01Purpose and principlesWhat the treatment does and how it fits into care.
Medicine selection starts after a complete obesity assessment: treatment goals, prior attempts, eating pattern, mental health, pregnancy plans, diabetes therapy, pancreatitis or gallbladder history, renal function, gastrointestinal motility, concomitant medicines and likely follow-up. BMI is part of eligibility but should not eclipse comorbidity and shared priorities.
Tirzepatide and GLP-1 agonists reduce appetite and delay gastric emptying, producing substantial average weight loss but also nausea, vomiting, diarrhoea, constipation and dehydration. Gallbladder disease can accompany rapid loss. Rare pancreatitis is a class safety focus, and semaglutide has a 2026 MHRA warning about very rare non-arteritic anterior ischaemic optic neuropathy; sudden visual deterioration requires urgent eye assessment.
Access is unusually volatile and must be separated into three decisions: UK marketing authorisation, NICE recommendation and local commissioning. On 27 August 2026, NICE TA875 described specialist NHS semaglutide injection up to 2.4 mg weekly. The MHRA had separately authorised 7.2 mg injected Wegovy for adults with obesity, oral Wegovy titrated to 25 mg daily (the approval announcement said it was not then available through the NHS), and Foundayo (orforglipron) for weight management and type 2 diabetes on 10 August 2026. These authorisations did not by themselves create NICE funding, NHS availability or a local prescribing route. Check the live SmPC, NICE guidance and commissioner before selecting a product, formulation or dose.
Key points
- Anti-obesity medicine is an adjunct to an individualised nutrition, activity and behavioural programme, not a cosmetic shortcut or a replacement for follow-up.
- Eligibility differs by product, NICE technology appraisal, comorbidity, BMI, ethnicity, service setting and local phased commissioning; verify the live pathway before promising access.
- As at 27 August 2026, licensing was broader than NHS access: NICE TA875 described the commissioned 2.4 mg weekly semaglutide injection route, while the MHRA had also authorised 7.2 mg injected Wegovy, 25 mg oral Wegovy and Foundayo (orforglipron); a licence does not itself create NICE recommendation, NHS funding or local availability.
- Tirzepatide is a weekly dual GIP/GLP-1 agonist; semaglutide and liraglutide are GLP-1 receptor agonists; orlistat reduces intestinal fat absorption.
- Escalate incretin doses gradually to reduce gastrointestinal adverse effects, and never switch products or strengths by presumed dose equivalence.
- Agree a stopping rule before treatment: NICE appraisals commonly use failure to lose a specified percentage after a defined period at treatment dose.
- The MHRA strengthened class warnings in 2026 for acute pancreatitis, including rare necrotising and fatal reports; severe persistent abdominal pain needs urgent assessment.
- GLP-1 and dual GIP/GLP-1 medicines should not be used during pregnancy, when trying to conceive or during breastfeeding, with product-specific washout advice.
- Tirzepatide can reduce oral contraceptive reliability during initiation and dose escalation; use the current MHRA barrier or non-oral contraception advice.
- When diabetes medicines include insulin or sulfonylurea, plan dose review and glucose monitoring to avoid hypoglycaemia as intake and weight change.
- Tell anaesthesia teams about incretin treatment because delayed gastric emptying can increase pulmonary aspiration risk; follow the current procedure-specific policy rather than stopping independently.
- Use only a legitimate prescribed product from a registered pharmacy and ask specifically about private treatment, which may be absent from the NHS medication record.
02Indications, selection and cautionsWho may benefit, who needs urgent treatment and important alternatives.
The person meets the live appraisal and local criteria, has weight-related risk likely to benefit, understands administration and adverse effects, and can access structured follow-up.
Severe persistent upper-abdominal pain, often radiating to the back with nausea or vomiting, is not ordinary titration discomfort; stop the incretin medicine and arrange urgent assessment.
Persistent vomiting or diarrhoea, postural symptoms, low urine output and rising creatinine indicate dehydration; temporarily review nephrotoxic or blood-pressure medicines and assess urgently when severe.
Sweating, tremor, confusion or low glucose is more likely when an incretin is combined with insulin or sulfonylurea, requiring proactive glucose and dose planning.
A delayed period, planned conception or confirmed pregnancy requires prompt prescriber contact and stopping the incretin under current MHRA advice; do not continue for weight control during gestation.
Oily spotting, faecal urgency and steatorrhoea increase with high dietary fat and may impair adherence; jaundice, severe abdominal symptoms or anticoagulant instability needs clinical review.
Sudden painless monocular visual loss or rapid deterioration may represent NAION; the 2026 MHRA communication advises urgent medical or eye-casualty assessment rather than waiting for routine review.
