Can You Take Saxenda with Fluoxetine? Safety & Guidance

Can you take Saxenda with fluoxetine? Many patients prescribed Saxenda (liraglutide) for weight management also take fluoxetine for depression or other mental health conditions. There is no absolute contraindication to using these medications together, and they can be co-prescribed under medical supervision. However, both affect appetite and gastrointestinal function through different mechanisms, requiring careful consideration of individual patient factors. The British National Formulary (BNF) documents no direct pharmacological interaction between liraglutide and fluoxetine, but the decision to combine them must always be made by your GP or prescribing clinician, who can assess your complete medical history and treatment goals.

Can You Take Saxenda with Fluoxetine?

Many patients prescribed Saxenda (liraglutide) for weight management are also taking fluoxetine (sometimes known by the brand name Prozac) for depression or other mental health conditions. A common question arises: can these two medications be taken together safely? The short answer is that there is no absolute contraindication to using Saxenda and fluoxetine concurrently, and these medications can be co-prescribed under medical supervision.

However, this does not mean the combination is without considerations. Both medications affect different systems in the body and can influence appetite, mood, and gastrointestinal function in distinct ways. Whilst there is no official pharmacological interaction documented between liraglutide and fluoxetine in major drug interaction databases such as the British National Formulary (BNF), individual patient factors must be carefully evaluated.

The decision to use both medications together should always be made by your GP or prescribing clinician, who can assess your complete medical history, current medications, and treatment goals. Self-medicating or combining prescription medications without professional guidance can lead to unforeseen complications, even when no direct drug interaction exists.

It's also important to note that Saxenda should not be used alongside other GLP-1 receptor agonists or other weight-loss medicines.

This article provides evidence-based information about how these medications work, potential considerations when using them together, and what you should discuss with your healthcare provider. It is intended for educational purposes and should not replace personalised medical advice from your GP or specialist.

How Saxenda and Fluoxetine Work in the Body

Saxenda (liraglutide) is a glucagon-like peptide-1 (GLP-1) receptor agonist licensed in the UK for weight management in adults with a body mass index (BMI) of 30 kg/m² or greater, or 27 kg/m² or greater with weight-related comorbidities, as an adjunct to a reduced-calorie diet and increased physical activity. It works by mimicking the action of GLP-1, a naturally occurring hormone that regulates appetite and food intake.

The medication acts on several levels: it slows gastric emptying (meaning food stays in the stomach longer, promoting feelings of fullness), reduces appetite through effects on brain centres that control hunger, and affects blood glucose levels. While Saxenda can lower blood glucose, this is not its licensed indication for weight management. Saxenda is administered as a once-daily subcutaneous injection, with doses gradually increased over several weeks to minimise gastrointestinal side effects. Common adverse effects include nausea, vomiting, diarrhoea, and constipation, particularly during the initial titration period.

Fluoxetine belongs to a class of antidepressants called selective serotonin reuptake inhibitors (SSRIs). It works by increasing the availability of serotonin in the brain by blocking its reabsorption (reuptake) into nerve cells. Serotonin is a neurotransmitter involved in regulating mood, anxiety, and emotional wellbeing.

Fluoxetine is prescribed for various conditions including major depressive disorder, obsessive-compulsive disorder (OCD), bulimia nervosa, and panic disorder. It typically takes 2–4 weeks to achieve therapeutic effects. Common side effects include nausea, headache, insomnia, drowsiness, and changes in appetite or weight. Interestingly, fluoxetine can cause either weight loss or weight gain in different individuals, though weight loss is more commonly observed initially.

Both medications affect appetite and gastrointestinal function, albeit through entirely different mechanisms—Saxenda through peripheral and central GLP-1 receptors, and fluoxetine through central serotonergic pathways.

Potential Interactions Between Saxenda and Fluoxetine

From a pharmacological perspective, there is no direct drug-drug interaction between liraglutide and fluoxetine according to the MHRA/EMC Summary of Product Characteristics (SmPC) for both medications. They are metabolised through different pathways: liraglutide is broken down by protein degradation (similar to endogenous peptides), whilst fluoxetine is metabolised primarily by the liver enzyme CYP2D6. Neither medication significantly affects the metabolism of the other.

However, indirect or additive effects warrant consideration. Both medications can cause gastrointestinal symptoms, particularly nausea. When used together, especially during the initial weeks of Saxenda titration, patients may experience more pronounced nausea or digestive discomfort. This is not a true interaction but rather an overlap of common side effects.

Another consideration involves appetite and weight changes. Saxenda is specifically designed to reduce appetite and promote weight loss, whilst fluoxetine can variably affect weight—some patients experience reduced appetite and weight loss, whilst others may gain weight over longer-term treatment. The combined effect on appetite regulation is difficult to predict and varies considerably between individuals.

Blood glucose effects should also be monitored, particularly in patients with type 2 diabetes. Saxenda improves glycaemic control, and whilst fluoxetine does not directly affect blood glucose, changes in eating patterns or weight can influence diabetes management. Patients taking diabetes medications alongside Saxenda and fluoxetine may require adjustments to their treatment regimen. In particular, the risk of hypoglycaemia increases when Saxenda is combined with insulin or sulfonylureas, and dose reductions of these medications may be necessary.

Patients taking warfarin or other coumarin anticoagulants should have their INR monitored more frequently when starting Saxenda, as limited experience suggests potential changes in anticoagulant effect.

SSRIs including fluoxetine can cause hyponatraemia (low sodium levels), particularly in older adults or those taking diuretics. This risk could potentially be exacerbated if dehydration occurs due to Saxenda-related gastrointestinal side effects such as vomiting or diarrhoea.

