Mounjaro For Type 2 Diabetes

Tirzepatide was developed as a diabetes medication. The first clinical trials, the first regulatory approvals, and the first SAHPRA registration in December 2024 were all for type 2 diabetes. The weight management indication came later, in October 2025. Although the popular conversation around Mounjaro is dominated by weight loss, the diabetes story is the founding one and remains a major part of how the medication is used in South Africa.

This page is for people with type 2 diabetes considering tirzepatide as part of their diabetes management.

The SURPASS Trial Programme

SURPASS was the clinical programme that built the case for tirzepatide in type 2 diabetes. Six trials, over 6,000 adults, comparing tirzepatide at three doses (5, 10, and 15 mg weekly) to placebo, to semaglutide, to insulin degludec, and to insulin glargine. The trials ran from 2019 to 2022 and produced consistently strong results across populations and comparators.

The headline outcomes:

The pattern is clear. Tirzepatide produces around 2 to 2.4 percentage points of HbA1c reduction, comfortably outperforming the older comparators and modestly outperforming semaglutide. A deeper review of the trials is here.

Who Tirzepatide Fits In The Diabetes Picture

Standard SA diabetes management still starts with metformin and lifestyle changes. Tirzepatide enters the picture for patients who:

• Have not achieved their HbA1c target on metformin alone or metformin plus one or two other oral medications
• Need significant glucose reduction with a low hypoglycaemia risk
• Would benefit from accompanying weight reduction
• Have established cardiovascular disease or significant cardiovascular risk
• Want to avoid or delay insulin initiation

It can be used as monotherapy (SURPASS-1), in combination with metformin, in combination with metformin and other oral agents, or alongside insulin. The combinations require dose adjustment of other diabetes medications to avoid hypoglycaemia.

Why It Works Differently Than Insulin

Insulin lowers blood glucose by adding more insulin to the body, regardless of food intake. This works, but it carries risks: hypoglycaemia, weight gain, and the practical burden of multiple daily injections. Tirzepatide works differently. It enhances the body's own glucose-dependent insulin release. Insulin is released when blood sugar is up, not when it is normal or low. This means the hypoglycaemia risk is much lower with tirzepatide than with insulin (or with sulfonylureas like glimepiride and gliclazide).

It also produces weight loss rather than weight gain, which compounds the cardiovascular and metabolic benefit. For people with type 2 diabetes who are overweight or obese (the majority), this is a significant advantage over insulin.

Combination With Other Diabetes Medications

Metformin

Continued. The combination of metformin and tirzepatide is well studied and is the standard backbone for most patients on tirzepatide for diabetes.

SGLT2 inhibitors

Often continued, particularly in patients with heart failure or chronic kidney disease where SGLT2 inhibitors provide additional benefit. The combination is generally well tolerated.

Sulfonylureas (gliclazide, glimepiride)

Usually reduced or stopped because of hypoglycaemia risk in combination.

DPP-4 inhibitors (sitagliptin, vildagliptin)

Usually stopped. They act on overlapping pathways with GLP-1 and add little benefit when tirzepatide is on board.

Insulin

Often continued but at reduced dose. Many patients on insulin can taper substantially when tirzepatide is added. Some are able to stop insulin entirely after several months on tirzepatide, particularly those whose diabetes was relatively mild.

The Cost And Cover Picture For Diabetes

This is where the diabetes indication has a significant advantage over the weight management indication. Type 2 diabetes is on the PMB Chronic Disease List under SA medical aid regulations. Medical aids are required to cover treatment.

Most major SA schemes have Mounjaro on the chronic medicine formulary for type 2 diabetes, with some scheme specific criteria. Compare this to weight management, where obesity is not on the CDL and cover is at scheme discretion. For someone with type 2 diabetes considering tirzepatide, the conversation with medical aid is usually substantially easier.

That said, formularies vary and prior authorisation is often needed. Call your scheme directly with the medication name and your diabetes diagnosis to clarify the specific cover and any criteria.

What To Expect Over A Year On Tirzepatide For Diabetes

Most type 2 diabetes patients starting tirzepatide can expect:

• HbA1c reduction of 1.5 to 2.5 percentage points at maintenance dose
• Weight reduction of 8 to 15 percent, depending on dose and individual response
• Reduced need for other diabetes medications over the first few months
• Improvement in blood pressure and lipid profile
• Side effects most prominent in the first weeks and after dose increases, mostly settling
• Eventual decision point at month 4 or 5 about whether to continue at 15 mg or hold at a lower dose

The treating doctor adjusts other medications as the picture evolves. Many patients with type 2 diabetes find their overall medication burden actually decreases over the first year on tirzepatide, even though tirzepatide itself has been added. The picture is one of simplification, not addition.

What Tirzepatide Does Not Replace

• Lifestyle interventions still matter. The trials all paired tirzepatide with diet and exercise advice.
• Annual diabetes review still matters. Eyes, feet, kidneys, cholesterol continue to need monitoring.
• Other cardiovascular medications (statins, blood pressure medications) continue alongside.
• Annual flu vaccination and pneumonia vaccine schedules continue.

Frequently Asked