Below is a list of possible complications that can be caused by badly controlled diabetes:

• Eye complications – glaucoma, cataracts, diabetic retinopathy, and some others.
• Foot complications – neuropathy, ulcers, and sometimes gangrene which may require that the foot be amputated
• Skin complications – people with diabetes are more susceptible to skin infections and skin disorders
• Heart problems – such as ischemic heart disease, when the blood supply to the heart muscle is diminished
• Hypertension – common in people with diabetes, which can raise the risk of kidney disease, eye problems, heart attack and stroke
• Mental health – uncontrolled diabetes raises the risk of suffering from depression, anxiety and some other mental disorders
• Hearing loss – diabetes patients have a higher risk of developing hearing problems
• Gum disease – there is a much higher prevalence of gum disease among diabetes patients
• Gastroparesis – the muscles of the stomach stop working properly
• Ketoacidosis – a combination of ketosis and acidosis; accumulation of ketone bodies and acidity in the blood.
• Neuropathy – diabetic neuropathy is a type of nerve damage which can lead to several different problems.
• HHNS (Hyperosmolar Hyperglycemic Nonketotic Syndrome) – blood glucose levels shoot up too high, and there are no ketones present in the blood or urine. It is an emergency condition.
• Nephropathy – uncontrolled blood pressure can lead to kidney disease
• PAD (peripheral arterial disease) – symptoms may include pain in the leg, tingling and sometimes problems walking properly
• Stroke – if blood pressure, cholesterol levels, and blood glucose levels are not controlled, the risk of stroke increases significantly
• Erectile dysfunction – male impotence.
• Infections – people with badly controlled diabetes are much more susceptible to infections
• Healing of wounds – cuts and lesions take much longer to heal