Starting a new medication like Mounjaro (tirzepatide) can feel like a big step. Knowing what to expect during your first dose can help you feel more confident and prepared. This guide covers how to take your first injection safely, and how to manage early side effects.
What is Mounjaro?
Mounjaro is a GIP and GLP-1 receptor agonist medication. That means it mimics two natural hormones—GIP and GLP-1—that help control blood glucose levels and reduce appetite.
Its dual action helps the body use insulin more effectively while helping you feel full after smaller meals.
What is the Mounjaro starting dose?
The initial dose for Mounjaro is 2.5 mg once weekly, delivered as a subcutaneous injection (just under the skin).
This starting dose is deliberately low to help your body get used to the medication and to reduce the risk of side effects. After several weeks, the dose may be increased based on your individual response.
How quickly should you expect weight loss changes?
During the first week, any weight change is often temporary water fluctuation. Measurable weight loss usually starts after 1–2 weeks once your body is used to the medication. Remember, the first dose is mainly an introduction—slow, steady progress is key.
How to prepare for your first Mounjaro dose
A little preparation makes the process much easier:
- Storage: Keep your Mounjaro pen refrigerated (between 2°C to 8°C).
- Before injecting: Allow it to warm to room temperature for about 30 minutes.
- Supplies: Have alcohol wipes and a sharps bin ready.
- Injection sites: You can inject into your abdomen, thigh, or upper arm—whichever feels most comfortable. Be sure to rotate sites each week to reduce the risk of irritation or discomfort.
Read our step by step for how to inject
Taking your injection can feel easier when you know what to expect. Use the steps below as a simple guide to help you prepare, inject, and dispose of your pen safely.
- Wash your hands and clean your chosen site with an alcohol wipe.
- Check that the medicine is clear and colourless.
- Prepare your pen: remove the cap, attach a new needle and prime by turning the dial, hold the pen needle-up, tap out any air bubbles, and press the knob to release a tiny drop of medicine.
- Set your dose: turn the dial to your prescribed amount.
- Hold the pen against your skin and press the injection button.
- Hold in place for the recommended few seconds to make sure the full dose is delivered.
- Safely dispose of the used pen in your sharps container.
For more information, check out our detailed guide below on how to administer Mounjaro, which walks you through the process step by step.
What side effect can you expect after your first Mounjaro dose?
It’s normal to feel some early changes when you take your first dose of Mounjaro, including:
- Mild nausea or stomach discomfort
- Feeling full more quickly after smaller meals
- Less hunger throughout the day
- Possible changes in thirst or urination
- A bit of fatigue or mild injection-site tenderness
These effects are usually mild and settle within a few days.
Common side effects in the first week
After your first dose, the next week might see you feeling a little differently, with some patients reporting the following:
- Some people notice improved blood glucose control within 24 hours.
- Appetite changes typically appear by day 2 or 3.
- Side effects, if they happen, tend to peak between 24–72 hours then ease off.
- Your digestive system gradually adjusts as your body adapts to the medication.
Mounjaro first dose FAQs
Can I take other medications whilst on my first dose?
Always tell your healthcare provider about any other medicines or supplements you use. Mounjaro can interact with some drugs that may affect blood sugar or digestion, so adjustments to dosing or timing may be needed for your safety. Read our guide to Mounjaro and drug interactions to get more information.
Can I drink alcohol when I first take Mounjaro?
While alcohol isn’t strictly off-limits, it can:
- Interfere with blood sugar control
- Worsen nausea or dehydration
- Reduce your energy or appetite
Limiting or avoiding alcohol, especially during your first few doses, is a good idea.
Can I exercise during my first Mounjaro dose?
Mild exercise is encouraged, but during your first week:
- Start with gentle activity like walking or stretching.
- Avoid intense workouts if you feel tired or nauseated.
- Gradually increase your activity as your body adjusts.
What to do if my side effects worsen during my first dose?
Reach out promptly if you experience:
- Severe or persistent nausea or vomiting
- Signs of an allergic reaction: swelling, rash, difficulty breathing
- Severe abdominal pain or side effects that don’t improve
- Concerns about blood sugar or dose adjustments
- If you have any concerns or questions about next steps in the titration process
Your first Mounjaro dose is the start of an exciting journey toward better health. It’s normal to take a few weeks to adjust. Be patient, listen to your body, and reach out to the Phlo Clinic team with any concerns—we’re here to guide and support you every step of the way.
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