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Can you have surgery if you're using a weight loss injection?
Using a GLP-1 means you need to prepare for your surgery carefully, to ensure your stomach is empty before your procedure. Here, we’ll take a closer look at all the factors to consider when having surgery while using a weight loss injection.
Medically reviewed by
Alexandra Cristina Cowell, Writer & Clinical Content Reviewer
- Having surgery when using a weight loss injection usually requires developing a plan with your hospital healthcare team.
- This can involve specific instructions about fasting and managing your doses, and in some cases an ultrasound scan to make sure your stomach is empty.
- GLP-1s are thought to put you more at risk of complications during surgery, so there are some things you need to be aware of.
- Remaining at a healthy weight can improve recovery post-surgery, so focus on a balanced diet while using a weight loss injection.
What are the risks of using GLP-1s when you’re having surgery?
The main risk when having surgery while you’re using a GLP-1 is pulmonary aspiration, which is when sick gets inhaled into your airways.
GLP-1 agonists such as Mounjaro, Saxenda and Wegovy slow down gastric emptying, so there’s an increased risk of food still being present in the stomach when it comes time to undergo surgery. Because general anaesthetics cause heavy sedation, there’s a risk that the contents of the stomach can be passively regurgitated into the airway, as the body loses control of its normal reflexes.
Pulmonary aspiration has been linked to a variety of life threatening conditions, such as adult respiratory distress syndrome, chemical pneumonitis, and bacterial pneumonia.
Is there official guidance on having surgery when you’re using a GLP-1?
The Medicines and Healthcare products Regulatory Agency (MHRA) published guidance in 2025 addressing the risks of pulmonary aspiration during surgery when using a weight loss injection.
They advise healthcare professionals to consider all the risks involved in surgery as early as possible, and modify the patient’s pre-surgery plan accordingly. Before most surgeries, you’ll be asked to take a preoperative assessment with a healthcare team at the hospital where your procedure will take place. This is often led by a doctor or nurse who will talk you through all the risks involved during your procedure.
The MHRA guidance also states that patients should continue using their medication as normal, and avoid stopping it before discussing things with a doctor. So if you’re scheduled for surgery, continue using your GLP-1 unless your prescriber or a member of your preoperative team tells you otherwise.
Will I need to stop using my GLP-1 before surgery?
You won’t necessarily be told to stop using your treatment ahead of your surgery.
Usually, your pre-operative assessment team will give you specific instructions about fasting before your surgery, and this will include amending your doses or stopping treatment for a period if you’re using a GLP-1. Your pre-assessment is the time to ask any questions you have, and discuss the best steps to take.
This might mean stopping your treatment or gradually reducing your doses in the lead up to your procedure, or it could be specific dietary advice that will help to fully empty your stomach.
Although weaning off your medication might seem like an easy way of ensuring your stomach is empty before you have surgery, this should always be done under medical supervision. Stopping your medication too soon, or attempting to decrease your dosage by yourself, can cause a range of side effects while also causing spikes in blood sugar that could be harmful to health.
If you’re using treatment to help control blood sugar, you might be told to continue using your medication before your surgery.
Having high blood sugar when going into an operation can slow down recovery, cause heart complications, increase your chances of infection, and might even mean you need to postpone your surgery.
So rather than stopping treatment altogether, you might instead be advised to tailor your diet to help with stomach emptying.
How long do you have to fast before surgery if you are taking a GLP-1?
Once your preoperative assessment team is aware you’re using a GLP-1, they’ll give you specific instructions about fasting before surgery. They’ll decide with you what the best plan of action is.
Usually, for anyone having surgery who isn’t using a weight loss treatment, often you’ll be advised to avoid eating around six hours before your procedure, but this can vary depending on the type of surgery you’re having and individual circumstances. This often means eating your last meal before midnight. Fluids are normally allowed after this time, but rules about what you can drink can depend on the time of your operation.
Your medical history will be considered, as will the kind of operation you’re having and the type of anaesthetic being used, when your preoperative assessment team develops your plan.
Will a doctor check you have no food in your stomach before surgery?
On the day of your operation, your hospital team will usually enforce fasting restrictions (no food after midnight) and then shortly before your procedure, ask you the times you last ate and drank.
If there’s doubt about whether you’re likely to have an empty stomach or not pre-surgery, you might be referred for a gastric ultrasound to check the contents of your stomach. But this would usually be in cases where the anaesthetist thinks you might be at an increased risk of aspiration.
Because current government guidance recommends the healthcare professionals involved in your operation identify aspiration risks as early as they can, you might be informed much earlier than the day of your operation that an ultrasound is needed.
Do GLP-1s affect recovery after surgery?
There is some evidence to suggest that using GLP1-s can impact the healing of surgical wounds, but this is something your perioperative team will take into consideration before your procedure and as you recover from surgery in hospital.
When you’re in hospital post-surgery, your healthcare team will monitor your surgical wound to make sure it’s healing well, and regularly check and change your dressings to look for signs of infection.
What foods should I eat after surgery while on a GLP-1?
Your diet following surgery when using a GLP-1 might be determined by several factors, including the type of surgery you’ve had. In some instances, you might need to follow a liquid-only diet in the early stages of recovery, which might also impact how much medication you can use during this period.
But generally, remaining at a healthy weight can help recovery, so you’ll be advised to eat a low-calorie, balanced diet that includes a wide range of essential vitamins and minerals. When using GLP-1s, diets often involve prioritising foods high in protein and fibre over calorie-dense foods or those with a high fat content, as these can help you feel fuller for longer throughout the day.
If you're due to have surgery, should you start weight loss treatment?
If you have a surgery date that is far in the future, it may still be beneficial to start weight loss treatment, as being at a healthy weight can help improve your recovery time and lower your risk of complications after surgery.
However, if you have a surgery date that is very near in the future, it might be best to discuss the potential risks involved with a clinician before starting treatment..
In any case, you should always disclose any information, including future-planned surgery, to your clinician when consulting about weight loss treatment. This will help them to ensure they’re giving you the safest and most suitable recommendation.
Reference Popover #ref1
Treated trusted source
Robinson, M. and Davidson, A. (2014).
Aspiration under anaesthesia: risk assessment and decision-making. Continuing Education in Anaesthesia Critical Care & Pain, 14(4), pp.171–175.
Reference Popover #ref2
Treated trusted source
MHRA (2025).
GLP-1 and dual GIP/GLP-1 receptor agonists: potential risk of pulmonary aspiration during general anaesthesia or deep sedation.
Reference Popover #ref3
Treated trusted source
Northern Lincolnshire and Goole NHS Foundation Trust. (2021).
Adult Fasting Guidelines – When and What You Are Allowed to Eat and Drink before Your Operation - Northern Lincolnshire and Goole NHS Foundation Trust.
Reference Popover #ref4
Treated trusted source
North Tees and Hartlepool NHS Foundation Trust. (2026).
Pre-surgery advice for Patients on Ozempic, Mounjaro, or Wegovy - PIL1594 version 1 - North Tees and Hartlepool NHS Foundation Trust.
Reference Popover #ref5
Treated trusted source
Lee, C. et al (2025).
Impact of GLP-1 Agonist on Surgical Wound Complications Following Plastic and Reconstructive Surgery: A Propensity Matched Cohort Large Database Analysis.
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