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
Weight, BMI and waist-related baselineFirst step - Why
- Confirm eligibility and provide reproducible outcomes for shared decisions.
- Interpretation and limitations
- Apply product, ethnicity and service criteria from the live appraisal; record baseline weight because percentage-loss stopping rules depend on it.
- 02
HbA1c and diabetes medicine review - Why
- Identify dysglycaemia and prevent hypoglycaemia during combined treatment.
- Interpretation and limitations
- Marked hyperglycaemia needs active diabetes care, while insulin or sulfonylurea may require specialist reduction as appetite and glucose fall; do not stop insulin abruptly.
- 03
Renal and liver profile - Why
- Establish organ function before treatment and guide response to adverse effects.
- Interpretation and limitations
- Renal decline may reflect dehydration from gastrointestinal loss; liver abnormalities prompt evaluation of MASLD, gallbladder or other disease rather than automatic attribution to obesity.
- 04
Pregnancy test when clinically indicated - Why
- Avoid starting or continuing a contraindicated weight-management incretin.
- Interpretation and limitations
- A positive result stops the weight-management prescription and triggers obstetric or diabetes medication review; document product-specific preconception washout.
- 05
Medication and anaesthetic history - Why
- Find interactions, duplicate incretins and procedures affected by delayed gastric emptying.
- Interpretation and limitations
- Reconcile private and NHS products, insulin, sulfonylurea, warfarin and oral contraception; planned sedation or anaesthesia needs team-specific aspiration planning.
- 06
Lipase and acute abdominal assessment - Why
- Investigate symptoms suggestive of pancreatitis rather than screen asymptomatic users.
- Interpretation and limitations
- Diagnose pancreatitis from compatible pain, enzymes and imaging under the acute pathway; routine lipase monitoring without symptoms is not a safety substitute.
- 07
Dietary and eating-disorder assessment - Why
- Ensure treatment does not compound restriction, malnutrition or binge-purge pathology.
- Interpretation and limitations
- Low protein or micronutrient intake, purging, extreme restriction or prior bariatric surgery changes suitability and requires dietetic or specialist input.
04Treatment approachPreparation, options, escalation and aftercare.
01StartSelect a medicine safelyFirst stepBehavioural care alone is insufficient and pharmacotherapy is being considered.+
- 1Verify the current NICE appraisal, local commissioning route and product licence, applying ethnicity-adjusted thresholds and weight-related comorbidity criteria correctly.
- 2Assess pregnancy plans, pancreatitis and gallbladder history, GI motility, diabetes medicines, renal function, eating disorder, anaesthetic plans and ability to follow up.
- 3Agree product choice, titration, adverse-effect actions, contraception, functional and weight outcomes, stopping rule and likely plan if weight returns after cessation.
02TitrationIncrease without outrunning tolerabilityA weekly or daily injectable incretin has been prescribed.+
- 1Teach the exact pen, route, weekly or daily schedule, missed-dose instructions, storage and sharps disposal using the product leaflet and pharmacist demonstration.
- 2EscalationEscalate only at the licensed interval and delay or step back through the prescriber if nausea, vomiting, intake or hydration makes the next increase unsafe.
- 3Review glucose-lowering and blood-pressure medicines as clinical parameters improve, while preserving essential insulin and avoiding unsupervised medicine changes.
03Acute abdominal painSeparate common nausea from pancreatitisPersistent severe abdominal pain develops during GLP-1 or GIP/GLP-1 treatment.+
- 1Stop the implicated medicine immediately and assess ABCDE, hydration, pain pattern, vomiting, gallbladder features and other acute-abdomen diagnoses.
- 2Arrange urgent lipase, laboratory and imaging assessment according to the pancreatitis pathway, asking about private incretins if none appears in records.
- 3Do not restart if pancreatitis is confirmed; report suspected serious harm through Yellow Card and formulate another weight-management plan after recovery.
04Review responseContinue for benefit, stop for futilityThe product-specific assessment interval or maximum treatment duration is reached.+
- 1Calculate percentage weight change from the documented baseline and review glycaemia, pressure, function, adverse effects, eating quality and the person's priorities.
- 2Apply the exact NICE stopping threshold for that product and dose exposure, considering whether interruption, shortage or intolerability invalidated the assessment period.
- 3When stopping, plan behavioural maintenance and follow-up, explain likely appetite return without blame, and consider another commissioned treatment or surgery assessment when eligible.
05Regimens, contraindications and interactionsTreatment details and the circumstances that modify them.
