Insulin safety: what is all the fuss about?

Insulin is a hormone produced in the pancreas by the islets of Langerhans (beta cells) and is essential for life. The lack or relative lack of insulin production results in raised blood glucose levels and causes diabetes. The prevalence of diagnosed diabetes in the UK is estimated at 4.8 million people, approximately 8% type 1 and 90% type 2 (Diabetes UK, 2020). Rates of insulin therapy in the UK continue to rise and approximately 30% of people with diabetes are treated with insulin – this includes people with type 1 and type 2 diabetes (Lipska et al, 2017).

In 2010 National Patient Safety Alerts (NPSA) produced a raid response report, Safer Use of Insulin, with regards to the increasing number of serious incidents leading to severe harm or death related to insulin therapy. Unfortunately, 10 years on we are still experiencing patient harm as a result of medication errors with insulin (England and NHS Improvement, 2019), with medication errors related to the administration of insulin and inaccurate prescribing being the commonest errors.

In 2017, the National Institute for Health and Care Excellence (NICE) produced information for safer insulin prescribing and the Primary Care Diabetes Society (PCDS) produced an e-learning module in association with TREND-UK to offer a learning opportunity for all health professionals called The Six Steps to Insulin Safety (PCDS, 2017).

In primary care, practice nurses and advanced nurse practitioners play a vital clinical role in screening, maintaining and supporting people with diabetes. They often initiate insulin therapy and also help support management of diabetes through glycaemic control and cardiovascular risk reduction ensuring annual review and regular monitoring.

This article aims to raise awareness of the risks of insulin therapy, the common mistakes that can be made in the prescribing, dispensing and administration of insulin, and to inform health professionals who are involved in caring for people using insulin therapy on how to reduce the risk of potential harm for patients.

The importance of a thorough assessment using the Six Steps to Insulin Safety

When a clinical decision is made to commence insulin therapy, the initial assessment and discussion with the person with diabetes is paramount, and using this framework will provide the reader with a comprehensive understanding of the importance of each step in maintaining patient safety.

1. Right person

Shared decision making is critical for understanding the risks and benefits of insulin therapy. Insulin treatment should be individualised to the person. During the assessment process there are multiple factors to consider before deciding on the best treatment to meet a person's clinical need:

• Patient preference regarding the number of injections required per day to maintain good blood glucose control. Insulin designed to be administered twice daily, eg a mixed insulin preparation, will not give the individual flexibility around working shift patterns, variable meal times or exercise. Therefore, lifestyle should be a consideration in the assessment process
• Patient skill: insulin is self administered via a pen device, disposable syringes or continuous subcutaneous insulin infusion (insulin pump). The practical use of devices requires a certain amount of dexterity to ensure safe and effective independent use
• Dependence on others. It is also important to note that not everyone will be self-caring with their insulin treatment and may require a 3rd party to assist, which could be a family member or a health professional. Again this would need to be taken into account to ensure suitable treatment
• Education on the safe administration of insulin is critical before starting treatment, and it is important to ensure the individual or carer understands all of the information that is given.

2. Right insulin

The World Health Organization (WHO, 2016) gave some insight into why medication errors can occur and this description certainly applies to insulin therapy.

‘Medicines are sometimes complex and can be puzzling in their names, or packaging and sometimes lack sufficient or clear information. Confusing “lookalike sound alike” medicines names and/or labelling and packaging are frequent sources of error and medication-related harm that can be addressed.’

(WHO, 2016)

Insulin concentration

The assessment for insulin therapy should also include a comprehensive understanding of the various types and strengths of insulin preparations available. Some people will require large doses of insulin and therefore a range of insulins have been produced in more concentrated versions. The most common strength of insulin is U100 (this means that 1 ml of solution contains 100 units of insulin). There are also U200, U300 and U500 preparations available.

Biosimilar insulins

Insulins have also been produced to replicate others and are referred to as biosimilar insulins. Diabetes UK (2019) wrote a position statement on biosimilar insulins and were quite clear on two aspects: firstly, that people who are stable on one insulin type should not be transferred onto biosimilar insulin for a cost cutting purpose only; secondly, to avoid confusion, insulin should be prescribed by the Brand name and not the generic name, ie prescribe ‘Lantus insulin’ or ‘Abasaglar insulin’ and not ‘glargine insulin’.

