Weight loss injections, particularly GLP-1 receptor agonists such as semaglutide (Wegovy) and liraglutide (Saxenda), are increasingly prescribed for weight management across the UK. Whilst back pain is not listed as a common side effect in the Summary of Product Characteristics for these medications, some patients report musculoskeletal discomfort during treatment. There is no established direct pharmacological link between GLP-1 receptor agonists and back pain; however, indirect factors such as rapid weight loss, postural changes, gastrointestinal side effects, and rare complications like gallbladder disease or pancreatitis may contribute to back discomfort. Understanding these potential mechanisms helps patients and healthcare professionals distinguish between expected treatment effects and symptoms requiring urgent medical evaluation.

Can Weight Loss Injections Cause Back Pain?

Weight loss injections, particularly glucagon-like peptide-1 (GLP-1) receptor agonists such as semaglutide (Wegovy) and liraglutide (Saxenda), have become increasingly prescribed for weight management in the UK. Back pain is not listed as a common adverse effect in the Summary of Product Characteristics (SmPC) for these medications, though some patients report experiencing musculoskeletal discomfort during treatment.

There is no established direct pharmacological link between GLP-1 receptor agonists and back pain. These medications work by mimicking the incretin hormone GLP-1, which regulates appetite and glucose metabolism. Their primary mechanism involves slowing gastric emptying, enhancing insulin secretion, and reducing glucagon release—none of which directly affect spinal structures or musculoskeletal tissues.

However, the relationship between weight loss injections and back pain is likely indirect and multifactorial. Clinical trials have documented gastrointestinal side effects (nausea, constipation, abdominal pain) in a significant proportion of patients, and these symptoms may occasionally manifest as referred pain to the back region. Additionally, weight loss can lead to postural changes and altered biomechanics, which may contribute to musculoskeletal discomfort.

Gallbladder disease, including gallstones (cholelithiasis), is a recognised risk with GLP-1 receptor agonists and can present with pain radiating to the back or right shoulder.

It is important to distinguish between back pain that may be coincidental, related to the weight loss process itself, or potentially indicative of more serious complications such as pancreatitis—a recognised adverse effect of GLP-1 receptor agonists. If you experience severe abdominal pain radiating to the back, particularly with nausea or vomiting, stop taking the medication immediately and seek urgent medical attention. Patients experiencing persistent or severe back pain whilst using weight loss injections should seek medical evaluation to determine the underlying cause.

Common Side Effects of Weight Loss Injections

GLP-1 receptor agonists are generally well-tolerated, but like all medications, they carry a recognised side effect profile. Understanding these common adverse effects helps patients and healthcare professionals distinguish between expected reactions and those requiring further investigation.

Gastrointestinal effects are the most frequently reported side effects, classified as 'very common' (affecting more than 1 in 10 people) in the SmPCs for both Wegovy and Saxenda. These include:

• Nausea and vomiting – typically most pronounced during dose escalation and often improving with continued use

• Diarrhoea or constipation – affecting bowel habit regularity

• Abdominal pain and discomfort – ranging from mild cramping to more significant discomfort

• Dyspepsia and gastro-oesophageal reflux – related to delayed gastric emptying

Injection site reactions are classified as 'common' (affecting up to 1 in 10 people) and may include redness, itching, bruising, or localised swelling at the subcutaneous injection site. These reactions are usually mild and self-limiting.

Other recognised side effects include:

• Fatigue and dizziness, particularly during the initial weeks of treatment

• Headache, classified as 'common' in product information

• Hypoglycaemia (low blood sugar), primarily a risk in patients also taking insulin or sulfonylureas; these medications may need dose adjustment

• Increased heart rate, typically a modest elevation

• Dehydration risk, especially with persistent vomiting or poor fluid intake, which can lead to acute kidney injury

According to MHRA guidance, rare but serious adverse effects include acute pancreatitis (inflammation of the pancreas), gallbladder disease including cholelithiasis (gallstones), and thyroid C-cell tumours (observed in rodent studies; relevance to humans is unknown). Patients should report any neck mass or persistent hoarseness to their healthcare provider.

The Medicines and Healthcare products Regulatory Agency (MHRA) continues to monitor the safety profile of these medications. Healthcare professionals and patients are encouraged to report suspected adverse reactions via the Yellow Card Scheme (yellowcard.mhra.gov.uk), and the overall benefit-risk profile remains favourable for appropriate patients.

Why Back Pain May Occur During Weight Loss Treatment

Whilst back pain is not a direct pharmacological effect of weight loss injections, several mechanisms may explain why patients experience musculoskeletal discomfort during treatment. Understanding these potential causes helps contextualise symptoms and guide appropriate management.

Rapid weight loss and postural adaptation represent a primary consideration. When patients lose significant weight with GLP-1 receptor agonists, the body's centre of gravity shifts, and the biomechanical load on the spine changes. The paraspinal muscles, which have adapted to supporting a heavier frame, must readjust to new postural demands. This adaptation period can result in muscular strain, particularly in the lumbar region. Some patients may also experience changes in the cushioning effect around joints and the spine during weight loss, though this mechanism is not well-established in research.

Referred pain from gastrointestinal side effects should be considered, particularly when back pain is accompanied by abdominal symptoms. Severe constipation, a recognised side effect of GLP-1 receptor agonists, can cause lower back discomfort. Similarly, gastric distension from delayed emptying may manifest as upper back or interscapular pain in some individuals.

Gallbladder disease is a recognised risk with GLP-1 receptor agonists and rapid weight loss. Gallstones (cholelithiasis) or inflammation of the gallbladder (cholecystitis) can present with pain in the right upper quadrant that may radiate to the back or right shoulder, often accompanied by nausea and sometimes fever or jaundice.

