Updated 27 January 2017

Diabetes: long-term complications

People who have had diabetes for many years may suffer certain complications as a result of the illness.



  • Diabetes affects the whole body.
  • People who have had diabetes for many years may suffer certain complications as a result of the illness.
  • This is particularly true if there is not strict attention to the control of blood glucose through diet and medication.
  • The eyes, the kidneys, the blood vessels, the nervous system and the feet can all be affected.
  • Any diabetic should have regular follow-up by their doctor to check for these complications.

Long-term complications

The risks of late complications of diabetes vary considerably among diabetics, but generally increase the longer the person has had diabetes. Hyperglycaemia (increased blood glucose) causes the initial metabolic alterations that damage the body, but there is evidence that later on in the disease, once the damage reaches a certain stage, there are other factors which determine the subsequent outcome.

Atherosclerosis of the coronary arteries, which can result in angina and heart attacks, and atherosclerosis of the peripheral arteries, which can result in intermittent claudication and gangrene, are more common in people with diabetes. (Intermittent claudication is pain on walking – generally in the calves – caused by reduced blood supply to the muscles).

Diabetic retinopathy

Damage to the retina, which can be seen when the eye is examined using an ophthalmoscope, results from diabetes in about 85% of patients. It is present at diagnosis in up to 20% of Type 2 diabetics. This is called background retinopathy.

Although background retinopathy is a leading cause of blindness in the USA, most diabetics never become blind.

Any diabetic who has background retinopathy needs to have regularly scheduled examinations by an ophthalmologist, since there is specific treatment for particular types of damage. Laser treatment is used to prevent the spread of any further retinopathy and to control swelling (oedema) of the macular area of the eye – the area of the retina which is vital to sight.

Diabetic nephropathy

Diabetic nephropathy involves damage to the kidney. It usually shows no symptoms until end-stage kidney disease develops. It is present in 30 to 50% of people with Type 1 diabetes, and in a smaller percentage of those with Type 2 diabetes. The first sign of the disease is protein in the urine.

Recent research into Type 2 diabetes has shown that if diabetic nephropathy is caught early, then treatment with ACE inhibitors (drugs for high blood pressure) can significantly decrease the progression of the disease. This is true even if the person does not have high blood pressure. It is also important to control any abnormal lipid levels.

This suggests that it is important that all diabetics have their urine checked regularly and that treatment should be considered at the first sign of protein in the urine.

Diabetic neuropathy

Diabetic neuropathy involves damage to the nerves. The most common form is a polyneuropathy which causes diminished sensation in the hands, and the feet and legs, where it is usually most marked.

Diabetic neuropathy is often symptomless, but may be associated with numbness, tingling, and pins and needles in the hands and feet. It is also less commonly associated with debilitating, severe, deep-seated pain and increased sensitivity to touch. Ankle jerks, which are elicited by the doctor with a small hammer during an examination of the nervous system, are decreased or absent.

Symptoms and signs of polyneuropathy can be present at diagnosis in patients with Type 2 diabetes, but it is not usually found in people with recently diagnosed Type 1 diabetes.

Older diabetics can suffer from acute and painful so-called mononeuropathies affecting the nerves of the head and neck (the cranial nerves). These symptoms may resolve spontaneously over a period of weeks to months.

Autonomic neuropathy occurs mainly in those diabetics who have polyneuropathy. This affects the part of the nervous system responsible for the control of bodily functions that are not consciously controlled. This includes regular beating of the heart, intestinal movements, sweating and salivation.

Diabetic neuropathy can cause postural hypotension, in which blood pressure falls when a person stands up suddenly. It can also cause disordered sweating, erectile dysfunction and retrograde ejaculation in men, impaired bladder function, delayed emptying of the gut, problems with swallowing, constipation and diarrhoea. Diarrhoea at night is very characteristic.

Foot ulcers

These are an important cause of problems in diabetics. The main predisposing cause is diabetic polyneuropathy. Because the person cannot feel their feet properly, they damage themselves if they wear poorly fitting shoes or hit their feet against obstacles.

Some diabetics also have problems with the part of the nervous system which allows you to know unconsciously the position and posture of the various parts of the body. This is called proprioception. Lack of normal proprioception can lead to abnormal weight-bearing and problems with the joints.

Infections commonly result from an ingrown toenail, plantar corn or callus. A fungal infection can also lead to wet lesions between the toes, cracks, fissures and eventually ulcers which then become secondarily infected with bacteria.

Patients with infected foot ulcers often feel no pain because of their neuropathy, and so the problem is detected late. The infection may extend into the deeper part of the soft tissue of the foot and even into the bones.

Deep ulcers, particularly if they show signs of surrounding infection and cellulitis (infection of soft tissue), require treatment in hospital. Diabetics are also more likely to develop complicated urinary tract infections and lung infections.

Reviewed by Dr Helmuth Reuter MRCP (UK), FCP (SA), MMed (Int), Senior specialist and lecturer, Department of Internal Medicine, University of Stellenbosch and Tygerberg Academic Hospital


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Dr. May currently works as a fulltime endocrinologist and has been in private practice since 2004. He has a variety of interests, predominantly obesity and diabetes, but also sees patients with osteoporosis, thyroid disorders, men's health disorders, pituitary and adrenal disorders, polycystic ovaries, and disorders of growth. He is a leading member of several obesity and diabetes societies and runs a trial centre for new drugs.

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