostly on the armpit, groins or neck, known as acanthosis nigricans.1,3

Risk factors of Type 2 diabetes

People have a higher risk of developing type 2 diabetes if they:

  • Have a close relative (parent or siblings) who has the disease.
  • Are of African Caribbean, Black African, South Asian or Chinese origin.
  • Have obesity or are overweight.
  • Are over 40.3,4

Type 2 diabetes is caused by insulin resistance

What is insulin?

Insulin is a hormone produced in the pancreas, an organ that is part of the digestive system. After eating, our body breaks down carbohydrates into glucose. Glucose is a type of sugar responsible for providing energy to our cells and body.

Insulin facilitates the entrance of glucose into the cells. It is a very important hormone, without which we cannot live. In severe cases of type 2 diabetes, insulin needs to be replaced to help the body function properly.5,6

The role of insulin in regulating blood sugar

After you eat, the digestion process begins and carbohydrates are broken down into glucose and other sugars.  Once this glucose reaches the bloodstream the pancreas receives a sign to start to produce and release insulin into your body.1,6

Insulin will then work to bring glucose inside the cells, where it will be the main source of energy for all the activities inside the cell. This makes the level of sugar in our blood drop and in response, the pancreas decreases the secretion of insulin to maintain blood sugar at normal levels.1,6

This hormone is also responsible for storing glucose in the liver and muscles; therefore, in between meals and when fasting, this stored glucose is used to maintain normal blood sugar levels.6,7

What happens when cells don’t respond to insulin?

Type 2 diabetes can happen when the pancreas does not produce enough insulin, but the main mechanism of this disease is insulin resistance. In this case, the pancreas is producing insulin, however, the cells do not respond well to it and therefore the glucose remains in the bloodstream, causing high blood sugar.

The pancreas tries to correct this by producing more insulin, but it eventually becomes overwhelmed, and symptoms start to appear. Without a source of energy in the cells, a person feels tired all the time. The body tries to compensate by increasing appetite in an attempt to get glucose into the body, but this energy never gets to the cells (due to insulin resistance). High glucose levels also trigger a mechanism that makes the person urinate (pee) a lot.

Over time, high glucose in the bloodstream can damage blood vessels, resulting in heart diseases, stroke, atherosclerosis, high blood pressure, kidney disease, and poor vision. It can also cause damage to the nerves, causing numbness, tingling, problems with the feet due to loss of sensation, erectile dysfunction in men, and digestive problems like diarrhoea and/or constipation.

Diabetes is a very serious condition which is related to several other diseases and therefore needs to be properly assessed and managed.1,8


Type 2 diabetes is the most common type of diabetes. It is characterised by high levels of sugar in the bloodstream. Symptoms include fatigue, weight loss, feeling excessively thirsty or hungry, urinating a lot, loss of sensation and blurred vision.

The main cause of type 2 diabetes is insulin resistance which is when the body is producing insulin to help glucose to enter the cells, but the cell doesn’t recognise it properly leading to high levels of sugar in the blood.

This leads to mechanisms that trigger the symptoms and also provoke complications like heart and kidney disease, stroke, nerve damage, eye problems and high blood pressure.

Therefore, it is important to diagnose and manage it properly in order to prevent its complications.


  1. Type 2 diabetes - Symptoms and causes [Internet]. Mayo Clinic. [cited 2022 Aug 29]. Available from:
  2. Type 2 diabetes | niddk [Internet]. National Institute of Diabetes and Digestive and Kidney Diseases. [cited 2022 Aug 29]. Available from:
  3. Type 2 diabetes - Symptoms [Internet]. 2018 [cited 2022 Aug 29]. Available from:
  4. Type 2 diabetes [Internet]. Diabetes UK. [cited 2022 Aug 29]. Available from:
  5. Insulin and diabetes [Internet]. Diabetes UK. [cited 2022 Aug 29]. Available from:
  6. Diabetes treatment: Using insulin to manage blood sugar [Internet]. Mayo Clinic. [cited 2022 Aug 29]. Available from:
  7. Insulin: types of insulin, needles, pumps, pens, and why insulin is so expensive [Internet]. [cited 2022 Aug 29]. Available from:
  8. Type 2 diabetes - Health problems [Internet]. 2018 [cited 2022 Aug 29]. Available from:

Renata Barbosa Rebuitti

Bachelor's Degree in Medicine,Federal University of Minas Gerais

Renata is a medical doctor passionate about her work and science. Currently exploring medical writing and medical communications. She loves to share information and scientific knowledge. presents all health information in line with our terms and conditions. It is essential to understand that the medical information available on our platform is not intended to substitute the relationship between a patient and their physician or doctor, as well as any medical guidance they offer. Always consult with a healthcare professional before making any decisions based on the information found on our website.
Klarity is a citizen-centric health data management platform that enables citizens to securely access, control and share their own health data. Klarity Health Library aims to provide clear and evidence-based health and wellness related informative articles. 
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