Mounjaro (tirzepatide) is a prescription medicine licensed in the UK for treating type 2 diabetes and weight management in adults with obesity. It is not approved for rheumatoid arthritis (RA), a chronic autoimmune inflammatory condition affecting the joints. Whilst some individuals may have both RA and metabolic conditions requiring Mounjaro, the medication does not treat RA itself. This article clarifies the relationship between Mounjaro and rheumatoid arthritis, explains when the medicine might be prescribed alongside RA treatment, and outlines important safety considerations for patients managing both conditions.
Quick Answer: Mounjaro (tirzepatide) is not licensed or approved for treating rheumatoid arthritis and does not address the autoimmune mechanisms underlying RA.
Mounjaro (tirzepatide) is a prescription medicine licensed in the UK for the treatment of type 2 diabetes mellitus in adults, as an adjunct to diet and exercise, and for weight management in adults with obesity or overweight with weight-related comorbidities. It is administered as a once-weekly subcutaneous injection and belongs to a novel class of medications known as dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonists.
The mechanism of action of Mounjaro involves mimicking the effects of two naturally occurring incretin hormones. GLP-1 enhances insulin secretion in response to elevated blood glucose levels, suppresses glucagon release (which reduces hepatic glucose production), slows gastric emptying, and promotes satiety. GIP also stimulates insulin secretion and may influence fat metabolism and energy balance. By activating both pathways simultaneously, tirzepatide offers enhanced glycaemic control and significant weight reduction compared to single-receptor agonists.
Treatment with Mounjaro begins at 2.5 mg once weekly for 4 weeks, then increases in 2.5 mg increments (to 5 mg, 7.5 mg, etc.) at 4-week intervals as tolerated, up to a maximum of 15 mg weekly depending on indication and response.
Clinical trials (SURPASS and SURMOUNT programmes) have demonstrated that Mounjaro effectively lowers HbA1c levels and body weight. Common adverse effects include gastrointestinal symptoms such as nausea, vomiting, diarrhoea, and constipation, which are typically mild to moderate and tend to diminish over time. Serious but rare side effects include pancreatitis (treatment should be discontinued if suspected), gallbladder disease, hypoglycaemia (particularly when used with insulin or sulfonylureas), and potential worsening of diabetic retinopathy in patients with pre-existing disease.
Important safety considerations include risk of dehydration and acute kidney injury with severe gastrointestinal symptoms, caution in patients with severe gastrointestinal disease including gastroparesis, and reduced absorption of oral medications due to delayed gastric emptying (particularly relevant for oral contraceptives, which may require additional contraceptive measures).
Mounjaro is not recommended during pregnancy or breastfeeding.
It is important to note that Mounjaro is not licensed for the treatment of rheumatoid arthritis or any other inflammatory joint condition. Its therapeutic indications are strictly limited to metabolic disorders, specifically type 2 diabetes and obesity management, as approved by the Medicines and Healthcare products Regulatory Agency (MHRA).
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Start HereRheumatoid arthritis (RA) is a chronic autoimmune inflammatory disease characterised by symmetrical polyarthritis, systemic inflammation, and progressive joint damage. Standard treatment involves disease-modifying antirheumatic drugs (DMARDs) such as methotrexate, biologic agents (e.g., TNF inhibitors, IL-6 inhibitors), and targeted synthetic DMARDs (e.g., JAK inhibitors), as outlined in NICE guidelines (NG100).
Currently, there is no official link between Mounjaro and the treatment of rheumatoid arthritis. Tirzepatide has not been studied, approved, or recommended for managing RA or its symptoms. The drug's pharmacological action targets metabolic pathways related to glucose homeostasis and appetite regulation, which are distinct from the immunological mechanisms underlying rheumatoid arthritis.
Some emerging research has explored whether GLP-1 receptor agonists may have anti-inflammatory properties beyond their metabolic effects. Preclinical studies suggest potential modulation of inflammatory pathways, but robust clinical evidence in humans with RA is lacking. Any purported benefits remain speculative and are not supported by regulatory bodies or clinical guidelines.
It is important to emphasise that using Mounjaro for RA would constitute off-label use, which is not recommended outside of clinical trials. The UK product licence (SmPC) for tirzepatide does not include any indication for inflammatory arthritis.
Patients with rheumatoid arthritis who also have type 2 diabetes or obesity may be prescribed Mounjaro for these metabolic conditions. In such cases, the medication addresses the diabetes or weight management needs but does not directly treat the RA itself. It is essential that RA continues to be managed with appropriate disease-modifying therapies as recommended by a rheumatologist.
If you have rheumatoid arthritis and are considering or have been prescribed Mounjaro for another indication, discuss your full medical history and treatment plan with your healthcare team to ensure coordinated, safe, and effective care.
For individuals living with both rheumatoid arthritis and type 2 diabetes or obesity, managing multiple conditions simultaneously requires careful coordination between healthcare professionals. If Mounjaro has been prescribed for glycaemic control or weight management, it is important to continue your established RA treatment regimen without interruption.