Similar sounding preparations

Insulin products can also have similar names and similar looking packaging to another preparation. The prescriber and the patient must therefore be aware of potential errors in prescribing or dispensing of such similar drugs, as the action of these insulins can be completely different to one another, eg Humalog Mix25 insulin is a mixed insulin containing 25% rapid acting insulin and 75% long acting insulin, whereas Humalog Mix50 is a mixed insulin containing 50% + 50% mixture. The error in prescribing Humalog Mix50 instead of Humalog Mix25 would result in the patient having twice as much rapid acting insulin per dose than they should, increasing their risk of hypoglycaemia. Insulin ID cards are a convenient way of confirming what insulin has been prescribed to avoid confusion.

Time action profiles

There are 4 broad categories of insulin preparations (rapid, short, intermediate and long acting insulins) which determine the time action profile of each, of how long they are active (duration) and speed of onset (intensity). Mixed insulins are a % combination of these (Table 1).

Insulin regimens

The common insulin regimens to help manage blood glucose levels include:

• Once daily basal insulin (usually in combination with other diabetes treatment)
• Twice daily mixed insulin (usually given with breakfast and evening meal)
• Basal bolus: bolus insulin administered with meals and a basal insulin as background (once or twice a day)
• Continuous subcutaneous insulin infusion: rapid/short acting insulin delivered continuously via insulin pump.

3. Right dose

The dose of treatment is individualised based on the glycaemic profile, fluctuations in blood glucose and clinical need. Insulin should always be prescribed in units regardless of the concentration of the insulin. There is no upper limit to the dose of insulin; therefore, there is a risk of overdose by inaccurate prescribing. NHS Improvement (2018) categorised an overdose of insulin by abbreviation of the word units as a reportable ‘never event’. Never events are wholly preventable patient safety incidents that should never happen. Therefore 16 units of insulin should not be written as 16U as this can easily be mistaken for 160 with a risk of 10-fold overdose and subsequent serious harm from hypoglycaemia.

4. Right device

Insulin can be self-administered by a number of different devices: insulin syringe and vial; cartridge in a pen; prefilled pen; and insulin pump. Insulin syringes are specific for insulin and no other type of syringe should be used. Serious patient harm has occurred due to error in using a different syringe and resulted in massive overdose of insulin and death (National Patient Safety Agency, 2010).

The Never Events policy (NHS Improvement, 2016) also categorised an overdose of insulin by use of the wrong device as a reportable ‘never event’. Specific insulin syringes should only be used when drawing insulin out of a vial. They must not be used to withdraw insulin from a cartridge or prefilled pen. Some higher concentrations of insulin are available, so there is therefore a real risk of fatal overdose if the pen device is not used to accurately measure the number of units required. For example, using the pen device a dose of 70 units of insulin is accurate whether the concentration is U100 or U300, as the pen is designed to measure the correct amount of units specific to that insulin. If an insulin syringe was used in error the result would mean drawing three times the amount – 210 units – of the concentrated preparation.

Cartridges are not interchangeable between different pen devices (Figure 1). The ends of the cartridges will differ.

Figure 1. Cartridges are not interchangeable between different pen devices

People using insulin pumps as their delivery system are required to have a structured education programme to ensure they are educated on how the pump works and what action to take in the event of a pump failure. Insulin pumps are initiated in a specialist centre under the supervision of the diabetes specialist team.

5. Right way

This section will focus on the common pitfalls and errors of insulin injection technique. As health professionals we should be reminded to ‘go back to basics’ when trying to identify why glycaemic control may be erratic. A thorough review of the practical skill of injection technique will prove to be invaluable, as regardless of how long someone has been injecting there are often short cuts and poor habits formed. Best practice would be to complete an assessment before considering swapping from one insulin therapy to another. Any insulin is only as good as the accuracy of the injection technique.

Injection technique

Insulin regimens can range from one to five or more injections a day. If you took an average of three per day that equates to over one thousand injections per year.

Insulin should be injected into the subcutaneous tissue as opposed to the muscle, as this will ensure the slower absorption required for insulin (Dougherty and Lister, 2015). There are complications to subcutaneous injections such as abscess at the injection site, but more common is the build up of fatty tissue beneath the skin known as lipohypertrophy (Figure 2). This can be caused by using the same site frequently or not changing pen needles after each use, and can be avoided by a systematic rotation of injection sites (Down and Kirkland, 2012). Lipohypertrophy can affect the rate of absorption of the insulin. During a general review, health professionals should ask about injection sites and examine them if appropriate. Lipohypertrophy can often be felt better than seen. It is important to ask about the frequency of rotation and the frequency of needle change – all of these factors will have an impact on the efficacy of insulin. Injection into an area of lipohypertrophy should be avoided to enable ‘healing’ and may take up to 3 months. This information should form part of the education on good injection technique.

Figure 2. Fat accumulation at insulin injection site, known as lipohypertrophy

Practical skill of injecting

As mentioned previously, regardless of how long someone has been self-administering insulin it is best practice to observe a demonstration to ensure all of the required steps of injecting are followed, which includes the preparing of the pen device, application of a new needle, test shot and angle of injection.

