Is Diabetes Genetic?

If you or someone in your family has diabetes, you might be wondering if it is genetic. There are different types of diabetes. For each type, there are specific risk factors that make someone more likely to develop it.

Having a parent or sibling with diabetes does mean you are more likely to develop it yourself. But diabetes isn't just caused by genetics. Having a relative with the disease doesn't guarantee you will get it.

This article discusses how genetics factor into diabetes development. It also covers the importance of screening and takes a closer look at how genetic testing is being used to diagnose specific types of diabetes.

Role of Genetics in Diabetes

Types 1 and 2 diabetes appear to be caused by an interplay of genetic, environmental, and lifestyle factors. Over the years, researchers have found an array of specific genes that are linked to diabetes risk.

The genes that have been identified have diverse functions and duties which can affect blood sugar (glucose) control. Such functions include controlling the release of insulin, pumping glucose into cells, and speeding up the breakdown of glucose.

But, in addition to genes, something in the environment must trigger diabetes to become active. Researchers have found a number of factors that could trigger type 1 diabetes in people who are predisposed to it, including:

• Exposure to some viruses
• Living in a cold climate
• Being introduced to solid foods at an earlier age
• Not being breastfed

Type 1 Diabetes

Type 1 diabetes is an autoimmune disease in which the body mistakenly attacks the beta cells of the pancreas. As a result, the affected person must rely on insulin in the form of an infusion or injection to live. Roughly 1.6 million Americans are living with type 1 diabetes.

People genetically predisposed to type 1 diabetes have a higher chance of developing it, but that does not mean they absolutely will.

The risk of developing diabetes varies depending on a person's relationship to a family member with the condition. For instance:

• Women with type 1 diabetes have a 1.3% to 4% chance of passing it on to their child
  
• Men with type 1 diabetes have a 6% to 9% chance of passing it on
• A non-identical sibling of someone diagnosed with type 1 diabetes has a 6% to 7% chance of developing the disease
• An identical twin of someone with type 1 diabetes has a more than 70% chance

In addition, type 1 diabetes is most common among non-Hispanic whites, especially those of Northern European descent. This is connected to genes called HLA-DR3 or HLA-DR4, which are linked to autoimmune disease.

Suspect genes in other ethnic groups may put people at increased risk. For example, scientists believe that the HLA-DR7 gene may put Black people at risk, and the HLA-DR9 gene may put Japanese people at risk.

Genetic predisposition alone is not enough to cause type 1 diabetes. And some people can develop type 1 diabetes even though no one in their family has it. It is estimated that 85% of the people diagnosed with type 1 diabetes do not have a family history of the disease.

Type 2 Diabetes

Type 2 diabetes is characterized by insulin resistance and the progressive loss of cells in the pancreas that are responsible for making insulin (beta cells). As a result, blood sugar levels go uncontrolled. This is the most common form of diabetes.

Many people who have type 2 diabetes may also have other underlying health conditions, such as high blood pressure, cholesterol, and excess weight in the abdominal area. In the past, type 2 diabetes was often referred to as adult diabetes, but it is now known that children can be affected too.

Some genes are related to insulin resistance, while others are related to beta cell function. Scientists continue to research genes involved in the development of type 2 diabetes and their role in disease progression and treatment.

Studies have shown a wide range of statistics for the heritability of type 2 diabetes—anywhere from 20% to 80% are thought to inherit it.

The lifetime risk of developing type 2 diabetes is 40% for individuals who have one parent with type 2 diabetes, and 70% if both parents are affected. People who have a first-degree relative with type 2 diabetes are estimated to be three times more likely to develop the disease.

But genetic factors are not the only risk. While type 2 diabetes has a stronger link to family history than type 1 diabetes, environmental and behavioral factors also play a role. As such, interventions can help to prevent or delay a diabetes diagnosis.

Gestational Diabetes

Gestational diabetes occurs during pregnancy when blood glucose levels become elevated. The placenta provides the baby with nutrients to grow and thrive. It also produces a variety of hormones during pregnancy.

