Short term (acute) complications

Uncontrolled diabetes can cause metabolic imbalance leading to acute complications that may require immediate medical attention. Hyperglycemia (high levels of glucose in blood) sets the stage for protein glycation, which in turn may lead to chronic conditions requiring constant monitoring and treatment. Individuals with diabetes may also develop high cholesterol and high blood pressure, which require medical management.

Acute complications 

Acute complications will require immediate medical intervention.

Hypoglycaemia

Hypoglycaemia occurs when blood glucose levels is below 4mmol/l. A hypoglycaemia episode can happen quickly therefore it is important to understand the signs and symptoms and treat hypoglycaemia correctly. People will experience different symptoms, but the most common symptoms are sweating, feeling shaky, being anxious or irritable, feeling disorientated, blurred vision, headache, palpitation and fast pulse rate.

Diabetes Ketoacidosis (DKA)

DKA is a serious and life-threatening complication of type 1 diabetes caused by absolute or relative insulin deficiency leading to severe hyperglycaemia with ketosis (fat metabolism). Rare cases occur (1:1000) in acutely unwell people with type 2 diabetes taking SGLT2 inhibitors. Patients in DKA require high intensity nursing usually within HDU / ICU. 

Insulin is a peptide hormone secreted by the pancreas which enables cellular uptake of glucose, thus maintaining blood glucose levels and proper cellular function. 

Absolute lack of insulin means, despite high levels of glucose in the blood, it cannot be utilised by the cells of the body to fuel cellular processes. As DKA progresses, levels of glucose in the blood increase, but this glucose cannot be utilised by the cells which need it. 

Cells may also  be deprived of glucose if the amount of food intake is low (such as during illness). 

When cells cannot obtain energy from glucose, cells start using fats as a source of energy. Liver cells produce ketone bodies from fatty acids. When blood glucose levels are low, brain cells can use ketone bodies, but not free fatty acids, for energy. High concentrations of ketones can make the urine acidic and cause fruity-smelling / acetone breath. If not managed, this condition can progress to coma (prolonged unconsciousness) and even death. 

Causes of DKA include: 

• complete or relative lack of insulin
• conditions increasing levels of stress hormones e.g. 
  - acute illness 
  - MI 
  - infections 
  - surgical emergencies
  - high dose steroids  
  - pancreatitis.

• errors of Insulin administration or deliberate omission (30%)
• new onset of type 1 diabetes (23 %).

Symptoms of Diabetes Ketoacidosis (DKA) are shown below.

Symptoms of Diabetes Ketoacidosis (DKA) include:

• high blood sugar levels
• complaints of stomach pains or nausea
• fruity smelling breath
• vomiting
• drowsiness leading in time to unconsciousness
• deep heavy breathing
• excessive thirst
• los of weight
• urinating much more often and in larger amounts
• dehydration: dry mouth and tongue, sore throat, dark circles under the eyes.

Signs of severe DKA include:

• Venous bicarbonate <5mmol/L
• pH <7.0
• Ketones > 6mmol/L
• Hyperventilation
• Hypotension (systolic BP <90)
• Depressed conscious level (document GCS) 
• BLOOD GLUCOSE IS NOT A GOOD GUIDE TO SEVERITY.

Measurement of ketones

Measurement of ketones can provide an effective estimation as to the severity of DKA.

All of these must be present to make the diagnosis: 

• The ‘D’ – a blood glucose concentration of >11.0 mmol/L or known to have diabetes mellitus 
• The ‘K’ – The ‘K’ – a capillary or blood ketone concentration of >3.0 mmol/L or significant ketonuria (2+ or more on standard urine sticks) 
• The ‘A’ – a bicarbonate concentration of <7.3

Management of DKA is complex - updated guidelines have been published by the Joint British Diabetes Societies, and endorsed by the RCN. The guidance contains a single page treatment pathway for DKA.

Hyperosmolar hyperglycaemic state

Hyperosmolar Hyperglycaemic State (HHS) occurs in people with Type 2 diabetes who experience very high blood glucose levels (often over 40mmol/l). It can develop over a course of weeks through a combination of illness (e.g.i nfection) and dehydration (Diabetes UK). High blood glucose level triggers increased urination. If liquids are not replaced, the individual can become severely dehydrated. High blood glucose levels can lead to altered mental states, confusion, seizures, coma, and even death.

Further resources

• Joint British Diabetes Societies (JBDS) (2012) Management of the hyperosmolar hyperglycaemic state (HHS) (PDF) in adults with diabetes.

The long term complications of both type 1 and type 2 diabetes are caused by chronic hyperglycaemia. Chronic hyperglycaemia causes both direct and indirect effects to the vascular system. The damaging effects can lead to microvascular complications and macro vascular complications.

Recent Diabetes UK data shows that diabetes contributes to more than 930 strokes, 660 heart attacks, and almost 3,000 cases of heart failure every week in the UK. These updated figures reflect the growing cardiovascular burden associated with diabetes and reinforce the importance of early detection, effective management, and proactive risk factor control (Diabetes UK, 2024).

Microvascular complications

Diabetes nephropathy

At least 10,350 people in the UK have end stage kidney failure disease because of diabetes. Diabetes nephropathy or kidney damage develops slowly over many years. High levels of blood glucose can cause the small blood vessels of the kidneys to become leaky and blocked. When this happens the kidneys will work less efficiently. In severe cases this can lead to kidney failure and the need for a kidney transplant. More than one in three people who need kidney dialysis or a transplant have diabetes. One in five people with diabetes will need treatment for kidney diseases during their lifetime.

