By Dr. Asnat Raziel, specialist in obesity treatment, metabolic health and healthy longevity; Director of the Multidisciplinary Center for Obesity Treatment, Assia Medical, Assuta Ramat HaChayal
Starting Mounjaro: a practical guide
Starting Mounjaro, a weekly injection for obesity and type 2 diabetes, calls for good planning from the very first week. In this guide I will not repeat all the research. Instead, I focus on practical questions: how to raise the dose, how to inject, what to eat and what to do when something goes wrong. That way, you can begin treatment with confidence and safety.
What Mounjaro is and how it works
The active ingredient in Mounjaro is tirzepatide. It mimics two natural gut hormones, GLP-1 and GIP, which affect hunger, fullness and blood sugar. As a result, most patients feel full sooner and think less about food, a pattern known as food noise.
The SURMOUNT-1 trial included 2,539 adults with obesity and without diabetes. After 72 weeks, average weight loss was 15.0% at 5 mg, 19.5% at 10 mg and 20.9% at 15 mg. In contrast, the placebo group lost 3.1%. You will find broader information in my complete article on the drug.
Who is a candidate for starting Mounjaro?
According to the European prescribing information, obesity treatment is for adults with a BMI of 30 or more. In addition, it also covers people with a BMI of 27 to 30 who have at least one weight-related condition, such as high blood pressure or sleep apnea. Doctors always prescribe the drug together with a tailored diet and physical activity.
On the other hand, in some situations you must not use it. For example, according to the US label, anyone who has, or whose family has had, medullary thyroid cancer or MEN2 syndrome must not take it. Pregnancy is also a reason not to use it. You can read more about who Mounjaro may suit in a separate article.
Starting Mounjaro: raising the dose step by step
Treatment always begins at a low dose, to give the body time to adjust. According to the US label for Zepbound, the US brand name of tirzepatide for obesity, the starting dose is 2.5 mg once a week for 4 weeks. After that, the dose rises to 5 mg. Each further increase is 2.5 mg, and only after at least 4 weeks on the current dose.
- Weeks 1 to 4: 2.5 mg, a starting dose for adjustment only.
- From week 5: 5 mg.
- Later, as needed: 7.5, 10, 12.5 and up to 15 mg.
The recommended maintenance doses are 5, 10 or 15 mg, and the maximum is 15 mg a week. Keep in mind that not everyone needs to reach the high dose. If your weight is falling at a good pace and side effects are tolerable, you can stay on the current dose. You and your doctor make this decision together.
How to inject Mounjaro correctly
You inject under the skin once a week, on the same day each week, at any time of day. You can inject in the abdomen or thigh. If someone else gives the injection, the back of the upper arm is also an option. It is a good idea to change the injection site each time.
And what if you forget? If up to 4 days have passed since the scheduled day, inject right away. If more than 4 days have passed, skip the dose and continue on your regular day. In addition, keep the pen in the fridge at 2 to 8 degrees Celsius, and do not freeze it. Check the patient leaflet for the time allowed outside the fridge, because it differs between pen types.
Daily routine when starting Mounjaro
When appetite drops, it is easy to eat too little and without structure. Therefore, it pays to build a simple routine from the start.
Nutrition
Eat small, regular meals, and stop at the first feeling of fullness. Make sure to include a protein source at every meal, for example eggs, yogurt, fish, chicken or legumes. Also, cut down on fatty and fried food, which makes nausea worse. You will find practical ideas in my nutrition guide for weight loss injections.
Fluids
Drink water throughout the day, even without thirst. Vomiting and diarrhea may cause dehydration, and according to the label this can harm kidney function. So it is especially important to drink in the first days after a dose increase.
Physical activity
Strength training helps preserve muscle during weight loss. In addition, a daily walk improves digestion and mood. A healthy lifestyle complements the drug and also protects the heart. It is also worth reading about preserving muscle during weight loss.
Side effects when starting Mounjaro
The most common side effects affect the digestive system: nausea, diarrhea, vomiting and constipation. Most are mild to moderate, and they appear mainly while the dose is rising. Usually they fade over time.
To ease them, eat slowly, avoid large meals and drink plenty. However, some symptoms require an immediate visit to a doctor. For example, strong and persistent abdominal pain, sometimes spreading to the back, may point to pancreatitis. I expand on this in my article on coping with the drug’s side effects.
Pregnancy, contraception and other medicines
According to the European label, women of childbearing age should use contraception during treatment. In addition, stop the drug at least one month before a planned pregnancy. The US label also recommends adding a barrier method, or switching to a non-pill method, for 4 weeks from the start of treatment and after each dose increase. Finally, tell your doctor about any other medicine, especially insulin and diabetes drugs.
Medical follow-up throughout treatment
Mounjaro is not a treatment for a month or two. Obesity is a chronic disease, so follow-up continues over time. At each visit, your doctor checks weight, blood pressure, blood tests and side effects, and decides on the dose. It is also worth considering a body composition test, to make sure the loss is mainly fat.
It is also important to know what happens when you stop. In the SURMOUNT-4 trial, people who switched from tirzepatide to placebo regained 14% of their weight on average over the following year. So do not stop on your own; plan the next steps with your doctor. Information on Mounjaro coverage in the health funds and on other obesity medications will help you plan for the long term.
Bottom line on starting Mounjaro
Mounjaro is very effective, but success also depends on the routine you build around it. When starting Mounjaro, you take 2.5 mg and increase gradually, inject once a week, eat small meals with protein, drink plenty and exercise. In addition, you stay under close medical follow-up and do not stop without a plan.
This article provides general information and is not personal medical advice. For any question about your treatment, please consult your doctor.
Questions and answers
How long does it take to reach the full dose?
Each increase comes after at least 4 weeks. Therefore, the path from 2.5 mg to 15 mg takes at least 20 weeks, and sometimes longer.
What if I miss a Mounjaro injection?
If up to 4 days have passed, inject right away. If more have passed, skip it and continue on your regular day.
Can I drink alcohol?
Alcohol adds calories and may worsen nausea. If you drink, it is better to have a little, with food and plenty of water.
When should I see a doctor after starting Mounjaro?
With strong abdominal pain, vomiting that does not stop, signs of dehydration or an allergic reaction. You can read more about my approach to treatment on my personal page.
References
Tirzepatide Once Weekly for the Treatment of Obesity
ZEPBOUND (tirzepatide) Prescribing Information
