Diabetes complications

Managing your blood-glucose levels is the key to effective treatment. If your glucose levels are carefully controlled, in both types 1 and 2 diabetes, serious complications may never develop.

But in order to achieve this, you’ll have to consistently maintain a healthy lifestyle and use your medication (if prescribed) religiously. If you don’t, you may face some of the common short- or long-term complications of diabetes.

Short-term complications include hypoglycaemia, diabetic ketoacidosis (DKA) and hyperosmolar hyperglycaemic state (HHS).

Long-term complications include eye damage (retinopathy), heart disease, kidney damage (nephropathy), nerve damage (neuropathy), and limb amputations.

1. Short-term complications:

1.1. Hypoglycamia

A “hypo” can occur when your blood-glucose level drops to below 4mmol/l. This can happen when the balance of the diabetes medication you take (especially your insulin), the food you eat, and the physical activity you do isn’t optimal. Note, however, that not everyone with diabetes get hypos.

A hypo can happen very quickly, which is why it’s important to know what the symptoms are (note that your symptoms may be slightly different to the below):

  • Trembling or feeling shaky
  • Sweating
  • Being anxious or irritable
  • Going pale
  • Palpitations and a fast pulse rate
  • Lips feeling tingly
  • Blurred vision
  • Being hungry
  • Feeling tearful
  • Feeling tired
  • Headache
  • Lack of concentration

Testing your blood-glucose levels regularly can help you to spot a hypo before symptoms appear.

Why do hypos happen?

Understanding why you get hypos can help you to prevent them. Possible factors include:

  • Missing or delaying a meal or snack.
  • Not having had enough carbohydrate during your last meal.
  • Doing a lot of exercise without having extra carbohydrate or without reducing your insulin dose (if you take insulin).
  • Taking more insulin or diabetes medication than you need.
  • Drinking alcohol on an empty stomach.

If you’re prone to hypos and/or on insulin, always make sure you have something sweet on you. You should be able to correct the hypo fairly quickly by eating or drinking 15-20g of glucose. This is equivalent to:

  • 15-20g of glucose powder or glucose tablets
  • 3-4 teaspoons of sugar/sucrose (glucose + fructose) dissolved in some water
  • ¾ cup or ½ can (17ml) of fruit juice or soft drink
  • 6-8 Lifesavers
  • 2-3 Super-C sweets
  • 1-1½ tablespoons (15-20ml) honey

If necessary, this step should be repeated within 10-15 minutes. Thereafter, you should consume slowly digestible carbohydrates (e.g. bread) and protein (e.g. milk) to restore your blood-glucose levels.

If you’re suffering from severe hypoglycaemia, you should receive medical treatment immediately.

If you experience repeated severe hypoglycaemia, are at high risk for hypoglycaemia, or are “hypoglycaemia unaware”, you should talk to your doctor about taking a glucagon kit home with you. Some of your family members will have to learn how to reconstitute the powder and solvent, and how to safely administer the glucagon by injection.

1.2 Hyperglycaemia

A “hyper” occurs when your blood-glucose levels are too high – usually above 13.9mmol/l two hours after a meal. There are several reasons why this may happen. It may be that you:

  • Have missed a dose of your medication.
  • Have eaten more carbohydrate than your body and/or medication can cope with
  • Are stressed
  • Have an infection
  • Have over-treated a “hypo”

Signs and symptoms of a hyper include: 

  • Passing more urine than normal, especially at night
  • Being very thirst
  • Headache
  • Tiredness and lethargy

Hyperglycaemic emergencies

The hyperglycaemic emergencies are diabetic ketoacidosis (DKA) and hyperglycaemic hyperosmolar state (HHS).

Diabetic ketoacidosis

This occurs when the body starts to break down fat at a very fast rate because insulin levels are too low to allow glucose into the cells. The liver processes the fat into a type of fuel called ketones, which cause the blood to become acidic.

Diabetic ketoacidosis carries a higher mortality rate in South Africa than in developed countries and can present at any age, although more common in young children.

It most commonly occurs in people with type 1 diabetes, but anyone who depends on insulin could develop diabetic ketoacidosis. In exceptionally rare cases, people controlling their diabetes with diet and tablets have been known to develop diabetic ketoacidosis when severely ill.

The most likely times for diabetic ketoacidosis to occur are:

  • At diagnosis (some people don’t realise they have type 1 diabetes until they’re in a severe state of diabetic ketoacidosis).
  • During times of illness.
  • During a growth spurt or puberty.
  • If you haven’t taken your insulin for whatever reason.

Diabetic ketoacidosis usually develops over a period of 24 hours but can develop faster – especially in young children. Hospital admission and treatment are essential to correct the life-threatening condition. Treatment involves closely monitoring intravenous fluids, as well as insulin and glucose levels.

Hyperglycaemic hyperosmolar state

This involves the slow development of marked hyperglycaemia (usually >50mmol/l), hyperosmolarity and severe dehydration.

It’s a life-threatening emergency that, although less common than diabetic ketoacidosis, has a much higher death rate. It most often occurs in people with type 2 diabetes who have an illness that results in reduced fluid intake.

2. Long-term complications

The long-term complications of diabetes can be sub-divided into microvascular complications (injury to the small blood vessels) and macrovascular complications (injury to the large blood vessels).

Microvascular complications include:

  • Eye damage (retinopathy), which may lead to blindness.
  • Kidney damage (nephropathy), which may lead to renal failure.
  • Nerve damage (neuropathy), which may lead to impotence and diabetic foot disorders (including severe infections leading to amputation).

Macrovascular complications include:

  • Cardiovascular disease (CVD), which may lead to heart attack or stroke.
  • Insufficiency in blood flow to the legs (peripheral arterial disease).