Diabetes retinopathy

Retinopathy is damage to the retina and is a complication that can affect anyone who has diabetes. Retinopathy is caused by damage to the blood vessels of the light-sensitive tissue at the back of the eye (retina). It is the most common cause of blindness among people of working age in the UK. When a patient is first diagnosed with diabetes they should be offered an appointment for eye screening for retinopathy with a special digital camera. They should then be sent for regular yearly eye tests. As with all complications of diabetes, the sooner any retinopathy problems are detected and treated the greater the chance of the treatment being successful. Treatment consists of laser surgery which will preserve the sight of the patient but will not make it better. The better the blood glucose levels are controlled, the less chance the patient has of developing serious eye problems.

Diabetes neuropathy

Over time, high blood glucose levels, high fat levels such as triglicerides in blood can cause damage to nerves. Hyperglycaemia damages nerves in the peripheral nervous system. Damage to the nerves of the feet can mean that small cuts and breaks in the skin, or damage caused by ill-fitting shoes are not noticed. This can lead to one in ten patients with diabetes developing a foot ulcer, which can ultimately cause a serious infection. Patients should be advised to check their feet every day looking for sores and cuts that aren’t healing along with puffiness, swelling and skin that feels hot to the touch. The patient should be advised to report any changes to a health care professional or podiatrist. They should have a foot examination at least once a year (In patients with diabetes should have their feet inspected on a daily basis and others such as those on renal replacement therapy should have their feet inspected whenever they attend the dialysis unit). High levels of blood glucose can damage the tiny vessels of the nerves. This can cause tingling or burning pain spreading from the fingers and toes and up through the limbs or loss of sensation. If this affects the nerves in the digestive system it could lead to nausea, vomiting, diarrhoea or constipation.

Macrovascular complications

Macrovascular complications affect larger blood vessels, such as those supplying the heart, brain, and extremities. The causes of these complications stem from narrowing of blood vessels due to glycation, inflammation, lipid deposition and other factors. Complications resulting from large vessel damage may lead to cardiomyopathy, stroke, rheumatoid arthritis, osteoporosis, and the degenerative process of aging (Singh et al., 2014). The major concern amongst these complications is myocardial infarction (heart attack). At present, it appears that blood glucose control does not significantly reduce the risks or delay the onset of macrovascular complications. Additional medical management is required.

Coronary artery disease (leading to myocardial infarction /heart attack)

Long term, poorly controlled blood glucose levels increase the likelihood of a person developing atherosclerosis (hardening and narrowing of the blood vessels). This could lead to poor blood supply to the heart, causing angina. The chance that a blood vessel in your heat or brain will become completely blocked, causing a heart attack or stroke is also increased. In addition to atherosclerosis, there is strong evidence of increased platelet adhesion and hypercoagulability in type 2 diabetes that promote platelet aggregation.

Cerebral vascular accident (CVA)

Diabetes is a strong independent predictor of risk of CVA as in coronary artery disease. People with type 2 diabetes have a much higher risk of stroke (Lehto et al, 1996).

Peripheral arterial disease (PAD)

Peripheral arterial disease occurs when fat deposits build up on the walls of the blood vessels of the lower extremities. PAD is a major risk factor for lowr-limb amputation. The most common symptom of PAD is intermittent claudication, cramping or aching in the calves, thighs or buttocks. Diabetes and smoking are the strongest risk factors for PAD. People with diabetes who have PAD are more prone to neuro ischemic ulceration (ADA, 2003).

Other complications

Miscarriage and stillbirth

Pregnant women with diabetes have an increased risk of miscarriage and stillbirth. There is an increased risk of the baby developing a serious birth defect if blood glucose levels are not carefully controlled in the early stages of pregnancy. Antenatal check-ups for pregnant women with diabetes usually take place in hospital or in a diabetic clinic. Here health care professionals can keep a close eye on blood glucose levels. Women planning a pregnancy would need to take a stronger dose of folic acid than is available over the counter. This should ideally be taken three months prior to conception.

Also all women of child bearing age with diabetes need pre-pregnancy counselling on an annual bases – the pregnancy should be planned if possible as diabetes medications may need to be changed pre-pregnancy to optimise diabetes control before conception. Where control is poor, the patient should be advised against becoming pregnant because the risks to the mother and baby are greater. Some blood pressure treatments are contraindicated in pregnancy and would need to be changed or stopped pre-conception.

Gestational diabetes is a type of diabetes, which affects women usually in the second or third trimester. Diabetes is not present before pregnancy and usually goes away after delivery. It is caused by pregnancy hormones affecting insulin use in the body. Women with GD are at an increased risk of type 2 diabetes in later life and should be monitored in order to prevent progression to type 2 diabetes.

Sexual dysfunction

Damage to the nerves and blood vessels can lead to erectile dysfunction in men with diabetes, particularly those who smoke. This can be treated with medication. Sometimes women with diabetes can experience a reduced sex drive, reduced pleasure from sex, lack of vaginal lubrication, reduced ability to orgasm or painful sex. A vaginal lubricant or water-based gel may prove helpful for women experiencing a lack of vaginal lubrication or painful sex. Sexual dysfunction is an often overlook element of the care of people with diabetes and practitioners should address this with their patients during consultations. 

Further resources

• Protein Data Bank PDB - 101. Diabetes Mellitus - Complications

References

• American Diabetes Association (2003) Peripheral Arterial Disease in People With Diabetes Diabetes Care, 2003 Dec; 26(12): 3333-3341
• Diabetes UK. Complications of diabetes