Hypoglycaemia affects the quality of life of patients with diabetes and can be fatal
In this article…
- Definition of hypoglycaemia
- What causes the condition
- How to identify and treat it
- Educating patients about prevention
5 key points
- Hypoglycaemia is common and can occur in people with either type 1 or type 2 diabetes who use insulin or oral medications that stimulate insulin production
- Maintaining well-controlled blood glucose levels can reduce the risk of diabetes complications
- Hypo-glycaemia is mild if people can treat it themselves, and severe if they require the help of a third party
- Some patients have “hypoglycaemia unawareness” – they have no symptoms and may lose consciousness without warning
- Anyone using a treatment that can cause hypoglycaemia should be warned about this risk and when it can occur
Jill Hill is a diabetes nurse consultant, Birmingham Community Healthcare Trust.
Hill J (2011) How to manage hypoglycaemia. Nursing Times; 107, 40, early online publication.
Hypoglycaemia is a common side-effect of insulin therapy and of some oral hypoglycaemic tablets that stimulate insulin production. It affects quality of life, can prevent people with diabetes from achieving the blood glucose control required to reduce their risk of diabetes complications, and can also be fatal. This article defines hypoglycaemia, what causes it, how can it be identified and treated, and how nurses can support people at risk of this disabling and frightening condition.
Keywords: Hypoglycaemia/Diabetes/Insulin therapy
- This article has been double-blind peer reviewed
- Figures and tables can be seen in the attached print-friendly PDF file of the complete article
Hypoglycaemia (low blood glucose levels) or “hypo” is a common side-effect of insulin therapy and some oral hypoglycaemic agents. It is more common in people with type 1 diabetes, who have, on average, two episodes of mild hypoglycaemia per week; 10% have a severe episode of hypoglycaemia annually (Cryer et al, 2003) compared with fewer than 5% of people with type 2 diabetes using insulin and fewer than 1% of those using sulphonylureas.
Evidence from the Diabetes Control and Complications Trial of people with type 1 diabetes (Diabetes Control and Complications Trial Research Group, 1993) and the UK Prospective Diabetes Study in people with type 2 diabetes (United Kingdom Prospective Diabetes Study Group, 1998) demonstrated an association between maintaining well-controlled blood glucose levels and a lower risk of diabetes complications. Tight blood glucose control, based on this evidence, is the therapeutic goal for most people with diabetes, but it increases the risk of hypoglycaemia for those using certain treatments.
For many, the cost of hypoglycaemia may be too high a price to pay for reducing the risk of possible long-term microvascular complications such as retinopathy, nephropathy and neuropathy. Hypoglycaemia or the fear of it may be a barrier to achieving ideal blood glucose levels (Alvarez Guisasola et al, 2008).
What is hypoglycaemia?
There is no consensus regarding a definition of hypoglycaemia but, for everyday clinical practice, “4 is the floor” and a glucose level of less than 4mmol/L in someone taking insulin or beta-cell stimulators (sulphonylureas and prandial regulators) is too low. Some people may have symptoms of hypoglycaemia at blood glucose levels higher than 4 mmol/L; this usually occurs in people whose blood glucose control is poor, with levels typically running in double figures. A fall to normoglycaemia can result in symptoms of low blood glucose, but this is not hypoglycaemia.
Why does it occur?
In a person without diabetes, prevailing blood glucose levels are constantly monitored by the insulin-producing beta cells in the pancreas and an appropriate amount of insulin is produced. So, after a carbohydrate meal containing sugars and/or starches, there is a rise in blood glucose as these foods are digested and broken down to glucose in the gut and absorbed into the circulation (Fig 1).
The rise in blood glucose triggers a response by the beta cells to produce a “burst” of insulin to transport the glucose into cells to be metabolised into energy or into the liver and muscles to be converted into glycogen. During fasting, when blood glucose levels are at the lower end of the normal range, the beta cells are subject to less stimulation, so produce a small constant trickle of insulin, which primarily acts to control the amount of glucose being released by the liver. Low levels of insulin promote the production of glucagon, another hormone produced by the pancreas from the alpha cells, which causes the liver to release glucose.
In individuals without diabetes there is a balance between the production of glucagon, which causes a rise in blood glucose, and insulin, which lowers blood glucose. This maintains the blood glucose within the normal range and avoids hypoglycaemia.
In someone with diabetes using insulin or treatments that stimulate the beta cells to produce insulin, this balance is over-ridden and the blood glucose level can fall below normal, inducing signs and symptoms of hypoglycaemia.
