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Home / Diabetes / What causes diabetes?

What causes diabetes?

Discover the environmental and genetic factors for developing diabetes

Diabetes is a condition that arises when there is too much sugar in your bloodstream. Long-term, it can cause a variety of health problems including heart disease, kidney disease and nerve damage.

In fact, diabetics are twice as likely Trusted source Centers for Disease Control and Prevention (CDC) Government Source Go to source to develop heart disease compared with non-diabetics.

Keep reading to discover the risk factors and lifestyle habits that increase your chances of developing this condition, as well as ways of reversing high blood sugar levels through diet and exercise.

How does the body control blood sugar?

An essential hormone called insulin plays a role in controlling blood sugar levels.

When we eat, food is broken down into sugar which enters your bloodstream. This rise in blood glucose (sugar) after a meal is sometimes referred to as a glucose spike.

Your body will then release insulin, which allows sugar from the blood to be transported into nearby cells. These cells use the sugar as a source of energy.

A graphic depicting sugar in the bloodstream

Any excess sugar that isn’t taken up by your cells is converted into glycogen and stored in the liver. When your body needs energy but isn’t eating (such as during sleep), this glycogen is converted back into glucose and used as fuel.

If there’s still excess glucose, this will be converted into fat.

Type 1 vs type 2 diabetes

There are two types of diabetes:

  • Type 1 (a lifelong condition where the body is unable to produce enough insulin)
  • Type 2 (over time, the body’s cells do not respond well to insulin or there isn’t enough insulin produced)

Type 1 diabetes is caused by a genetic fault and is diagnosed from an early age. The body destroys some of its own cells, making it impossible for the pancreas to produce insulin.

As a result, type 1 diabetics have to inject themselves with insulin to keep their blood glucose levels healthy. Moreover, the condition cannot be reversed with specific lifestyle changes.

Type 2 diabetes, however, develops over time and is largely impacted by lifestyle factors including your weight and diet. Type 2 diabetics either:

  • can’t produce enough insulin to bring glucose levels down, or
  • have cells that don’t respond to insulin (insulin resistance), meaning that blood sugar cannot be used to fuel your body
Type 1 diabetes Type 2 diabetes
  • Diagnosed at an early age
  • Cannot be reversed
  • Lifestyle factors/diet will not improve the condition
  • Unable to produce the hormone insulin
  • Requires insulin injections
  • Diagnosed later on in life
  • Can be improved or even reversed with diet changes and weight loss
  • The body’s cells stop properly responding to insulin
  • You are unable to produce enough insulin

Type 2 diabetes is much more common than type 1. Globally, more than 95% of adults Trusted source World Health Organization (WHO) Government Source International Public Health Information Go to source with diabetes have type 2.

What causes type 2 diabetes?

What causes diabetes exactly is difficult to know. Ultimately, it is caused by too much sugar building up in the bloodstream.

Over time, your cells stop responding to insulin (insulin resistance). This means that sugar stays in the blood instead of being taken up by cells and used for energy.

As blood sugar levels continue to rise, your body may even receive hunger cues in an attempt to get more energy to your cells. However, as your cells have stopped responding to insulin, the sugar ends up staying in the bloodstream.

An infographic displaying how high blood sugar causes hunger

Excess blood sugar is sent by the liver to fat cells and stored as body fat, which causes weight gain.

The following genetic and environmental factors are some of the most common causes of diabetes.

Diabetes and diet

A long-term diet that consists of lots of sugar can impact your ability to produce insulin and contribute towards the development of diabetes.

Sugary foods cause blood sugar levels to spike quickly. To combat this spike you need to produce higher amounts of insulin. Over time, your body struggles to keep up with this high demand for insulin and your blood sugar levels remain too high.