Tirzepatide for weight management
Start 2.5 mg subcutaneously once weekly for 4 weeks, then 5 mg weekly; if needed increase in 2.5 mg steps after at least 4 weeks at a dose, to maximum 15 mg weekly.Avoid pregnancy and breastfeeding; stop at least one month before planned conception under current MHRA advice. Add barrier or use non-oral contraception for four weeks after starting and each dose increase; assess pancreatitis, dehydration, gallbladder and anaesthetic aspiration risk.
Semaglutide for weight management
For the NICE TA875 commissioned injection route, start 0.25 mg subcutaneously once weekly and escalate at 4-week intervals through licensed strengths toward 2.4 mg weekly, delaying escalation when tolerability requires. The separately authorised 7.2 mg injected dose is not evidence of NHS funding; use only the exact live SmPC and commissioned pathway.NICE limits this indication and recommends considering stopping for less than 5% loss after 6 months. Avoid pregnancy, stop at least two months before conception, assess pancreatitis and aspiration risk, and urgently evaluate sudden visual loss under 2026 MHRA NAION advice.
Liraglutide for weight management
Start 0.6 mg subcutaneously once daily and increase by 0.6 mg at intervals of at least one week to the 3 mg daily maintenance dose if tolerated.Apply the TA664 stopping rule and live access criteria. Avoid pregnancy and breastfeeding, review pancreatitis, gallbladder, dehydration and aspiration risk, and reconcile any other GLP-1 prescription to prevent duplication.
Orlistat
Take 120 mg orally immediately before, during or up to one hour after each main meal containing fat, up to three times daily; omit when the meal contains no fat.Continue beyond 12 weeks only if the BNF response criterion is met, usually more than 5% baseline loss. Counsel on oily stool, fat-soluble vitamins, warfarin and ciclosporin interactions, malabsorption and pregnancy; dietary fat excess worsens adverse effects.
06Complications, monitoring and follow-upAdverse effects, response and longer-term review.
- Review during each escalation step for nausea, vomiting, diarrhoea, constipation, hydration, intake quality and injection technique before increasing the dose.
- Measure weight at the product-specific decision point and calculate percentage change from the recorded baseline, rather than estimating by clothing size or memory.
- In diabetes, increase glucose monitoring during initiation and substantial intake change, with an accountable plan for insulin or sulfonylurea adjustment.
- Reassess pregnancy intentions and contraception throughout treatment; tirzepatide initiation and each increase trigger a four-week oral-contraceptive reliability safeguard.
- Ask directly about severe abdominal pain, gallbladder symptoms, new visual change and any planned anaesthesia or sedation at follow-up.
- Monitor renal function when prolonged gastrointestinal symptoms or dehydration occurs, and review diuretics, renin-angiotensin medicines and metformin according to sick-day context.
- Record functional and cardiometabolic benefit as well as adverse effects and weight, then revisit the continuation decision when public commissioning or licence conditions change.
07Special situationsVariants, exceptions and circumstances that change the usual approach.
Brands are not interchangeable
The same molecule may have different licensed indications, pens and doses; a diabetes product should not be silently converted into a weight-management regimen.
Nausea has a severity boundary
Mild transient nausea is common during escalation, but persistent vomiting, inability to drink or focal severe pain demands assessment rather than automatic reassurance.
Licence, appraisal and access are separate
MHRA authorisation establishes a product's UK licence; NICE appraisal assesses NHS use; commissioners determine local access. At the 27 August 2026 snapshot, newer semaglutide formulations and Foundayo were licensed but should not be presented as automatically funded or available.
Private use can be invisible
Ask explicitly before anaesthesia, acute abdominal assessment and diabetes dose change, because online or private prescriptions may not populate NHS records.
Stopping needs aftercare
Biological appetite returns when therapy stops. Maintenance support and an alternative plan reduce the chance that predictable regain is experienced as personal failure.
08Common pitfallsFrequent interpretation and management errors.
- 01
Promising an NHS medicine solely from BMI without checking the live appraisal and local rollout.
- 02
Escalating despite ongoing vomiting or dehydration because the calendar says four weeks.
- 03
Missing insulin-associated hypoglycaemia as appetite and glucose improve.
- 04
Reassuring severe radiating abdominal pain as an expected gastrointestinal side effect.
- 05
Using an incretin during pregnancy, planned conception or breastfeeding.
- 06
Forgetting tirzepatide's temporary additional contraception requirement with the oral pill.
- 07
Stopping treatment before anaesthesia without involving the procedural team, or failing to disclose it at all.
- 08
Buying, recommending or administering an unregulated pen or compounded powder from social media.