Signs and symptoms
These can be categorised into autonomic –the early “stress response” – and neuroglycopenic, where brain function and behaviour is affected by diminishing blood glucose levels. Ideally, people at risk of hypoglycaemia should be able to recognise the early symptoms and treat themselves promptly and appropriately before brain function is affected. The onset of signs and symptoms is usually rapid, and people can quickly lose consciousness if not treated.
Signs and symptoms vary in individuals. Some have “hypoglycaemia unawareness” – they have no symptoms and may lose consciousness without warning. This can occur due to autonomic neuropathy (damage to the microvascular circulation to the autonomic nerves from long-standing diabetes) or may be a temporary situation brought on by frequent hypoglycaemia or tight blood glucose control. Drivers with hypoglycaemia unawareness should inform the Driver and Vehicle Licensing Agency and not drive until the condition has resolved and they have sufficient warning of impending hypoglycaemia to enable them to treat it quickly. The signs and symptoms of hypoglycaemia are summarised in Box 1.
Box 1. signs and symptoms of hypoglycaemia
At the early stage (the autonomic stage) blood glucose is usually between <4mmol/L and 2.8mmol/L. Symptoms include:
- Feeling hungry
- Looking pale
- Feeling anxious
Later signs and symptoms, at the neuroglycopenic stage, where blood glucose is below 2.8mmol/L include:
- Blurred vision
- Difficulty concentrating
- Slurring of speech
- Change in behaviour (such as being aggressive, acting as if drunk)
Source: Krentz and Bailey (2001)
Management of hypoglycaemia
Hypoglycaemia is mild when people are able to self-treat and severe when they require the help of a third party ( DCCTRG, 1993). The aim of treatment is to bring the blood glucose level rapidly back up to target before neuroglycopenic effects occur, but without overcompensating and causing high blood glucose levels afterwards.
Approximately 15-20g of rapid-acting carbohydrate should be taken orally. Examples are listed in Box 2.
Box 2. carbohydrate treatments
Examples of 15-20g rapid-acting carbohydrate treatments for hypoglycaemia include:
- 150ml non-diet Coca-Cola (small tin)
- 100ml of Lucozade Original
- 5-6 dextrose tablets
- Four GlucoTabs
- 200ml smooth orange juice (small carton)
The blood glucose should be checked after about five minutes and the rapid-acting treatment should be repeated every 5-10 minutes until the blood glucose has risen to 4mmol/L or greater (or, if no blood glucose monitoring is available, until symptoms have resolved). The person should then eat some starchy carbohydrate if they are not due to eat a meal within the next hour.
If someone is not able to self-treat competently, these treatments can be given by another person. However, if a person is unconscious or unable to swallow safely, glucose should not be given orally (this includes rubbing glucose gel or honey on the inside of the cheek). The priority is not to increase the blood glucose levels but to maintain a patent airway. Patients should be put in the recovery position and medical or paramedic assistance sought.
A GlucaGen HypoKit can be prescribed for people using insulin who have frequent episodes of severe hypoglycaemia or are at risk of them (Royal Pharmaceutical Society and British Medical Association, 2011). These kits contain a syringe drawn up with 1ml of sterile water and a vial containing 1mg of dried glucagon. The water is inserted into the vial so the glucagon is rapidly reconstituted and can be injected intramuscularly or subcutaneously by a trained member of the family or carer.
Glucagon has an opposite effect to insulin – it raises blood glucose by mobilising glycogen stored in the liver. It takes about 10 minutes to be effective and patients may be nauseated and vomit as they recover. A rapid-acting carbohydrate followed by some starchy longer-acting carbohydrate needs to be consumed as the liver will need to replenish its glycogen stores, potentially causing another episode of hypoglycaemia within a short period of time.
Glucagon may not be effective, especially in patients with liver disease or if the hypoglycaemia is associated with excessive alcohol consumption. If patients have not recovered after 10 minutes, 50ml of IV glucose 20% infusion will be required, given into a large vein through a large-gauge needle. Once a person has regained consciousness and is able to eat or drink some carbohydrate, it is not usually necessary for them to be admitted to hospital unless the hypoglycaemia is caused by a sulphonylurea.
A severe hypoglycaemia episode is likely to affect people’s confidence in their diabetes treatment significantly. The National Institute for Health and Clinical Excellence’s quality standards for diabetes recommends all people with the condition should be referred to a diabetes specialist team following an episode of severe hypoglycaemia to have counselling, a medication review and education (NICE, 2011).
After treating a hypoglycaemic episode, ask the question: why did it happen? The cause is the amount of insulin injected or the effect of oral hypoglycaemic agents that are greater than those needed for the prevailing blood glucose. Possible causes of hypoglycaemia are listed in Box 3.
