If you’re on GLP‑1 medication (Ozempic, Wegovy, Mounjaro / tirzepatide), chances are the medication is doing its job — your appetite is down, portions are smaller, and weight loss is happening.
But the side effects can feel like a tax you didn’t agree to pay.
This guide is designed to be a practical troubleshooting page you can come back to weekly. It’s built around real‑world experience (including my own), and evidence-led principles.
Quick links :
– GLP‑1 medication access (UK): https://www.alanspicer.com/mounjaro
– Daily support supplements (fibre + protein + gut support): https://www.alanspicer.com/lilyandloaf
Anchor guides:
– MedExpress + Mounjaro (full guide): https://alanspicer.com/medexpress-weight-loss-review-mounjaro-guide/
– Lily & Loaf Daily Essentials (full guide): https://alanspicer.com/daily-essentials-the-best-supplements-for-sustained-weight-loss-on-glp-1s-by-lilyloaf-2026-guide/
TL;DR: why GLP‑1 side effects happen
Most GLP‑1 side effects come from three things:
- Slower gastric emptying (food sits longer)
- Lower overall food + fluid intake (you simply consume less)
- Dose escalation (your body adapts over time)
The goal isn’t to “power through”. The goal is to build a routine that makes side effects less frequent and less intense.
Real‑world authority (why I’m writing this)
In 2025 I lost over 6 stone (86lbs) using Mounjaro, and I’ve personally dealt with most common GLP‑1 issues: nausea, constipation, fatigue, dehydration signals, appetite swings, and the practical weirdness of learning how to eat again.
I documented it publicly as a near‑daily video diary: https://www.youtube.com/@AlanSpicerisLosingIt
The “GLP‑1 Side Effects Matrix” (use this first)
| Symptom | Most common cause | First fix (fastest win) | If it keeps happening |
| Nausea | Dose increase, eating too fast, high-fat meals | Smaller meals + slower eating | Adjust meal timing; speak to clinician |
| Constipation | Less fibre + less water + slower motility | Hydration + fibre + gentle movement | Review diet; consider daily support stack |
| Fatigue | Low calories, dehydration, low electrolytes | Fluids + salt/electrolytes + protein | Check intake; discuss labs with clinician |
| Bloating / reflux | Large meals, spicy/fatty foods, late eating | Smaller meals, earlier dinner | Review triggers; clinician advice |
| Diarrhoea | Dose escalation, food choices, sensitivity | Simple meals; avoid heavy fat | Clinician advice if persistent |
1) Nausea on GLP‑1s
What it feels like
- Background nausea even when you haven’t eaten
- Nausea after “normal” meals that used to be fine
- Nausea that spikes after injection days
What triggers it most
- Eating quickly
- Fatty meals (especially fried foods)
- Large portions (even if they’re “healthy”)
- Skipping food all day then eating a big dinner
Practical fixes that work
- Eat smaller meals more often
- Keep meals bland and protein-first
- Don’t eat within 2–3 hours of bed
- Slow down: put the fork down between bites
Related reading: – What to eat on Mounjaro (protein-first): (support post to be added)
2) Constipation on GLP‑1s
Constipation is the side effect that quietly breaks people.
Not because it’s dramatic — but because it turns every day into a low-level struggle.
Why it happens
- You’re eating less food overall
- You’re often eating less fibre
- You’re drinking less without noticing
- Motility slows due to GLP‑1 action
The “3-part constipation fix”
Part 1: hydration (non-negotiable) – Sip regularly, not just at meals
Part 2: fibre (food first, then support) – Aim for consistent daily fibre, not bursts
Part 3: movement – Gentle daily walking helps motility more than people think
If you need a low-friction daily baseline, this is where the Daily Essentials approach can help: https://www.alanspicer.com/lilyandloaf
3) Fatigue on GLP‑1s
GLP‑1 fatigue is often not “sleep tired”. It’s a flat, foggy feeling.
Common causes
- You’re under-eating protein
- You’re unintentionally dehydrated
- Electrolytes are low (especially if you’re eating very little)
Practical fixes
- Protein-first meals (even if small)
- Hydration targets and routine
- Consider electrolytes if you’re struggling
4) Bloating and reflux
A lot of people blame the medication, when it’s often the food timing + portion size.
Quick wins: – Smaller portions – Earlier dinner – Reduce high-fat meals on injection day
5) Appetite swings (the thing nobody warns you about)
Some days you have no appetite. Other days you suddenly want everything.
This is normal, and it’s why systems beat motivation.
Quick wins: – Keep 2–3 reliable “safe meals” – Don’t wait until you’re starving
The GLP‑1 daily routine that prevents most side effects
| Time | Habit | Why it helps |
| Morning | Fluids + protein-first start | Reduces nausea, fatigue |
| Midday | Small meal + fibre | Prevents constipation |
| Afternoon | Fluid top-up | Stops dehydration creep |
| Evening | Smaller dinner, earlier | Reduces reflux |
| Daily | Light movement | Improves motility |
FAQs (snippet-first)
How long do GLP‑1 side effects last?
Most people find GI side effects are worst during dose escalation and ease over time, especially with hydration, meal size control, and routine.
Why do GLP‑1s cause constipation?
Because appetite and intake drop, gastric emptying slows, and motility changes — often leading to lower fibre and fluid intake.
What should I eat when I feel nauseous on Mounjaro?
Small, bland, protein-first meals (and slower eating) are usually the best starting point.
Do I need supplements on GLP‑1s?
Not always. But many people struggle to hit protein, fibre, and micronutrients early on due to reduced intake. A simple daily baseline can help.
What’s the simplest “support stack” if I’m struggling?
A practical baseline is: protein + fibre + gut support. That’s why the Daily Essentials Bundle exists.
Next steps
If you need medication support in the UK: https://www.alanspicer.com/mounjaro
If side effects are making the journey harder than it needs to be: https://www.alanspicer.com/lilyandloaf
Transparency: Some links are affiliate links. Using them supports my free GLP‑1 content at no extra cost to you.
