Mounjaro (tirzepatide) is a once-weekly injectable medication licensed in the UK for treating type 2 diabetes in adults. As a dual GIP and GLP-1 receptor agonist, it helps regulate blood glucose levels and often leads to weight loss. Whilst Mounjaro can cause various side effects—predominantly gastrointestinal symptoms such as nausea, vomiting, and diarrhoea—there is currently no established link between this medication and swollen lymph nodes. Understanding the known adverse effects of Mounjaro and recognising when lymphadenopathy requires medical assessment helps patients make informed decisions about their diabetes management and overall health.
Quick Answer: There is no established causal link between Mounjaro (tirzepatide) and swollen lymph nodes based on current UK product information and clinical trial evidence.
Mounjaro (tirzepatide) is a prescription medicine licensed in the UK for the treatment of type 2 diabetes mellitus in adults. It belongs to a novel class of medications known as dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonists. Mounjaro is administered as a once-weekly subcutaneous injection, typically into the abdomen, thigh, or upper arm.
The mechanism of action involves mimicking two naturally occurring incretin hormones that play crucial roles in glucose regulation. By activating both GIP and GLP-1 receptors, tirzepatide enhances insulin secretion when blood glucose levels are elevated, suppresses inappropriate glucagon release, and slows gastric emptying. These combined effects help improve glycaemic control in people with type 2 diabetes.
Tirzepatide appears to influence appetite regulation through central nervous system pathways, leading to reduced caloric intake and subsequent weight loss in many patients. Clinical trials have demonstrated significant reductions in HbA1c levels and body weight compared to placebo and other diabetes medications. The Medicines and Healthcare products Regulatory Agency (MHRA) approved Mounjaro in the UK based on evidence from the SURPASS clinical trial programme.
It is important to note that Mounjaro is not insulin and should not be used to treat type 1 diabetes or diabetic ketoacidosis. The medication requires careful dose titration, starting at 2.5 mg weekly and increasing by 2.5 mg at intervals of at least 4 weeks as tolerated, up to a maximum maintenance dose of 15 mg weekly.
Important safety information: Patients should stop taking Mounjaro and seek urgent medical attention if they experience severe abdominal pain (possibly radiating to the back) which could indicate acute pancreatitis. Other important warnings include monitoring for gallbladder disease (right upper abdominal pain, jaundice), maintaining adequate hydration to prevent acute kidney injury, awareness of potential worsening of diabetic retinopathy (especially with rapid improvement in blood glucose), and signs of serious hypersensitivity reactions. Mounjaro should not be used during pregnancy or breastfeeding, and women of childbearing potential should use contraception.
Patients should receive comprehensive education about injection technique, storage requirements, and the importance of adhering to their prescribed regimen alongside lifestyle modifications including diet and physical activity.
Mounjaro® is the most innovative GLP-1 medication proven to dramatically curb appetite, hunger, and cravings to help professional men achieve substantial weight loss.
Start Here
Wegovy® is a weekly injectable GLP-1 medication with proven effectiveness in reducing appetite, hunger, and cravings to help busy professionals lose significant weight.
Start HereLike all medicines, Mounjaro can cause side effects, although not everyone experiences them. The most frequently reported adverse effects are gastrointestinal in nature, reflecting the drug's mechanism of slowing gastric emptying and affecting gut motility. According to the Summary of Product Characteristics and clinical trial data, these include:
Nausea – often most pronounced during dose escalation
Diarrhoea – can range from mild to moderate severity
Vomiting – particularly in the initial weeks of treatment
Constipation – affecting a significant proportion of users
Abdominal pain or discomfort
Decreased appetite – which contributes to weight loss
Dyspepsia (indigestion)
These gastrointestinal symptoms typically diminish over time as the body adjusts to the medication. Starting at the lowest dose and following the recommended titration schedule helps minimise these effects.
Serious side effects requiring immediate medical attention include:
Symptoms of acute pancreatitis (severe abdominal pain, sometimes radiating to the back)
Signs of gallbladder problems (pain in the right upper abdomen, fever, yellowing of skin/eyes)
Severe vomiting or diarrhoea leading to dehydration
Sudden vision changes (which may indicate worsening diabetic retinopathy)
Signs of serious allergic reactions (breathing difficulties, swelling of face/throat, severe rash)
Other notable side effects include injection site reactions (redness, itching, or swelling at the injection site), fatigue, and hypoglycaemia, particularly when Mounjaro is used in combination with insulin or sulfonylureas. Dose adjustments of these medications may be needed when starting or increasing Mounjaro. Patients may also experience increased heart rate in some cases.
Regarding swollen lymph nodes specifically, there is no established causal link between Mounjaro and lymphadenopathy in the current evidence base. Swollen lymph nodes are not listed among the known side effects in the UK product information or major clinical trials. However, as with any medicine, rare side effects may be identified through post-marketing surveillance.
If you experience any side effects, including swollen lymph nodes, while taking Mounjaro, talk to your doctor or pharmacist. You can also report side effects directly via the Yellow Card Scheme at https://yellowcard.mhra.gov.uk/ or search for MHRA Yellow Card in the Google Play or Apple App Store. By reporting side effects, you can help provide more information on the safety of this medicine.
