Are weight loss injections safe?
Weight loss injections have been a breakthrough for many people striving to achieve their health goals. However, it’s normal to have concerns, especially when there’s increased public attention on the potential risks and side effects of these treatments.
At ZAVA, we’re here to support you with accurate and reliable information to help you make informed choices about your health. On this page, you will find clear guidance on the safety of weight loss injections, what side effects you might experience, how to manage them, and when to seek medical advice.
Medically reviewed by
Dr Babak AshrafiLast reviewed: 12 Nov 2024
What are weight loss injections?
Weight loss injections, such as Mounjaro and Wegovy, are a type of treatment designed to help people manage their weight more effectively. They contain active ingredients, such as GLP-1 analogues, that mimic hormones your body naturally produces. These hormones help control appetite, slow digestion, and regulate how your body processes food.
By making you feel full sooner and reducing hunger, weight loss injections make it easier to eat less and stick to healthier habits.
Why they are effective
These injections are not a quick fix—they work best when used alongside healthy eating and regular exercise.
Studies have shown that they can help people lose a significant amount of weight and keep it off when used as prescribed. For example, the weight loss injection Wegovy can help you lose around 15% of your weight after 68 weeks of using 2.4mg weekly. Similarly, Mounjaro is reported to be able to help you lose 22.5% of body weight on average after 72 weeks of using 15mg per week. Weight loss injections are also usually well-tolerated by those who take them, with more than 80% of those taking 2.4mg Wegovy reporting weight loss of at least 5% of their initial body weight.
By combining weight loss injections with healthy habits, many people can achieve meaningful and lasting results on their weight loss journey.
Who might benefit?
Weight loss injections are usually prescribed to people who:
- have a Body Mass Index (BMI) of 30 or more (this is classed as obese).
- have a BMI of 27 or more and a health condition linked to their weight, like raised cholesterol or high blood pressure.
If you’re unsure if weight loss injections are right for you, speak to a healthcare professional or contact our doctors. They can help you decide.
Are weight loss injections safe?
Weight loss medications might not be right for everyone, that is why it’s important to speak to a doctor or medical prescriber before starting weight loss injections. They’ll review your medical history, including any conditions, medications, or allergies, to ensure the treatment is safe for you. Being open about your health helps your doctor recommend the best option and reduce potential risks. Never start these injections without professional advice.
When prescribed by a doctor and used correctly, weight loss injections are generally safe and work well. They have been carefully tested in clinical trials and approved by the Medicines and Healthcare products Regulatory Agency (MHRA) in the UK. This means they meet strict safety standards.
Like all medicines, weight loss injections can cause side effects. Most side effects are mild and go away on their own, but rare, more serious problems can happen. Knowing what to expect can help you feel prepared and confident.
Who shouldn’t use them?
Weight loss injections may not be safe if you:
- have certain health conditions, like heart failure or a history of severe gastrointestinal disease.
- are pregnant or breastfeeding.
Always check with your doctor to see if weight loss injections are right for you.
Common side effects: What to expect
Some people may experience side effects when they start using weight loss injections. These are usually mild and go away as your body adjusts. Common side effects include:
- feeling sick (nausea)
- constipation or diarrhoea
- feeling tired or low on energy
How to manage side effects
Here are some tips to help manage mild side effects:
- eat smaller meals and avoid rich or greasy foods
- drink plenty of water to stay hydrated
- rest if you feel tired
If the side effects don’t go away or bother you, speak to your prescriber. For detailed information about side effects, specifically for Mounjaro, visit our Mounjaro side effects page.
Uncommon risks such as pancreatitis: When to seek help
Serious side effects from weight loss injections are not common, but it’s important to know the warning signs. You should stop treatment and seek medical help if you experience:
- severe stomach pain, especially if it spreads to your back. This could be a sign of pancreatitis.
- yellowing of your skin or eyes (jaundice) or very dark urine. These could be signs of liver problems, gallstones or pancreatitis.
- difficulty breathing or swelling in your face or throat. This could mean you’re having a severe allergic reaction.
Pancreatitis and weight loss injections: what you need to know
Pancreatitis, or inflammation of the pancreas, is one of the uncommon but serious risks linked to some weight loss medications, including Mounjaro. Pancreatitis happens when the pancreas becomes irritated or damaged, which can lead to severe symptoms.
Signs of pancreatitis
- Severe and ongoing stomach pain, often spreading to the back.
- Nausea or vomiting that won’t stop.
- Fever or feeling unusually weak.
If you think you may have pancreatitis, stop using the medication immediately and seek emergency care.
Who may be at higher risk?
Certain conditions can increase the risk of pancreatitis regardless of any treatment used, such as:
- a history of pancreatitis
- gallstones or high levels of fat in the blood
What if you had pancreatitis in the past?
- If you’ve had pancreatitis before and the cause was treated (e.g. your gall bladder was removed), you might still be eligible to use weight loss injections
- If you’ve been told you may develop pancreatitis again, or the cause was unknown, you should consider a different treatment option.
In both cases, it’s important to consult a doctor. Your medical history will need to be carefully reviewed to assess the risks and determine if treatment is right for you.
Staying safe
If you notice any of these symptoms, go to A&E or call 999 immediately. Acting quickly can make a big difference.
What to do if you’re concerned
When to contact 111
Call 111 for advice if you have symptoms that are worrying but not urgent, like:
- nausea or vomiting that won’t go away.
- mild stomach pain that lasts for a few days.
- diarrhoea that doesn’t stop after two days.
111 can give you advice and tell you if you need to see a doctor.
When to go to A&E
Go to A&E or call 999 if you have serious symptoms, like:
- severe stomach pain that doesn’t go away.
- trouble breathing, wheezing, or swelling in your face or throat.
- signs of liver or gallbladder problems, like yellowing of your skin or eyes.
How to stay prepared
- Keep your medication details handy in case you need them in an emergency.
- Write down any symptoms you notice and tell your doctor at your next appointment.
Supporting you every step of the way
At ZAVA, we’re here to support you through every stage of your weight loss journey. If you have questions or concerns, you can contact our team for advice.
Explore the ZAVA weight loss service
Finding reliable information
Make sure to use trusted sources when learning about weight loss injections. If you’d like to learn more, visit our dedicated weight loss pages.
Last reviewed: 12 Nov 2024