Diabetes mellitus is a condition that affects how the body regulates blood sugar. A person’s genetics can increase their likelihood of developing the condition.

The term “diabetes” refers to a group of conditions that prevent the body from properly producing or using blood glucose. Glucose is a sugar that comes from foods and drinks. Diabetes causes abnormally high blood glucose levels, which can harm the body.

Over 37 million people in the United States have some form of diabetes, reports the Centers for Disease Control and Prevention (CDC). Around 8.5 million people have diabetes but have not received a formal diagnosis.

There are three main types of diabetes:

  • Type 1 diabetes results from the immune system mistakenly attacking healthy tissues. It typically starts during childhood.
  • Type 2 diabetes develops more slowly. It strongly relates to lifestyle, such as a diet high in sugar and processed foods.
  • Gestational diabetes develops in pregnancy. It typically goes away after birth.

Genetics plays a role in all types of diabetes. This article discusses the genetics of diabetes, including genetic testing and preventing diabetes.

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The relationship between genetics and diabetes is complex and varies by type. People typically inherit a genetic predisposition to diabetes, which other factors, such as obesity, can trigger.

Type 1 diabetes is the result of genetics and factors in the environment. People with certain genetic patterns are more likely to develop type 1 diabetes. However, there is also typically an environmental trigger, such as a virus.

Type 2 diabetes results from several risk factors, which include low physical activity, diet, and overweight or obesity. However, certain genes increase the chances of developing type 2 diabetes. Type 2 diabetes can run in families.

Gestational diabetes is the result of pregnancy. However, genetics also increase the risk of a pregnancy leading to gestational diabetes.

Genetics increase the risk of diabetes but are not the only cause. For example, the American Diabetes Association (ADA) states that there is only a 50% chance that one twin develops diabetes if the other has type 1 diabetes. If one twin has type 2 diabetes, the other’s risk is around 75%.

Scientists have been studying which genes increase the risk of someone developing diabetes. Most types of diabetes are polygenic, which means they result from multiple genes.

For example, there are strong links between the HLA genes and diabetes. These genes have various functions, such as making proteins central to how the immune system works.

According to the ADA, most white people with type 1 diabetes have HLA-DR3 or HLA-DR4 genes. The HLA-DR7 gene may increase the risk of diabetes in African Americans. The HLA-HR9 gene may increase the risk of diabetes in Japanese people.

More research is needed to explore the links between genes and diabetes in other groups.

Changes in one specific gene can cause some rare forms of diabetes. For example, maturity onset diabetes of the young (MODY) occurs when there is a change in one gene that reduces the capacity of the pancreas to produce insulin. For example, this could be a change to the GCK gene.

According to the CDC, risk factors for diabetes depend on the type.

Risk factors for type 1 diabetes include family history and age, as it typically develops in childhood.

Type 2 diabetes risk factors include:

  • having prediabetes
  • having overweight or obesity
  • being over age 45 years
  • having a family history of diabetes
  • living a sedentary lifestyle
  • having a current or former gestational diabetes diagnosis

Risk factors for gestational diabetes include:

  • having a previous gestational diabetes diagnosis
  • giving birth to a baby over 9 pounds
  • having overweight or obesity
  • being older than age 25 years
  • having a family history of type 2 diabetes
  • having polycystic ovary syndrome (PCOS)

Genetic testing looks for changes in genes that could lead to a health condition. It can help people determine the risk of a condition in themselves or their children and take steps to try to prevent it.

Genetic testing in diabetes is complex because both genetics and other factors cause the condition. For example, people with HLA genes linked with type 1 diabetes may only develop the condition sometimes.

The ADA states that a male with type 1 diabetes only has a 1 in 17 chance of their child developing the condition. The chances are lower for females, with a 1 in 25 chance.

Genetic testing may help some people adapt their lifestyle to reduce their risk of diabetes. Genetic testing is most useful in MODY and other rare types of diabetes, where it can reveal the exact genes that cause the condition.

There are several steps someone can take to reduce their risk of type 2 diabetes regardless of genetics.

The National Institute of Diabetes and Digestive and Kidney Disorders (NIDDK) suggests tips for reducing a person’s risk of type 2 diabetes. These tips include:

  • losing weight if needed and maintaining a moderate weight
  • exercising regularly and staying physically active
  • eating a balanced diet

Type 1 diabetes cannot be prevented because it results from genetics and an autoimmune reaction.

The following are some questions people frequently ask about diabetes and genetics.

Is diabetes transferable from person to person?

Diabetes is not contagious and cannot be transmitted from person to person. While genetics may play a role in the development of diabetes, people cannot transfer the condition to someone else through contact.

Is diabetes mellitus heritable?

Diabetes is heritable and can pass down through families. However, having family members with diabetes does not necessarily mean someone will develop the condition.

Diabetes is a common group of conditions that affect blood glucose levels. The causes of diabetes include genetics and environmental factors.

Some types of diabetes, such as type 1 diabetes, have a stronger genetic link. However, these types may still require an environmental trigger, such as a virus, to develop.

Several other factors increase the risk of diabetes, such as obesity, diet, and a sedentary lifestyle. People can reduce their risk by maintaining a moderate weight, eating a balanced diet, and exercising regularly.

Individuals who have concerns about their risk of diabetes can speak with a healthcare professional.