Pancreatitis has been reported in patients using GLP-1 receptor agonists. Acute pancreatitis characteristically presents with severe epigastric pain radiating to the back, often accompanied by nausea and vomiting. If these symptoms occur, the medication should be discontinued immediately and urgent medical assessment sought.

Musculoskeletal deconditioning may also play a role. Some patients experience reduced physical activity during the initial treatment phase due to gastrointestinal side effects or fatigue, leading to weakened core musculature and subsequent back pain. Conversely, patients who significantly increase physical activity as part of their weight loss programme may experience exercise-related musculoskeletal strain. Pre-existing spinal conditions may also become more apparent or symptomatic during the weight loss process, though this represents coincidental timing rather than causation.

When to Seek Medical Advice About Back Pain

Whilst mild, transient back pain during weight loss treatment may not require immediate medical attention, certain features warrant prompt evaluation to exclude serious underlying conditions. Patients and healthcare professionals should be alert to red flag symptoms that necessitate urgent assessment.

Seek immediate medical attention (contact 999 or attend A&E) if back pain is accompanied by:

• Severe, unrelenting abdominal pain radiating to the back, particularly if associated with nausea and vomiting—this may indicate acute pancreatitis. Stop taking the GLP-1 receptor agonist immediately.

• Pain in the right upper abdomen radiating to the back or right shoulder, especially with fever or yellowing of the skin/eyes (jaundice)—this may indicate gallbladder disease

• Fever, chills, or signs of systemic infection

• Sudden onset of bowel or bladder dysfunction, which may suggest cauda equina syndrome

• Progressive leg weakness or numbness, indicating potential neurological compromise

• Chest pain, breathlessness, or cardiovascular symptoms

Contact your GP or prescribing clinician within 24–48 hours if you experience:

• Back pain that persists beyond two weeks despite simple analgesia

• Pain that progressively worsens rather than improves

• Back pain accompanied by unexplained weight loss (beyond expected treatment effects), night sweats, or general malaise

• Significant functional impairment affecting daily activities

• New or worsening pain following a change in medication dosage

• Signs of dehydration (dark urine, dizziness, reduced urine output) with persistent vomiting

Routine review may be appropriate for mild, intermittent back pain that:

• Responds to over-the-counter analgesia and self-care measures

• Appears related to postural changes or increased physical activity

• Improves with rest and does not significantly impact quality of life

According to NICE guidance on low back pain (NG59), most episodes of non-specific back pain improve within six weeks with conservative management. However, in the context of weight loss injection use, maintaining a lower threshold for medical review is prudent given the potential for rare but serious complications. Healthcare professionals should conduct a thorough assessment including abdominal examination, review of gastrointestinal symptoms, and consideration of serum lipase testing (preferred over amylase) if pancreatitis is suspected. Liver function tests and ultrasound of the right upper quadrant may be appropriate if gallbladder disease is suspected.

Managing Side Effects While Using Weight Loss Injections

Effective side effect management enhances treatment adherence and optimises outcomes for patients using weight loss injections. A proactive, multifaceted approach addresses both the prevention and mitigation of adverse effects, including musculoskeletal discomfort.

Optimising medication administration forms the foundation of side effect management. Following the prescribed dose escalation schedule is crucial—GLP-1 receptor agonists are typically initiated at low doses and gradually increased. The titration period varies by product: approximately 16 weeks for semaglutide (Wegovy) and about 5 weeks for liraglutide (Saxenda), according to their respective SmPCs. This titration minimises gastrointestinal side effects and allows the body to adapt. Patients should inject at consistent times, rotate injection sites (abdomen, thigh, upper arm), and ensure proper subcutaneous technique to reduce injection site reactions.

Dietary modifications significantly impact tolerability:

• Consume smaller, more frequent meals rather than large portions

• Avoid high-fat, spicy, or heavily processed foods that may exacerbate nausea

• Maintain adequate hydration (1.5–2 litres daily for most people, though this may need adjustment for those with heart or kidney conditions)

• Increase dietary fibre gradually to support regular bowel movements

• Eat slowly and chew thoroughly, as gastric emptying is delayed

Physical activity and postural support help address musculoskeletal symptoms:

• Engage in regular, moderate exercise including core-strengthening activities

• Consider physiotherapy assessment if back pain persists

• Maintain good posture and ergonomic practices, particularly during sedentary activities

• Use appropriate footwear and consider orthotics if biomechanical changes are significant

• Incorporate stretching and flexibility exercises into daily routines

Pharmacological adjuncts may be appropriate for specific symptoms. For nausea, antiemetics may provide short-term relief but should be used under healthcare professional guidance. If considering domperidone, note that MHRA restrictions apply due to cardiac risks; it should be used at the lowest effective dose for the shortest possible duration. Constipation can be managed with osmotic laxatives (macrogol) or stimulant laxatives if needed. Simple analgesia (paracetamol, topical NSAIDs) may help with musculoskeletal discomfort. Oral NSAIDs should be used cautiously given potential gastrointestinal, cardiovascular, and renal risks, particularly in older adults or those with pre-existing conditions.

Regular monitoring and communication with healthcare providers ensures timely identification of concerning symptoms. Patients should maintain a symptom diary, attend scheduled follow-up appointments, and report persistent or worsening side effects. If side effects become intolerable despite optimisation strategies, dose reduction or treatment discontinuation may be necessary. The decision to continue, modify, or cease treatment should be made collaboratively between patient and prescriber, weighing individual benefits against adverse effects whilst considering alternative weight management strategies.

If you experience any suspected adverse reactions to weight loss injections, report them to the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk).

Frequently Asked Questions