Is Mounjaro an SGLT2 inhibitor? No, Mounjaro (tirzepatide) is not an SGLT2 inhibitor. It belongs to an entirely different class of diabetes medication. Mounjaro is a dual glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist, approved by the MHRA for treating type 2 diabetes in adults. Whilst both Mounjaro and SGLT2 inhibitors lower blood glucose, they work through distinct mechanisms and have different benefits, side effects, and clinical applications. Understanding these differences is essential for making informed treatment decisions in collaboration with your healthcare team.
Quick Answer: Mounjaro is not an SGLT2 inhibitor; it is a dual GIP and GLP-1 receptor agonist that works through a different mechanism to lower blood glucose in type 2 diabetes.
Mounjaro is not an SGLT2 inhibitor. It is the brand name for tirzepatide, a novel glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist. This dual incretin mimetic represents a distinct class of medication approved by the Medicines and Healthcare products Regulatory Agency (MHRA) for the treatment of type 2 diabetes mellitus in adults.
Tirzepatide works through a dual mechanism of action that differentiates it from other diabetes medications. By activating both GIP and GLP-1 receptors, Mounjaro enhances glucose-dependent insulin secretion from pancreatic beta cells, suppresses inappropriately elevated glucagon secretion, and slows gastric emptying. These combined effects lead to improved glycaemic control and reduced postprandial glucose excursions.
The medication is administered as a once-weekly subcutaneous injection, starting at 2.5 mg for 4 weeks as an initiation dose to improve tolerability, before potentially titrating up to 15 mg based on individual response. Clinical trials have demonstrated substantial HbA1c reductions (often exceeding 2%) alongside significant weight loss. It's important to note that while tirzepatide is licensed for type 2 diabetes under the brand name Mounjaro, tirzepatide for weight management is authorised under a separate brand name (Zepbound) in the UK.
Common adverse effects include gastrointestinal symptoms such as nausea, vomiting, diarrhoea, and decreased appetite, particularly during dose escalation. These effects typically diminish over time. Patients should be counselled about the risk of hypoglycaemia when Mounjaro is used in combination with insulin or sulphonylureas, and dose adjustments of these concomitant medications may be necessary. Concomitant use with DPP-4 inhibitors is not recommended.
Patients should be advised to seek urgent medical attention if they experience severe, persistent abdominal pain (with or without vomiting) as this may indicate acute pancreatitis. There is also an increased risk of gallbladder disease with tirzepatide use.
Suspected adverse reactions should be reported via the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk).
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Start HereSodium-glucose co-transporter 2 (SGLT2) inhibitors represent an entirely different class of antidiabetic medication with a distinct mechanism of action that operates independently of insulin. These agents work primarily in the kidneys by blocking the SGLT2 protein in the proximal convoluted tubule, which is responsible for reabsorbing approximately 90% of filtered glucose back into the bloodstream.
By inhibiting this reabsorption process, SGLT2 inhibitors promote urinary glucose excretion (glycosuria), typically eliminating 60–80 grams of glucose daily. This insulin-independent mechanism results in modest HbA1c reductions (approximately 0.5–1.0%), alongside weight loss of 2–3 kg and small reductions in blood pressure due to osmotic diuresis and natriuresis.
Commonly prescribed SGLT2 inhibitors in the UK include dapagliflozin (Forxiga), empagliflozin (Jardiance), canagliflozin (Invokana), and ertugliflozin (Steglatro). NICE guidelines recommend these agents as treatment options for type 2 diabetes, with specific recommendations for patients with established cardiovascular disease, heart failure, or chronic kidney disease due to demonstrated cardio-renal protective benefits. For some indications, these medications can be used in patients with eGFR as low as 20 mL/min/1.73m² depending on the specific agent and indication.
The adverse effect profile of SGLT2 inhibitors differs markedly from incretin-based therapies. The increased urinary glucose creates a favourable environment for genital mycotic infections (thrush), particularly in women, and increases the risk of urinary tract infections. Patients may experience polyuria and should maintain adequate hydration to reduce the risk of volume depletion and hypotension.
Rare but serious complications include euglycaemic diabetic ketoacidosis (DKA), which can occur even with near-normal blood glucose levels, and Fournier's gangrene, a life-threatening necrotising infection of the perineum. Patients should be educated to recognise symptoms of DKA (nausea, vomiting, abdominal pain, unusual fatigue) and seek immediate medical attention if these develop.
Importantly, SGLT2 inhibitors should be temporarily stopped during periods of acute illness, dehydration, or fasting, and for at least three days before planned surgical procedures to reduce the risk of DKA. These medications are not indicated for type 1 diabetes in the UK due to increased DKA risk.
Understanding the fundamental differences between Mounjaro and SGLT2 inhibitors is essential for both healthcare professionals and patients navigating diabetes treatment options. These medications operate through different physiological pathways and offer distinct clinical benefits and risk profiles.
