Saxenda and Belviq together is a question that has become largely academic, as Belviq (lorcaserin) was withdrawn from global markets in 2020 due to safety concerns and was never licensed in the UK. Saxenda (liraglutide), a GLP-1 receptor agonist, remains available for weight management under medical supervision. Combining prescription weight loss medications without robust clinical evidence poses significant safety risks, including additive side effects and unpredictable interactions. The Saxenda Summary of Product Characteristics explicitly advises against concurrent use with other weight-loss products. This article examines why such combinations are discouraged, the mechanisms of these medications, and evidence-based alternatives available through the NHS.

Can You Take Saxenda and Belviq Together?

The question of whether Saxenda (liraglutide) and Belviq (lorcaserin) can be taken together is now largely academic, as Belviq has been withdrawn from the market worldwide, including in the UK where it was never licensed. However, understanding the principles behind combining weight loss medications remains important for patient safety and informed decision-making.

Historically, there was no official guidance supporting the concurrent use of these two medications. Combining prescription weight loss drugs typically requires careful medical supervision due to the potential for additive side effects, unpredictable drug interactions, and increased cardiovascular or metabolic risks. Both Saxenda and Belviq work through different mechanisms, which theoretically could offer complementary effects, but this combination was never studied in clinical trials or approved by regulatory authorities such as the MHRA (Medicines and Healthcare products Regulatory Agency) or FDA.

Importantly, the Saxenda Summary of Product Characteristics (SmPC) specifically advises against using it with other weight-loss products and states it must not be used with other GLP-1 receptor agonists. This reflects the lack of safety data for such combinations.

Clinical practice generally discourages combining weight loss medications unless there is robust evidence of safety and efficacy. The lack of data on this specific combination meant that prescribers would have been unable to counsel patients adequately on risks or benefits. Furthermore, polypharmacy in weight management increases the complexity of monitoring for adverse effects and may complicate the identification of which medication is responsible for any problems that arise.

Patients should never combine prescription weight loss medications without explicit guidance from their prescribing clinician, and should never attempt to source withdrawn medications like lorcaserin through unregulated online channels, which is both unsafe and illegal in the UK. If you are currently taking Saxenda or considering weight loss treatment, discuss all options with your GP or specialist weight management service to ensure a safe, evidence-based approach tailored to your individual health needs.

How Saxenda and Belviq Work for Weight Loss

Understanding the distinct mechanisms of action of these medications helps explain why their combination was theoretically considered, though never validated.

Saxenda (liraglutide 3.0 mg) is a glucagon-like peptide-1 (GLP-1) receptor agonist administered via daily subcutaneous injection. It mimics the action of the naturally occurring hormone GLP-1, which is released from the gut in response to food intake. Liraglutide works by:

• Slowing gastric emptying, which prolongs the feeling of fullness after meals

• Acting on appetite centres in the hypothalamus, reducing hunger and food cravings

• Improving glycaemic control through enhanced insulin secretion and reduced glucagon release

• Promoting weight loss of approximately 8% of body weight at 56 weeks (compared to 2.6% with placebo) when combined with lifestyle modification, based on clinical trial data

Saxenda is licensed in the UK for weight management in adults with a BMI of 30 kg/m² or greater, or 27 kg/m² or greater in the presence of weight-related comorbidities such as type 2 diabetes, prediabetes, hypertension, dyslipidaemia or obstructive sleep apnoea.

Important safety information: Patients taking Saxenda should seek urgent medical attention if they experience severe, persistent abdominal pain, with or without vomiting, as this may indicate pancreatitis or gallbladder disease—rare but serious potential side effects.

Belviq (lorcaserin), by contrast, was a selective serotonin 2C (5-HT2C) receptor agonist taken orally. It worked by:

• Activating specific serotonin receptors in the brain's appetite control centres

• Promoting satiety and reducing food intake through central nervous system pathways

• Potentially reducing cravings for high-calorie foods

The different mechanisms—peripheral and central GLP-1 effects versus selective serotonergic modulation—suggested potential complementary action. However, no clinical trials ever evaluated this combination, and the theoretical benefits remained unproven. The withdrawal of Belviq due to safety concerns has rendered this question moot for clinical practice.

Safety Concerns When Combining Weight Loss Medications

Combining pharmacological agents for weight loss raises several important safety considerations that extend beyond the specific case of Saxenda and Belviq.

Additive adverse effects represent a primary concern. Saxenda commonly causes gastrointestinal side effects including nausea (occurring in approximately 40% of patients), vomiting, diarrhoea, and constipation. Belviq was associated with headache, dizziness, fatigue, and nausea. When medications with overlapping side effect profiles are combined, patients may experience more severe or prolonged symptoms that could affect adherence and quality of life.

Cardiovascular safety is paramount in weight loss medication use. Saxenda carries warnings regarding increased heart rate (typically 2-3 beats per minute elevation). While cardiovascular outcome trials have been conducted for GLP-1 receptor agonists, including liraglutide 1.8 mg (LEADER trial) in type 2 diabetes, Saxenda 3.0 mg itself does not have a dedicated cardiovascular outcome trial. Belviq's withdrawal was specifically due to an increased risk of cancer identified in long-term safety data, but cardiovascular effects were also monitored closely during its availability. Combining medications without understanding their interactive cardiovascular effects could potentially increase risk.

Serious adverse events that require immediate medical attention include:

• Symptoms of pancreatitis or gallbladder disease: severe, persistent abdominal pain, sometimes radiating to the back, with or without vomiting

• Severe, persistent vomiting leading to dehydration

• Signs of allergic reactions including difficulty breathing, swelling, or rash

Serotonin syndrome, though rare, represents a theoretical risk when combining medications affecting serotonergic pathways. Whilst Saxenda does not directly affect serotonin, patients taking multiple medications—including antidepressants, migraine treatments, or other agents—alongside a serotonergic weight loss drug like Belviq could face increased risk.

