01Purpose and principlesWhat the treatment does and how it fits into care.
Sick-day rules are a personalised action plan covering monitoring, fluids, carbohydrate, insulin, temporarily paused medicines and thresholds for advice. A memorised list without dose and restart instructions is unsafe, especially when multiple prescribers use different rules.
Surgery combines fasting, stress hyperglycaemia, altered medicine absorption and handovers. The central decision is whether usual therapy can safely cover the fasting period or whether an intravenous insulin–glucose plan and specialist support are required.
Diabetes technology can often continue for selected procedures when the person is capable and the team understands it, but diathermy, imaging, perfusion, anaesthesia and inability to self-manage may require a documented alternative.
Key points
- 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.
- 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.
02Indications, selection and cautionsWho may benefit, who needs urgent treatment and important alternatives.
Mild infection with preserved drinking, normal ketones and manageable glucose may be treated at home using increased monitoring, correction insulin and clear review thresholds.
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.
Type 1 diabetes, poor control, major or emergency surgery, prolonged fasting, insulin pump uncertainty, recent SGLT2 exposure or inability to self-manage warrants early inpatient diabetes involvement.
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.
03Assessment before treatmentTests and checks that guide safe selection.
Read from the initial assessment onwards. Tests may run in parallel in urgent care; first-line, preferred, confirmatory, definitive and gold-standard labels appear only when the chapter explicitly states them.
- 01
Frequent capillary glucoseFirst step - Why
- Guide insulin, carbohydrate and escalation during illness and fasting.
- Interpretation and limitations
- Use the person's written interval and increase frequency when values change rapidly. Glucose alone cannot exclude ketonaemia, and CGM should be confirmed when perfusion or symptoms make readings unreliable.
- 02
Blood beta-hydroxybutyrate - Why
- Detect insulin deficiency and SGLT2-associated ketoacidosis early.
- Interpretation and limitations
- Apply the individual's sick-day threshold and hospital DKA criteria. Prefer blood to urine in hospital, particularly during SGLT2 interruption, and act on rising trend with symptoms.
- 03
Venous blood gas and electrolytes - Why
- Confirm acidosis and quantify potassium and bicarbonate disturbance.
- Interpretation and limitations
- Anion-gap metabolic acidosis with ketonaemia requires the DKA pathway; mixed disorders occur with vomiting, sepsis and kidney failure, so interpret the whole physiology.
- 04
Renal function and volume assessment - Why
- Identify dehydration and determine safe medicine restart.
- Interpretation and limitations
- Postural hypotension, oliguria or rising creatinine supports temporary withdrawal of volume- or kidney-sensitive medicines and clinical fluid assessment; recovery must be confirmed before resumption.
- 05
Preoperative HbA1c - Why
- Identify modifiable risk and plan elective surgery rather than act as a day-of-operation surprise.
- Interpretation and limitations
- Use the current CPOC or JBDS optimisation threshold and timeline. A high result prompts diabetes optimisation and shared delay decisions, but urgent cancer or emergency surgery may proceed with mitigation.
- 06
Medication, device and self-management assessment - Why
- Create the exact perioperative insulin and non-insulin plan.
- Interpretation and limitations
- Record diabetes type, every product and last dose, pump or CGM model, usual basal need, hypo awareness and who can manage the device while sedated.
- 07
Procedure-specific fasting and aspiration review - Why
- Coordinate medication and airway safety for the planned anaesthetic.
- Interpretation and limitations
- Duration, bowel preparation, morning versus afternoon list and GLP-1 gastrointestinal symptoms change risk. Use current UK multidisciplinary guidance and local policy rather than a generic instruction.
04Treatment approachPreparation, options, escalation and aftercare.
01Home illnessSick-day self-managementFirst stepAcute illness with preserved consciousness and ability to drink and monitor.+
- 1Increase glucose checks and measure blood ketones when type 1, SGLT2 treatment, marked hyperglycaemia or DKA symptoms apply; document readings and correction doses.
- 2Continue basal insulin, take correction rapid insulin using the learned algorithm, maintain sugar-free fluids and use carbohydrate-containing fluids when unable to eat normally.
- 3Pause 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.
- 4Contact 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.
02PreoperativePlan elective surgeryA person with diabetes is listed for an operation or procedure requiring fasting or sedation.+
- 1At referral and pre-assessment record HbA1c, complications, diabetes type, medicines, devices, hypoglycaemia, renal function, usual meals and the expected fasting and discharge pathway.
- 2Issue medicine-specific instructions from the current local JBDS/CPOC policy, including SGLT2 interruption, insulin adjustment and GLP-1 aspiration-risk disclosure, without asking the patient to improvise.
- 3Schedule early where possible, permit clear fluids according to anaesthetic policy, provide glucose and ketone monitoring and decide whether self-management, subcutaneous insulin or VRIII is appropriate.
- 4Communicate the plan across ward, theatre, recovery and pharmacy, including basal insulin, device handling, postoperative nausea, nutrition and explicit medicine restart criteria.
