Most of us are guilty of thinking excess intake of industry sugar causes Diabetes. Some others believe by not using table sugar to drink tea or custard, they are keeping themselves away from having diabetes. The real truth is, we cannot survive without sugar. The two most important cells of our body system can not function without sugar. Sugar serves as their primary source of energy to function. These cells are The Brain cells and the Red blood cells. 
Scientifically proven, 70-85% of what we consume as humans contain a significant amount of sugar. It is therefore hard for any living animal especially human beings to live without consuming sugar. The best we can do for those with High level Sugar intolerance, is to consume food with low, or insignificant amounts of Sugar. Note further, the excessive consumption of low sugar also has an adverse effect on the efficiency and efficacy of the brain and red blood cells. 
Two main causes of diabetes in the body are:
Insulin Deficiency: Insulin is the hormone in-charge of converting excess blood sugar into glycogen for storage. The deficiency of this hormone leads to Type 2 Diabetes. 
Deficiency of the Beta cell of the Pancreas : Type 1 Diabetes. This is more like a chronic Type of Diabetes disease. 
Diabetes mellitus is a global health burden accounting for increased hospitalization, morbidity and mortality. High body weight variability is closely linked to diabetes, and can be caused by family/genetic history, environment, behavioral and poor nutritional lifestyles among other factors. Increase body weight variability does not only increase an individual’s risk of developing Type 2 Diabetes Mellitus (T2DM), but also increases the risk of microvascular and macrovascular complications especially cardiometabolic and cardiovascular diseases (CVDs). CVDs – such as ischemic heart attack, cerebrovascular accident (Stroke), fatal myocardial infarction, heart failure (HF), coronary artery disease (CAD), and peripheral artery disease– are the main cause of death among people with diabetes mellitus. Additionally, poor management of the diabetic condition can contribute to uncontrolled weight gain and aggravate the diabetes condition.
Eventually all man shall one day die. Diabetes is one of the major cause of death globally, and for that it is a topic of global discussion, study and research. As a common man, it is of great importance and an act of self love to regularly check the blood sugar level. Balanced diet, and regulated sugar intake( all high carbohydrate containing food ) is a disciplined way to play safe as no one can detect for sure when his or her Insulin/Pancreas might likely fail.
Do well to share your experience or leave an advice if you have any from your experience either as a diabetic patient or someone who has been around or taken care of a diabetic patients.