Perioperative medicines management

01Core principlesThe concepts and mechanisms needed to understand the subject.

Perioperative medicine management starts with reconciliation and ends only after safe reintroduction. The same tablet may be used for different reasons, and the harm of interruption depends on the indication. Formulation and timing matter: a weekly injection, modified-release tablet, insulin pump, anticoagulant or depot preparation cannot be managed from a drug-class name alone. The plan must follow the patient across clinic, ward, theatre, recovery and discharge.

Each drug is judged against four questions: what happens if it continues during fasting and anaesthesia, what happens if it is omitted, what monitoring or substitute reduces either risk, and what physiological conditions permit restart? Bleeding, hypoglycaemia, aspiration, ketoacidosis, hypotension, withdrawal, adrenal crisis, rejection, seizure and disease rebound have different time courses. A blanket instruction to stop all tablets therefore creates preventable harm.

The 2025 UK multidisciplinary consensus resolves an important elective adult conflict. GLP-1 receptor agonists and dual GIP/GLP-1 agonists continue, alongside an individual aspiration-risk assessment and mitigation such as regional anaesthesia when suitable, gastric ultrasound where expertise exists, airway protection and awake extubation. SGLT2 inhibitors are omitted the day before and day of procedure because perioperative starvation can promote euglycaemic ketoacidosis.

Diabetes management remains meal- and insulin-specific. Sulfonylureas are withheld when the patient is not eating; short-acting mealtime insulin is omitted with the missed meal. Basal insulin is preserved, often at an adjusted dose from the exact adult table. A variable-rate IV insulin infusion is used selectively, including fasting beyond one missed meal or decompensation, with glucose-containing substrate and frequent capillary checks. The goal is safe control, not tight 4–6 mmol/L treatment.

Antithrombotics demand a separate written plan. The agent, last dose, renal clearance, thrombotic indication, procedure bleeding risk, consequence of bleeding and planned neuraxial technique determine interruption and restart. Some minor procedures continue therapy; high-consequence sites may need a longer interval. Therapeutic bridging is reserved for selected high thrombotic risk and differs from standard prophylactic LMWH. A generic interval copied between agents is unsafe.

Key points

Reconcile every prescribed, injected, over-the-counter and herbal product with indication, formulation, dose and last administration; then record an exact continue, omit, substitute and restart instruction with an owner.
For elective adults, continue GLP-1 receptor agonists and dual GIP/GLP-1 agonists under the 2025 UK consensus, while assessing drug, patient and procedure aspiration risks and using appropriate mitigation.
Omit SGLT2 inhibitors the day before and day of the procedure. Stop them when a preoperative very-low-energy liver-reduction diet begins; provide sick-day rules and avoid prolonged starvation.
Restart an SGLT2 inhibitor after day surgery once eating and drinking normally, usually 24–48 hours. For inpatients, also require capillary ketones below 0.6 mmol/L and clinical stability.
Under corrected 2026 Association guidance, adults having planned surgery normally take antihypertensives, including ACE inhibitors and ARBs, on the day; reintroduce postoperatively according to blood pressure.
Antithrombotic interruption and bridging are drug-, renal-, indication-, procedure- and neuraxial-specific. Record the last dose and restart condition; prophylactic LMWH is not therapeutic bridging.

02Mechanisms and patternsImportant relationships and how to distinguish them.

Reconcile the actual product

Ask the patient, prescription record and pharmacy sources about generic and brand name, formulation, route, dose, timing, adherence, recent changes and non-prescribed products.

Identify the indication

Distinguish diabetes from weight, heart-failure or kidney indications; primary from secondary cardiovascular prevention; atrial fibrillation from recent thrombosis; and replacement steroids from anti-inflammatory use.

Map continuation harm

Consider bleeding, aspiration, hypoglycaemia, hypotension, renal accumulation, interactions, altered absorption, sedation and impaired haemostasis in relation to the exact operation and anaesthetic.

Map omission harm

Consider thrombosis, ketoacidosis, adrenal crisis, severe hypertension, seizure, rejection, withdrawal, psychiatric relapse and loss of symptom control over the likely interruption period.

Define restart physiology

Eating, drinking, haemostasis, renal and liver function, blood pressure, consciousness, bowel absorption, ketones and infection may matter more than a calendar date.

Recognise euglycaemic ketoacidosisRed flag

Nausea, abdominal pain, tachypnoea, dehydration or high-anion-gap acidosis during recent SGLT2 exposure requires urgent ketone testing despite a glucose below classic DKA ranges.

