You might be familiar with some of the common side effects of GLP-1 weight loss medication – nausea, bloating and constipation. They affect around one in 10 patients and they’re usually mild and manageable.

However, there are some more serious side effects and complications to be aware of. While they aren’t as common, you need to know what they are so you can get urgent medical attention if required.

To keep you safe and healthy, this article outlines what they are – and the symptoms to look out for.

GLP-1 Holiday Risks

Thinking of taking a break from Mounjaro, Wegovy or Saxenda? This is common around Christmas and New Year, as patients want to indulge in festive feasts and alcoholic drinks.

However, we advise you not to do this. When you stop using GLP-1 weight loss injections the level of medication in your body drops. So the same dose could be too high for your system when you start taking it again. This increases your risk of serious adverse effects, including pancreatitis.

If you plan to take a break from your medication, please tell your healthcare provider. They’ll be able to guide you through the process in the safest way possible.

Misusing your medication in other ways – like “microdosing” or using the “fifth dose” – can also be risky. Not using the pen as prescribed also makes it harder for your healthcare provider to support you, as they won’t know how much you’ve injected.

The best thing you can do is follow the manufacturer’s guidance and stick to the dosing schedule your healthcare provider has given you. And if you’re concerned about balancing festive fun and GLP-1s, this article gives you tips on how to stay on track while enjoying Christmas and New Year celebrations.

Side Effects of GLP-1s You Shouldn’t Ignore

Pancreatitis

The most serious side effects of GLP-1s are pancreatitis and gallbladder disorders. According to the MHRA, these can occur in between one in 100 and one in 10,000 patients, depending on the type of GLP-1 weight loss jab you are using.

Pancreatitis is when the pancreas becomes inflamed. It requires urgent medical attention and can cause complications. In some cases, it can be fatal.

Please seek urgent medical attention if you have the following symptoms:

  • Severe abdominal pain. This is the main symptom of pancreatitis. It can feel like sudden, sharp, or burning pain in the upper abdomen, which often radiates to the back. It can also get worse after eating
  • Persistent nausea – with or without vomiting
  • Fever
  • Elevated heart rate
  • Jaundice – a yellowing of the skin
  • Bloating
  • Tender abdomen that’s sensitive to touch
  • Fatty stools

Severe Dehydration

Severe dehydration is not a direct side effect of GLP-1 weight loss medication. But vomiting, nausea, diarrhoea and constipation may result in dehydration. That’s why it’s so important to drink enough water when you’re using weight loss jabs.

Drinking alcohol alongside Mounjaro can also make these common side effects worse. Alcohol also causes the body to get rid of excess fluid and salt, making dehydration more likely. It’s one of the reasons why we recommend you avoid alcohol when taking Mounjaro. Women using Wegovy shouldn’t drink more than one glass a day, while men should stick to two.

If dehydration is severe it may lead to other serious health complications such as kidney damage, which can result in hospitalisation.

Go to a GP or call NHS 111 if you have symptoms that indicate severe dehydration. According to the NHS, these include:

  • Feeling unusually tired
  • Feeling confused and disorientated
  • Feeling dizzy when you stand up and it does not go away
  • Dark yellow pee or peeing less than normal
  • Breathing quickly with a fast heart rate

Serious Allergic Reactions

Severe allergic reactions to Wegovy and Mounjaro, like anaphylaxis, are rare. They affect one in 1,000 patients and usually new users of GLP-1 medication.

You should get immediate medical help and inform your doctor if you experience breathing problems. Or if you get rapid swelling of the lips, tongue and/or throat with difficulty swallowing and a fast heartbeat.

Get tailored weight loss advice with our Renu app

Sign Up Now

Key Takeaways

  • Serious side effects aren’t that common. But it’s still important to know what they are, so you know when to see a doctor. The most severe risks of GLP-1 medications include pancreatitis, severe dehydration and allergic reactions.
  • Misusing your GLP-1 weight loss injections can increase your risk of severe side effects. So please follow your dosing schedule. Let your healthcare provider know if you want to take a break from your treatment.
  • Symptoms of pancreatitis include severe abdominal pain (the main symptom) radiating to the back, nausea, bloating, fever, jaundice and fatty stools.
  • Look out for symptoms of severe dehydration too. See your GP or call NHS 111 if you feel dizzy, unusually tired or are confused and disorientated.
  • For non-urgent queries, remember we’re always here to support you. If you have any questions or concerns about your GLP-1 weight loss treatment, please don’t hesitate to contact us. Call us on 0141 774 5023.

References

MHRA (2024). GLP-1 receptor agonists: reminder of the potential side effects and to be aware of the potential for misuse. [online] GOV.UK. Available at: https://www.gov.uk/drug-safety-update/glp-1-receptor-agonists-reminder-of-the-potential-side-effects-and-to-be-aware-of-the-potential-for-misuse.

NHS (2022). Dehydration. [online] NHS. Available at: https://www.nhs.uk/conditions/dehydration/.

Package leaflet: Information for the patient Wegovy FlexTouch. (n.d.). Available at: https://www.medicines.org.uk/emc/files/pil.13800.pdf.

Package leaflet: Information for the patient Mounjaro KwikPen (n.d.). Available at: https://www.medicines.org.uk/emc/files/pil.15481.pdf.