Your Top 5 Questions About Weight Loss Injections

Weight loss injections are everywhere in the headlines right now. For some people, they represent hope. For others, they raise a lot of questions and even some anxiety. If you are curious, you might be feeling both at once.

In the UK, a few of these medications are now licensed (1). The two you are most likely to hear about are Wegovy (semaglutide) and Mounjaro (tirzepatide). More are being studied, so other options may follow in the future.

Over the past year or two, more and more people have been asking me about weight loss injections.

In this guide, I will share the five questions I hear most often. My aim is not to tell you what to do, but to help you understand the facts, the pros and cons, and the things to weigh up before deciding what feels right for you.

1. How do weight loss injections work, and how much weight could I lose?

Both Wegovy and Mounjaro are weekly injections designed to help with weight loss. They do this by mimicking hormones that regulate appetite (1).

Wegovy (semaglutide) acts on GLP-1, a hormone we naturally release after eating. It slows how quickly food leaves the stomach, reduces hunger signals to the brain, and supports blood sugar control (2,3).

Mounjaro (tirzepatide) acts on both GLP-1 and another hormone, GIP. Working on two hormones together can further enhance feelings of fullness. Early studies suggest this might lead to greater weight loss than GLP-1 alone. Although, with newer higher doses of Wegovy now available, outcomes between the two are now broadly comparable (4,5).

By enhancing these hormones, the injections can help you feel fuller for longer, quieten constant thoughts about food (sometimes called ‘food noise’), and help you feel more in control around food (1,6).

What the research shows

• With Wegovy, people lost on average 20.7% of their body weight at the highest dose over 72 weeks, with one in three losing 25% or more (5). It is also the first and only medication proven to reduce the risk of major cardiovascular events like heart attack and stroke (7).
• With Mounjaro, people lost on average 22.5% of their body weight. This was measured at the highest dose over 72 weeks, making it one of the most effective weight loss medications studied so far (8).

Everyone responds differently. For some, the appetite changes feel life-changing and side effects are manageable. For others, tolerance is more difficult. Your response, alongside lifestyle factors like diet, movement, sleep, and stress, will shape how effective the injections are and how sustainable the results feel.

2. Are they safe, and do they have side effects?

Like all medications, weight loss injections can cause side effects. The most common are digestive issues such as nausea, constipation, diarrhoea, or stomach discomfort (1). These usually happen in the early weeks or after a dose increase, and for most people they are mild to moderate and settle with time (1).

In clinical trials, around 5–6% of people stopped treatment because of side effects at higher doses (5,8,9). More serious risks are rare but possible, which is why these injections should only be used with medical supervision (1).

There is also growing discussion around nutritional risks. Because weight loss injections suppress appetite, many people eat much less overall and with it, fewer nutrients such as protein, fibre, calcium, vitamin D, iron and B-vitamins (10). Side effects like diarrhoea may also reduce how well absorbed some nutrients are, and some people may already have nutrient gaps before starting treatment (5,10).

Rapid weight loss itself can also mean the body loses muscle and bone as well as fat. Lower protein intake, fast weight reduction and little strength training can increase this risk, especially in older adults and women around menopause (10). Getting enough nutrients and including some resistance exercise can reduce these risks and are key to protecting long-term health (10). Working with a dietitian or healthcare professional can help monitor your intake and lower the chance of deficiencies.

It’s also important to think about the emotional side. These medications can change eating patterns quickly. For some people that brings relief, but for others it may heighten anxiety about food, mask disordered eating, or create a sense of dependence (11). Professional support can help you navigate this, making side effects easier to manage while keeping your relationship with food healthy as you focus on the benefits.

3. Where can I get weight loss injections in the UK?

In the UK, weight loss injections can be accessed through the NHS or privately. Exactly what is available, and how quickly, can depend on where you live. The best first step is to speak with your GP. They can explain whether you might qualify on the NHS or guide you towards safe private options (1,13).

If you do go private, make sure your provider is properly regulated:

• Pharmacies should be registered with the General Pharmaceutical Council (GPhC)
• Clinics with the Care Quality Commission (CQC) in England or the equivalent in Scotland and Wales
• Prescribers with the General Medical Council (GMC).

