New weight loss prescriptions are reshaping medical weight management in the UK, offering clinicians and patients more effective options than ever before. Medicines such as semaglutide (Wegovy) and tirzepatide (Mounjaro) have received MHRA approval and are generating considerable clinical interest alongside established treatments like liraglutide and orlistat. However, eligibility criteria, NHS commissioning rules, and important safety considerations mean these treatments are not suitable for everyone. This guide explains how the latest approved medicines work, who qualifies, what NICE recommends, and how to have an informed conversation with your GP or specialist.

New Weight Loss Prescriptions Available in the UK

MHRA-approved new weight loss prescriptions in the UK include semaglutide (Wegovy), tirzepatide (Mounjaro), liraglutide (Saxenda), and orlistat, though NHS funding depends on separate NICE and ICB commissioning decisions.

The landscape of medically supervised weight management has changed considerably in recent years. Several new weight loss prescriptions have received regulatory approval in the UK, offering clinicians and patients additional tools beyond lifestyle intervention alone. The Medicines and Healthcare products Regulatory Agency (MHRA) evaluates and approves medicines for use in Great Britain; the European Medicines Agency (EMA) retains a role for Northern Ireland under the Windsor Framework. Authoritative product information for UK-licensed medicines is available via the Electronic Medicines Compendium (EMC).

The most widely discussed newer agents are semaglutide (brand name Wegovy), a glucagon-like peptide-1 (GLP-1) receptor agonist approved by the MHRA for chronic weight management in adults, and tirzepatide (brand name Mounjaro), a dual glucose-dependent insulinotropic polypeptide (GIP) and GLP-1 receptor agonist that has also received UK approval for weight management in adults. Both are administered as once-weekly subcutaneous injections. Tirzepatide has generated significant clinical interest owing to its dual mechanism of action and the weight-loss outcomes observed in clinical trials.

Alongside these newer agents, liraglutide (Saxenda, 3.0 mg once daily) remains available as a once-daily injectable option. Orlistat continues to be prescribed as an oral medication; it is available on prescription at 120 mg (Xenical) and over the counter at 60 mg (alli) for adults with a BMI of 28 kg/m² or above (OTC) or 30 kg/m² or above on prescription, with lower thresholds applying where weight-related comorbidities are present.

It is important to note that MHRA licensing and NHS commissioning are distinct. A medicine may hold a UK marketing authorisation yet not be routinely funded by all integrated care boards (ICBs). Understanding what is available — and through which route — is an essential first step for anyone considering medical weight management.

How These Medications Work and Who They Are For

GLP-1 receptor agonists reduce appetite by mimicking gut hormones, while orlistat blocks dietary fat absorption; both are licensed for adults with a BMI of 30 kg/m² or above, or 27 kg/m² or above with a weight-related comorbidity.

GLP-1 receptor agonists work by mimicking the action of the naturally occurring hormone glucagon-like peptide-1, which is released from the gut in response to food. These medicines stimulate insulin secretion in a glucose-dependent manner, suppress glucagon release, slow gastric emptying, and act on appetite-regulating centres in the brain to reduce hunger and increase feelings of fullness. Tirzepatide additionally activates GIP receptors, which may further enhance metabolic effects and weight reduction.

Orlistat works through an entirely different mechanism: it inhibits pancreatic lipase in the gastrointestinal tract, reducing the absorption of dietary fat by approximately 30%. It is taken orally with meals and requires adherence to a reduced-fat diet to minimise gastrointestinal side effects.

These medicines are intended for adults who meet specific clinical thresholds. They are not suitable for everyone seeking to lose weight and are designed to be used alongside dietary changes, increased physical activity, and behavioural support — not as a standalone solution. Broadly, MHRA-licensed indications include:

• Adults with a BMI of 30 kg/m² or above (obesity)

• Adults with a BMI of 27–30 kg/m² who also have at least one weight-related comorbidity, such as type 2 diabetes, hypertension, or obstructive sleep apnoea

NHS commissioning criteria (set by NICE and local ICBs) are generally more restrictive than the licensed indications — see the NICE Guidelines section below for detail.

