Metabolic syndrome promotes coronary heart disease through several mechanisms. It increases the thrombogenicity of circulating blood, in part by raising plasminogen activator type 1 and adipokine levels, and it causes endothelial dysfunction.  Metabolic syndrome may also increase cardiovascular risks by increasing arterial stiffness.  Additional mechanisms include oxidative stress,  which has been associated with numerous components of metabolic syndrome. 
Cataracts and glaucoma are also more common among diabetics. It is also important to note that since the lens of the eye lets water through, if blood sugar concentrations vary a lot, the lens of the eye will shrink and swell with fluid accordingly. As a result, blurry vision is very common in poorly controlled diabetes. Patients are usually discouraged from getting a new eyeglass prescription until their blood sugar is controlled. This allows for a more accurate assessment of what kind of glasses prescription is required.
Most people who have metabolic syndrome have insulin resistance. The body makes insulin to move glucose (sugar) into cells for use as energy. Obesity, commonly found in people with metabolic syndrome, makes it more difficult for cells in the body to respond to insulin. If the body can’t make enough insulin to override the resistance, the blood sugar level increases, causing type 2 diabetes. Metabolic syndrome may be a start of the development of type 2 diabetes.
Insulin is vital to patients with type 1 diabetes - they cannot live without a source of exogenous insulin. Without insulin, patients with type 1 diabetes develop severely elevated blood sugar levels. This leads to increased urine glucose, which in turn leads to excessive loss of fluid and electrolytes in the urine. Lack of insulin also causes the inability to store fat and protein along with breakdown of existing fat and protein stores. This dysregulation, results in the process of ketosis and the release of ketones into the blood. Ketones turn the blood acidic, a condition called diabetic ketoacidosis (DKA). Symptoms of diabetic ketoacidosis include nausea, vomiting, and abdominal pain. Without prompt medical treatment, patients with diabetic ketoacidosis can rapidly go into shock, coma, and even death may result.