Mechanism and site of action: Mounjaro works centrally and in the pancreas by mimicking incretin hormones, enhancing insulin secretion, suppressing glucagon, and slowing gastric emptying. In contrast, SGLT2 inhibitors act peripherally in the kidneys, promoting glucose excretion through urine independently of insulin or pancreatic function. This fundamental difference means they can be used complementarily in combination therapy.
Efficacy and metabolic effects: Mounjaro typically achieves greater HbA1c reductions (1.5–2.5%) compared to SGLT2 inhibitors (0.5–1.0%). Weight loss is also more pronounced with tirzepatide (often 5–10 kg or more) versus the modest 2–3 kg typically seen with SGLT2 inhibitors. However, SGLT2 inhibitors offer established cardiovascular and renal benefits that extend beyond glucose control, including reduced hospitalisation for heart failure and slowed progression of chronic kidney disease. These benefits have been demonstrated through extensive cardiovascular outcome trials, whereas long-term cardiovascular outcome data for tirzepatide are still emerging.
Administration and tolerability: Mounjaro requires weekly subcutaneous injection, whilst SGLT2 inhibitors are oral tablets taken once daily, which may influence patient preference and adherence. The adverse effect profiles differ substantially: Mounjaro predominantly causes gastrointestinal symptoms and has risks of pancreatitis and gallbladder disease, whereas SGLT2 inhibitors are associated with genitourinary infections, volume depletion, and risk of DKA.
Clinical positioning: According to NICE guidance (NG28), SGLT2 inhibitors may be considered as first-line therapy (with or without metformin) for patients with established cardiovascular disease, heart failure, or chronic kidney disease, or when metformin is contraindicated or not tolerated. Mounjaro, as a newer agent, is typically considered when existing therapies prove inadequate, though its positioning continues to evolve as more real-world evidence emerges. Neither medication causes hypoglycaemia when used as monotherapy, making both attractive options for patients at risk of low blood glucose episodes.
Selecting appropriate diabetes medication requires individualised assessment considering multiple factors including glycaemic control, comorbidities, patient preferences, tolerability, and cost-effectiveness. The decision between Mounjaro, SGLT2 inhibitors, or other agents should be made collaboratively between patients and their healthcare team.
NICE guidelines (NG28) provide a structured approach to type 2 diabetes management. First-line therapy typically involves metformin alongside lifestyle modification, though SGLT2 inhibitors may be considered first-line (with or without metformin) for those with established atherosclerotic cardiovascular disease, heart failure, or chronic kidney disease due to proven cardio-renal benefits. The eGFR thresholds for SGLT2 inhibitors vary by agent and indication, with some cardio-renal indications permitting use down to eGFR 20 mL/min/1.73m². GLP-1 receptor agonists (a class related to Mounjaro's mechanism) may be considered when significant weight loss would benefit the patient or when other therapies are contraindicated.
Practical considerations influence treatment selection. Patients uncomfortable with injections may prefer oral SGLT2 inhibitors, whilst those prioritising weight loss might favour Mounjaro despite the injection requirement. Cost and NHS funding criteria also play a role; Mounjaro availability may be restricted to specialist initiation or specific clinical scenarios, whereas SGLT2 inhibitors are widely accessible in primary care.
Combination therapy is increasingly common, and there is no official contraindication to using Mounjaro alongside an SGLT2 inhibitor. Their complementary mechanisms may provide additive benefits, though this approach requires careful monitoring and is typically reserved for patients with inadequate control on dual therapy. It should be noted that combining GLP-1/GIP receptor agonists with DPP-4 inhibitors is not recommended.
When to seek medical advice: Patients should contact their GP or diabetes specialist if they experience inadequate glucose control (persistent high readings), troublesome side effects, or symptoms suggesting complications. Specific red flags include severe, persistent abdominal pain (possible pancreatitis) when taking Mounjaro, or symptoms of DKA (nausea, vomiting, abdominal pain, unusual fatigue) when taking SGLT2 inhibitors, both requiring urgent medical attention. Regular monitoring of HbA1c, renal function, and cardiovascular risk factors remains essential regardless of which medication is prescribed.
Diabetes management is dynamic, and treatment regimens should be reviewed at least annually or whenever clinical circumstances change, ensuring therapy remains optimally aligned with individual needs and evidence-based guidelines. Patients should report suspected side effects via the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk).
Yes, Mounjaro and SGLT2 inhibitors can be used together as they work through different mechanisms. This combination therapy is typically reserved for patients with inadequate glucose control on dual therapy and requires careful monitoring by a healthcare professional.
Mounjaro typically produces greater weight loss compared to SGLT2 inhibitors. Clinical trials show tirzepatide can lead to substantial weight reduction, whilst SGLT2 inhibitors typically result in modest weight loss of 2–3 kg.
SGLT2 inhibitors have established cardiovascular and renal protective benefits demonstrated through extensive outcome trials, including reduced heart failure hospitalisation and slowed kidney disease progression. Long-term cardiovascular outcome data for tirzepatide are still emerging, though early evidence is promising.
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