Alarms, occlusions and fail-safes on an insulin pump
A pump holds only short-acting insulin, so a blocked set or a failed pump can matter within hours. Here is what alarms signal and what UK bodies say to keep to hand.
An insulin pump is a small electronic device that releases insulin through the day and night. Because it is a device, it can run low, lose power, jam or simply stop working, and it is built to tell its wearer when something needs attention. This page explains those warnings and the back-up plan behind them. The user manual and the person's own diabetes team set the actual response.
What pump alarms and alerts are
A published analysis of US insulin pump adverse-event reports describes the job of an alarm system in two parts: detecting a change in the wearer's health status (for example low blood glucose) or another circumstance that could cause harm (for example loss of device power), and then warning the wearer through an alarm, an alert or a notification. The same analysis looked at 40 different alarm signals and found that about a third were not referenced in the instructional materials supplied with the pump. The manual for the specific pump is therefore the reference. See alarm in the glossary.
Some warnings concern supplies and power. The analysis gives loss of device power as one example, and Diabetes UK notes that a disposable patch pump alerts its wearer when the whole device needs changing, rather than just the set. Where a model warns about a low cartridge or battery, the manual says what to do. Other warnings point to a delivery problem, and those deserve more care.
Occlusions: when insulin cannot get through
An occlusion is a blockage somewhere between the pump and the body. Diabetes UK notes that the infusion set can sometimes become blocked or come unattached, which could lead to high blood glucose levels and raise the risk of diabetic ketoacidosis, so a set may need changing at short notice. The Medicines and Healthcare products Regulatory Agency (MHRA) also lists physical failures such as leaks and cracks, and concerns about accuracy of delivery, among the pump problems it wants reported.
In the safety-report analysis, two obstruction-of-flow alarms were among the ten most frequently cited signals and accounted for just under half of the reports that mentioned any alarm. That figure comes from adverse-event reports, which record what went wrong rather than how often occlusions occur. Checking and changing a set is covered in infusion sets, cannulas and site rotation.
Why an interruption matters quickly
Diabetes UK explains that a pump needs only one type of insulin, known as fast-acting insulin. The consequence is spelled out on the same page: a person can develop life-threatening diabetic ketoacidosis (DKA) very quickly if a problem stops the pump delivering, because the insulin in the pump is fast-acting rather than long-acting. The basics of this are in how an insulin pump works.
Why back-up supplies are advised
Diabetes UK says it is important to always carry a back-up diabetes kit when using a pump, so that an injection can be given if the system does not work for any reason. It adds that a person should also have a supply of long-acting insulin and know what doses to take in the event of pump failure. Those doses are worked out with the diabetes team in advance, not by a website.
The MHRA gives a similar message. Its advice to patients is to use an alternative device if they suspect the current one is not performing adequately, and to ensure an alternative device is available at all times.
What to do when a pump stops working
Diabetes UK says that if the pump breaks, the person should contact the pump company straight away, and the company will organise a replacement. For unexplained high glucose, Diabetes UK says the causes can include problems with the infusion set or cannula, or pump failure, and advises speaking to the diabetes team about when to check for ketones.
The NHS gives clearer markers for when to escalate. It says to call the diabetes care team now, or get help from NHS 111, if blood glucose is high and insulin treatment is not working to reduce it, even when ketones are normal. It says to call 999 or go to A&E for a high ketone level or for symptoms of DKA such as thirst, needing to pee often, sleepiness or confusion, and breath that smells fruity. Thresholds and the full symptom list are on sick days with a pump, and the glossary explains blood ketones.
Reporting device problems to the MHRA
The MHRA describes insulin pumps and continuous glucose monitoring devices as complex devices with the potential to cause serious harm in the event of error. Its 2024 guidance for users explains reporting through the Yellow Card scheme. Reports are valuable even when no harm resulted, incidents put down to user error should still be reported, and a repeat problem needs a fresh report. The MHRA says it cannot give medical advice and will not contact the person's GP or clinic, so a health worry must be raised directly with a healthcare professional.
Low glucose suspend and predictive features
Some pumps work with a glucose sensor to reduce one particular risk. A pump linked to a sensor can suspend insulin automatically when sensor glucose is low (low glucose suspend) or when a low is predicted about 30 minutes ahead (predictive low glucose suspend), then resume delivery as the low is avoided, according to a published five-year follow-up study of one such system. Diabetes UK describes a further step, the hybrid closed loop, in which the glucose monitor talks to the pump, so a pump that can connect to a monitor is needed.
These features address low glucose or fine-tune dosing. The sources opened for this page do not say they replace a back-up kit, and the advice from Diabetes UK and the MHRA to keep one applies to every pump wearer. For who is offered what, see pump or injections? what NICE says.
Questions people ask
How can someone tell which alarm needs urgent action?
A webpage cannot rank them for a particular model. The analysis cited above found that signals vary widely and some are missing from the packaged instructions, so the manual and the team's training matter more than any general list.
What if a pump seems faulty but no alarm has sounded?
The MHRA's advice to patients is to use an alternative device if they suspect the current one is not performing adequately. Diabetes UK adds that the pump company should be contacted straight away if the pump breaks.
Can a problem be reported if nobody was hurt?
Yes. The MHRA guidance says reports are valuable regardless of whether the issue led to injury or harm.
In short
Pump alarms exist because the device carries only short-acting insulin, so a blockage, a failed pump or a loose set can lead to high glucose and ketones within hours. UK bodies, including Diabetes UK and the MHRA, advise keeping a back-up kit and a plan for injections, contacting the pump company if the pump breaks, and seeking medical help quickly when glucose stays high. The person's own diabetes team has the final word on what to do.