DPP-4 inhibitors, GLP-1 receptor agonists and tirzepatide

01Purpose and principlesWhat the treatment does and how it fits into care.

Incretin therapy is heterogeneous. Oral DPP-4 inhibitors preserve physiological incretins and usually suit people prioritising simplicity and low hypoglycaemia. GLP-1 agonists and tirzepatide produce stronger glucose and weight effects but bring injection or oral-administration complexity, gastrointestinal intolerance and specific safety counselling.

The central decision is whether the class meets the person's glycaemic, weight and cardiorenal goals under current NICE eligibility, while remaining safe with renal impairment, pancreatitis history, frailty, pregnancy potential, insulin treatment and planned procedures.

A successful prescription includes titration, nutrition and resistance-exercise support, contraception and sick-day advice, plus a stop rule. Rapid or excessive weight loss with loss of muscle, inability to eat or repeated vomiting is harm rather than automatic success.

Key points

DPP-4 inhibitors prolong endogenous incretin action, are weight neutral and have low hypoglycaemia risk alone; their glucose-lowering effect is modest compared with injectable GLP-1 or tirzepatide.
GLP-1 receptor agonists increase glucose-dependent insulin, suppress glucagon, slow gastric emptying and promote satiety; tirzepatide activates both GIP and GLP-1 receptors.
Use the February 2026 NICE NG28 phenotype-based algorithm and licensed indication; diabetes and weight-management brands, doses and eligibility are not interchangeable.
Do not combine a DPP-4 inhibitor with a GLP-1 receptor agonist or tirzepatide because overlapping incretin mechanisms add burden without recommended benefit.
Titrate GLP-1 or tirzepatide slowly through the product schedule and review nausea, intake, hydration, weight trajectory and renal function rather than escalating automatically.
MHRA strengthened the whole-class pancreatitis warning in January 2026, including rare necrotising and fatal cases; persistent severe pain warrants immediate discontinuation and investigation.
Do not stop or rapidly reduce insulin when starting a GLP-1 medicine; stepwise adjustment with glucose monitoring prevents hyperglycaemia and ketoacidosis.
GLP-1 medicines and tirzepatide are unsuitable during pregnancy and breastfeeding; tirzepatide can reduce oral-contraceptive reliability after initiation and dose escalation, so follow current MHRA advice.
UK perioperative guidance generally continues these medicines but requires explicit disclosure, delayed-gastric-emptying and aspiration-risk assessment; follow the anaesthetist's current local plan.

02Indications, selection and cautionsWho may benefit, who needs urgent treatment and important alternatives.

Expected gastrointestinal effects

Early satiety, nausea, diarrhoea, constipation or reflux often follows initiation or dose increase and may settle; severity, hydration and nutrition determine whether escalation should pause.

Acute pancreatitisRed flag

Severe persistent epigastric pain that may radiate to the back, commonly with nausea or vomiting, needs immediate medicine cessation and urgent assessment; common nausea should not obscure this pattern.

Dehydration and kidney injuryRed flag

Persistent vomiting or diarrhoea with reduced intake, postural symptoms or oliguria can cause acute kidney injury, particularly with diuretics, metformin, SGLT2 inhibitors or baseline CKD.

Gallbladder diseaseRed flag

Right upper-quadrant pain, fever or jaundice during rapid weight loss suggests gallstones or cholecystitis and requires standard urgent biliary assessment rather than attributing all pain to injection nausea.

Insulin-deficient deteriorationRed flag

Ketones, weight loss, polyuria or marked hyperglycaemia after insulin reduction indicates that incretin therapy has not replaced essential insulin; urgent DKA-capable assessment may be needed.

Frailty or undernutrition

Progressive low intake, sarcopenia, weakness, low BMI or inability to meet protein needs changes the benefit–harm balance and may meet NICE stopping criteria.

Perioperative aspiration riskRed flag

Active nausea, vomiting, abdominal distension, severe reflux, gastroparesis or recent dose escalation raises concern for retained gastric contents despite fasting and needs anaesthetic planning.

03Assessment before treatmentTests and checks that guide safe selection.