Paediatric use: Licensing is product-specific. Liraglutide (Saxenda) holds a UK licence for weight management in adolescents aged 12 years and over who meet defined criteria; semaglutide (Wegovy) and tirzepatide (Mounjaro) are not currently licensed for use in under-18s for weight management. Any use in children or adolescents should occur only within specialist paediatric services. All three injectable agents are contraindicated in pregnancy and breastfeeding (see below).

Key contraindications and cautions (per UK SmPCs):

• GLP-1 receptor agonists are contraindicated in pregnancy and must not be used during breastfeeding.

• They should be used with caution — or avoided — in individuals with a history of pancreatitis or severe gastrointestinal disease such as gastroparesis, as these conditions may be exacerbated.

• UK SmPCs for GLP-1 receptor agonists note that rodent studies identified C-cell tumours at supratherapeutic exposures; the relevance to humans is currently unknown. This is a precautionary note, not an established contraindication in UK practice — clinicians should refer to the current EMC SmPC for each product for the most up-to-date warnings.

• Tirzepatide may reduce the systemic exposure of oral contraceptives, particularly during initiation and dose escalation. Women using oral contraceptives should be advised to use an additional barrier method of contraception for at least four weeks after starting tirzepatide and for four weeks after each dose increase, in line with Faculty of Sexual and Reproductive Healthcare (FSRH) guidance.

• All GLP-1 receptor agonists and tirzepatide are contraindicated in pregnancy. Women of childbearing potential should use effective contraception during treatment. Semaglutide should be stopped at least two months before a planned pregnancy; tirzepatide should be stopped at least one month before planned conception. Patients should discuss pregnancy planning with their prescriber.

• Orlistat is contraindicated in pregnancy and chronic malabsorption syndromes.

NHS and Private Prescribing: What to Expect

NHS access typically requires referral to a Tier 3 or Tier 4 specialist weight management service; private prescribing is available but patients must verify CQC and prescriber registration to avoid unregulated or counterfeit products.

Access to new weight loss prescriptions in the UK varies considerably depending on whether treatment is sought through the NHS or via private healthcare. On the NHS, prescribing is governed by NICE technology appraisals and local ICB commissioning decisions. As a result, availability can differ between regions, and some patients may find that a nationally approved medicine is not yet funded locally.

Through the NHS, weight management medicines are typically initiated within Tier 3 or Tier 4 specialist weight management services — multidisciplinary teams providing intensive dietary, psychological, and medical support — rather than in routine GP consultations. Referral pathways usually require documented evidence of lifestyle intervention and confirmation of eligibility criteria. Waiting times for specialist services can be lengthy in some areas. Some ICBs offer self-referral routes; your GP surgery or ICB website can advise on local options.

Private prescribing has expanded rapidly, with a growing number of online clinics and independent prescribers offering GLP-1 medicines. Whilst this can improve access, it also raises important safety considerations. The MHRA has issued safety alerts warning patients about the risks of purchasing weight loss injections from unregulated sources, including counterfeit products (for example, counterfeit Ozempic pens have been identified in the UK supply chain). Patients should ensure that any private provider is registered with the Care Quality Commission (CQC) and that the prescriber holds current registration with the General Medical Council (GMC), Nursing and Midwifery Council (NMC), or General Pharmaceutical Council (GPhC) as appropriate. A full medical assessment — including review of contraindications, current medications, and relevant comorbidities — must be completed before any prescription is issued.

Cost is a significant factor in private treatment. Monthly costs for injectable GLP-1 medicines are indicative only, vary widely between providers, and change over time; patients should obtain current pricing directly from their chosen provider. Treatment is typically long-term, and discontinuation is associated with weight regain in many cases. Patients should factor ongoing costs into their decision-making.

