Health Hub · Weight loss

Weight Loss Injection Side Effects — and How to Actually Manage Them

By the Lyng Pharmacy team · Clinically reviewed by Jeetender Singh Sahota, Superintendent Pharmacist (GPhC 2048691) · Updated August 2026 · 4 min read
Pharmacist talking through a patient’s symptoms in the consultation room
Our pharmacist can assess your symptoms in the private consultation room — no appointment needed.

Almost everyone starting Mounjaro, Wegovy or an oral GLP-1 gets some side effects in the first few weeks. Most are predictable, most are manageable, and most settle. Knowing which is which is the difference between pushing through a rough fortnight and abandoning a treatment that would have worked.

This is the advice we give at check-ins at our West Bromwich clinic — and the reason we build check-ins into treatment in the first place.

Nausea: the common one

Nausea is the side effect people notice most, usually in the days after a dose increase. What helps: smaller portions, eating slowly and stopping before you are full, avoiding fatty and fried food, sipping water through the day rather than gulping, and not lying down straight after eating. Ginger and plain, dry food genuinely help some people. If a dose step is rough, staying at your current dose for another few weeks instead of climbing is a legitimate option — tell us rather than quietly stopping.

Person holding excess weight around the waistline
Treatment is licensed from a BMI of 30 — or 27 with a weight-related health condition.

Constipation and the fluid problem

These treatments slow the gut, and appetite suppression means most people eat and drink less, so constipation is almost inevitable without a plan. Keep fluids up deliberately, get fibre in from wholegrains, fruit, vegetables and beans, and move every day. If it persists, ask us — the right laxative depends on the problem, and matching one properly to your situation is a two-minute conversation at the counter.

Tiredness, and why protein matters

Feeling flat in the early weeks usually reflects eating far less than before. Protein at every meal protects muscle while you lose fat, keeps you fuller, and steadies energy. Losing weight quickly without enough protein and some resistance exercise means losing muscle alongside fat — the outcome nobody wants, and the one we most often have to steer people away from.

What needs attention, not patience

Come back to us or seek medical advice promptly for severe or persistent tummy pain, especially pain that goes through to your back, or vomiting you cannot keep on top of. The same applies to signs of dehydration, or any severe pain in the upper right of your tummy. These are uncommon, but they are the ones that are not part of “settling in”. If you are ever unsure, call us on 0121 500 5756 — we would far rather check.

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Frequently asked questions

How long do weight loss injection side effects last?
For most people the early nausea and constipation ease within a couple of weeks at a given dose, then may return briefly after each dose increase. That pattern is why doses build up slowly over months.
Should I stop treatment if the side effects are bad?
Speak to your pharmacist before stopping. Very often the answer is to hold at your current dose for longer rather than climbing, or to change what and how you are eating — not to abandon treatment altogether.
Will I lose muscle as well as fat?
You can, if you lose weight quickly without enough protein or any resistance exercise. Prioritising protein at every meal and doing some strength work two or three times a week protects muscle while the fat comes off.
Can I drink alcohol on a GLP-1 treatment?
Many people find they simply want it less. Alcohol adds calories, irritates a slowed stomach and worsens nausea, so keeping it low, especially around a dose increase, is sensible.
Which side effects mean I should get help the same day?
Severe or persistent tummy pain — particularly pain radiating to your back — relentless vomiting, or signs of dehydration all warrant prompt advice. Call us, your GP or NHS 111, and 999 in an emergency.

Related reading

Mounjaro in West Bromwich: How It Works and How to Start →Wegovy Injections: How Semaglutide Works →What Weight Loss Treatment Actually Costs →All health articles →

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Weight loss clinic — check your suitability →Online shop →NHS blood pressure checks →Contact us & opening hours →
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