This helps ensure the medication is genuine, the dose is safe, and the care meets UK standards. Avoid unregulated websites or providers offering injections without medical checks. They may be unsafe, counterfeit, or unsuitable for you. The MHRA’s #FakeMeds campaign has tools and resources to help you check for safe suppliers (14).

4. What happens when you stop taking weight loss injections?

When you stop treatment, the medication leaves your system within a few weeks and its effects fade. The changes you noticed when starting the injections begin to work in reverse (14). Food moves through the stomach more quickly, hunger hormones return to their previous levels, and “food noise” often makes a comeback (2,6).

Your body may also try to restore some of the weight it sees as “lost,” a natural process called homeostasis (9,12).

Research shows that many people regain a large share of the weight they lost after stopping weight loss injections. This also means some of the health benefits, such as improved blood pressure and blood sugar, can also fade (9,12).

Research is underway to understand the best ways to help people maintain weight loss long term. Methods could include continuing treatment for longer, moving to a lower dose, or combining medication with structured lifestyle support (16).

How to protect your progress

• Build new habits while on treatment: Use the quieter appetite window to practise long-term skills. This includes balancing your meals, becoming aware of your hunger, regular movement, sleep, and stress management.
• Plan your transition: Some people taper gradually or move to a lower maintenance dose with clinical guidance, which may help prevent a sharp rebound in appetite.
• Lean on support: Professional guidance from someone like a dietitian can help. From setting expectations, adapting as things change, and protecting your relationship with food. A dietitian can support you in building habits that last beyond the injections.

It is normal for some weight regain to happen after stopping weight loss injections. Long-term progress is supported by the habits and routines you establish alongside them.

5. Should I take weight loss injections?

There is no single right answer. It depends on your health, your goals, and your circumstances. These medications can be very effective, but they are not right for everyone.

They may be worth considering if you:

• Meet the medical criteria, such as a certain BMI and a weight-related health condition, or as advised by your clinician.
• Have tried other approaches and found it difficult to lose or maintain weight.
• Would benefit from extra support to manage hunger, cravings, or “food noise.”

They may not be suitable if you (1):

• Are pregnant, breastfeeding, or trying to conceive.
• Have certain health conditions such as a history of pancreatitis, severe kidney or liver problems, or some thyroid cancers.
• Feel that medication might add to, rather than reduce, stress or anxiety around food.

Other things to consider include the cost of ongoing treatment and your willingness to accept possible side effects. It’s also worth considering whether you feel ready to make the lifestyle changes alongside the medication.

Even if you are eligible, injections are a tool, not a solution on their own. They absolutely can make progress easier in the short term. Lasting results come from combining them with changes to eating, movement, sleep, and stress management. With the right support, they can be part of a wider plan that protects your health and your relationship with food.

Final thoughts

Weight loss injections are one option that can help, but they are not the whole story. They work best when combined with sustainable lifestyle changes.

It is also important to think about the practical side. Consider the cost, the potential side effects, and what happens once treatment stops. Planning ahead is just as important as the decision to start.

I hope this guide has answered some of your questions and left you feeling clearer about what these medications can and cannot do. If you are considering weight loss injections, or if you have already started and want help making the results last, professional guidance can make all the difference. Together we can look at your options, weigh up the pros and cons, and create a plan that supports your health and your long-term goals.

Still have questions about weight loss injections or how to make the results last?

Let’s talk it through. Book a consultation and we’ll create a plan that supports both your goals and your relationship with food.