2.1. Microvascular complications

Diabetic retinopathy

This refers to damage to the retina – the “seeing” part at the back of the eye. A delicate network of blood vessels supplies the retina with blood.

Over time, uncontrolled blood-glucose levels can cause damage to these vessels.

This can cause vision loss in two ways:

  • Fluid can leak from the blood vessels into the centre of the macula (the small, highly sensitive central area of the retina that provides our central vision), causing it to swell. This is known as macular oedema and can occur at any stage of diabetic retinopathy.
  • Weak, abnormal blood vessels can develop on the surface of the retina and leak fluid onto the vitreous – the gel-like fluid that fills the back of the eye. This is known as proliferative retinopathy and is the most advanced stage of the disease.

If left untreated, people with diabetic retinopathy run the risk of severe vision loss or even blindness in one or both eyes.


This refers to a variety of eye conditions that involve damage to the optic nerve, visual field loss and, quite often, the presence of raised pressure within the eyeball. Diabetes doubles your risk for glaucoma, which can lead to blindness if not treated early.

Diabetic nephropathy

This term is used when the kidneys can no longer function properly as a result of diabetes. Nephropathy can cause kidney failure and, ultimately, death.

Kidney disease tends to develop very slowly in people with diabetes and is most common in those who have had the condition for more than 20 years. About one in three people with diabetes may go on to develop kidney disease. However, as treatments improve, fewer people are affected.

Diabetic neuropathy

This is a type of nerve damage that can occur as a result of diabetes. Nerves carry messages between the brain and every part of the body, making it possible for us to see, hear, smell, taste, feel and move. When the nerves are damaged, it can cause problems in various parts of the body.

Diabetes causes nerve damage through different mechanisms, including direct damage by high blood-glucose levels as well as decreased blood flow to the nerves as a result of damage to the small blood vessels. This nerve damage can, for example, lead to sensory loss, damage to the limbs and impotence in diabetic men. It’s the most common complication of diabetes.

There are three types of neuropathy:

  • Sensory neuropathy affects the nerves that carry messages of touch, temperature, pain and other sensations from the skin, bones and muscles to and from the brain. It mainly affects the nerves in the feet and the legs, but people can also develop this type of neuropathy in their arms and hands.
  • Autonomic neuropathy affects nerves that carry information to and from the organs and glands. They help to control some functions without us consciously directing them, such as stomach emptying, bowel control and sexual function.
    Damage to these nerves can result in:
    - Gastroparesis, i.e. when food can’t move through the digestive system efficiently. Symptoms may include bloating, constipation or diarrhoea.
    - Loss of bladder control, leading to incontinence.
    - An irregular heartbeat.
    - Problems with sweating – either a reduced ability to sweat and intolerance to heat or sweating related to eating food (gustatory sweating).
    - Impotence (an inability to maintain an erection).
  • Motor neuropathy affects the nerves that control movement. Damage to these nerves leads to weakness and wasting of the muscles that receive messages from them. This can lead to problems such as:
    - Muscle weakness, which could cause falls or problems with tasks such as fastening buttons.
    - Muscle wasting, where muscle tissue is lost due to lack of activity.
    - Muscle twitching and cramps.

2.2. Macrovascular complications

High blood-glucose levels damage the blood vessels through a process called “atherosclerosis” (clogging of the arteries). This narrowing of the arteries may lead to decreased blood flow to the heart muscle, the brain and/or the extremities.

Diabetes increases an individual’s risk for:

Cardiovascular disease (CVD)

This is a group of disorders of the heart and blood vessels and is the leading cause of death in people with type 2 diabetes (approximately 70%).

People with diabetes have a four-fold increased risk for having a CVD event (e.g. heart attack) than people who don’t have diabetes, even after controlling for traditional risk factors (e.g. age, obesity, tobacco use, dyslipidaemia and hypertension).

Cerebrovascular disease

Cerebrovascular disease, a group of diseases that involve the blood flow to the brain, includes stroke, aneurysms, vascular malformations, and more.

Diabetes is an independent risk factor across all ages for stroke – a major cause of death in South Africa and across the world. Ten people suffer from a stroke in South Africa every hour.

Peripheral artery disease (PAD)

Peripheral artery disease is characterised by blockage of the lower-extremity arteries. This can cause intermittent pain and/or cramping, especially during exercise and activity, which can result in functional impairment and disability.

Common complications of more severe PAD are foot ulcers and foot/leg amputation. People with diabetes are 15 times more likely to suffer from a lower-extremity amputation than people without diabetes.

To conclude

Diabetes is associated with both microvascular and macrovascular diseases that affect numerous organs, including the muscles, skin, heart, brain and kidneys.

Common risk factors for vascular disease in diabetes include hyperglycaemia (high blood glucose), insulin resistance, dyslipidaemia (a blood lipid profile that increases the risk for atherosclerosis), hypertension (high blood pressure), tobacco use, and obesity.

Living well with diabetes involves:

  • Understanding your condition.
  • Carefully monitoring your blood-glucose levels.
  • Getting the right health care.
  • Understanding the role of your medication and how to use it.
  • Learning more about how what you eat affects your condition.
  • Getting active and exercising safely. 
  • Getting enough sleep.
  • Smoking cessation.
  • Looking after your emotional state and accepting diabetes as part of your life.
  • Taking good care of your feet.

Very important: All the complications of diabetes can be prevented or delayed with good diabetes control.

Information supplied by Jeannie Berg, diabetes educator and Chairperson of the Diabetes Education Society of South Africa (DESSA), and reviewed by Dr Joel Dave (MBChB PhD FCP Cert Endocrinology), Senior Specialist in the Division of Diabetic Medicine and Endocrinology, University of Cape Town. August 2018.

Read more:

Who gets diabetes?


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