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Consequences of diabetes

If you have type 1 or type 2 diabetes you are at risk of developing serious health complications if your diabetes is not controlled. These include premature cardiovascular disease, kidney disease, foot problems and amputation, blindness and depression. Diabetes can also affect your relationships and lifestyle.

Some of these complications are discussed below.

Long-term complications

Cardiovascular disease

If you have diabetes, you are 2 to 3 times more likely to develop cardiovascular disease (which includes heart attack, heart failure, angina, stroke) compared to someone who is non-diabetic (1). Furthermore, as the duration of diabetes increases, so does the risk of fatal heart disease (2). This means that adolescents, who acquire diabetes at a young age, are at high lifetime risk of heart disease.


Poor control of blood glucose levels over extended periods of time is strongly associated with diabetic retinopathy. This is damage to the small blood vessels in the back of the eye (retina) and can ultimately lead to blindness (3).


Amputations of the lower extremities (toes, feet, legs) are a severe consequence of diabetes, and can occur as a result of continuous high blood glucose levels. If you have diabetes, you are 20 times more likely to have an amputation (4), and up to 100 people a week have a leg amputated in the UK (5).

Kidney disease

Being obese and having type 2 diabetes predisposes you to developing chronic kidney disease: Diabetes is one of the biggest causes of end stage renal disease, or kidney failure (6), often requiring dialysis or transplantation. High blood glucose levels can damage the small blood vessels in the kidney disrupting their ability to filter urine efficiently. This can lead to protein in the urine, and as kidney disease progresses the amount of protein found in the urine increases. High blood glucose levels can also lead to damage to the nerves which signal your bladder is full, leading to infrequent emptying of urine, and increase your chances of developing a urinary tract infection.


There is an association between type 2 diabetes and depression, although the causal factor between the two diseases is unknown. Nearly one in five people with diabetes have clinical depression (7). A recent systematic review found that depression was nearly twice as high in people with type 2 diabetes compared to those without the condition (19.1% compared to 10.7%), with higher rates among women than men (8).

Short-term complications

Diabetic ketoacidosis

When your body does not have enough insulin and is unable to obtain the energy it needs from glucose, it will use up fat stores, a process which produces ketones. Ketones are fat-derived chemicals which enter the circulation. They are acidic, and in high quantities, these ketones cause a life-threatening condition known as diabetic ketoacidosis (DKA). DKA may develop in newly-presenting (undiagnosed) patients with type 1 diabetes, or in those with well-established type 1 diabetes when they have some other illness, eg an infection. It is extremely rare in patients with true type 2 diabetes.

The symptoms of DKA include excessive thirst and urination, nausea and vomiting, rapid breathing and a fruity-smelling breath odour, and confusion. More specific tests include blood glucose levels and testing for ketones in the urine.


Hypoglycemia, or having a “hypo” as its often called, occurs when your blood glucose levels are too low (below 4mmol/l). This can occur when you have taken too much insulin, medications, or improper amounts of medication, or you have eaten too little carbohydrate, missed a meal, or over exercised. Drinking too much alcohol with or without food can also lead to hypoglycaemia as alcohol inhibits the liver from producing glucose from its glycogen stores.

Symptoms of a hypo can vary between individuals but often include rapid heart rate, blurred vision, headache, sweating, sense of hunger, numbness in the fingers and toes or around the mouth, confusion, anxiety and pallor. Importantly, some patients with longer duration diabetes may have reduced hypo awareness – they don’t get symptoms until blood glucose levels are very low and therefore they only have a short window of opportunity to correct the hypo before becoming unconscious or confused. Because the brain cannot use alternative fuels when glucose levels are low, the symptoms of severe hypoglycaemia reflect brain dysfunction, e.g confusion, disorientation, unconsciousness and seizures. Prompt treatment for a hypo includes drinking or eating something containing sugar, eg a glass of orange juice, or glucose tablet. Some patients will have an injection of glucagon at hand, in case they take too much insulin.


This occurs when your blood glucose levels are too high, over 7 mmol/L before a meal and above 8.5 mmol/L two hours after a meal. This can occur from missing a dose of medication, having overeaten carbohydrates, if you are unwell for some other reason, or from over-treating a hypo.

Symptoms of hyperglycemia include passing urine more often, thirst, headaches and fatigue. If you are hyperglycemic and have type 1 diabetes, your urine will also need to be checked for ketones to rule out the possibility of developing diabetic ketoacidosis.

Treatment involves increasing your dose of insulin or adding an extra dose of medication, and drinking lots of sugar-free liquids.

You can prevent the occurrence of hypos and hypers by monitoring your blood glucose levels regularly, particularly if there has been any change in the management of your diabetes.

— May Meleigy


  1. Sarwar N, Gao P, Seshasai SR, et al. Diabetes mellitus, fasting blood glucose concentration, and risk of vascular disease: a collaborative meta-analysis of 102 prospective studies. Lancet 2010;375(9733):2215-22. doi: 10.1016/S0140- 6736(10)60484-9.
  2. Caroline S. Fox, MD, MPH12, Lisa Sullivan, PHD13, Ralph B. D’Agostino, Sr, PHD13 and Peter W.F. Wilson, MD. The Significant Effect of Diabetes Duration on Coronary Heart Disease Mortality. The Framingham Heart Study. Diabetes Care, doi: 10.2337/diacare.27.3.704Diabetes Care March 2004 vol. 27 no. 3 704-708
  3. Yau JW, Rogers SL, Kawasaki R, et al. Global prevalence and major risk factors of diabetic retinopathy. Diabetes Care 2012;35 (3):556-64. doi: 10.2337/dc11-1909. Epub 2012 Feb 1.
  4. Vamos EP, Bottle A, Edmonds ME, et al. Changes in the incidence of lower extremity amputations in individuals with and without diabetes in England between 2004 and 2008. Diabetes Care 2010;33(12):2592-7.
  5. Diabetes UK and NHS Diabetes. Putting feet first. Commissioning specialist services for the management and prevention of diabetic foot disease in hospitals, 2009.
  6. Outhwaite H, Hollinshead J, Bartlett C, et al. Diabetes with Kidney Disease: Key Facts: Yorkshire and Humber Public Health Observatory, East Midlands Public Health Observatory, NHS Kidney Care, NHS Diabetes, 2011
  7. Ali S, Stone MA, Peters JL, et al. The prevalence of co-morbid depression in adults with Type 2 diabetes: a systematic review and meta-analysis. Diabet Med 2006;23 (11):1165-73.
  8. Roy T, Lloyd CE. Epidemiology of depression and diabetes: a systematic review. J Affect Disord 2012;142 Suppl:S8-21.