Swollen lymph nodes (lymphadenopathy) warrant medical assessment to determine the underlying cause and appropriate management. Whilst there is no official link between Mounjaro and lymph node swelling, patients taking this medication who develop this symptom should seek professional evaluation.
You should contact your GP or healthcare provider if you notice:
Lymph nodes that are persistently enlarged for more than two weeks
Nodes that continue to increase in size over time
Swelling accompanied by unexplained fever, night sweats, or unintentional weight loss
Lymph nodes that feel hard, fixed, or irregular rather than soft and mobile
Swelling in multiple areas of the body simultaneously
Associated symptoms such as persistent fatigue, skin changes, or difficulty breathing
Seek urgent medical attention (contact NHS 111 or attend A&E) if swollen lymph nodes are accompanied by severe symptoms such as difficulty swallowing or breathing, high fever with rigors, or signs of severe infection. Call 999 immediately if you experience severe breathing difficulty, throat swelling, or symptoms of anaphylaxis.
When you consult your healthcare provider, they will take a thorough history and perform a physical examination. According to NICE guidance (NG12: Suspected cancer: recognition and referral), the clinical assessment should include the location, size, consistency, and duration of lymphadenopathy, along with associated symptoms. Your doctor may arrange blood tests (including full blood count, inflammatory markers, and specific infection screens) or imaging studies if indicated.
It's worth noting that recent vaccinations can cause temporary swelling of lymph nodes in the area draining the injection site, particularly in the armpit after COVID-19 or flu vaccines. This typically resolves within 1-2 weeks.
For patients taking Mounjaro, it is essential to inform your doctor about all medications you are using. Keep a record of when the lymph node swelling began relative to starting or changing your Mounjaro dose. This temporal relationship, whilst unlikely to be causal, helps clinicians build a complete clinical picture and exclude other potential causes requiring specific treatment.
Lymph nodes are small, bean-shaped structures that form part of the immune system, filtering lymphatic fluid and housing immune cells. Lymphadenopathy has numerous potential causes, most of which are benign and self-limiting. Understanding these helps contextualise why swollen lymph nodes are unlikely to be related to Mounjaro.
Infections represent the most common cause of swollen lymph nodes:
Viral infections – including upper respiratory tract infections, influenza, infectious mononucleosis (glandular fever), and COVID-19
Bacterial infections – such as streptococcal throat infections, skin infections (cellulitis), or dental abscesses
Other infections – including toxoplasmosis, tuberculosis, or HIV (in specific contexts)
The lymph nodes typically swell in the region draining the infected area. For example, a throat infection commonly causes cervical (neck) lymphadenopathy.
Inflammatory and autoimmune conditions can also trigger lymph node enlargement, including rheumatoid arthritis, systemic lupus erythematosus (SLE), and sarcoidosis. These conditions involve immune system dysregulation leading to chronic inflammation.
Medications other than Mounjaro can occasionally cause lymphadenopathy as a side effect. These include certain anticonvulsants (such as phenytoin and carbamazepine), allopurinol, sulfonamide antibiotics, and other medications associated with drug reactions with eosinophilia and systemic symptoms (DRESS). Some vaccines may cause temporary regional lymph node swelling as part of the normal immune response.
Malignancies must be considered, particularly when lymphadenopathy is persistent, progressive, or accompanied by constitutional symptoms. These include lymphomas, leukaemias, or metastatic spread from solid tumours. However, cancer represents a minority of cases, especially in younger patients without other concerning features.
NICE guidance (CKS: Lymphadenopathy and NG12: Suspected cancer) recommends a systematic approach to investigating unexplained lymphadenopathy, with urgent referral (within two weeks) for suspected cancer when specific criteria are met. Most cases of swollen lymph nodes resolve spontaneously once the underlying trigger, typically an infection, has been addressed. Maintaining good glycaemic control reduces infection risk and supports overall health in people with diabetes.
The most common side effects of Mounjaro are gastrointestinal, including nausea, diarrhoea, vomiting, constipation, and abdominal discomfort. These symptoms typically diminish over time as the body adjusts to the medication, particularly when following the recommended dose titration schedule.
You should contact your GP if lymph nodes remain enlarged for more than two weeks, continue increasing in size, feel hard or fixed, or are accompanied by unexplained fever, night sweats, or unintentional weight loss. Seek urgent medical attention if swelling causes difficulty breathing or swallowing.
The most common cause of swollen lymph nodes is infection, including viral illnesses like colds, flu, and COVID-19, or bacterial infections such as throat or skin infections. Lymph nodes typically swell in the region draining the infected area and usually resolve once the infection clears.
All medical content on this blog is created based on reputable, evidence-based sources and reviewed regularly for accuracy and relevance. While we strive to keep content up to date with the latest research and clinical guidelines, it is intended for general informational purposes only.
DisclaimerThis content is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare professional with any medical questions or concerns. Use of the information is at your own risk, and we are not responsible for any consequences resulting from its use.