Potential Side Effects and Safety Considerations

The most common side effects of GLP-1 agents are gastrointestinal, including nausea and vomiting; serious risks include acute pancreatitis, gallbladder disease, dehydration-related acute kidney injury, and hypoglycaemia in patients on antidiabetic medicines.

As with all prescription medicines, new weight loss prescriptions carry a risk of side effects, and patients should be fully informed before commencing treatment. The most commonly reported adverse effects with GLP-1 receptor agonists and tirzepatide are gastrointestinal in nature and include:

• Nausea (very common, particularly during dose escalation)

• Vomiting

• Diarrhoea or constipation

• Abdominal discomfort or bloating

These effects are generally dose-dependent and tend to improve over time as the body adjusts. Gradual dose escalation — as recommended in prescribing guidelines — helps to minimise their severity. Eating smaller, lower-fat meals and staying well hydrated can also help.

Dehydration and acute kidney injury (AKI): Persistent vomiting or diarrhoea can lead to dehydration and, in some cases, acute kidney injury. Patients should seek urgent medical assessment if they are unable to keep fluids down, notice a significant reduction in urine output, or feel faint or confused.

Acute pancreatitis: This has been reported in association with GLP-1 receptor agonists. Patients should seek urgent medical attention if they develop severe, persistent abdominal pain, particularly if it radiates to the back.

Gallbladder disease: An association with gallstones and cholecystitis has been observed, particularly with rapid weight loss. Patients should report persistent right upper abdominal pain, jaundice, or fever to their prescriber.

Diabetic retinopathy: Rapid improvement in blood glucose control — which can occur when GLP-1 receptor agonists are used in people with diabetes — has been associated with worsening of diabetic retinopathy in some patients. People with pre-existing diabetic retinopathy should discuss this risk with their prescriber and seek prompt review if they notice any change in their vision.

Orlistat-specific effects: The primary side effects relate to fat malabsorption: oily or fatty stools, faecal urgency, and flatulence are common, especially if dietary fat intake is not reduced. Orlistat can impair absorption of fat-soluble vitamins (A, D, E, and K); a multivitamin supplement is advisable, taken at bedtime or at least two hours after the orlistat dose. Rare cases of severe liver injury have been reported with orlistat; patients should seek medical advice promptly if they develop jaundice, dark urine, itching, or right upper abdominal pain. Important interactions with orlistat include: warfarin (monitor INR closely), ciclosporin (take ciclosporin at least three hours after orlistat), levothyroxine (separate doses by several hours; monitor thyroid function), and antiepileptic medicines (monitor for loss of seizure control).

Hypoglycaemia: Patients taking medicines for type 2 diabetes, particularly sulfonylureas or insulin, should be monitored carefully, as weight loss and the pharmacological effects of GLP-1 agents may increase the risk of hypoglycaemia. Dose adjustments to antidiabetic medicines may be required.

Any concerns about side effects should be reported to a prescriber promptly. Suspected adverse drug reactions can be reported directly to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk — this applies to patients, carers, and healthcare professionals alike.

NICE Guidelines and Eligibility Criteria

NICE TA875 recommends semaglutide and TA1026 recommends tirzepatide for adults with a BMI of 35 kg/m² or above plus at least one comorbidity, delivered within a specialist multidisciplinary weight management service.

NICE has published specific guidance governing the use of newer weight loss medicines in England. Patients and clinicians should consult the NICE website directly for the most current recommendations, as guidance is periodically reviewed as new evidence emerges.