Red flags requiring action

An SGLT2 inhibitor plus nausea, abdominal pain, tachypnoea, malaise or unexpected acidosis requires blood ketones and acid-base assessment even when glucose is not markedly raised.
Type 1 diabetes must never be left without basal insulin; fasting changes prandial insulin and may require IV insulin, but complete insulin omission risks ketoacidosis.
A patient taking anticoagulant or antiplatelet therapy without a written last-dose and restart plan needs resolution before a procedure where bleeding consequences are significant.
Long-term glucocorticoid use, known adrenal insufficiency, unexplained perioperative hypotension, vomiting, hyponatraemia or hypoglycaemia requires an adrenal replacement assessment.
A GLP-1 or dual GIP/GLP-1 drug can delay gastric emptying; upper-gastrointestinal symptoms alone neither prove nor exclude retained gastric content, so use individual aspiration-risk assessment.
New acute kidney or liver injury, bleeding, ileus, inability to swallow or prolonged starvation invalidates a prewritten postoperative restart date and requires review.

03Interpreting evidenceInformation, measurements and their limitations.

Reasoning sequence

Consider the information, its meaning and its limitations before deciding what follows.

01
Structured medicine reconciliation
Why
Create a trustworthy list with indications, last doses, formulations, interactions and intended perioperative changes.
Interpretation and limitations
Discrepancy between patient report, repeat record and supplied medicines must be resolved; uncertainty is clinically significant for insulin, anticoagulants, steroids and weekly injections.
02
Capillary glucose and blood ketones
Why
Detect hypo- or hyperglycaemia and SGLT2-associated ketogenesis during fasting, illness and postoperative restart decisions.
Interpretation and limitations
Euglycaemic DKA can occur with glucose below 11 mmol/L. Inpatients should not restart SGLT2 therapy until eating and drinking normally and capillary ketones are below 0.6 mmol/L.
03
Renal and liver function
Why
Assess clearance and organ safety for anticoagulants, diabetes medicines, analgesics and other renally or hepatically handled drugs.
Interpretation and limitations
An acute change may lengthen anticoagulant effect, increase toxicity or prevent restart even if the planned clock interval has elapsed.
04
Haemoglobin, platelets and targeted coagulation tests
Why
Assess bleeding and haemostatic context when antithrombotic exposure, liver disease or active loss makes results actionable.
Interpretation and limitations
Routine coagulation tests do not quantify every DOAC effect; interpret the exact agent, timing, renal function and procedure and seek specialist assays when necessary.
05
Supine and standing blood pressure
Why
Identify medication-related hypotension and guide planned-surgery antihypertensive management in selected older, diabetic or symptomatic adults.
Interpretation and limitations
A fall of at least 20 mmHg systolic or 10 mmHg diastolic within three minutes warrants medicine review and use of standing pressure for management.
06
Focused gastric risk assessment
Why
Estimate retained-content and aspiration risk in an adult taking GLP-1 or dual agonist therapy.
Interpretation and limitations
Symptoms alone are insufficient. Combine drug phase, comorbidity, fasting, procedure and anaesthetic factors; gastric ultrasound can assist where appropriate expertise exists.

04Applied reasoningWorked examples connecting principles to decisions.

01Worked case: diabetes medicinesElective surgery with semaglutide and empagliflozinAn adult using weekly semaglutide and morning empagliflozin for diabetes is scheduled for a planned procedure under general anaesthesia.

1Confirm indications, dose timing, recent GLP-1 escalation and gastrointestinal history, diabetes type and control, renal function, fasting plan, other glucose-lowering therapy and expected missed meals.
2Continue semaglutide under the 2025 UK elective consensus, complete an individual aspiration-risk assessment and agree mitigation rather than assuming that omission for one dosing interval empties the stomach.
3Omit empagliflozin on the day before and day of the procedure, avoid prolonged fasting and provide written sick-day guidance. Because this patient has diabetes and uses an SGLT2 inhibitor, measure capillary blood ketones daily until eating and drinking normally, even when blood glucose is normal.
4Preserve basal insulin using the applicable adult regimen and omit meal-linked secretagogues or rapid insulin only when that meal is missed; use IV insulin selectively when fasting or decompensation requires it.
5After day surgery restart empagliflozin only once eating and drinking normally, usually 24–48 hours; if admitted, also require clinical stability and capillary ketones below 0.6 mmol/L.

02Antithrombotic pathwayElective high-consequence procedureAn adult takes an anticoagulant or antiplatelet drug and the planned site makes even modest bleeding consequential.

1Identify exact agent, dose, indication, thrombotic history, last administration, renal function and concomitant antiplatelet or interacting medicines.
2Have the proceduralist and anaesthetic team classify bleeding risk and consequence, including any neuraxial technique, then obtain the current agent-specific interruption interval.
3Use therapeutic heparin bridging only when the defined thrombotic risk and guidance support it; do not call routine postoperative prophylactic LMWH bridging.
4Write the last-dose, day-of-surgery and restart plan, including haemostasis and organ-function conditions, dose sequence and responsibility after discharge.