An unhealthy, very sugary glass of fizzy soda

Common foods that spike your blood sugar levels quickly include:

  • sugar and sugary foods (sweets, honey, chocolates, pastries and cakes)
  • sugary soft drinks (fizzy sodas, fruit juices, energy drinks)
  • highly processed white bread (bagels, sliced bread, buns, wraps)
  • white rice
  • white potatoes
  • breakfast cereals (coco pops, cornflakes, cheerios)

Obesity and excess weight

People of all shapes and sizes can develop diabetes. However, if you are not physically active and have higher levels of visceral fat (the fat which forms around your organs), you are more at risk of developing type 2.

The larger your waist size, the more visceral fat you have around your vital organs. This kind of fat is much more dangerous than subcutaneous fat (which is fat on your body you can pinch).

A close-up of an obese person in a grey T-shirt

Obesity causes your body to become more resistant to insulin. This affects how much sugar is taken up by your cells and used for energy.

People living with obesity often eat high-sugar diets, which further contributes to dangerously high blood glucose levels.

Diabetes also promotes fat storage, making it more challenging for diabetics to lose weight and improve their condition.

Family history

People with a family history of type 2 diabetes are more likely to develop it themselves. If you have a close blood relative living with diabetes, you’re 2-6 times more likely to develop the condition yourself.

Close blood relatives include:

  • parents
  • siblings (brothers or sisters)
  • children


Research Trusted source National Center for Biotechnology Information (NCBI) Government Source Biomedical Research and Literature Go to source has shown that people from the following backgrounds are more likely to develop type 2 diabetes at a younger age:

  • Black African
  • African Caribbean
  • Indian
  • Pakistani
  • Bangladeshi

It is important to be aware of your blood glucose levels and make correct diet choices if you are at an increased risk due to your ethnicity or family history. Prevention is always better than treatment.


Certain medications can disrupt how your body produces insulin and increase blood sugar levels.

For example, steroid (corticosteroid) medications can cause the liver to produce more glucose or reduce the cells’ absorption of glucose, which can increase your chances of developing diabetes.

A variety of different pills and tablets

Other medications that can contribute to diabetes include:

  • a type of vitamin B called Niacin
  • anti-seizure drugs
  • psychiatric drugs
  • some diuretics (which help reduce fluid build-up in the body)
  • some HIV medicines
  • anti-rejection medicines (taken after an organ transplant)

If you are taking any of the above medications and have concerns about the potential side effects, please consult with your doctor.


Some women develop high blood sugar levels during pregnancy, which results in something called gestational diabetes.

The condition can develop at any stage of the pregnancy but is most common in the second and third trimesters.

The hormonal changes of pregnancy can disrupt insulin production. As a result, some women have to make diet changes to help control their blood sugar. In rarer cases, they may also be prescribed medication.

However, things usually return to normal shortly after delivery.

Damage to the pancreas

The pancreas is responsible for producing insulin. Therefore, any trauma or damage to the pancreas can increase your chances of developing diabetes if your insulin supply is affected.

A woman pointing towards a graphic of the pancreas.

The same goes for the removal of the pancreas. Under these circumstances, you will likely have to start taking insulin injections to maintain healthy blood sugar levels.

Can diabetes be reversed?

Some people can put their diabetes into remission by losing weight. If a disease is in remission, it hasn’t necessarily been cured. However, it does mean that signs and symptoms have disappeared and you are much less at risk.

By losing weight, you reduce how much fat is stored around your liver and pancreas. This visceral fat (fat that lies internally around your organs) is what’s considered to be a main contributor to the development of diabetes.

Diet to reverse type 2 diabetes

Changes to your diet don’t only improve your chances of weight loss. In some cases, a change in diet can reverse pre-diabetes and even diabetes.

The most important factor when following a diabetes food guide is to eliminate very sugary and starchy foods and to focus on a diet made up of mostly whole foods (with lots of vegetables).

If you usually eat a bacon and egg sandwich for breakfast, consider replacing this with scrambled eggs, bacon medallions and half an avocado. White bread is one of the worst culprits for spiking blood sugar levels.

Want to learn more about diabetes?

Click here

Medically reviewed by Dr. Caroline Fontana Written by our editorial team Last reviewed 28-02-2024

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