Managing Side Effects
With Confidence
Evidence-based strategies for managing the most common side effects of medicated weight loss treatment — nausea, reflux, constipation, fatigue, injection site reactions, and mood changes — with a personal symptom diary workbook.
How to Use This Guide
Work through the sections relevant to the side effects you are experiencing. Each section provides evidence-based strategies and a workbook exercise to help you manage symptoms and track your progress. Use the Symptom Diary in Section 8 to record your symptoms week by week.
Click "Save to Device" to download your answers, and "Load Answers" to continue where you left off. Bring your completed diary to your next consultation — it will help your Nurse Consultant Prescriber understand your experience and provide targeted support.
✦ Evidence Base
GLP-1 receptor agonists are among the most thoroughly studied weight management medications available. The most common side effects — nausea, vomiting, diarrhoea, and constipation — are gastrointestinal in nature and occur because GLP-1 receptors are found throughout the digestive system. Clinical trial data from the STEP and SURMOUNT programmes show that gastrointestinal side effects affect 40–70% of patients at some point during treatment, but the vast majority are mild to moderate and resolve within the first 4–8 weeks as the body adapts (Wilding et al., NEJM, 2021; Jastreboff et al., NEJM, 2022).
The 'start low, go slow' dose escalation approach used in your programme is specifically designed to minimise side effects by allowing your body to adapt gradually to the medication. Most patients find that side effects are at their worst during the first 1–2 weeks at each new dose level, and then improve significantly. Understanding this pattern — that discomfort is temporary and a sign the medication is working — helps many patients persist through the early weeks and reach the point where treatment becomes much more comfortable.
Side Effect Frequency Overview
| Side Effect | How Common | Typical Onset | Usually Resolves |
|---|---|---|---|
| Nausea | Very common (40–60%) | Week 1–2 of each dose | 4–8 weeks |
| Vomiting | Common (20–30%) | Week 1–2 of each dose | 4–6 weeks |
| Diarrhoea | Common (20–30%) | Variable | Weeks to months |
| Constipation | Common (15–25%) | Week 2–4 | With dietary changes |
| Reflux / heartburn | Common (15–20%) | Week 1–4 | 4–8 weeks |
| Fatigue | Common (10–20%) | Week 1–2 | 2–4 weeks |
| Headache | Common (10–15%) | Week 1–2 | 1–2 weeks |
| Injection site reaction | Common (5–15%) | After each injection | Hours to days |
| Reduced appetite | Very common (>80%) | Week 1 | Ongoing (intended effect) |
The Most Important Thing to Know
Side effects are not a sign that the medication is harming you — they are a sign that it is active in your body. The discomfort is temporary. The vast majority of patients who persist through the early weeks report that side effects resolve significantly, and that the benefits — reduced appetite, weight loss, improved energy and health — far outweigh the initial discomfort.
If your side effects are severe, persistent, or significantly affecting your quality of life, contact your Nurse Consultant Prescriber. Dose adjustments, timing changes, or additional support can make a significant difference.
Seek Medical Attention
Contact your Nurse Consultant Prescriber promptly or seek urgent medical attention if you experience:
Severe, persistent abdominal pain (possible pancreatitis)
Persistent vomiting preventing you from eating or drinking
Signs of an allergic reaction: rash, swelling, difficulty breathing
Severe or persistent diarrhoea causing dehydration
Significant changes in mood, thoughts of self-harm
Vision changes or severe headache
Rapid heart rate at rest
Any symptom that seriously concerns you
Workbook Exercises
References & Further Reading
Wilding, J.P.H. et al. (2021). Once-weekly semaglutide in adults with overweight or obesity. New England Journal of Medicine, 384(11), 989–1002.
Jastreboff, A.M. et al. (2022). Tirzepatide once weekly for the treatment of obesity. New England Journal of Medicine, 387(3), 205–216.
Gorgojo-Martínez, J.J. et al. (2022). Clinical recommendations to manage gastrointestinal adverse events in patients treated with GLP-1 receptor agonists. Journal of Clinical Medicine, 12(1), 145.
NICE. (2014). Gastro-oesophageal reflux disease and dyspepsia in adults: investigation and management (CG184). National Institute for Health and Care Excellence.
NICE. (2010). Constipation in adults: management (CG99). National Institute for Health and Care Excellence.
Leidy, H.J. et al. (2015). The role of protein in weight loss and maintenance. American Journal of Clinical Nutrition, 101(6), 1320S–1329S.
Gentile, S. et al. (2016). Insulin injection technique and its impact on glycaemic control. Diabetes Care, 39(10), e176–e177.
MHRA. (2023). GLP-1 receptor agonists: reports of suicidal thoughts — review of evidence. Drug Safety Update.
NHS. (2023). Side effects of GLP-1 receptor agonists. NHS.uk.
Important: This guide is for educational and supportive purposes only. It does not constitute personalised medical advice. Always follow the guidance of your Nurse Consultant Prescriber regarding your medication and treatment plan. If you experience severe, persistent, or concerning symptoms, contact LSJ Rejuvenate or seek medical attention promptly. In an emergency, call 999. For mental health support, call the Samaritans on 116 123 (free, 24/7).
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