Written by: the Medetone Medical Team
Medically reviewed by: Dr Abdullah and the Medetone clinical team
Reading time: 8 minutes · Guidance verified: August 2026
What is Mounjaro, and why is it now one of the most searched-for medicines in Spain? A great deal of what circulates about it is imprecise, particularly on how it works, who it's actually for, and how you legally obtain it. This guide brings together what matters before you speak to a doctor: what the medicine is, how it acts on the body, the dosing schedule, the results seen in trials, the side effects, and its prescription status in Spain. Mounjaro is a prescription-only medicine, and this article is informational rather than a substitute for your doctor's advice.
Key facts at a glance
Active ingredient: tirzepatide
How it's taken: once-weekly subcutaneous injection
Strengths: six, from 2.5 mg to 15 mg
Licensed for: weight management and type 2 diabetes
Status in Spain: prescription-only, not financed by the SNS
What is Mounjaro?
Mounjaro is the brand name for tirzepatide, given as a subcutaneous injection once a week. The European Medicines Agency authorised it in September 2022 for type 2 diabetes and extended the indication to weight management in November 2023. That matters in Europe, and therefore in Spain: the single Mounjaro brand covers both indications, unlike the separate branding used in some other markets. It has been available in Spanish pharmacies since 1 July 2024, dispensed with a prescription.
It comes in six strengths, from 2.5 mg to 15 mg, supplied in single-dose prefilled pens and in the multi-dose KwikPen.
How Mounjaro works
Here is where Mounjaro differs from what came before. It is the first and only dual GIP and GLP-1 receptor agonist, meaning it mimics two gut hormones your body naturally releases after eating. Earlier medicines in this class, such as semaglutide, act on one receptor only.
Four effects follow from that dual action:
-
Insulin is released when blood sugar rises.
-
Glucagon is reduced, the hormone that prompts the liver to release stored sugar.
-
Gastric emptying slows, so fullness lasts longer.
-
Appetite drops, including the constant "food noise" many people describe.
The practical result is that you eat less without fighting hunger all day. One condition from the product information stays fixed: treatment must always be combined with a reduced-calorie diet and increased physical activity. For the wider context on this class of medicines, see our guide to GLP-1 weight-loss injections.
Who Mounjaro is for
Under the European product information, Mounjaro is indicated for adults in two situations.
For weight management, alongside diet and exercise:
-
BMI ≥ 30 kg/m² (obesity), or
-
BMI between 27 and 29.9 kg/m² (overweight) with at least one weight-related condition, such as hypertension, dyslipidaemia, obstructive sleep apnoea, cardiovascular disease, prediabetes or type 2 diabetes.
For type 2 diabetes, where blood sugar isn't adequately controlled by diet and exercise alone, either on its own or combined with other antidiabetic medicines.
Outside these criteria it is not an appropriate medicine. There is no cosmetic use of Mounjaro for people at a normal weight, and eligibility is a clinical judgement rather than a personal preference.
Who should not use it
The main contraindications are:
-
Personal or family history of medullary thyroid carcinoma or MEN 2 syndrome
-
Hypersensitivity to tirzepatide or any excipient
-
Pregnancy and breastfeeding
-
Being under 18 for weight management
Particular caution and a thorough assessment are also needed with previous pancreatitis, gallbladder disease, gastroparesis or other serious gastrointestinal disorders, diabetic retinopathy, and in patients already taking insulin or sulfonylureas because of hypoglycaemia risk. Mounjaro must never be combined with another GLP-1 medicine.
Mounjaro dosing: the titration schedule
Dosing does not start at the full dose. You step up gradually, and this is the part most often misunderstood.
|
Stage |
Dose (once weekly) |
Minimum time before next step |
|
Starting dose |
2.5 mg |
4 weeks |
|
Step up |
5 mg |
4 weeks |
|
Step up |
7.5 mg |
4 weeks |
|
Step up |
10 mg |
4 weeks |
|
Step up |
12.5 mg |
4 weeks |
|
Maximum |
15 mg |
— |
You begin on 2.5 mg once weekly for four weeks, a starter dose meant to let the body adjust rather than deliver the treatment result. From 5 mg onward, your doctor can increase by 2.5 mg at a time after at least four weeks on each dose, up to a maximum of 15 mg weekly. The most commonly used maintenance doses are 5, 10 and 15 mg.
