Is Type 1 Diabetes Common in Siblings?

If you have a family member with type 1 diabetes, you are probably wondering if you or your sibling will get it too. Or if you have the condition, how likely is it to pass down type 1 diabetes to your kids?

A diagnosis of type 1 diabetes will affect the whole family. There is a marginally increased risk of another family member developing type 1 diabetes if one family member already has it.

But many patients don’t have a history of diabetes in their family. And sometimes, one identical twin with the same genes can have the condition while the other does not.

According to research, a combination of genetic and environmental factors contributes to the development of type 1 diabetes. So, if your child inherits the bunch of genes involved in diabetes, they are more likely to get it. And sometimes, the other sibling may not get it, and that’s where the environment comes into play.

How common is type 1 diabetes in siblings? Let’s explore.

Can Type 1 Diabetes Run in the Family?

Type 1 diabetes, a less common type frequently diagnosed in children and young adults, is undoubtedly influenced by genes. But they do not tell the entire tale. It’s a combination of nature and nurture, like much in life.

There is no specific gene for type 1 diabetes that can be turned on or off. Instead, a number of them (about a dozen) play an active role.

A child’s chances of developing diabetes depend significantly on which genes they inherit from their parents. Some increase the risk of contracting it, while others can help shield the child from it.

If the father has type 1 diabetes, there is a 1 in 15 chance that the child will get it too. If the mother has type 1 diabetes, the odds are slightly lower, with 1 in 40 chances of the child developing the condition. However, 80 percent of people with type 1 diabetes have no family history.

A few things can boost the odds of getting type 1 diabetes. For instance, if the parents had diabetes before age 11, the child’s chances of having it double. Also, if both parents suffer from it, the likelihood could be as high as 1 in 4. 

Now, you might be thinking, “One of my kids has diabetes, do his/her siblings have it?” According to research, the likelihood of developing type 1 ranges from 1 in 12 to 1 in 25. The risk is significantly higher if a sibling was diagnosed with the condition before age seven than in those diagnosed much later in life. The risk is as high as 1 in 3 if your child’s identical twin suffers from type 1 diabetes.

All those numbers can be overwhelming and confusing. But remember, most people with type 1 diabetes don’t have relatives who do. And it often seems to come out of nowhere. So, who is at risk of getting it?

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Who Is at The Highest Risk of Developing Type 1 Diabetes?

In the United States alone, 1 in 300 children and adolescents develop type 1 diabetes by 20 years old. Some children may not show any symptoms, leading to a later diagnosis.

The increased risk of developing type 1 diabetes in family members can be due to shared genetic and environmental factors. However, your environment, which includes your upbringing and the foods you consume, is also important.

Researchers are unsure how and to what extent each factor influences the risk of contracting the illness. So, although your genes have set the stage, you cannot predict how everything will turn out.

Other factors can increase the risk. For instance, exposure to viral infections in the womb, from birth to early childhood, is likely to contribute. And contrary to popular belief, there is no association between childhood vaccination and Type 1 diabetes.

Males are more likely to develop type 1 diabetes than females. In addition, some groups of people have a higher prevalence of particular genes than others. Because of this, race and ethnicity have an impact as well. For instance, white people are more likely than others to have type 1 diabetes.

Other possible triggers include cold weather. In areas with cold climates, type 1 diabetes is more common and develops more frequently in the winter than in the summer.

An early diet may also be important. For example, type 1 diabetes is less prevalent in breastfed people and those who start eating solid foods later in life.

At What Age Do Most Kids Develop Type 1 Diabetes?

Another common question in many people’s minds is, what is the average age of getting Type 1 diabetes?

Childhood is a common time for type 1 diabetes diagnosis, most frequently between the ages of 4 and 14. However, there are two noticeable peaks of diagnosis. The first peak occurs between the ages of 4 and 7 and the second between 10 and 14.

The most common symptoms of diabetes are:

  • Increased thirst than usual
  • Urinating more frequently (bed wetting in children who never do so).
  • Feeling very hungry.
  • Tingling in extremities.
  • Unexplained weight loss.
  • Feeling weak and tired.
  • Blurred vision.
  • Mood changes and feeling irritable.

Several blood tests can diagnose type 1 diabetes in children, such as:

  • Random blood test
  • Fasting blood sugar test
  • Glycated hemoglobin (HbA1c) test

How Long Can Type 1 Diabetes Go Undiagnosed?

Thousands of children worldwide are diagnosed every day, but many go undetected. Sometimes children may have high blood sugar but may not show symptoms. It can take months or years before they are noticed.  

When the condition is undiagnosed, complications may develop due to persistent high blood sugar levels. 

If you, another parent, or your child’s brother or sister have diabetes, your child is more likely to get diabetes. 

Talk to your healthcare provider if type 1 diabetes runs in your family. They may schedule tests for you and your children to spot them early.

Final Thoughts

The genes you inherit are thought to be the leading cause of Type 1 diabetes. Although there are some non genetic causes as well, people who have a sibling or parent with type 1 diabetes may be at an increased risk.

Type 1 cannot be prevented, but early detection can stop potentially harmful complications. If you notice any symptoms, you should seek medical advice right away.


  1. Rewers, Marian, et al. “Risk Factors for Type 1 Diabetes.” Diabetes in America, edited by Catherine C. Cowie et. al., 3rd ed., National Institute of Diabetes and Digestive and Kidney Diseases (US), August 2018.
  2. Harding, Jessica L et al. “The Incidence of Adult-Onset Type 1 Diabetes: A Systematic Review From 32 Countries and Regions.” Diabetes care vol. 45,4 (2022): 994-1006. doi:10.2337/dc21-1752

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