NICE technology appraisal TA875 (semaglutide 2.4 mg, Wegovy) recommends semaglutide as an option for managing overweight and obesity in adults when all of the following criteria are met:

• BMI of at least 35 kg/m² with at least one weight-related comorbidity (such as type 2 diabetes, hypertension, obstructive sleep apnoea, or cardiovascular disease), or a BMI of 30–34.9 kg/m² in specific circumstances defined within the appraisal (for example, recent-onset type 2 diabetes)

• Treatment is delivered as part of a specialist multidisciplinary weight management service (Tier 3 or equivalent)

• Use is recommended for a maximum of two years under current NHS commissioning arrangements

NICE technology appraisal TA1026 addresses tirzepatide (Mounjaro) for weight management, recommending it for adults with a BMI of 35 kg/m² or above alongside at least one weight-related comorbidity, again within a specialist service context. Patients and clinicians should verify the current criteria directly on the NICE website, as commissioning arrangements may be updated.

NICE technology appraisal TA664 covers liraglutide (Saxenda) for weight management in a defined population of adults with non-diabetic hyperglycaemia and high cardiovascular risk. Eligibility criteria are specific; clinicians should refer to the full appraisal.

NICE guidance for all agents emphasises that pharmacological treatment should complement — not replace — behavioural and dietary interventions.

Ethnicity and BMI thresholds: NICE guidance (including public health guidance PH46) and NHS advice recognise that people from Black, Asian, and minority ethnic backgrounds are at increased risk of obesity-related comorbidities at lower BMI values. For these groups, intervention thresholds may be reduced by approximately 2.5 kg/m² (for example, a threshold of 32.5 kg/m² rather than 35 kg/m²). Clinicians are encouraged to apply clinical judgement alongside BMI when assessing suitability.

Local ICB policies may impose additional criteria or restrictions beyond national NICE guidance, and commissioning decisions can vary between regions.

Talking to Your GP or Specialist About Your Options

Arrange a GP consultation to assess BMI, medical history, contraindications, and current medications before starting any weight loss prescription; urgent help should be sought for severe abdominal pain, signs of allergic reaction, or inability to keep fluids down.

If you are considering new weight loss prescriptions, the most appropriate first step is to arrange a consultation with your GP or a qualified healthcare professional. A thorough assessment will typically include a review of your current weight and BMI, medical history, existing medications, and any relevant comorbidities. This helps to establish whether you meet eligibility criteria and whether any contraindications are present.

It is helpful to come prepared to your appointment. Consider noting:

• Your weight history and any previous attempts at weight management

• Current medications, including over-the-counter products, supplements, and hormonal contraception

• Any relevant medical conditions, such as diabetes, cardiovascular disease, thyroid disorders, or a history of pancreatitis

• Pregnancy plans or breastfeeding status — all injectable weight management medicines are contraindicated in pregnancy and breastfeeding, and specific stop times before planned conception apply (see the section above)

• Your expectations and goals — clinically meaningful weight loss is typically defined as 5–10% of body weight, though greater losses are observed with newer agents in clinical trials

Your GP may refer you to a Tier 3 or Tier 4 specialist weight management service if you meet the criteria for NHS-funded treatment. Some services accept self-referrals; your GP or ICB website can advise on local pathways. If NHS access is limited locally, your GP can advise on alternative options and help you make an informed decision about private treatment.

If you are considering a private provider, check that the service is registered with the Care Quality Commission (CQC) and that your prescriber is registered with the GMC, NMC, or GPhC. Be cautious of online services that offer prescriptions without a thorough medical assessment, as these may not adequately screen for contraindications or monitor for adverse effects.

Weight management is a long-term endeavour, and medication is most effective when combined with sustained lifestyle changes. Your healthcare team can help you set realistic goals, monitor your progress, and adjust your treatment plan as needed.

When to seek urgent help: If you experience severe or persistent abdominal pain (which may indicate pancreatitis or a gallbladder problem), signs of a serious allergic reaction (such as swelling of the face, lips, or throat, or difficulty breathing), inability to keep fluids down, or a significant reduction in urine output, contact NHS 111 or seek emergency care via 999 or your nearest A&E as appropriate. Any change in vision should be reported promptly to your prescriber or optometrist. Suspected adverse reactions to any medicine can be reported to the MHRA via the Yellow Card scheme at yellowcard.mhra.gov.uk.

Frequently Asked Questions