If gastrointestinal effects are strong, titration can be slowed. That is a clinical decision, never something to adjust on your own. Our Mounjaro dosage guide covers this in detail.
How and where to inject
Inject once a week, on the same day each week, at any hour and regardless of meals. Approved sites are the abdomen (at least 5 cm from the navel), the thigh, or the back of the upper arm, rotating the site each time. You can change your injection day provided at least 72 hours separate two doses. If you miss a dose, take it within four days; beyond that, skip it and resume your usual schedule. Pens are stored in the fridge between 2 and 8 °C, never frozen.
How much weight you lose, and how long it takes
In the registration trial of 2,539 adults with obesity or overweight plus a weight-related condition, 72 weeks of treatment produced average weight loss of 16.0% at 5 mg, 21.4% at 10 mg and 22.5% at 15 mg, against 2.4% on placebo. 89% of participants lost at least 5% of their starting weight, compared with 28% on placebo.
On timing, the pattern is:
-
First 1 to 2 weeks: mainly a drop in appetite
-
4 to 12 weeks: clinically meaningful weight loss begins, once past the starter doses
-
6 to 18 months: the plateau described in the trials
Anyone expecting ten kilos in a month will be disappointed. Weight loss here is gradual and proportional to consistency, not immediate.
Side effects
The most common effects are gastrointestinal and cluster in the first weeks or straight after a dose increase: nausea, diarrhoea, vomiting, constipation, indigestion, abdominal pain and reduced appetite. In most cases they ease within 4 to 8 weeks.
Rare but requiring immediate medical attention: acute pancreatitis (severe, persistent abdominal pain that may radiate to the back), gallbladder problems, dehydration with possible effects on kidney function, serious allergic reactions, vision changes, and hypoglycaemia when combined with insulin or sulfonylureas.
One point that gets less attention: rapid weight loss can also cost lean muscle mass. Adequate protein intake and resistance training are the standard countermeasure.
How long do you take it?
Obesity and type 2 diabetes are chronic conditions, and treatment is designed as a long-term therapy with periodic review. Trial evidence is clear on what happens if you stop: participants who continued treatment lost a further 5.5%, while those switched to placebo regained 14% over the following year. Your doctor reassesses at intervals and may stop treatment if response is insufficient or tolerance is poor. Our guide on what happens when you stop weight-loss medication explains why.
Frequently asked questions
What is Mounjaro used for?
Two licensed indications: weight management in adults meeting the BMI criteria, and type 2 diabetes where blood sugar isn't adequately controlled.
Is Mounjaro financed by the Seguridad Social in Spain?
No. It is not financed by the SNS for obesity and remains a private prescription, following the Comisión Interministerial de Precios decision.
Can you buy Mounjaro without a prescription?
No. Any channel offering it without a prescription is illegal and potentially dangerous.
How long does Mounjaro take to work?
Reduced appetite is often noticeable in the first weeks; significant weight loss usually arrives after 1 to 3 months, as the dose steps up.
Does Mounjaro cause muscle loss?
Rapid weight loss can include lean mass. Adequate protein and resistance training are the standard countermeasure.
Your next step
If you meet the BMI criteria and you're considering a weight-management pathway, the first step is a medical assessment: history, contraindications, current medicines and realistic goals. You can read more on the Mounjaro treatment page or start an assessment with a licensed clinician.
Medical information: this article is for information only and does not replace diagnosis, prescription or medical advice. Mounjaro is a prescription-only medicine. Financing decisions can change, so confirm your situation with your doctor.
References :
AEMPS, Agencia Española de Medicamentos y Productos Sanitarios: https://www.aemps.gob.es
CIMA, AEMPS medicines information centre: https://cima.aemps.es
Ministerio de Sanidad: https://www.sanidad.gob.es
European Medicines Agency, Mounjaro EPAR: https://www.ema.europa.eu/en/medicines/human/EPAR/mounjaro
