Synopsis
Maintain essential insulin, prevent dehydration and ketoacidosis during illness, and create a safe medicine, fasting and glucose plan for procedures and surgery.
- Illness usually raises insulin need through stress hormones, but vomiting, renal decline and poor intake can lower it; monitoring decides rather than a blanket dose rule.
- Never stop basal insulin in type 1 diabetes, even when not eating. Pump users must correct delivery failure quickly because they have no long-acting depot.
- Check glucose more frequently during illness and measure blood ketones in type 1 diabetes, SGLT2 use or symptoms of ketoacidosis. For surgical patients with diabetes taking an SGLT2 inhibitor, check capillary blood ketones every day until normal food and fluid intake resumes, irrespective of glucose.
- Maintain fluids and carbohydrate in tolerable forms, use the written correction algorithm and seek help early when ketones rise or oral intake fails.
- Temporarily pause SGLT2 inhibitors during significant illness, dehydration, major surgery or prolonged fasting and restart only after normal ketones and clinical recovery.
- Metformin and other kidney- or volume-sensitive medicines may need temporary interruption during dehydrating illness; provide an individual list and restart criteria rather than the acronym alone.
- Elective surgery requires early HbA1c, diabetes type, medicine, device, fasting, hypoglycaemia and discharge planning across primary care, surgical, anaesthetic and diabetes teams.
- Minimise fasting and place people with diabetes early on the operating list; variable-rate intravenous insulin is for defined circumstances, not a universal substitute for planning.
- Current UK consensus generally continues GLP-1 and tirzepatide perioperatively with individual aspiration-risk assessment, while local policy and anaesthetic judgement remain decisive.
Key red flags
Thirst, polyuria, nausea, abdominal pain, vomiting, deep breathing, ketone odour or drowsiness with rising blood ketones signals insulin deficiency and needs urgent escalation.
Ketoacidosis symptoms with only modest glucose during SGLT2 treatment, fasting or after surgery are time critical; blood ketones and venous gas are required.
Profound dehydration, neurological change and very high glucose in type 2 diabetes can indicate HHS, often with infection or missed care, requiring the JBDS hospital pathway.
Vomiting or diarrhoea while taking metformin, SGLT2 inhibitors, diuretics, ACE inhibitors, ARBs or NSAIDs increases kidney and metabolic risk and triggers individual temporary-stop advice.
GLP-1 or tirzepatide use with active nausea, vomiting, abdominal distension, reflux, gastroparesis or recent dose escalation suggests retained gastric contents and needs anaesthetic mitigation.
Investigation priorities
Guide insulin, carbohydrate and escalation during illness and fasting.
Management branches
Acute illness with preserved consciousness and ability to drink and monitor.
- Increase glucose checks and measure blood ketones when type 1, SGLT2 treatment, marked hyperglycaemia or DKA symptoms apply; document readings and correction doses.
- Continue basal insulin, take correction rapid insulin using the learned algorithm, maintain sugar-free fluids and use carbohydrate-containing fluids when unable to eat normally.
- Pause the person's listed dehydration-sensitive medicines, including SGLT2 and often metformin when indicated, while continuing medicines that must not stop; avoid a one-size-fits-all acronym.
- Contact the diabetes or urgent-care service for rising ketones, persistent high or low glucose, vomiting, inability to hydrate or uncertainty, and call emergency services for breathing or consciousness change.