Box 3. Causes of hypoglycaemia
The insulin action did not match the expected rise in blood glucose after a meal
- This can occur if a meal is delayed after an insulin injection or sulphonylurea has been given and has started to be effective
- The carbohydrate portion of the meal is smaller than required by the dose of insulin given
- The insulin works too rapidly because it was injected into a muscle instead of subcutaneous fat
- Too high a dose of insulin or oral hypoglycaemic agents was given
- The wrong insulin was given. If rapid-acting insulin is given instead of long-acting insulin, as the large dose at bedtime without food, sudden hypoglycaemia will occur within an hour or so at the beginning of the night
- Unusual or unplanned physical activity. Exercise increases the body’s sensitivity to insulin, lowering blood glucose more than usual unless the dose is reduced or additional carbohydrate is consumed to compensate for this
- Excessive alcohol, especially when combined with increased physical activity. People’s sensitivity to the effects of alcohol will vary, depending on whether they consume alcohol regularly
Frequent low blood glucose levels
- Hypoglycaemia symptoms may be dulled or lost if blood glucose levels are frequently below target. This increases the risk of severe hypoglycaemia as the person with diabetes gets few or no warning symptoms of their blood glucose dropping and is unable to treat it in time to avoid coma
Reduced renal function
- Insulin and oral hypoglycaemic agents need to be taken regularly as they are eliminated from the body by the kidneys. Where renal function is deteriorating, medications can accumulate, leading to a gradual increase in the frequency of hypoglycaemic episodes
- Losing weight, intentionally or through loss of appetite or illness, means less insulin is required to maintain normal blood glucose. If the dose of sulphonylureas or insulin is not adjusted, the patient is at risk of hypoglycaemia
Unfortunately, hypoglycaemia can occur through mistakes made by health professionals giving the incorrect dose. The National Patient Safety Agency (2010) issued an alert and e-learning package about the safe use of insulin to highlight common mistakes made through incorrect prescribing of insulin dose. For example, the use of “u” instead of “units” resulted in one case where a person was injected with 40 units when the dose was written as 4u. The e-learning about safe use of insulin can be accessed at www.tinyurl.com/safe-use-insulin.
Anyone using a treatment that can cause hypoglycaemia should be warned about this risk and the circumstances in which it can occur. They should be informed about the signs and symptoms, advised to carry glucose with them at all times, and given instructions about treatments to alleviate hypoglycaemia. People should be questioned on their understanding of hypoglycaemia as part of their annual diabetes review, and information gained regarding any episodes of, for example, dizziness or sweating that may be unrecognised hypoglycaemia.
There are several oral and injectable treatments for blood glucose control that do not stimulate insulin production as sulphoylureas do and, therefore, have a low risk of inducing hypoglycaemia. These include pioglitazone, DPP1V inhibitors and GLP-1 mimetics. These alternative agents may be preferable, especially in people who drive regularly or older people in whom an episode of hypoglycaemia can have particularly devastating effects.
Hypoglycaemia is common and can occur in people with either type 1 or type 2 diabetes who use insulin or oral medications that stimulate insulin production. Nurses can help address this condition by ensuring people at risk are aware of symptoms, carry glucose with them at all times, and know how to treat hypoglycaemia promptly before low blood glucose levels affect brain function.
Useful national guidance for specific hospital management circumstances is available from NHS Diabetes (2010) The Hospital Management of Hypoglycaemia in Adults with Diabetes Mellitus, accessed at www.tinyurl.com/inpatient-diabetes.
Alvarez Guisasola F et al (2008) Hypoglycaemic symptoms, treatment satisfaction, adherence and their associations with glycaemic goal in patients with type 2 diabetes mellitus: findings from the Real-Life Effectiveness and Care Patterns of Diabetes Management (RECAP-DM) Study. Diabetes, Obesity and Metabolism; 10: S1, 25-32
Cryer PE et al (2003) Hypoglycaemia in diabetes. Diabetes Care; 26: 1902-1912.
The Diabetes Control and Complications Trial Research Group (1993) The effect of intensive treatment of diabetes on the development and progression of long-term complications in IDDM. The New England Journal of Medicine; 329: 977-986.
Krentz AJ, Bailey CJ (2001) Type 2 Diabetes in Practice. London: Royal Society of Medicine Press.
National Institute for Health and Clinical Excellence (2011) Diabetes in Adults Quality Standard. London: NICE.
National Patient Safety Agency (2010) Rapid Response Report NPSA/2010/RRR013 Safer Administration of Insulin. London: NPSA.
Royal Pharmaceutical Society and British Medical Association (2011) British National Formulary. Basingstoke: Pharmaceutical Press.
United Kingdom Prospective Diabetes Study (1998) Intensive blood-glucose control with sulphonylureas or insulin compared with conventional treatment and risk of complications in patients with type 2 diabetes. Lancet; 352: 837-853.