Prescribing GLP-1 Agonists for Weight Management: A Clinical Framework for UK Independent Prescribers
Overview
This guide provides a clinical framework for independent prescribers considering GLP-1 receptor agonist therapy for weight management. It covers patient selection criteria, required investigations, prescribing protocols, monitoring schedules, and safety considerations in line with MHRA guidance and NICE guidelines.
Regulatory Context
Licensed Indications (UK, as of 2024)
| Drug | Licence | Indication |
|---|
| Semaglutide 2.4mg sc weekly (Wegovy) | MHRA approved | Weight management in adults: BMI ≥30, or ≥27 with ≥1 weight-related comorbidity |
| Tirzepatide 2.5–15mg sc weekly (Mounjaro) | MHRA approved | Same as above |
| Semaglutide 0.5–2mg sc weekly (Ozempic) | Licensed for T2DM only | Off-label use for obesity — prescriber assumes full clinical responsibility |
| Liraglutide 3mg sc daily (Saxenda) | Licensed for weight management | BMI ≥30, or ≥27 with comorbidity |
Prescribing Ozempic (semaglutide) for weight management without a diabetes diagnosis is off-label. Document your clinical rationale, obtain informed consent, and ensure adequate clinical monitoring.
Patient Selection Criteria
Inclusion Criteria
- BMI ≥30 kg/m² OR BMI ≥27 kg/m² with ≥1 weight-related comorbidity:
- Type 2 diabetes mellitus
- Hypertension
- Dyslipidaemia
- Obstructive sleep apnoea
- Cardiovascular disease
- Non-alcoholic fatty liver disease (NAFLD/NASH)
- Failed conventional weight management strategies (diet, exercise, behavioural interventions)
- Motivated to make lifestyle changes alongside pharmacotherapy
Absolute Contraindications
- Personal or family history of medullary thyroid carcinoma (MTC)
- Multiple Endocrine Neoplasia type 2 (MEN2)
- Known hypersensitivity to the active substance or excipients
- Pregnancy or breastfeeding
- Active pancreatitis or history of recurrent pancreatitis
Relative Contraindications / Use With Caution
- History of gallbladder disease or gallstones (GLP-1 agonists associated with increased gallstone risk)
- Gastroparesis or severe GI dysmotility
- Severe renal impairment (eGFR <30 ml/min/1.73m²) — tirzepatide: use with caution; semaglutide: no dose adjustment needed but monitor
- Serious hepatic impairment
- Resting heart rate persistently >100 bpm (GLP-1 agonists can increase heart rate by 2–4 bpm)
- Severe depression or active suicidal ideation (post-marketing signals; counsel patients)
Pre-Prescribing Investigations
Mandatory Baseline Tests
| Test | Purpose |
|---|
| HbA1c | Diagnose T2DM; baseline glycaemic status |
| Fasting lipid profile | Screen for dyslipidaemia |
| Liver function tests (LFTs) | NAFLD screening; baseline hepatic function |
| Renal function (eGFR, creatinine) | Assess renal clearance |
| Full blood count (FBC) | Baseline |
| Thyroid function tests (TFTs) | Thyroid disease screening |
| Blood pressure and heart rate | Baseline cardiovascular |
| Weight, height, BMI, waist circumference | Baseline anthropometrics |
Recommended Additional Investigations
- Fasting glucose or oral glucose tolerance test (OGTT) if HbA1c is borderline
- ECG if significant cardiac history
- Pregnancy test (women of childbearing age)
- Vitamin D, B12 (as these are often deficient in obesity)
Prescribing Protocols
Semaglutide (Wegovy) — Dose Escalation
| Week | Dose |
|---|
| 1–4 | 0.25mg once weekly |
| 5–8 | 0.5mg once weekly |
| 9–12 | 1.0mg once weekly |
| 13–16 | 1.7mg once weekly |
| 17+ | 2.4mg once weekly (maintenance) |
If GI side effects are intolerable at dose escalation, delay escalation by 4 weeks at the current dose before attempting to increase.
Tirzepatide (Mounjaro) — Dose Escalation
| Week | Dose |
|---|
| 1–4 | 2.5mg once weekly |
| 5–8 | 5mg once weekly |
| 9–12 | 7.5mg once weekly (if tolerating and further weight loss desired) |
| 13–16 | 10mg once weekly |
| 17–20 | 12.5mg once weekly |
| 21+ | 15mg once weekly (maximum maintenance) |
The minimum recommended doses for this protocol are 5mg; 2.5mg is initiation dose only. Some patients achieve adequate weight loss at 5–7.5mg.
Monitoring Schedule
| Timepoint | Clinical Review |
|---|
| Baseline | Full assessment as above |
| 4 weeks | Tolerability, side effects, dose escalation decision |
| 12 weeks | Weight, BP, HR, HbA1c if diabetic, assess adherence |
| 6 months | Full metabolic panel, assess ≥5% weight loss (continue if achieved) |
| 12 months | Full review: benefits vs risks, continuation decision |
| Annually thereafter | Full metabolic review |
Discontinue treatment if <5% body weight lost at 6 months. Apply same principle to tirzepatide.
Drug Interactions
| Interaction | Clinical Significance |
|---|
| Insulin / sulfonylureas | Increased hypoglycaemia risk — reduce insulin/SU dose at initiation |
| Oral contraceptives | GLP-1 slows gastric emptying — advise additional contraception for 4 weeks after starting or dose change |
| Warfarin | Monitor INR more closely during initiation |
| Cyclosporin | Monitor levels — absorption may be altered |
Managing Side Effects
Nausea / Vomiting
- Most common (40–60% of patients). Usually mild-moderate, resolves within weeks.
- Advise: eat smaller portions, avoid fatty/spicy foods, avoid lying down after eating.
- If severe: antiemetics (metoclopramide, ondansetron). If persistent >2 weeks at current dose — delay escalation.
Diarrhoea
- Usually resolves within weeks. Ensure adequate hydration.
- Consider loperamide for symptomatic relief.
Pancreatitis (Rare, ~0.1%)
- Counsel patients: seek immediate medical attention for severe/persistent abdominal pain.
- Discontinue GLP-1 immediately if pancreatitis confirmed. Do not restart.
Gallbladder Events
- 2–3x increased risk of gallstones with rapid weight loss.
- Discuss with patients with prior biliary symptoms. Consider ursodeoxycholic acid in high-risk patients.
Informed Consent Documentation
Ensure your consultation notes document:
- Patient's BMI and weight-related comorbidities
- Failed prior weight management attempts
- Baseline investigations reviewed
- Contraindications excluded
- Off-label use disclosed and consented (if applicable)
- Dose escalation plan agreed
- Monitoring plan discussed
- Side effects and when to seek urgent help explained
Supply Considerations
Due to global supply constraints (particularly for Ozempic/Wegovy), ensure:
- Patients with type 2 diabetes are prioritised for Ozempic supplies
- Consider tirzepatide (Mounjaro) as an alternative if semaglutide unavailable
- Document dispensing pharmacy and batch number for traceability
Professional Responsibility
As an independent prescriber operating privately, you retain full clinical and legal responsibility for prescribing decisions. Ensure:
- You are prescribing within your agreed scope of practice
- You have adequate indemnity insurance covering independent prescribing
- Your CPD includes obesity medicine
- You have access to clinical supervision and escalation pathways
Clinical Disclaimer: This guide is designed to support clinical decision-making and does not replace individual clinical judgement. Always prescribe in accordance with the patient's individual clinical circumstances.