A new study now suggests that type 2 diabetes signs can appear more than 20 years before a patient is diagnosed.
According to the study involving more than 2,700 people, dangerously high blood sugar levels and insulin resistance can be seen two decades before a person is eventually diagnosed with the condition.
According to Japanese researchers healthy lifestyle interventions may be required as soon as a person's blood sugars start to rise to prevent 'full blown diabetes'.
The research, carried out at Aizawa Hospital in Matsumoto analysed 27,392 adults who did not have diabetes at the start between 2005 and 2016.
Weight and blood sugar measurements were taken at the start of the study and they found that over the next 11 years, 1,067 of the participants developed type 2 diabetes.
Results showed those who went on to get the disease had a raised BMI, blood sugar levels and insulin resistance up to 10 years before they were diagnosed.
These became more severe in the lead up to their diagnosis.
For example, those with a fasting blood sugar level of 101.5mg/dL went on to develop type 2 diabetes 10 years later, unlike people with 94.5mg/dL.
Of the 15,778 participants with a healthy blood glucose level at the start, 4,781 developed prediabetes during the experiment.
Their eventual prediabetes diagnosis could also be predicted by their blood sugar levels decades before.
The study was presented at the European Association for the Study of Diabetes conference in Berlin.
Type 2 diabetes occur when a person does not produce enough insulin or doesn't respond to the hormone that is made. It is associated with obesity.