Hyperglycemia is the main cause of a series of pathologies termed ‘complications.’
Diabetes can cause, in a specific and direct manner – especially if it is not kept under control – a series of pathologies of micro-vascular nature due, that is, to the occlusion and deterioration of the small blood vessels of many organs.
These are:

• diabetic retinopathy (the capillaries of the retina deteriorate and gradually make vision troublesome)
• diabetic nephropathy (the ‘filters’ present in the kidney gradually lose their functionality)
• peripheral diabetic neuropathy (the nerves, especially in the area most distant from the brain, such as the foot and the leg, lose sensitivity)
• diabetic foot (the decreased sensitivity makes the formation of ulcers and infections easier, the often occluded capillaries obstruct the natural reaction of the organism, making the natural healing of the tissues difficult or impossible).

The macro-vascular complications

In the most serious of cases, these complications can have very dangerous outcomes. However, the attention of doctors in these last few years has been oriented especially to the role of diabetes as a factor of cardiovascular risk. Basically, diabetes – especially if not kept under control – by favoring the process of obstruction of the arteries, multiplies the risk of developing strokes or heart-attacks. A person with diabetes runs the same risk of suffering a heart-attack as a person with the same age, gender, and weight, who has already suffered a heart-attack.
It is important to notice that – while it takes many years, at times decades, for a person with diabetes to develop the most serious consequences of a ‘micro-vascular complication (for example, for that person to develop eyesight problems or loss of sensitivity in the foot), the cardiovascular risk increases from the first day of diabetes, because the stages of moderate alteration of the glycaemia, commonly defined ‘pre-diabetes,’ are already sufficient to considerably increase the risk of heart-attacks and strokes.
Diabetes, therefore, is harmful for the heart and the brain.

Acute conditions

The complications of diabetes are due to the cumulative effect of continuous hyperglycemias. Diabetes also has certain acute conditions, which are much rarer.
Hyperosmolarity. The person with type 2 diabetes, especially if elderly or alone, can develop hyperosmolarity, a condition characterized by very high glycaemia and dehydration, and which displays symptoms of drowsiness and stupor.
Ketoacidosis. Ketoacidosis, which is characterized by strong thirst, frequent stimulus to urinate, tiredness, and rapid loss of weight, is due to the absence of insulin. It is detected at the onset of type 1 diabetes and in the cases in which the intake of insulin is omitted.
Hypo-glycaemia. Hypo-glycaemia is detected in persons treated with insulin or with certain categories of oral pharmaceuticals (sulphanilureas with a long-lasting effect), when the intake of pharmaceuticals is excessive with respect to the quantity of sugars taken in. Hypo-glycaemia is foreshadowed by nervousness and hunger, and proceeds with tremors and states of confusion.
These three conditions can lead to serious neurological manifestations (all the way to a coma), almost always irreversible.