03Inpatient fastingInsulin through surgeryMore than one missed meal, unstable glucose, major surgery or inability to manage usual insulin.+
- 1Continue an appropriate background insulin dose and start variable-rate intravenous insulin with substrate only when the current JBDS criteria are met; avoid insulin infusion without glucose and potassium planning.
- 2Monitor capillary glucose at the specified perioperative frequency and check blood ketones in type 1 or after SGLT2 exposure when glucose or symptoms warrant.
- 3Ensure the infusion, fluid, pump and CGM are accessible and clearly owned during transfers, with anaesthesia directing management while the patient cannot self-manage.
- 4Transition back to subcutaneous treatment with adequate overlap and meal timing, involving the diabetes team after DKA, major change or prolonged infusion.
04EmergencyKetones or hyperosmolar deteriorationRising ketones, acidosis, marked dehydration, neurological change or failed home management.+
- 1Use ABCDE, venous access and urgent blood gas, ketones, glucose, electrolytes, renal function, osmolality where indicated and precipitant assessment; stop SGLT2 treatment.
- 2Apply the current JBDS DKA or HHS pathway rather than mixing protocols, with carefully monitored fluid, fixed-rate insulin or HHS-specific insulin timing and potassium replacement.
- 3Continue necessary basal insulin alongside intravenous treatment and involve diabetes specialists, critical care and surgery or infection teams according to the trigger.
- 4Before discharge identify why the plan failed, replace equipment and supplies, provide psychological or social support where relevant and rehearse revised sick-day actions.
05Regimens, contraindications and interactionsTreatment details and the circumstances that modify them.
Subcutaneous basal insulin
Continue at the sick-day or perioperative dose specified in the individual plan.Never omit in type 1 diabetes. Dose may need reduction for renal decline or fasting but must remain adequate; check product, timing and concentration at every handover.
Rapid-acting correction insulin
Use the written glucose and ketone algorithm with repeat monitoring at defined intervals.Avoid stacking before prior insulin has acted, and seek urgent advice for rising ketones or vomiting. Pump failure may require correction by pen rather than the suspect device.
Variable-rate intravenous insulin infusion
Prescribe through the current JBDS chart with substrate fluid and hourly monitoring.It is not a replacement for basal insulin in type 1 diabetes. Prevent infusion interruption, hypoglycaemia, hypokalaemia and transition gaps; use trained staff and a named owner.
Oral or intravenous glucose
Give according to the hypoglycaemia algorithm and recheck within the specified interval.Do not stop essential insulin solely because glucose is low; identify the responsible dose, maintain airway safety and monitor for recurrence, especially after sulfonylurea.
06Complications, monitoring and follow-upAdverse effects, response and longer-term review.
- During home illness, record glucose, blood ketones, temperature, intake, urine, insulin and symptoms at the frequency in the written plan, with defined contact thresholds.
- During surgery, monitor glucose at JBDS intervals and ketones when indicated; document which clinician owns each device and infusion during every transfer.
- Trend renal function, electrolytes, acid-base status and volume before restarting metformin, SGLT2 inhibitors, ACE inhibitors, ARBs or diuretics after a dehydrating illness.
- After GLP-1 or tirzepatide use, anaesthesia should reassess nausea, vomiting, distension and aspiration risk even when standard fasting instructions were followed.
- Before discharge ensure normal oral intake, stable glucose, resolved ketones, safe subcutaneous insulin overlap, working equipment and a written restart and follow-up plan.
07Special situationsVariants, exceptions and circumstances that change the usual approach.
Basal insulin is anti-ketosis
A fasting person with type 1 diabetes still needs background insulin to suppress lipolysis. Dextrose can support glucose while insulin continues; omission invites DKA.
Sick-day lists need restart rules
Telling someone to stop several medicines without saying when and how to restart creates long-term undertreatment. Clinical recovery and renal status should be explicit.
Bowel preparation is illness
Prolonged low intake, fluid loss and altered absorption during bowel preparation require a diabetes plan even when the endoscopic procedure itself is brief.
CGM may lag under anaesthesia
Perfusion, pressure and rapid glucose change can reduce sensor reliability. Perioperative decisions usually require validated capillary or blood-gas glucose under local policy.
UK GLP-1 guidance evolved
The current position generally continues therapy with individual aspiration mitigation. Ask the local anaesthetic team rather than importing a blanket hold interval from another jurisdiction.
Emergency surgery is not unplanned diabetes
Even without optimisation time, teams can identify insulin dependence, stop SGLT2, measure ketones, protect basal insulin and write safe recovery orders before theatre.
08Common pitfallsFrequent interpretation and management errors.
- 01
Telling a person with type 1 diabetes to stop insulin because they cannot eat.
- 02
Checking glucose but not ketones during SGLT2-associated illness.
- 03
Giving a generic sick-day acronym without individual restart instructions.
- 04
Using variable-rate intravenous insulin while accidentally omitting basal insulin.
- 05
Failing to identify a privately prescribed GLP-1 medicine before anaesthesia.
- 06
Restarting metformin or SGLT2 treatment before hydration, renal function and intake recover.