Mounjaro is tirzepatide, a once-weekly injection given under the skin. It is used to control blood sugar in type 2 diabetes, and it produces substantial weight loss — which is why demand for it far exceeds its medical use. It is a Schedule 4 prescription medicine, not a lifestyle product.
What is Mounjaro?
Mounjaro contains tirzepatide. The South African Medicine Price Registry lists it as Schedule 4 injections across a full range of strengths:
| Presentation | Strengths |
|---|---|
| Mounjaro (vial) | 2.5 mg, 5 mg, 7.5 mg, 10 mg |
| Mounjaro KwikPen | 2.5 mg, 5 mg, 7.5 mg, 10 mg, 12.5 mg, 15 mg |
That ladder of strengths is not a menu. Tirzepatide is titrated — started at the lowest dose and increased in steps every four weeks or so, to let the digestive system adapt. Starting high causes severe nausea and vomiting rather than faster results.
Tirzepatide is the first medicine of its kind: a dual GIP and GLP-1 receptor agonist. GLP-1 and GIP are gut hormones released when you eat. Acting on both receptors, tirzepatide:
- prompts the pancreas to release insulin when blood sugar is high, and reduces glucagon,
- slows how quickly the stomach empties, so food stays longer and you feel full,
- reduces appetite through effects on the brain’s appetite centres.
The first of those is why it treats diabetes. The second and third are why it causes weight loss — and also why nausea is its defining side effect. It is closely related to semaglutide (Ozempic, Wegovy), which acts on GLP-1 alone.
It is an injection, given once a week, under the skin of the abdomen, thigh or upper arm, on the same day each week.
What is Mounjaro commonly used for?
- Type 2 diabetes — improving blood sugar control alongside diet and exercise, either on its own or with other diabetes medicines. This is what it is registered for.
- Weight management, in people with obesity or with overweight plus a weight-related condition such as high blood pressure, sleep apnoea or fatty liver disease. Whether that use falls inside or outside the registered indication depends on the product and the current approval, and it is the prescriber’s decision — not something to arrange around a doctor.
It is not for type 1 diabetes, and it is not a substitute for insulin.
It is also not a short course. Tirzepatide treats obesity and diabetes as chronic conditions, and its effects last while you take it. Weight regain after stopping is the usual pattern, not a personal failure — which is a conversation to have with a prescriber at the start, not two years in.
Two things deserve saying plainly.
It works alongside diet and activity, not instead of them. Muscle loss during rapid weight loss is a real problem, and adequate protein and resistance exercise matter more on this medicine, not less.
The counterfeit and compounded market is dangerous. Demand has created a large informal trade in unregistered “tirzepatide” sold online, through gyms and via social media. Products sold this way have been found with wrong doses, wrong drugs, and no sterility. There is no way to check any of it from the outside, and injecting an unknown substance carries risks that no weight goal justifies.
How Mounjaro fits into this medicine category
| Group | Examples | How it works |
|---|---|---|
| Dual GIP/GLP-1 agonists | Tirzepatide (Mounjaro) | Both incretin pathways; weekly injection |
| GLP-1 agonists | Semaglutide, liraglutide, dulaglutide | GLP-1 alone; weekly or daily injection |
| Biguanides | Metformin | First-line in type 2 diabetes; oral |
| SGLT2 inhibitors | Empagliflozin, dapagliflozin | Glucose excreted in urine; heart and kidney benefits |
| Sulfonylureas | Gliclazide, glimepiride | Stimulate insulin release; can cause low blood sugar |
| Insulin | Various | Replaces or supplements the body’s own |
Tirzepatide is usually added to, rather than replacing, an existing regimen — most often to metformin. See the general medicines hub, and note that ordinary pain and anti-inflammatory products such as K-Fenak OTC and compound remedies such as HP553 sit in the same broad category but do entirely different work.
What to check before using Mounjaro
Tirzepatide must not be used if you or a close family member has had medullary thyroid carcinoma, or if you have multiple endocrine neoplasia type 2 (MEN 2). This is an absolute exclusion, based on thyroid tumours seen in animal studies.
Tell your doctor if you:
- Have had pancreatitis, or have gallstones.
- Have type 1 diabetes or have had diabetic ketoacidosis.
- Have diabetic retinopathy. Rapid improvement in blood sugar can temporarily worsen it, so your eyes may need monitoring.
- Have gastroparesis or another condition that slows stomach emptying, or significant kidney disease.
- Take insulin or a sulfonylurea such as gliclazide. Tirzepatide alone rarely causes low blood sugar, but combined with these it can — doses of those medicines are often reduced.
- Take the oral contraceptive pill. Tirzepatide can reduce its absorption. Use an additional barrier method for four weeks after starting and after each dose increase, or discuss a non-oral contraceptive.
- Are pregnant, planning pregnancy or breastfeeding. It is not used in pregnancy, and weight loss treatment should be stopped well before conception.
- Are due for surgery or a procedure under anaesthetic — tell the anaesthetist you take it, because food may remain in the stomach longer than expected.
Practical points: inject on the same day each week, rotate injection sites, store it as directed in the fridge, and never share a pen. Eat smaller meals, more slowly, and stop when full — this does more to control nausea than anything else.
Possible cautions and when to ask a pharmacist or doctor
The most common effects are nausea, vomiting, diarrhoea, constipation, indigestion, reduced appetite and stomach discomfort. These are worst in the first weeks and after each dose increase, and usually settle.
Get emergency or urgent help for:
- Severe, persistent abdominal pain, often radiating to the back, with vomiting — possible pancreatitis. Stop the medicine and seek care.
- Severe pain in the upper right abdomen, fever, or yellowing of the skin or eyes — possible gallbladder problems.
- Signs of dehydration — dizziness on standing, very dark or reduced urine, confusion — after prolonged vomiting or diarrhoea. This can cause acute kidney injury.
- Severe low blood sugar — sweating, shaking, confusion, palpitations — particularly if you also take insulin or a sulfonylurea.
- Swelling of the face, lips or tongue, or difficulty breathing.
- A lump or swelling in the neck, difficulty swallowing, persistent hoarseness or shortness of breath.
Contact your doctor if nausea is stopping you eating or drinking normally, if weight loss is very rapid, if blood sugars run low, if vision changes, or if you are struggling with the cost and considering an informal source. That last one is worth raising honestly — a doctor can discuss registered alternatives far more safely than an online seller can supply an unregistered one.
Related medicine guides
Frequently asked questions
What is Mounjaro used for? Controlling blood sugar in type 2 diabetes, and — depending on the approved indication and the prescriber’s judgement — managing obesity. It contains tirzepatide.
Is it the same as Ozempic? No. Ozempic is semaglutide, which acts on GLP-1 only. Tirzepatide acts on both GIP and GLP-1 receptors.
Is it a weight-loss injection? It causes substantial weight loss by reducing appetite and slowing stomach emptying. It is a prescription medicine for defined medical conditions, not a cosmetic product.
How often is it given? Once a week, injected under the skin, on the same day each week.
Do I need a prescription in South Africa? Yes. It is Schedule 4. Products sold without one are not legitimate.
What happens if I stop? Appetite generally returns and weight is commonly regained. It treats chronic conditions rather than curing them — discuss the long-term plan with your doctor.
Why does it make me so nauseous? It slows stomach emptying. Nausea is worst after starting and after each dose increase; smaller, slower meals help, and it usually settles.
Can I buy it online more cheaply? Unregistered and compounded tirzepatide sold online has been found with wrong doses, wrong drugs and no sterility assurance. Speak to a doctor about affordable registered options instead.