Key Takeaways
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More than 40 million people in the United States live with diabetes, and more than a quarter of adults with the condition don’t know they have it. Another 115 million adults have prediabetes, a stage where blood sugar is higher than normal but not yet in the diabetes range. This November, during National Diabetes Month, we’re taking a closer look at the genetics behind different types of diabetes.
How Your Genes and Your Habits Shape Type 2 Diabetes
Type 2 diabetes accounts for about 90% to 95% of diabetes cases in the U.S. It develops when your cells stop responding well to insulin, the hormone that moves sugar from your blood into your cells for energy. This is called insulin resistance. Your pancreas makes more insulin to compensate, but over time it can’t keep up and your blood sugar rises.
Studies estimate that genetics may explain anywhere from 20% to 80% of the risk for type 2 diabetes. The range is wide because genes and environment overlap. Your weight, for example, can reflect both your DNA and the habits your family shares.
Type 2 diabetes is polygenic, meaning it is influenced by many genetic variants that each have a small effect. 23andMe researchers have identified thousands of genetic variants associated with the condition. Scientists can combine these variants into a polygenic score, a single estimate of your genetic predisposition. This is the basis of the 23andMe Type 2 Diabetes PRS report*.
Type 2 diabetes does not affect all communities equally. African American, Hispanic or Latino, American Indian and Alaska Native people are at higher risk, as are some Pacific Islander and Asian American people. Some of this may be due to differences in access to healthcare, healthy food or physical activity, but genetics may also play a role. However, because genetic research has relied mostly on people of European descent, genetic scores often work less well in other populations. This is why it is important to increase the number and diversity of people who contribute to genetic research. Learn more about our research.
Type 1 Diabetes: An Autoimmune Condition With Genetic Roots
Type 1 diabetes is an autoimmune condition, meaning the immune system mistakenly attacks the cells in the pancreas that make insulin. While many people think type 1 diabetes is a childhood form of diabetes, it can start at any age and makes up about 5% to 10% of diabetes cases worldwide. About 1 in 300 people in the U.S. develop type 1 diabetes by age 18.
Variants in genes that help the immune system tell the body’s own cells apart from invaders like viruses can raise a person’s likelihood of developing type 1 diabetes, but other factors still impact the chances of developing this condition. When one identical twin has type 1 diabetes, the other develops it at most half the time, which may point to environmental triggers that researchers are still working to identify. Family history matters as well. If a father has type 1 diabetes, his child’s odds are about 1 in 17. If a mother has it, her child’s odds are about 1 in 25 if the child was born before she turned 25 and about 1 in 100 if born after.
Gestational Diabetes and Your Long-Term Health
Gestational diabetes is diabetes that first develops during pregnancy. Pregnancy hormones make the body less responsive to insulin, and in some people blood sugar rises enough to affect both parent and baby. It affects about 6% of pregnancies in the U.S. and usually causes no noticeable symptoms.
Blood sugar typically returns to normal after delivery, but that isn’t the end of the story. Gestational diabetes is associated with an increased risk for type 2 diabetes and heart disease in both the parent and child. A family history of gestational or type 2 diabetes raises a person’s chances. Genetics plays a role here too. 23andMe’s Gestational Diabetes PRS report** looks at more than 6,000 genetic variants to estimate the likelihood of developing this condition.
MODY: The Diabetes That Often Goes Unrecognized
Maturity-onset diabetes of the young, or MODY, is a form of monogenic diabetes. That means it is caused by a variant in a single gene rather than by the combined effect of many variants in many genes. MODY typically starts early in life and it often shows up across several generations of a family.
MODY is uncommon, making up an estimated 2% to 5% of diabetes, and is most often diagnosed in people under 30. Yet 50% to 90% of cases are thought to be misdiagnosed as type 1 or type 2 diabetes. The right diagnosis can change care: some forms of MODY respond well to oral medications, and one common form usually needs no treatment at all. If diabetes appeared at a young age in several generations of your family, ask your doctor or a genetic counselor whether MODY testing makes sense for you.
What You Can Do
Your genes may influence your likelihood of developing different forms of diabetes, but your daily choices still carry real weight. In a large clinical trial, people at high risk who completed a structured lifestyle program lowered their chances of developing type 2 diabetes by 58%. A few practical steps:
- Map your family history. Ask about relatives who have had type 2, gestational or early-onset diabetes and at what age.
- Get screened. A simple blood test can show whether you have prediabetes or diabetes.
- Stay active and eat well. Regular physical activity, a healthy diet and losing weight if you are overweight can help prevent or delay type 2 diabetes.
- Share your pregnancy history. If you’ve had gestational diabetes, tell your doctor so they can plan follow-up screening.
- Ask about a prevention program. CDC-recognized lifestyle change programs are designed for people with prediabetes or at high risk.
If you’re a 23andMe Premium Ancestry + Health member, you can explore your Type 2 Diabetes report and Gestational Diabetes report (available to those who report their birth sex as female), then bring your results and family history to your next doctor’s visit.
* The 23andMe Type 2 Diabetes PRS report is based on a genetic model that includes data and insights from 23andMe consented research participants and incorporates more than 1,000 genetic variants to provide information on the likelihood of developing type 2 diabetes. The report does not describe a person’s overall likelihood, does not account for lifestyle or family history and has not been reviewed by the US Food and Drug Administration. The Type 2 Diabetes PRS report is not intended to tell you anything about your current state of health, or to be used to make medical decisions or determine any treatment.
** The 23andMe Gestational Diabetes PRS report is based on a genetic model that includes data and insights from 23andMe consented research participants and incorporates more than 6,000 genetic variants to provide information on the likelihood of developing gestational diabetes. The report does not describe a person’s overall likelihood, does not account for lifestyle or family history and has not been reviewed by the US Food and Drug Administration. The Gestational Diabetes PRS report is not intended to tell you anything about your current state of health, or to be used to make medical decisions or determine any treatment.