There is no evidence that combining these medications increases the risk of serious adverse events such as serotonin syndrome (a rare but serious condition associated with excessive serotonergic activity). Saxenda does not have serotonergic properties and therefore does not contribute to this risk.

Safety Considerations When Using Both Medications

When taking Saxenda and fluoxetine concurrently, several safety considerations should guide your treatment:

Gastrointestinal tolerability is often the primary concern. To minimise nausea and digestive upset:

• Follow the recommended Saxenda dose escalation schedule carefully—do not increase doses too quickly

• Take fluoxetine with food if nausea occurs (unless otherwise directed)

• Eat smaller, more frequent meals rather than large portions

• Stay well hydrated, particularly if experiencing vomiting or diarrhoea

• Contact your GP if gastrointestinal symptoms become severe or persistent

Mental health monitoring remains important. Whilst Saxenda does not directly affect mood, significant weight changes and dietary restrictions can impact mental wellbeing. Some patients experience mood improvements with weight loss, whilst others may find the process psychologically challenging. Maintain regular contact with your mental health provider and report any worsening of depression, anxiety, or emergence of suicidal thoughts immediately.

Hypoglycaemia awareness is crucial for patients with diabetes. Although Saxenda alone rarely causes low blood glucose, the combination of weight loss, dietary changes, and any concurrent diabetes medications may increase this risk. Learn to recognise symptoms of hypoglycaemia (shakiness, sweating, confusion, rapid heartbeat) and discuss blood glucose monitoring with your healthcare team.

Thyroid considerations: The Saxenda SmPC includes a special warning regarding thyroid C-cell tumours observed in animal studies. Whilst the relevance to humans remains uncertain, patients with a personal or family history of medullary thyroid carcinoma or Multiple Endocrine Neoplasia syndrome type 2 should discuss this risk with their healthcare provider before using Saxenda.

Gallbladder disease risk: Saxenda and weight loss in general can increase the risk of gallstones and gallbladder inflammation. Seek medical attention if you experience symptoms such as right upper abdominal pain, fever, or yellowing of the skin or eyes.

Heart rate increases: Saxenda can cause increases in resting heart rate. This should be monitored, particularly in patients with pre-existing cardiovascular conditions.

Renal considerations: Dehydration from gastrointestinal side effects can potentially lead to acute kidney injury. Maintain adequate hydration, especially if experiencing vomiting or diarrhoea.

Pancreatitis risk: Saxenda has been associated with acute pancreatitis in rare cases. If pancreatitis is suspected (severe, persistent abdominal pain, particularly if accompanied by vomiting), stop taking Saxenda and seek immediate medical attention.

If you experience any suspected side effects, report them to the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk).

What to Discuss with Your GP Before Starting Treatment

Before commencing treatment with both Saxenda and fluoxetine, or if you are already taking one and considering adding the other, have a comprehensive discussion with your GP covering the following areas:

Complete medication review: Provide a full list of all medications, including over-the-counter products, herbal supplements, and vitamins. Some medications may interact with either Saxenda or fluoxetine, even if the two do not interact with each other. For example, fluoxetine can interact with other medications metabolised by CYP2D6, and Saxenda may affect the absorption of oral medications due to delayed gastric emptying. Fluoxetine has a long half-life, meaning interactions may persist for up to 5 weeks after stopping the medication.

Fluoxetine can increase bleeding risk, particularly when combined with NSAIDs, aspirin, anticoagulants or antiplatelet drugs. Seek medical advice before combining these medications.

Medical history: Disclose any history of:

• Pancreatitis or gallbladder disease

• Thyroid disorders

• Kidney or liver impairment

• Eating disorders (particularly relevant given fluoxetine's use in bulimia nervosa)

• Bipolar disorder (SSRIs can trigger manic episodes in susceptible individuals)

• Bleeding disorders (fluoxetine can affect platelet function)

• Cardiovascular disease (relevant due to potential heart rate increases with Saxenda)

Treatment goals and expectations: Discuss realistic weight loss targets with Saxenda. According to the Saxenda SmPC, treatment should be discontinued if patients do not lose at least 5% of initial body weight after 12 weeks on the 3.0 mg/day dose. Clarify how weight management fits within your overall mental health treatment plan.

Monitoring plan: Establish a clear schedule for follow-up appointments to assess:

• Weight loss progress and tolerability of Saxenda

• Mental health status and effectiveness of fluoxetine

• Blood glucose levels (if diabetic)

• Blood pressure and heart rate

• Any adverse effects or concerns

Pregnancy planning: Both medications require careful consideration in pregnancy. Saxenda is not recommended during pregnancy and should be discontinued if pregnancy occurs. Fluoxetine use requires risk-benefit assessment. Discuss contraception and family planning if relevant.

Cost considerations: Saxenda is not routinely available on NHS prescription for weight management in all areas, as availability varies by local formulary and commissioning decisions. Private prescription costs can be substantial. Ensure you understand the financial commitment involved.

Your GP may also recommend referral to specialist services, such as a tier 3 weight management programme or mental health specialist, to optimise your treatment outcomes. Never start, stop, or adjust doses of either medication without professional guidance, as both require careful management to ensure safety and effectiveness.

Remember that Saxenda should not be used alongside other GLP-1 receptor agonists or other weight-loss medicines.

Scientific References

1. Saxenda 6 mg/mL solution for injection in pre-filled pen - Summary of Product Characteristics.
2. Fluoxetine 20mg Capsules - Summary of Product Characteristics.
3. Liraglutide for managing overweight and obesity (TA664).
4. Obesity - Treatment.
5. British National Formulary - Interactions A to Z.
6. Saxenda - European Public Assessment Report.

Frequently Asked Questions