Some of these hormones block the effect of insulin and can make after-meal blood sugars harder to control. This "contra-insulin effect" usually happens around 20 to 24 weeks of pregnancy, which is why people are screened for gestational diabetes at this time.

The US Preventive Services Task Force advises screening for diabetes in women who:

• Are planning a pregnancy, especially if they have type 2 diabetes risk factors
• Are pregnant and have diabetes risk factors—healthcare providers should consider screening them before 24 weeks of pregnancy
• Are pregnant and were not screened before conception—they should be screened at their first prenatal visit

Normally, the pancreas will produce more insulin to make up for hormonal insulin resistance. For some people, their pancreas cannot keep up with insulin production, which results in elevated blood sugar and a gestational diabetes diagnosis. Most women who develop gestational diabetes will have no symptoms.

Several genes have been identified in people with gestational diabetes. Studies suggest there may be a link between genes for gestational diabetes and type 2 diabetes.

Many people diagnosed with gestational diabetes have a close family member such as a parent or sibling with the disease or another form of diabetes, such as type 2 diabetes. Gestational diabetes appears to run in families.

Like other forms of diabetes, having a genetic predisposition doesn't mean you are guaranteed to get gestational diabetes. Other risk factors include gestational age, weight, activity level, diet, previous pregnancies, and smoking, to name a few. Maintaining adequate blood sugar control is important for the health of the mother and baby.

Genetic Testing

Genetic testing can be used to identify certain forms of diabetes that are monogenic, meaning that they are related to a change or defect in a single gene. Both neonatal diabetes and MODY are monogenic, and both tend to be incorrectly diagnosed.

Genetic testing is important for making a precise diagnosis, particularly for these monogenic types of diabetes. Furthermore, without a correct diagnosis, the affected person cannot get the proper treatment for the type of diabetes they have.

Physicians often recommend genetic testing when a diabetes diagnosis appears to be atypical. For example, a person who is around age 20 to 25, has abnormal blood sugars, and who does not have any typical risk factors for type 1 or type 2 diabetes, may have MODY.

Genetic diagnosis of MODY additionally allows for the identification of at-risk first-degree family members, who have a 50% chance of inheriting a gene mutation.

If you suspect that you or your child are at increased risk of developing type 1 diabetes, you might be eligible for a risk screening offered through TrialNet Pathway to Prevention Study.

The screening is free for relatives of people with type 1 diabetes. It uses a blood test to detect diabetes-related antibodies, the presence of which means that the immune system has begun to attack cells in the pancreas. The screening can detect these antibodies years before diabetes symptoms even begin.

People found to be in the early stages of developing type 1 diabetes may also be eligible for the prevention study. Ask your healthcare provider whether genetic testing is available and how helpful it is in determining if you will get diabetes.

Whereas MODY and neonatal diabetes are monogenic, diabetes type 1 and type 2 are polygenic, meaning they are related to changes in multiple genes.

Currently, researchers do not feel that genetic testing is ready to diagnose type 2 diabetes. Because there are so many variants of genes and subtypes of type 2 diabetes, they feel as though better methods and more research need to be done in this area before putting it to practical use.

Similarly, genetic testing is not yet clinically useful for diagnosing polygenic gestational diabetes, as researchers have yet to identify a clear pattern of inheritance.

Can You Reduce Your Risk?

If you have a family history of gestational diabetes or type 2 diabetes, there are ways to reduce your risk of developing the disease.

Maintain a healthy weight or lose weight. If you are overweight, particularly in the abdominal area, losing weight will reduce your risk. Even modest weight reduction, about 5% to 10% weight loss, can reduce your risk.

While weight gain is important for a healthy pregnancy, people who are pregnant should try to gain weight slowly rather than excessively. This will help prevent gestational diabetes.

Stay active. Aim to exercise at least 150 minutes per week and avoid sitting for long periods of time.

Eat more plants. Add more fruits, vegetables, legumes, nuts, seeds, and whole grains to your diet, and cut out processed, pre-packaged foods where possible.