Investigation order

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
HbA1c and glucose profileFirst step
Why
Measure glycaemic response and guide co-therapy adjustment.
Interpretation and limitations
Review at the NICE interval and assess symptomatic hyperglycaemia and lows. Hypoglycaemia usually reflects concurrent insulin or sulfonylurea, which may need careful reduction.
02
Weight and nutritional assessment
Why
Distinguish useful weight change from malnutrition or muscle loss.
Interpretation and limitations
Track percentage and rate with appetite, protein intake, strength and function. Becoming underweight or failing to meet the agreed goal triggers NICE review or stopping rather than endless escalation.
03
Renal function and hydration assessment
Why
Select DPP-4 dose and detect dehydration-related injury.
Interpretation and limitations
Most DPP-4 inhibitors need renal dose adjustment, whereas linagliptin generally does not. GLP-1 product restrictions differ; acute vomiting can reduce renal function regardless of chronic eligibility.
04
Serum lipase and pancreatitis work-up
Why
Investigate compatible severe abdominal pain after immediate cessation.
Interpretation and limitations
Use clinical features, lipase and imaging under the acute pancreatitis pathway. Routine asymptomatic enzyme monitoring is not a substitute for symptom education.
05
Pregnancy and contraception review
Why
Prevent fetal exposure and unsafe conception during treatment.
Interpretation and limitations
Apply current product washout advice. With tirzepatide, advise non-oral or additional barrier contraception for four weeks after starting and after each dose increase when oral contraception is used.
06
Retinal status and visual symptoms
Why
Identify risk around rapid glucose improvement and separate other ocular events.
Interpretation and limitations
Established retinopathy may need closer eye follow-up when HbA1c falls quickly. Sudden visual loss is an ophthalmic emergency and should not wait for routine diabetes review.
07
Preoperative gastric-risk assessment
Why
Plan fasting and anaesthesia for delayed gastric emptying.
Interpretation and limitations
Ask explicitly about private as well as NHS prescriptions, dose escalation, symptoms and gastroparesis. The UK consensus generally continues treatment but individual anaesthetic technique and local policy govern.

04Treatment approachPreparation, options, escalation and aftercare.

01DPP-4Choose a gliptin rationallyFirst stepLow-hypoglycaemia oral treatment is appropriate within NICE NG28.

1Review renal and hepatic function, heart failure, pancreatitis history, co-prescribed incretin therapy and the desired size of glucose reduction before selecting a specific agent.
2Use the current BNF dose for kidney function, explain that weight effect is neutral and reduce insulin or sulfonylurea only when glucose patterns justify it.
3Recheck HbA1c after enough time to demonstrate effect and stop or switch when the agreed target is not met rather than maintaining ineffective polypharmacy.
4Investigate severe abdominal pain, blistering skin disease or hypersensitivity promptly and report suspected serious reactions through MHRA Yellow Card.

02GLP-1Start and titrate safelyA GLP-1 receptor agonist or tirzepatide is selected under current NICE eligibility.

1Confirm indication, product, baseline weight, HbA1c, renal function, retinopathy, pancreatitis or gallbladder history, pregnancy intentions and current insulin or sulfonylurea.
2Teach the device or oral administration, start at the licensed introductory dose and increase only at product-defined intervals when intake and adverse effects are acceptable.
3Provide written advice on hydration, gastrointestinal symptoms, pancreatitis, gallbladder disease, pregnancy, contraception, sick days and disclosure before anaesthesia.
4Review weight, HbA1c, nutrition and adverse effects against NICE continuation criteria; discontinue for confirmed pancreatitis, pregnancy, underweight status or inadequate agreed benefit.

03InsulinCombine without provoking DKAIncretin therapy is added to an insulin-containing regimen.

1Determine diabetes classification, C-peptide context when relevant and which insulin is essential; GLP-1 treatment is not a replacement for basal insulin in insulin deficiency.
2Use recent glucose or CGM to make a conservative stepwise reduction only when hypoglycaemia risk justifies it, with increased monitoring after each change.
3Teach ketone testing and urgent action for nausea, vomiting or high glucose, because gastrointestinal adverse effects can mimic or precipitate DKA.
4Review within the planned early interval and reverse excessive insulin reduction promptly if glucose, ketones or catabolic symptoms worsen.

