Family history

Studies have shown that if someone in your family has type 2 diabetes, you are at increased risk of also developing the condition.

A review carried out by Diabetes NSW of a range of international studies shows that family history is an important predictor of type 2 diabetes. If one identical twin has type 2 diabetes, the chance of glucose intolerance in the other twin is up to 90%. It’s further estimated that people with one parent with diabetes have double the risk, while both parents increase the risk up to six times. If you have a brother or sister with type 2 diabetes the risk increases more than four times. The closer the relative, the greater the risk and the more relatives with type 2 diabetes then the greater the odds for other family members. Having three or more relatives with the condition can increase the risk almost 15 times.

Another risk factor associated with family history is lifestyle. A study completed in the United Kingdom and the United States found obese and overweight adults are more likely to have a family history of diabetes. Overweight adults are almost twice as likely to have type 2 diabetes, and obese adults are nearly four times as likely to have type 2 diabetes.

Because type 2 diabetes is known to run in families – along with other common conditions such as high blood pressure, heart disease and cancer – it’s important that people learn as much as possible about the health history of their relatives. Diabetes NSW encourages everyone to learn their family health history and to contact us on 1300 342 238 for more information, support and resources.

The more relatives you have with diabetes,
the higher your risk is!

The more relatives with diabetes, the higher your risk

New Australian research has found type 2 diabetes develops earlier in families where there are more cases of the condition. The average age of diagnosis when six relatives, other than parents, have diabetes was found to be 42 years of age, compared with 52 years of age when only one family member had it.

The study(2) found a strong relationship between the number of affected family members with diabetes and age of developing diabetes. The more cases of diabetes found in a family, the younger the age of onset of type 2 diabetes.

The American Diabetes Association estimates that a child has a 1 in 7 chance of developing diabetes if the parent is diagnosed before the age of 50, compared to a 1 in 13 chance if the parent is diagnosed after that age.

An ‘action plan’ to reduce your family’s risk

For those with a family history of type 2 diabetes, the good news is that you can reduce your family’s risk.

A number of international landmark studies have found that after adopting simple lifestyle changes, people with pre-diabetes reduced their risk of developing type 2 diabetes by 58%.

High risk categories with family links

People are at risk of developing diabetes if they are:

  • Over 45 years of age and one of more members of the family has/had diabetes (People with a family history of diabetes have 2 to 6 times the risk of developing type 2)
  • Over 35 years of age and are an Aboriginal or Torres Strait Islander (Indigenous Australians are 10 times as likely to have diabetes than other Australians (3). In 2000-01, death rates from diabetes among Indigenous Australians were almost 15 times as higher than other Australians (2))
  • Over 35 years of age and from Pacific Islands, Indian subcontinent or Chinese background (Certain overseas born Australians have a higher prevalence of diabetes than people born in Australia (2)


1. Preventing Chronic Disease, CDC. Family History, Diabetes and other Demographic and Risk Factors among participants of the National Health and Nutrition Examination Survey 1999-2002
2. Strong family History Predicts a younger age of onset for subjects diagnosed with type 2. Molyneaux, Constantino, Yue
3 American Diabetes Association. The Genetics of Diabetes
4. Sergeant LA. European Prospective Investigation into Cancer.
5. Jones Donald. Impact and Evaluation of Recent campaigns run by Diabetes Australia. 2004
6. 2004 HealthStyles Survey. CDC
7. Characterisation of subjects with early abnormalities of glucose tolerance in the Stockholm Diabetes Prevention Program/ Kuhl. Diabetologia