Disease-modifying antirheumatic drugs (DMARDs) remain the cornerstone of RA management. Medications such as methotrexate, sulfasalazine, hydroxychloroquine, and biologic agents should be continued as prescribed by your rheumatologist. There is no evidence to suggest that Mounjaro interferes with the efficacy of these RA therapies, but be aware that tirzepatide's effect on gastric emptying may affect the absorption of oral medications. Medicines with a narrow therapeutic index may require additional monitoring.
If you are taking corticosteroids (e.g., prednisolone) for RA, be aware that these can raise blood glucose levels. Your diabetes treatment may need adjustment, so regular glucose monitoring is important when starting or changing steroid doses.
Monitoring and follow-up are essential. Regular blood tests to monitor inflammatory markers (e.g., CRP, ESR), liver and kidney function, and disease activity scores should continue as part of your RA care. Similarly, if you are taking Mounjaro, your GP or diabetes specialist will monitor your HbA1c, weight, and any adverse effects related to the medication. If you have pre-existing diabetic retinopathy, regular eye examinations are particularly important as rapid improvement in glucose control may temporarily worsen retinopathy.
Lifestyle modifications can benefit both conditions. Maintaining a healthy weight reduces mechanical stress on inflamed joints and improves metabolic health. A balanced diet, regular physical activity tailored to your joint capabilities, and smoking cessation (if applicable) are all important. Mounjaro's weight-reducing effects may indirectly ease joint burden, though this is not a substitute for RA-specific treatment.
Gastrointestinal side effects from Mounjaro, such as nausea or diarrhoea, may affect your ability to take oral RA medications consistently. Maintaining adequate hydration is crucial, especially if you also take NSAIDs for RA pain, as the combination of dehydration and NSAIDs increases the risk of kidney problems. If you experience persistent gastrointestinal symptoms, speak to your doctor, as adjustments to timing, formulation, or supportive treatments (e.g., antiemetics) may be needed to ensure adherence to your RA therapy.
Open communication with your healthcare team is vital when managing multiple chronic conditions. Contact your GP or specialist if you experience any of the following while taking Mounjaro alongside RA treatment:
New or worsening joint symptoms: If you notice increased pain, swelling, stiffness, or reduced function in your joints, this may indicate inadequate RA control and requires rheumatology review, not a change in Mounjaro.
Severe gastrointestinal symptoms: Persistent nausea, vomiting, or diarrhoea can lead to dehydration and may interfere with oral RA medications. Seek advice if symptoms do not improve or worsen, as there is a risk of acute kidney injury, particularly if you also take NSAIDs.
Signs of pancreatitis: Severe, persistent abdominal pain radiating to the back, accompanied by nausea or vomiting, requires urgent medical attention. Stop taking Mounjaro immediately and seek urgent assessment if pancreatitis is suspected. Do not restart if pancreatitis is confirmed.
Gallbladder problems: Right upper abdominal pain, fever, jaundice (yellowing of skin/eyes), or clay-coloured stools could indicate gallbladder disease, which requires prompt medical evaluation.
Hypoglycaemia: If you are also taking insulin or sulfonylureas for diabetes, be alert for symptoms of low blood sugar (sweating, tremor, confusion, palpitations). Dose adjustments may be necessary.
Visual changes: Sudden vision changes or worsening eyesight should prompt immediate ophthalmology assessment, especially if you have pre-existing diabetic retinopathy.
Unexplained weight loss or fatigue: While weight loss is expected with Mounjaro, excessive or rapid loss, or new-onset fatigue, could indicate other issues requiring investigation.
Concerns about drug interactions: If new medications are prescribed for RA or other conditions, confirm with your pharmacist or doctor that they are compatible with Mounjaro. Women using oral contraceptives should use additional contraception for 4 weeks after starting Mounjaro and after each dose increase, or consider non-oral contraceptive methods.
Before starting Mounjaro, ensure your prescriber is aware of your RA diagnosis and all current medications, including DMARDs, biologics, corticosteroids, and NSAIDs. This enables comprehensive risk assessment and tailored monitoring.
If you experience any suspected side effects from Mounjaro, report them to the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk), which helps monitor the safety of medicines in the UK.
No, Mounjaro (tirzepatide) is not licensed or approved for treating rheumatoid arthritis. It is only indicated for type 2 diabetes and weight management in the UK.
Yes, if you have type 2 diabetes or obesity requiring treatment, Mounjaro may be prescribed for these conditions. However, you must continue your disease-modifying antirheumatic drugs (DMARDs) for RA as prescribed by your rheumatologist.
There is no evidence that Mounjaro interferes with DMARDs or biologics used for RA. However, its effect on gastric emptying may affect absorption of oral medications, and gastrointestinal side effects combined with NSAIDs may increase dehydration risk.
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