Week 3 on Mounjaro: Side Effects, Weight Loss, Blood Sugar, and Dose Rules

Week 3 on Mounjaro: Side Effects, Weight Loss, Blood Sugar, and Dose Rules

In your third week on Mounjaro, you body starts to get used to the medication and start to feel a bit normal: that’s your stomach is getting used to the meds, your blood sugar is settling down, and during this period you figure out what to eat that won’t make you feel rough – but you still need to be smart about the side effects, safety, and dose changes. 

 

Quick snapshot: week 3 on Mounjaro 

 

 

  • Most people are still on the 2.5 mg dose in week 3 and shouldn’t increase it on their own. 

  • At this period your Gut side effects like (nausea, diarrhoea, constipation, bloating) starts to relax, but can flare if you don’t watch what you eat. 

  • You’ll usually notice steadier blood sugar and maybe the first real signs of weight loss, mostly from eating less without feeling as hungry. 

  • It should not be understated how important you watch out for red-flag symptoms like severe stomach pain or repeated vomiting and get urgent medical help if they show up. 

  • If you’re on the pill, you still need backup contraception for the first 4 weeks and for 4 weeks after any dose increase. 

 

What week 3 on Mounjaro actually feels like 

 

You’re not completely new to Mounjaro by week 3 – you know which day you inject, you’ve most likely eaten some weird things already, and you’re slowly learning “what my body does” on these drugs. 

Most people are: 

  • Still on 2.5 mg once a week. 

  • Most people are now starting to get used to having a slower digestion and eating smaller meals. 

  • Noticing that their hunger is very different from before – you might want your old portions in your head, but your stomach taps out halfway through. 

This week is kind of a “transition phase”: 

  • The shock of starting is wearing off. 

  • The long-term benefits (steadier blood sugar, slow but real weight change) are beginning to kick in. 

  • You’re learning how to live with this medication, rather than just “trying it out.” 

 

You’re not supposed to be great at it in week 3. You’re supposed to be learning: which foods always make you feel sick, how long it’ll take before slow eating is your normal pattern, which between-meal snacks you tolerate and when you feel best. 

 

Common side effects in week 3 (and what to do) 

 

 

And then the most irritating part of Mounjaro is your stomach in the beginning. By week 3, a lot of people are feeling things easing up — but that doesn’t mean being totally zero symptoms. Picture it more as “less of a hellstorm, but can still be sensitive.” 

 

What you might notice 

 

  • You feel queasy, especially after eating large or fatty meals. 

  • Vomiting in some individuals; this may be related to overeating or eating too quickly. 

  • Constipation or diarrhoea (and occasionally rotating between the two). 

  • Reduced appetite that feels weirdly strong – like your brain wants food, but your body is saying “nah.” 

 

Easy tweaks that actually help 

 

These aren’t magic, but they can make week 3 a lot more manageable: 

 

If your symptoms are brutal – like you can’t keep food or fluids down, you’re barely peeing, or pain is strong – that’s not something to just push through. That’s a “call a professional” moment.

 

Weight and blood sugar in week 3: what’s normal? 

 

By week 3, you might finally feel like you’re “seeing something” for all the effort. Just remember: it’s not a race, and everyone’s speed is different. You just need to remain patience and let Mounjaro work it’s magic. 

 

Blood sugar changes 

 

If you’re using Mounjaro for type 2 diabetes, week 3 is often when things start to feel more steady: 

  • You tend to have less spikes after eating. 

  • You’ll feel motivated and happy with readings that are closer to your target more often. 

  • Less of that “sugar rollercoaster” feeling (jittery highs, drained lows) if your other meds have been adjusted properly. 

But if you’re also on insulin or sulfonylureas, there’s still a risk of low blood sugar, especially as your appetite drops. Learn your hypo signs: 

  • Shaky, sweaty, fast heart rate. 

  • Sudden hunger, dizziness, or feeling weirdly anxious. 

  • Confusion or trouble concentrating. 

If that’s the case and your number is low, you treat the hypo the way your diabetes team taught you and then let them know if it keeps happening. 

 

Weight loss in week 3 

 

Some people see the scales move by this point, some don’t — that’s all fine. 

 

A few key reminders: 

  • The 2.5 mg dose is intentionally low – it’s more about letting your body adjust than smashing the weight off straight away. 

  • Most of the big weight-loss results you see in ads come from higher doses taken for months, not from week 3. 

  • Your main goal right now: build habits you can actually sustain – smaller portions, more mindful eating, better food choices – not crash dieting. 

 

If you noticed that the number on the scale hasn’t moved much yet towards your desired target but your appetite lever is lower and your blood sugar is better, then trust that’s still a win. The first 3 weeks is about building a solid foundation. 

 

Managing your dose in week 3 (don’t freestyle this) 

 

This part is simple but really important: you should not be changing your dose on your own in week 3. 

 

Most plans look like this at the start: 

  • 2.5 mg once a week for 4 weeks. 

  • Only after that does your prescriber decide if you move up to 5 mg, based on how you’re doing. 

Basic dose rules for week 3 

  • Inject on the same day each week. 

  • If you forget a dose and it’s more than 4 days after when you were supposed to take it, you should generally wait until the next scheduled time to resume. If it’s been longer than that, rest until your next scheduled day instead of trying to double up. 

  • You can switch your injection day if you absolutely have to, but try to leave three days between doses. 

 

If week 3 is rough and your side effects are making life miserable, that’s something to talk about before your dose is increased. Sometimes the answer is to stay at 2.5 mg for longer, rather than forcing your body to level up when it’s clearly not ready. 

 

How Cured Pharmacy can help in week 3 

 

By week 3, it’s not just information you need — it’s navigation. t is at this point that Cured Pharmacy can help you by: 

  • Helping you determine if that thing you’re feeling is “normal adjustment” or something to flag. 

  • Looking at what you’re currently taking in terms of meds and supplements to spot anything that might have a clash with Mounjaro. 

  • Offering practical advice on side effect management (such as which over‑the‑counter products are rarely harmful to try for nausea or constipation, and when not to self‑treat). 

It’s only three weeks — you’re not going to have it all sorted at this point. You’re simply supposed to keep showing up for your injections, pay attention to how they make you feel — and be honest about what it is about them that makes your life harder or easier, so your care team (and pharmacy) can help fix things. 

If you treat week 3 as a chance to learn your patterns instead of chasing instant results, you set yourself up for a much smoother next few months on Mounjaro. 

 

 

 

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