References

1. Medicines and Healthcare products Regulatory Agency (MHRA). GLP-1 medicines for weight loss and diabetes: what you need to know [Internet]. London: GOV.UK; 2025. Available from: https://www.gov.uk/government/publications/glp-1-medicines-for-weight-loss-and-diabetes-what-you-need-to-know/glp-1-medicines-for-weight-loss-and-diabetes-what-you-need-to-know#summary-what-do-those-taking-or-planning-to-take-these-medicines-need-to-remember
2. Heise T, DeVries JH, Urva S, Li J, Maggs D, Gumbiner B, et al. Tirzepatide reduces appetite, energy intake, and fat mass in people with type 2 diabetes. Diabetes Care. 2023;46(5):998-1004. doi:10.2337/dc22-1710
3. Garvey WT, Batterham RL, Bhatta M, et al. Two-year effects of semaglutide in adults with overweight or obesity: the STEP 5 trial. Nat Med. 2022;28:2083-91. doi:10.1038/s41591-022-02026-4
4. Rodriguez PJ, Goodwin Cartwright BM, Gratzl S, et al. Semaglutide vs tirzepatide for weight loss in adults with overweight or obesity. JAMA Intern Med. 2024;184(9):1056-64. doi:10.1001/jamainternmed.2024.2525
5. Wharton S, Freitas P, Hjelmesaeth J, Kabisch M, Kandler K, Lingvay I, et al. Efficacy and safety of semaglutide 7.2 mg in obesity: the STEP UP trial. Presented at: American Diabetes Association 85th Scientific Sessions; 2025 Jun 20-23; Chicago, IL, USA. ClinicalTrials.gov identifier: NCT05646706.
6. Diktas HE, Cardel MI, Foster GD, LeBlanc MM, Dickinson SL, Ables EM, et al. Development and validation of the Food Noise Questionnaire. Obesity (Silver Spring). 2025. doi:10.1002/oby.24216
7. Lincoff AM, Brown-Frandsen K, Colhoun HM, Deanfield J, Emerson SS, Esbjerg S, et al. Semaglutide and cardiovascular outcomes in obesity without diabetes. N Engl J Med. 2023;389(24). doi:10.1056/NEJMoa2307563
8. Jastreboff AM, Aronne LJ, Ahmad NN, Wharton S, Connery L, Alves B, et al. Tirzepatide once weekly for the treatment of obesity. N Engl J Med. 2022;387(3):205-16. doi:10.1056/NEJMoa2206038
9. Wilding JPH, Batterham RL, Calanna S. Once-Weekly Semaglutide in Adults with Overweight or Obesity. N Engl J Med. 2021 Feb 10;384(11):989–1002. doi:10.1056/NEJMoa2032183
10. ​​Mozaffarian R, Glynn RJ, Ridker PM, et al. Nutritional priorities to support GLP-1 therapy for obesity. Obesity Pillars. 2025. doi:10.1016/j.obpill.2025.2400
11. Arillotta D, Floresta G, Guirguis A, Corkery J, Catalani V, Martinotti G, et al. GLP-1 receptor agonists and related mental health issues: insights from a range of social media platforms using a mixed-methods approach. Brain Sci. 2023;13(11):1503. doi:10.3390/brainsci13111503
12. Aronne LJ, Sattar N, Horn DB, et al. Continued treatment with tirzepatide for maintenance of weight reduction in adults with obesity: the SURMOUNT-4 randomized clinical trial. JAMA. 2024;331(1):38-48. doi:10.1001/jama.2023.24945
13. National Institute for Health and Care Excellence. Obesity: identification, assessment and management (NG246) [Internet]. London: NICE; 2025. Available from: https://www.nice.org.uk/guidance/ng246
14. Medicines and Healthcare products Regulatory Agency (MHRA). FakeMeds: Safely buy medication online [Internet]. FakeMeds. Available from: https://fakemeds.campaign.gov.uk
15. Rubino D, Abrahamsson N, Davies M, Hesse D, Greenway FL, Jensen C, et al. Effect of continued weekly subcutaneous semaglutide vs placebo on weight loss maintenance in adults with overweight or obesity: the STEP 4 randomized clinical trial. JAMA. 2021;325(14):1414-25. doi:10.1001/jama.2021.3224
16. Quarenghi M, Capelli S, Galligani G, Giana A, Preatoni G, Turri Quarenghi R. Weight regain after liraglutide, semaglutide or tirzepatide interruption: a narrative review of randomized studies. J Clin Med. 2025;14(11):3791. doi:10.3390/jcm14113791