Health maintenance and regular checkups are important. If you've recently gained weight or are feeling very sluggish and tired, you may be experiencing high blood sugar, which is characterized by insulin resistance.

Screening

Because type 2 diabetes often takes years to develop, people can be walking around with impaired glucose tolerance (insulin resistance) or prediabetes for years without knowing it. If you catch this condition early, you may be able to prevent or delay diabetes from occurring.

Screening is recommended for the following groups:

• Anyone over age 35: If your results are normal, testing should be repeated at least every three years. Depending on your initial results, your healthcare provider may recommend more frequent testing. If you have prediabetes, you may be tested yearly.
• Younger adults with high BMI and risk factors: A BMI of more than 25 kg/m² or a waist circumference of more than 40 inches in men or 35 inches in women is a risk factor. The BMI cut-off for Asian-Americans is lower (23 kg/m²).

Among this latter group, risk factors warranting screening include:

• Belong to a high-risk population: Populations with a higher risk of prediabetes include Black Americans, Hispanic/Latinx Americans, Native Americans, Alaska Natives, Asian Americans, and Pacific Islanders.
• Family history: This includes having a parent or sibling with diabetes.
• Gestational diabetes: A history of gestational diabetes or having given birth to a baby weighing more than 9 pounds are risk factors.
• Lifestyle: Typically, a physically inactive lifestyle is a risk factor.
• Hypertension: This is defined as a blood pressure that's equal to or greater than 140/90 mmHg or taking therapy for hypertension.
• High fat and cholesterol levels: If you have low levels of high-density lipoprotein (HDL) cholesterol or high levels of triglycerides, you have a higher risk.
• Predisposing conditions: These include acanthosis nigricans, nonalcoholic steatohepatitis, polycystic ovary syndrome, and atherosclerotic cardiovascular disease.

In addition, people with HIV, a history of pancreatitis, or use of certain high-risk medications such as atypical antipsychotics or glucocorticoids should be screened.

There are several tests that can alert you if you are at increased risk of developing type 2 diabetes. These include hemoglobin A1C, blood pressure, cholesterol, and triglycerides.

Other Things to Consider

Sometimes people who have a family history of gestational diabetes can develop diabetes during pregnancy despite their efforts to keep weight gain within a healthy range, exercise, and eat a fiber-rich diet. Do not beat yourself up if this happens.

Pregnancy hormones and insulin resistance (which is typical during pregnancy) can make controlling blood sugar in pregnancy difficult for some people with genetic risk. Your medical team will help you reach your blood sugar goals during pregnancy to make sure that you and your baby are healthy and thriving.

Once you have delivered your baby, your blood sugars should go back to normal. But it's still important to continue to eat a well-balanced diet, maintain a healthy weight, and exercise; these steps can help reduce your risk of developing type 2 diabetes later in life.

Although type 1 diabetes cannot be prevented or cured, if you are genetically predisposed to type 1 diabetes, regular vaccinations and wellness visits will be important.

There is no vaccine to prevent type 1 diabetes, but some research suggests that viruses can trigger type 1 diabetes in people that are predisposed. Therefore, preventing catching these viruses may reduce the risk of developing diabetes.

Understanding the warning signs of type 1 diabetes will also help prevent a dangerous situation like diabetic ketoacidosis.

Summary

Having a family history of diabetes doesn't necessarily mean you will develop it. Scientists believe that diabetes develops when a person has a genetic predisposition to it then an interplay of environmental and/or lifestyle factors triggers it.

Genetic testing allows physicians to make the most precise diabetes diagnoses and to get their patients the right treatment for the type of diabetes they have. If you think you could be at risk for diabetes, talk to your healthcare provider about being screened. Doing so may catch diabetes early so that you can stop it from progressing.

A Word From Verywell

There are many different types of diabetes, so your risk depends on what type of diabetes you are genetically predisposed to. If you have concerns about your family history of diabetes, be sure to take it up with your medical team.

Genetic testing may not be helpful in certain instances; however, you may be screened for the disease. You will be educated on your individual risk, steps to take to prevent or delay it (if possible), and coping strategies.