04ProcedurePerioperative incretin planGeneral anaesthesia or deep sedation is planned.

1EscalationIdentify the exact medicine, dosing day, indication, recent escalation, gastrointestinal symptoms and coexisting gastroparesis or reflux during pre-assessment.
2Follow the current UK multidisciplinary and local policy, which may continue therapy while modifying aspiration precautions; do not adopt non-UK withholding rules without reconciliation.
3The anaesthetist should individualise fasting, airway and gastric-content risk, particularly when symptoms or recent titration suggest delayed emptying.
4AlternativeCoordinate alternative glucose treatment if the medicine is withheld and give explicit restart instructions once oral intake and clinical status are appropriate.

05Regimens, contraindications and interactionsTreatment details and the circumstances that modify them.

Provides modest glucose lowering with weight neutrality and little hypoglycaemia when used alone.

DPP-4 inhibitor

Use the licensed once- or twice-daily regimen with product-specific renal adjustment.

Do not combine with GLP-1 or tirzepatide. Review pancreatitis, severe joint pain, hypersensitivity, bullous pemphigoid and heart-failure considerations for the selected product.

Lowers glucose, supports satiety and weight reduction, with product-specific cardiovascular indications.

GLP-1 receptor agonist

Start at the product's introductory dose and escalate only at licensed intervals.

Gastrointestinal effects, dehydration, gallbladder disease and pancreatitis require counselling. Avoid pregnancy and breastfeeding, review retinopathy during rapid improvement and disclose before anaesthesia.

Dual GIP and GLP-1 agonism provides potent glucose and weight effects in eligible type 2 diabetes.

Tirzepatide

Start with the licensed weekly initiation regimen and increase no faster than specified.

Apply 2026 NICE criteria and MHRA pancreatitis warning. Avoid pregnancy and breastfeeding; oral contraception needs additional or non-oral protection after initiation and dose increases.

06Complications, monitoring and follow-upAdverse effects, response and longer-term review.

Review HbA1c, home glucose and hypoglycaemia after the clinically appropriate interval, adjusting concurrent insulin or sulfonylurea rather than assuming the incretin drug caused lows alone.
At each titration ask about nausea, vomiting, constipation, abdominal pain, fluid intake, urine output, gallbladder symptoms and whether meals remain nutritionally adequate.
Track weight with strength and function, especially in older adults, CKD and rapid loss; pause escalation when sarcopenia or undernutrition appears.
Check eGFR for DPP-4 dosing and after significant gastrointestinal fluid loss; document product-specific eligibility as renal function changes.
Revisit pregnancy plans, contraception, private prescribing, insulin doses and future procedures because these risks are commonly missed on repeat prescriptions.

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

Two incretin classes do not stack

A DPP-4 inhibitor adds little rational benefit to pharmacological GLP-1 receptor stimulation. NICE advises against combining it with GLP-1 agonists or tirzepatide.

Nausea can hide pancreatitis

Common transient nausea is expected, but severe persistent pain radiating to the back is a different syndrome. Stop treatment and investigate rather than prescribing an antiemetic remotely.

Weight loss can be excessive

Loss of muscle, dehydration and inadequate protein are not acceptable collateral effects. Dose escalation can pause even when the scale is moving in the intended direction.

Private medicines may be invisible

Ask directly about online or private injections before anaesthesia or when pancreatitis is suspected, because these products may not appear in the NHS medication list.

Insulin reduction needs data

Abrupt withdrawal has caused DKA. Use glucose patterns and change one component stepwise while retaining essential basal coverage and ketone education.

Perioperative advice is jurisdictional

Current UK consensus generally favours continuation with risk mitigation, differing from some overseas guidance. The anaesthetic team and local policy make the final plan.

08Common pitfallsFrequent interpretation and management errors.

01
Combining a DPP-4 inhibitor with a GLP-1 agonist or tirzepatide.
02
Escalating the dose despite persistent vomiting and declining kidney function.
03
Dismissing severe radiating abdominal pain as an expected side effect.
04
Stopping insulin abruptly when starting an incretin medicine.
05
Missing tirzepatide contraception advice after each dose escalation.
06
Applying overseas perioperative withholding advice without checking the UK local policy.