Stomach Discomfort, Heartburn, Cramps
Why it happens:
Food sits longer in your stomach, and rich meals can hit harder.
You might notice:
Heartburn after heavy or greasy meals.
Cramps at night if you’ve used your “off day” to have stodgy/heavy food when suppression wears off before your next jab.
Tip:
Pay attention to what you’re eating, especially in that last day before your next dose.
Constipation
Very common.
Why it happens:
Slower emptying = slower transit through the whole system.
Drink plenty of water.
Include fibre in meals.
Stay active if you can.
If it’s painful or persistent, talk to your prescriber.
Diarrhoea
Less common than constipation, but can happen.
Usually mild and short-lived.
Stay hydrated.
Persistent or severe? Get medical advice.
Injection Site Reactions
Redness, itching, or slight swelling where you inject.
Usually mild and temporary.
Always clean the area properly and rotate spots each week.
Low Blood Pressure
GLP-1s can sometimes lower blood pressure slightly.
If you’re already on blood pressure meds, tell your doctor.
Feeling lightheaded on standing? Move slowly and stay hydrated.
Itching or Rash
Mild skin reactions can occur.
Usually self-resolving.
Severe rash? Contact your prescriber.
Hair Loss (Less Common)
Some users report increased shedding, but research is limited.
May be related to rapid weight loss itself, not the medication directly.
Significant hair loss? Discuss with your prescriber.
Remember: Most Side Effects Ease Over Time
Many of these peak in the first month or two and then settle down, and your body often adjusts, but you don’t have to suffer in silence if something feels wrong.
When to Contact Your Prescriber or GP
Side effects that are unbearable or affecting daily life.
Repeated vomiting or signs of dehydration.
Severe abdominal pain.
Allergic reactions, like a significant rash or swelling.
Your prescriber wants you to have safe, effective treatment, and they want to know if something’s not right.
One Last Thought
These side effects can be annoying, embarrassing, or downright gross, but they’re usually manageable.
Know what’s normal.
Know when to get help.
And don’t ever feel you have to tough it out alone.
Because this journey isn’t about punishment or suffering, it’s about giving yourself the tools and support to live better, healthier, and with more control.
You deserve nothing less.
Why Do These Side Effects Happen?
GLP-1 medications work by slowing down how your stomach empties, regulating blood sugar, and changing appetite signals in the brain.
This is great for reducing cravings. But it can mean your digestive system doesn’t move at its usual pace.
Slower digestion = more time for food to sit around = more chance of gas, bloating, and other fun surprises.
The Most Common Side Effects (And What’s Really Going On)
These are the most frequently reported side effects on GLP-1 meds like Ozempic, Wegovy, and Mounjaro.
Not everyone gets all of them. You might have a few, or none at all. But it helps to know what’s normal and why it happens.
Feeling Sick (Nausea)
Why it happens:
GLP-1s slow stomach emptying. That full signal is stronger, but so is the chance of feeling queasy, especially after big meals.
Real Talk:
Early on, odd triggers might catch you off guard. Brushing your teeth too far back? Instant gag. One bite too many when your brain is already saying "stop"? Suddenly, you’re queasy.
And certain smells, like a cold coffee cup left on your desk, can flip you into the ick without warning.
Tip:
Eat small, balanced meals. Don’t force the last bite “just to finish.” Listen to that stop signal.
Being Sick (Vomiting)
Less common than nausea, but it happens if you push past those cues.
More likely early in treatment or after ignoring fullness signals.
If you're vomiting repeatedly or can’t keep fluids down, speak to your prescriber immediately.
Burping (Especially Sulphur Burps) and Excess Wind
Why it happens:
Slower digestion means more time for gas to build up.
Real Talk:
It often starts with harmless little burps… then turns into full-on sulphur burps that taste like rotten eggs.
They can even wake you up at night.
What helps?
Usually worse in the 2–3 days after the jab.
Skipping meals or eating too little makes them worse.
Eating small, frequent meals reduces them a bit.
Antacids? Pepto? Not much use.
Disclaimer: This article is for general information only and isn’t medical advice. Always talk to your prescribing professional or GP if you’re unsure about symptoms, side effects, or treatment decisions.
By now, you’ve probably realised these medications can be life-changing for appetite, food noise, and weight management. But they can also come with side effects, some expected, some surprising, and a few that no one really warns you about upfront.
If you've been on Ozempic, Wegovy, or Mounjaro for a while, chances are you’ve already met a few of these.
Let’s talk honestly about what they are, why they happen, and what you can do about them. Because understanding them can make all the difference between feeling blindsided and feeling in control.
A Word About Side Effects
Most people experience mild to moderate side effects, especially early on, or after a dose change. Some settle over time. Others come and go depending on what you eat, your dose, or even where you are in your weekly cycle.
But if you’re dealing with anything unbearable, severe, or unusual?
Stop.
Talk to your prescriber.
Don’t try to tough it out alone.
Your health always comes first.
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Pen Hub Team
Published:
4 Jul 2025
Updated:
6 Oct 2025
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