03Steroid pathwayAdrenal suppression risk before major surgeryAn adult has adrenal insufficiency or credible HPA suppression from chronic glucocorticoid exposure and will undergo major surgery.

1Confirm diagnosis, all steroid routes and doses, duration, recent taper, sick-day plan and the magnitude of surgery; prednisolone at least 5 mg daily for at least one month can suppress the axis.
2Continue the usual steroid and add stress replacement; the corrected major-surgery adult regimen uses hydrocortisone 100 mg IV at induction followed by 200 mg over 24 hours while nil by mouth.
3When recovery is uncomplicated and enteral absorption returns, resume enteral glucocorticoid at double the pre-surgical therapeutic dose for 48 hours, then return to the usual plan.
4Treat unexplained hypotension, vomiting, electrolyte disturbance or hypoglycaemia urgently as possible adrenal insufficiency while seeking endocrine and anaesthetic review.

05Relevant medicines and safetySpecific regimens and precautions where medicines are relevant.

Preserves cardiac, renal or glycaemic benefit outside the fasting period while reducing perioperative ketoacidosis risk.

SGLT2 inhibitors

Omit on the day before and day of elective procedure; restart only after eating and drinking normally.

Stop when a very-low-energy liver diet begins; for inpatients also require stability and capillary ketones below 0.6 mmol/L before restart.

Maintains indicated glycaemic or weight treatment while aspiration risk is managed through assessment and anaesthetic mitigation.

GLP-1 or dual GIP/GLP-1 agonists

Continue the usual scheduled adult dose through elective perioperative care under the 2025 UK consensus.

Recent escalation, delayed emptying risks and procedure factors matter; symptoms alone cannot determine gastric content, and emergency applicability differs.

Prevents uncontrolled hyperglycaemia and ketosis when fasting removes meal-related insulin requirements.

Long-acting basal insulin

Continue basal insulin using the product and timing-specific adult table, commonly at about 80% when IV insulin is used.

Never omit basal insulin in type 1 diabetes; monitor glucose frequently and match dose to regimen, intake, renal function and any IV insulin.

Provides stress replacement for adults with adrenal insufficiency or credible glucocorticoid-induced suppression undergoing major surgery.

Major-surgery adrenal replacement

Hydrocortisone 100 mg IV at induction, then 200 mg over 24 hours while nil by mouth.

Give in addition to usual therapy; this is not for every steroid exposure, and the corrected postoperative transition depends on recovery and absorption.

06Checking understandingVerify the reasoning, revisit uncertainties and apply feedback.

On admission, compare the written plan with actual last doses, current physiology, renal function, intake and any new medicines or illness.
During diabetes care, monitor capillary glucose at a frequency matched to treatment; on a variable-rate IV insulin infusion check hourly initially and provide glucose-containing substrate.
For a patient with diabetes using an SGLT2 inhibitor, measure capillary blood ketones daily until eating and drinking normally even if glucose is normal; also test with illness, persistent hyperglycaemia, starvation or acidosis and document the below-0.6 mmol/L inpatient restart criterion.
After surgery, reassess haemostasis, pressure, renal and liver function, swallowing, bowel absorption and nausea before restarting withheld medicines.
At discharge, list every temporary change, the intended restart dose and date or physiological criteria, monitoring, sick-day rules and the clinician responsible for follow-up.

07Special situationsVariants, exceptions and circumstances that change the usual approach.

Indication changes risk

Stopping an SGLT2 inhibitor used for heart failure or an antiplatelet used after recent coronary intervention has consequences beyond its familiar drug-class label.

Restart is a clinical decision

A planned date is overridden by bleeding, acute kidney injury, ileus, hypotension, ketonaemia or inability to eat and absorb medicines safely.

Basal is not prandial

Fasting removes meal-related carbohydrate exposure but not background insulin need; confusing the two can produce either severe hypoglycaemia or ketoacidosis.

Consensus changed GLP-1 practice

The current UK elective recommendation continues therapy and manages aspiration risk; copying an older blanket weekly-withholding rule does not reflect the 2025 body.

Bridging has a dose

Therapeutic LMWH or UFH used during warfarin interruption is bridging; ordinary low-dose surgical thromboprophylaxis serves a different purpose.

08Common pitfallsFrequent interpretation and management errors.

01
Writing stop oral medication without naming the product, last dose, indication and restart condition.
02
Withholding basal insulin from a fasting person with type 1 diabetes.
03
Continuing an SGLT2 inhibitor through the day before surgery or a preoperative liver-reduction diet.
04
Stopping GLP-1 therapy by an obsolete blanket rule without applying the current UK elective consensus.
05
Copying a DOAC interval between agents without renal function, bleeding consequence and neuraxial context.
06
Restarting antihypertensive, anticoagulant or diabetes therapy by calendar alone despite postoperative instability.
07
Treating prophylactic LMWH as if it were therapeutic anticoagulant bridging.

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