Saxenda and Hashimoto's thyroiditis can be used together, but careful medical supervision is essential. Saxenda (liraglutide 3.0 mg) is a GLP-1 receptor agonist licensed in the UK for weight management in adults with obesity or overweight with comorbidities. Hashimoto's thyroiditis, the most common cause of hypothyroidism in the UK, often makes weight loss challenging due to reduced metabolic rate. Whilst having Hashimoto's does not automatically prevent Saxenda use, patients require stable thyroid function on levothyroxine, regular monitoring of thyroid hormone levels, and awareness of potential thyroid-related adverse events. This article examines the safety considerations, monitoring requirements, and alternative options for weight management in patients with Hashimoto's disease.

Understanding Saxenda and Hashimoto's Thyroiditis

Saxenda (liraglutide 3.0 mg) is a prescription medication licensed in the UK for weight management in adults with obesity (BMI ≥30 kg/m²) or overweight (BMI ≥27 kg/m²) with weight-related comorbidities. It belongs to a class of medicines called glucagon-like peptide-1 (GLP-1) receptor agonists, which work by mimicking a naturally occurring hormone that regulates appetite and food intake. Saxenda is administered as a once-daily subcutaneous injection and is intended to be used alongside a reduced-calorie diet and increased physical activity.

The medication works by acting on receptors in the brain that control appetite, helping patients feel fuller for longer and reducing hunger signals. This mechanism can lead to a reduction in calorie intake and subsequent weight loss. According to NICE Technology Appraisal (TA664), liraglutide is recommended for use within specialist weight management services for appropriate patients. Treatment should be discontinued if at least 5% weight loss has not been achieved after 12 weeks on the 3 mg daily maintenance dose.

Hashimoto's thyroiditis, also known as chronic lymphocytic thyroiditis, is an autoimmune condition and the most common cause of hypothyroidism (underactive thyroid) in the UK. In this condition, the immune system mistakenly attacks the thyroid gland, gradually reducing its ability to produce thyroid hormones (primarily thyroxine, or T4, and triiodothyronine, or T3). These hormones are essential for regulating metabolism, energy levels, and numerous bodily functions.

Patients with Hashimoto's disease often experience symptoms including fatigue, weight gain, cold intolerance, constipation, dry skin, and depression. Weight management can be particularly challenging for individuals with Hashimoto's, as the reduced metabolic rate associated with hypothyroidism makes it more difficult to lose weight, even with diet and exercise. Many patients with well-controlled thyroid function on levothyroxine replacement therapy still struggle with weight, leading them to explore additional weight management options such as Saxenda.

Can You Use Saxenda If You Have Hashimoto's Disease?

Having Hashimoto's thyroiditis does not automatically prevent you from being prescribed Saxenda, provided your thyroid condition is appropriately managed with levothyroxine replacement therapy and your thyroid function tests are stable.

However, there are important considerations. The UK Summary of Product Characteristics (SmPC) for Saxenda notes that thyroid adverse events, including goitre, have been reported in clinical trials, particularly in patients with pre-existing thyroid disease. Therefore, caution is advised if you have Hashimoto's or other thyroid conditions. You should report any new or worsening neck symptoms such as lumps, difficulty swallowing, or hoarseness to your healthcare provider.

It's important to note that Saxenda should not be used during pregnancy or while breastfeeding. It should also not be used in combination with other GLP-1 receptor agonists, and co-administration with insulin is not recommended.

Before prescribing Saxenda to a patient with Hashimoto's, healthcare professionals will typically assess several factors:

• Thyroid function stability: Your TSH (thyroid-stimulating hormone) and thyroid hormone levels should be within the target range on a stable dose of levothyroxine.

• Overall health status: Assessment of other comorbidities, particularly cardiovascular disease, pancreatitis history, or gallbladder disease.

• BMI criteria: Confirmation that you meet the licensing criteria for Saxenda use.

• Realistic expectations: Understanding that weight loss may be more challenging in patients with thyroid conditions, even when optimally treated, though individual responses vary.

Your GP or endocrinologist should conduct a thorough medical history and examination before initiating Saxenda. If you have Hashimoto's disease and are considering Saxenda for weight management, it is essential to have an open discussion with your healthcare provider about the potential benefits and risks in your individual circumstances.

Potential Interactions Between Saxenda and Thyroid Function

There is no official pharmacological interaction between liraglutide (Saxenda) and levothyroxine, the standard replacement therapy for Hashimoto's thyroiditis. Saxenda does not directly affect thyroid hormone production, thyroid antibody levels, or the absorption of levothyroxine. The two medications work through entirely different mechanisms and are metabolised via separate pathways.

However, there are several indirect considerations worth noting. Saxenda slows gastric emptying as part of its mechanism of action, which theoretically could affect the absorption of oral medications, including levothyroxine. The Saxenda SmPC notes that this delayed gastric emptying may impact the absorption of concomitantly administered oral medicines. Levothyroxine is typically taken on an empty stomach, at least 30 minutes before food, to ensure optimal absorption. Patients should maintain consistent timing of their levothyroxine dose and report any symptoms suggestive of altered thyroid function.

Weight loss itself can influence thyroid hormone requirements. As patients lose weight, their metabolic demands may change, potentially requiring adjustment of levothyroxine dosage. Some patients may need a reduction in their thyroid hormone replacement as they lose weight, whilst others may require no change. This is not specific to Saxenda but applies to any significant weight loss.

Regular monitoring of thyroid function is advisable when starting Saxenda in patients with Hashimoto's disease. NICE guidance (NG145) on thyroid disease management recommends checking TSH levels:

• Every 3 months when adjusting levothyroxine doses

• Annually once stable on a consistent dose

• When symptoms suggest under- or over-replacement

For patients with Hashimoto's starting Saxenda, it would be prudent to check thyroid function tests approximately 8–12 weeks after initiating treatment and then as clinically indicated. This allows healthcare professionals to identify any need for levothyroxine dose adjustment and ensures thyroid function remains optimised during the weight loss process.