Monitoring challenges multiply with polypharmacy. Clinicians must track, as clinically indicated:

• Blood pressure and heart rate changes

• Weight response to treatment

• Glycaemic control (particularly in diabetic patients)

• Symptoms of potential adverse effects

• Gastrointestinal tolerance

NICE guidance on obesity management emphasises that pharmacological treatment should only be prescribed as part of a comprehensive weight management programme, with regular review of efficacy and tolerability. Combining medications outside of licensed indications or clinical trial settings contravenes this evidence-based approach and potentially exposes patients to unquantified risks.

If you experience side effects from any medication, report them through the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk).

Belviq Withdrawal from the UK and Global Markets

Belviq (lorcaserin) was voluntarily withdrawn from the US market in February 2020 following a request from the FDA based on safety data from the CAMELLIA-TIMI 61 cardiovascular outcomes trial. This large post-marketing study, which followed over 12,000 patients for a median of approximately 3.3 years, identified a statistically significant increase in cancer diagnoses among patients taking lorcaserin compared to placebo.

The types of cancer showing increased incidence included:

• Pancreatic cancer

• Colorectal cancer

• Lung cancer

Whilst the absolute increase in risk was modest, the FDA concluded that the risks outweighed the benefits, particularly given the availability of alternative weight loss treatments. The manufacturer, Eisai Inc., subsequently withdrew the medication globally.

In the UK, Belviq was never granted marketing authorisation by the MHRA or the European Medicines Agency (EMA). This means it was not legally available for prescription through the NHS or private healthcare providers in the UK. The EMA had previously declined approval due to concerns about the benefit-risk profile, including questions about long-term safety and the magnitude of weight loss achieved in clinical trials.

The withdrawal of Belviq highlights the importance of long-term safety monitoring for weight loss medications, which are typically intended for extended use in chronic weight management. Post-authorisation safety studies and long-term monitoring are usually required for obesity medicines; some also have dedicated cardiovascular outcome data.

For patients who may have obtained lorcaserin through international sources or online pharmacies, the withdrawal serves as a reminder of the risks associated with using medications outside of regulated healthcare systems. Anyone who has previously used Belviq should inform their GP, particularly if they have concerns about cancer screening or ongoing symptoms. It is important to note that the increased cancer risk was identified through large-scale epidemiological data, and individual risk remains low.

Never attempt to source withdrawn medications like lorcaserin through unregulated online channels. This practice is both unsafe and potentially illegal in the UK.

Alternative Weight Loss Options Available in the UK

The UK offers several evidence-based weight management options, both pharmacological and non-pharmacological, that are safer and better studied than experimental drug combinations.

Licensed pharmacological treatments currently available in the UK include:

• Orlistat (Xenical, Alli): A lipase inhibitor that reduces dietary fat absorption by approximately 30%. Available over-the-counter (for BMI ≥28 kg/m²) at lower doses and on prescription (for BMI ≥30 kg/m² or ≥28 kg/m² with risk factors) at higher doses. Common side effects include gastrointestinal symptoms, particularly with high-fat meals.

• Saxenda (liraglutide 3.0 mg): As discussed, this GLP-1 receptor agonist is administered daily by injection and is suitable for patients with BMI ≥30 kg/m² or ≥27 kg/m² with comorbidities.

• Wegovy (semaglutide 2.4 mg): A newer, once-weekly GLP-1 receptor agonist that has shown significant weight loss in clinical trials, with average weight loss of around 15% at 68 weeks in the STEP clinical trial programme. NICE recommends its use within specialist weight management services, with treatment reviewed after 2 years. Availability in the UK has been limited due to supply constraints.

NICE recommends a tiered approach to weight management:

Tier 1: Lifestyle modification including dietary changes, increased physical activity, and behavioural support. This remains the foundation of all weight management strategies.

Tier 2: Structured weight management programmes, often delivered through NHS services or commercial providers, combining dietary advice, physical activity plans, and psychological support.

Tier 3: Specialist weight management services for patients with complex needs, including those with BMI ≥40 kg/m² or ≥35 kg/m² with comorbidities. These multidisciplinary services may include dietitians, psychologists, and specialist physicians.

Tier 4: Bariatric surgery (such as gastric bypass or sleeve gastrectomy) for patients meeting specific criteria, typically BMI ≥40 kg/m² or ≥35 kg/m² with obesity-related conditions.

Tirzepatide (Mounjaro) has recently received MHRA authorisation for weight management in the UK and has shown substantial weight loss in clinical trials. Check with your healthcare provider regarding current availability and NICE guidance.

Important safety information: Weight loss medications are generally contraindicated during pregnancy and breastfeeding. Women of childbearing potential should use effective contraception while taking these medications and should stop treatment if pregnancy occurs.

When to contact your GP:

• If you are struggling with weight management despite lifestyle changes

• If you have a BMI ≥30 kg/m² or ≥27 kg/m² with weight-related health conditions

• If you are experiencing side effects from current weight loss medications

• If you have previously used unlicensed weight loss medications and have health concerns

• If you are considering weight loss surgery

Your GP can assess your suitability for different treatments, provide referrals to specialist services where appropriate, and ensure that any weight management approach is safe and tailored to your individual circumstances. Never combine prescription medications or use unlicensed treatments without medical supervision, as the risks may outweigh any potential benefits.

If you experience side effects from any medication, report them through the MHRA Yellow Card scheme (yellowcard.mhra.gov.uk).

Frequently Asked Questions