• The pen device: the pens for use with cartridges should be replaced every 3–5 years (check manufacture recommendations) or before if damaged
• Pen needles: single use and should be replaced for every injection. The size of the needle is also important, generally needles 4–6 mm are safe and effective regardless of body mass index (Hirsch et al, 2010)
• Priming of pen device: this is a 2 unit test shot before each injection once a new needle has been applied, and is applicable to both cartridge pens and prefilled pens to ensure the device is working
• Angle of injection: subcutaneous injection should be at 90° angle, with needle length 6 mm or less. The need for a skin fold pinch only applies to adults who are very thin. There is not a requirement to prepare the skin by any special cleansing prior to injection (Hicks et al, 2011)
• 10 seconds: to avoid leakage of insulin from the site (which can equate to a couple of units lost) it is advised slowly to count to 10 after the button on the pen has been depressed before withdrawing needle from skin
• Sharps disposal: safe disposal of sharps is a health and safety requirement for all people using syringes and pen needles, a sharps disposal container is available on prescription and each local council should have their own process for the collection of used containers.

6. Right time

The timing of insulin injection is directly related to the anticipated time action profile of the preparation. Insulins containing rapid/short acting insulin, and this includes mixed insulins, should be administered at meal times as the quick acting insulin will start to work to reduce blood glucose and this will need to coincide with the rise in blood glucose following a meal. See Table 1.

If a person requires a district nurse to administer insulin and then rely on a carer to prepare the meal, there is potentially a time delay. Matching times will prove difficult and the risk of hypoglycaemia increases. This is something for the prescriber to be aware of. This may require an individual assessment to mitigate risk and may entail a consideration of, for example, long-acting insulin only which could give reasonable glycaemic control but reduction of hypoglycaemic risk. This should be discussed with your local diabetes team for advice.

Blood glucose monitoring, hypoglycaemia and driving

Every person having insulin therapy should be shown how to monitor blood glucose levels and, most importantly, how to interpret the results. Hypoglycaemia (less than 4 mmols/l) is a real risk with insulin therapy. The main causes of hypoglycaemia are missed/delayed meals, too much insulin, or increased activity. Education and providing information on the signs, symptoms and treatment of hypoglycaemia should form part of the assessment and review for patients on insulin or any other diabetes medication that has the potential to lower blood glucose.

The Driver and Vehicle Licencing Agency (DVLA) have regulations for people who drive and take insulin (Gov. uk, 2020). As health professionals we have a duty to inform patients of these regulations, including safe levels of blood glucose to drive (‘5’ before you drive) and to clearly document that this information has been provided.

Conclusion

Medication errors with insulin continue to be high risk for patient safety. The errors can occur at any stage of the process from prescription and dispensing to administration. The complexity of insulin as identified in this article emphasises the importance of careful consideration by any health professional dealing with insulin and awareness of the common pitfalls will hopefully prevent medication errors in clinical practice. Health professionals caring for and supporting patients on insulin therapy need to be aware of the potential hazards with insulin and ensure they have sufficient knowledge and skills to enable them to provide safe and effective care. There are plenty of online resources available to support staff (Box 1).

Box 1.Useful resources

• Diabetes UK: https://www.diabetes.org.uk/professionals/resources
• Primary Care Diabetes Society. How to minimise insulin errors. https://www.pcdsociety.org/resources/details/how-minimise-insulin-errors
• TREND-UK: https://trend-uk.org
• The Six Steps to Insulin Safety Continuing Professional Development module is available for all healthcare professionals and it is free via Diabetes on the Net. https://www.diabetesonthenet.com/resources/details/six-steps-to-insulin-safety-e-learning-module
• Forum for Injection Technique. Diabetes care in the UK. The first UK Injection Technique Recommendations. 2011. http://www.fit4diabetes.com/files/2613/3102/3031/FIT_Recommendations_Document.pdf

KEY POINTS:

• In primary care, practice nurses and advanced nurse practitioners play a vital clinical role in screening, maintaining and supporting people with diabetes
• Shared decision making is critical for understanding the risks and benefits of insulin therapy
• Insulin products can also have similar names and similar looking packaging to another preparation. The prescriber and the patient must therefore be aware of potential errors in prescribing or dispensing of such similar drugs
• Insulin should be injected into the subcutaneous tissue as opposed to the muscle. Correct injection technique is vital

CPD reflective practice:

• What are the key points to remember when checking a person's injection technique?
• Where could you find additional information on insulin safety?
• How will this article affect your clinical practice?