If you are also taking warfarin or other coumarin anticoagulants, more frequent INR monitoring is recommended when starting liraglutide, as noted in the SmPC.

Safety Considerations and Monitoring Requirements

When using Saxenda in patients with Hashimoto's thyroiditis, several safety considerations and monitoring protocols should be implemented to ensure optimal outcomes and minimise potential risks.

Gastrointestinal adverse effects are the most commonly reported side effects with Saxenda, affecting a significant proportion of users. These include:

• Nausea (very common, affecting more than 1 in 10 people)

• Diarrhoea and constipation

• Vomiting

• Abdominal pain and dyspepsia

These effects are usually mild to moderate and tend to diminish over time. The dose escalation schedule for Saxenda is designed to minimise these symptoms. Patients with Hashimoto's may already experience gastrointestinal symptoms related to their thyroid condition, so distinguishing between thyroid-related and medication-related symptoms is important.

Gallbladder disease is an important risk with Saxenda. The medication can increase the risk of gallstones and related complications such as cholecystitis. Patients should seek urgent medical attention if they experience severe right upper abdominal pain, fever, or yellowing of the skin or eyes (jaundice).

Pancreatitis is a rare but serious potential adverse effect of GLP-1 receptor agonists. Patients should be counselled to seek immediate medical attention if they experience severe, persistent abdominal pain, which may radiate to the back and be accompanied by vomiting. Saxenda should be discontinued if pancreatitis is suspected.

For patients with diabetes, Saxenda may increase the risk of hypoglycaemia, particularly if used with sulfonylureas or insulin. Blood glucose monitoring is essential, and dose adjustments of diabetes medications may be necessary.

Key monitoring parameters for patients with Hashimoto's using Saxenda include:

• Thyroid function tests (TSH, free T4) at baseline, 8–12 weeks after starting, and then as clinically indicated

• Weight and BMI at each follow-up appointment to assess if the 5% weight loss target is achieved after 12 weeks at the 3 mg dose

• Blood pressure and pulse regularly

• Blood glucose if diabetic or pre-diabetic

• Symptoms review for both thyroid-related and medication-related adverse effects

When to contact your GP or seek medical attention:

• Severe or persistent abdominal pain

• Right upper abdominal pain, fever or jaundice (gallbladder issues)

• Signs of thyroid dysfunction (significant fatigue changes, palpitations, temperature intolerance)

• New or worsening neck symptoms (lumps, difficulty swallowing, hoarseness)

• Symptoms of dehydration from vomiting or diarrhoea

• Unexplained weight loss exceeding expected rates

• Signs of allergic reaction (rash, difficulty breathing, swelling)

Patients should report any suspected side effects via the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk).

Alternative Weight Management Options for Hashimoto's Patients

For patients with Hashimoto's thyroiditis who are unable to use Saxenda, prefer not to use injectable medications, or do not achieve adequate results, several alternative weight management strategies are available.

Optimising thyroid hormone replacement is the foundational step. Ensuring TSH levels are within the laboratory reference range, as recommended by NICE guidance (NG145), can help support metabolic function. Treatment should be individualised based on symptoms and response. Some patients may benefit from assessment by an endocrinologist if standard levothyroxine therapy does not adequately control symptoms, though combination T4/T3 therapy remains controversial and is not routinely recommended by NICE.

Structured lifestyle interventions remain the cornerstone of weight management. NICE recommends multicomponent interventions including:

• Dietary modification: A balanced, reduced-calorie diet (typically 600 kcal/day deficit) with emphasis on whole foods, adequate protein, and fibre. Some patients with Hashimoto's report benefits from reducing gluten or dairy, though there is limited scientific evidence for these dietary modifications specifically for weight loss in thyroid disease. Such elimination diets should only be undertaken with appropriate clinical guidance, particularly if coeliac disease or lactose intolerance is suspected.

• Physical activity: At least 150 minutes of moderate-intensity activity weekly, with resistance training to preserve muscle mass during weight loss. Patients with Hashimoto's may need to start gradually and build up activity levels.

• Behavioural support: Cognitive behavioural approaches, goal-setting, self-monitoring, and addressing emotional eating patterns.

Pharmacological alternatives to Saxenda include:

• Orlistat: A lipase inhibitor that reduces fat absorption, available on prescription or over-the-counter. It requires adherence to a low-fat diet and may cause gastrointestinal side effects.

• Wegovy (semaglutide 2.4 mg): Another GLP-1 receptor agonist, approved in the UK for weight management. NICE Technology Appraisal (TA875) recommends its use within specialist weight management services, subject to specific criteria and current supply constraints.

Specialist weight management services may be appropriate for patients with complex needs. These multidisciplinary services, often available through NHS referral, provide intensive support including dietetic input, psychological support, and medical management. NICE guidance (CG189) provides detailed criteria for referral to specialist services.

Bariatric surgery may be considered for patients meeting specific criteria as outlined in NICE guidance (typically BMI ≥40 kg/m² or ≥35 kg/m² with comorbidities) who have not achieved adequate weight loss with non-surgical interventions. Hashimoto's disease is not a contraindication to bariatric surgery, though thyroid function should be optimised pre-operatively.

Ultimately, the most effective approach is individualised, taking into account the patient's preferences, comorbidities, previous weight loss attempts, and the degree of thyroid function optimisation. Regular follow-up and adjustment of the management plan based on response and tolerability are essential for long-term success.

Frequently Asked Questions