What to do if…
your glucose monitor or insulin device alarms and you are not sure what it means

What to do now

1. Check how you feel first. If you have signs of a hypo, such as shaking, sweating, confusion, blurred vision, sudden weakness, hunger, or tingling lips, treat it as low blood sugar right now.

2. If possible, do a finger-prick blood glucose check now. Treat lows based on the finger-prick result and symptoms, not only on a sensor reading you do not trust.

3. If your blood glucose is low, commonly below 4.0 mmol/L, or you feel low: take 15–20g of fast-acting carbohydrate, wait 10–15 minutes, then recheck. Repeat if still low. When you are back above 4.0 mmol/L and feel steadier, follow your own plan about whether you need a longer-acting carbohydrate snack or meal; children and some pump or closed-loop users may have different instructions from their diabetes team.

4. If someone is unconscious, having a seizure, not responding normally, or cannot swallow safely: call 999. Do not give them food or drink. Put them in the recovery position if you can do this safely, stay with them, and use prescribed emergency glucagon if it is available and someone present knows how to use it.

5. Look at the alarm message and sort it into one quick bucket, without deep troubleshooting:

   • Low or urgent low: treat as a hypo.
   • High: confirm with a finger-prick check; if you feel unwell, think about ketones.
   • Delivery problem, occlusion, no delivery, or pump stopped: assume insulin may not be getting in.
   • Sensor error, signal loss, calibration needed, or app disconnected: assume the reading may be unreliable.
   • Low reservoir, low battery, or change set or sensor soon: fix it once you have confirmed your glucose is safe.

6. If a pump alarm suggests insulin delivery may have failed: check for obvious problems only: pump suspended or stopped, kinked tubing, disconnected tubing, dislodged or painful site, wet or leaking adhesive, empty reservoir or cartridge, or insulin that may be spoiled or expired. If your pump, cannula, reservoir, or infusion set may be the problem, follow your device instructions and your written backup plan. If you do not have a clear backup plan, call your diabetes team’s urgent line, NHS 111 if available where you are, or your local urgent medical advice route rather than guessing doses.

7. If glucose is high and you feel unwell, or you use a pump and think insulin may have been interrupted: check ketones if you have ketone strips or a meter. Call 999 or go to A&E now if you have symptoms that could be DKA, such as vomiting, stomach pain, deep or fast breathing, fruity-smelling breath, unusual sleepiness, or confusion, or if your ketones are high for you. As an NHS guide, blood ketones over 3.0 mmol/L, or urine ketones over 2+, need urgent emergency help; follow any stricter personal ketone plan from your diabetes team.

8. If you need A&E because of possible DKA, do not drive yourself. Ask someone else to drive you or call 999 for an ambulance.

9. If the alarm comes through a phone or app: quickly check the basics so you do not miss the next alert: phone not on silent, volume up, Do Not Disturb off or exceptions set, notifications allowed, Bluetooth connected, and battery saver not blocking alerts. Then check the device screen itself to confirm the alarm state.

10. Make the next hour safer. Tell someone nearby, or call someone, what is happening. Keep fast-acting carbohydrate, your meter, strips, ketone supplies, insulin backup supplies, and device instructions with you. Recheck until you feel steady and the readings make sense.