Potential for harm
Inadvertent selection of the incorrect brand, strength, or insulin device may occur at any stage in the medication journey, including procurement, prescribing, supply and administration. Confusion between insulin types with different release profiles can result in inappropriate timing or frequency of administration. Errors may lead to hypoglycaemia or hyperglycaemia leading to loss of glycaemic control and potentially severe harm, including death.
Loss of glycaemic control
Reports of inadvertent loss of glycaemic control have resulted from:
- prescribing, supply or administration of the incorrect insulin
- prescribing or advising an incorrect number of units when switching between different strengths of the same insulin brand, due to not understanding that insulin units are equivalent across strengths
- prescribing and supplying a device with dose-step increments that do not align with the prescribed dose, leading to inaccurate or omitted administration.
Where a supplied cartridge is incompatible with the available device, the insulin cannot be safely delivered and may promote unsafe practices. A healthcare professional withdrawing insulin from an insulin cartridge or pen and administering it using a syringe and needle may result in overdose and may be considered a Never Event.
Omissions or delays
Insulin is a time‑critical medicine, and delays or omissions in dosing can result in serious and potentially life‑threatening harm.
Where a lower strength insulin than intended is selected, larger injection volumes are required for each dose meaning supply may deplete sooner than expected causing dose delay or omission.
Where a supplied cartridge is incompatible with the available device, the insulin cannot be safely delivered which may lead to a delay.
Injection burden
Where a lower-strength insulin than intended is selected, larger injection volumes are required to deliver the required number of units and may require multiple injections to deliver a single dose. Larger injection volume and higher frequency increases the risk of lipohypertrophy.
Causes of mis-selection
There is a risk of selecting the wrong insulin product due to similarities in naming convention and presentation between different strengths and devices.
Some brands of insulin are available in multiple strengths (for example 100 units/mL and 200 units/mL) or in different delivery devices.
The risk may be exacerbated by:
- Lack of product differentiation within digital prescribing and dispensing systems.
- Using insufficient detail in documentation and communication of the intended insulin product and dose. Where a single insulin brand is available in multiple strengths or delivery devices, using only a brand name is insufficient.
Supporting product differentiation
Our advice on Preventing errors on the medicine journey (SPS page) provides guidance to support practices and medicines related processes which may minimise the risk of mis-selection.
Product verification
Showing the insulin container to the patient or carer at the point of administration or supply, to verify that the correct insulin and device have been dispensed, may prevent use of an incorrect product.
Understanding insulin release profiles
Understanding how insulin products differ in release profile and dose delivery is essential to prevent confusion and the incorrect selection of insulin.
Insulins are broadly grouped by their time-action profiles into short-acting (including soluble and rapid-acting), intermediate-acting and long-acting. The duration of action of each insulin type can vary considerably from one person to another.
Understanding insulin strength
Understanding how insulin products differ in strength and dose delivery is essential to prevent confusion and the incorrect selection of insulin.
Insulin strength is expressed as the amount of insulin in units per millilitre (mL) of solution. Sometimes this is referred to as concentration.
Historically, the only insulin strength available was 100units/mL. More recently, 200units/mL and 300units/mL products have become readily available.
Higher-strength insulin products without a UK license, such as 500units/mL are also available. See the Unlicensed medicines (SPS page) for all our advice relating to making, purchasing and using unlicensed medicines.
Any insulin product with a strength greater than 100 units/mL is considered a high‑strength insulin.
The dose counter on an insulin pen device displays the number of insulin units of insulin irrespective of product strength.
Understanding dose delivery
Understanding how a dose is delivered and device specific dose steps will minimise the risk of selecting an incorrect product.
People living with diabetes can administer their insulin in a variety of ways, including using disposable pre-filled pen devices (available as different device types), or insulin cartridges inserted into a reusable pen. Insulin doses may alternatively be drawn up from a vial and administered using an insulin syringe or delivered via a pump device.
Dose step
The term ‘dose step’ refers to how an insulin dose (in units) is selected on a pen device. While older devices delivered insulin in 1-unit dose step increments, some newer high-strength insulin pens use larger increments (for example, 2 units). There are also formulations aimed at paediatric patients that deliver 0.5-unit dose increments.
The Summary of Product Characteristics specifies the available ‘dose step’ for each insulin product.
Mitigate risks to prevent mis-selection
Standardise formularies
Rationalise and standardise the range of insulin products routinely used and included in local guidelines, formularies and prescribing systems to reduce confusion between different brands, strengths and devices.
Ensure processes are in place to review any non‑formulary insulin on admission to hospital or on transfer to a new care setting. Consideration should be given to switching to a formulary option if appropriate, ensuring any decision to continue non‑formulary insulin is clinically justified and communicated.
Digital systems
Review functionality within digital prescribing, dispensing and supply systems to support correct product selection and clearly distinguish between strengths and device types within the same insulin brand.
Review electronic prescribing functionality to ensure that prescribed doses can only be selected and delivered in dose‑step increments that are compatible with the specified insulin device.
Consider the need for processes and systems that require additional clinical verification prior to the supply of high-strength insulins that are not routinely used.
Prescribing
Review prescribing practices to support opportunities for product differentiation prescribing different brands and/or device types for an individual to create clear visual and practical distinctions, reducing the likelihood of one insulin being selected or administered in place of the other.
Utilise digital functionality to ensure the brand name, and where appropriate the device, are specified at the point of prescribing.
Administration and supply
Ensure administration and supply processes include the requirement to verify with the individual the correct insulin product, where this is appropriate.
Handling and storage
Review guidance with our series of articles Preventing errors on the medicine journey (SPS page) to identify opportunities to prevent mis-selection.