Written by: Isabel Finch
Published: September 12, 2025
Alternative obesity management treatments available
While most users tolerate it well, Wegovy (semaglutide) has some side effects.
The most common ones will be fairly mild. They should improve over time, as you get used to your new medication. And some small tweaks to your lifestyle will help you manage them.
Like most drugs, there is a risk of more serious effects too. And it’s important you know the risks before you start the treatment.
In this guide, you’ll learn the side effects of the Wegovy injection – from the most common to rarer side effects. And we’ll give you some tips for managing side effects. So you can make your weight management journey as comfortable as possible.
Very common
(may affect more than 1 in 10 people), are:
Common
(may affect up to 1 in 10 people), are:
Yes, Wegovy can make you tired. The patient information leaflet lists it as a common side effect of the medication.
Experts aren’t sure exactly why it can make you tired. But it could be for a number of reasons:
Yes. Wegovy can cause headaches. And it’s an official side effect of the medication.
If you’re experiencing headaches on Wegovy, it could be down to a number of factors. A common cause is dehydration, because you’ll likely be eating and drinking less during treatment. Side effects, like diarrhoea and vomiting, also cause you to lose fluids.
A number of other factors (alcohol, sleep and stress) can also cause headaches. So drink enough water (aim for 2-3l per day) and get plenty of sleep. Some fresh air and doing some gentle exercise can also make a difference.
Yes, Wegovy can cause heartburn (AKA acid reflux).
This is because, on Wegovy, food moves slower through the digestive system and stays in your stomach longer.
While this helps you get full quicker (and stay fuller for longer), you might experience some acid reflux too.
Head to the section below for tips on how to manage it.
Stomach pain is one of the most common side effects of Wegovy. Because Wegovy slows down the digestive system, your risk of abdominal pain and discomfort increases.
See a doctor immediately if stomach pain is severe. It could be a sign of acute pancreatitis (an inflamed pancreas). The pain may last a long time and it may move to your back.
Pain in the back or lower abdomen might also be a sign of kidney or bladder stones. With kidney stones, peeing can be difficult. And you might notice a change in the colour of your urine.
Diarrhoea is one of the most common side effects of Wegovy.
The medication works because it slows down the rate at which food leaves the stomach. This slowing down of the digestive system can increase your risk of stomach-related side effects. For some patients, this causes diarrhoea.
The diarrhoea should subside once your body adapts to the medication. The most important thing is to drink enough water, because diarrhoea causes you to lose fluids.
Head to the section below for tips on how to manage diarrhoea.
Yes, Wegovy can cause hair loss and the patient information leaflet lists it as a side effect. But it’s likely an indirect cause of the medication. No strong research suggests it’s caused by Wegovy itself.
Losing weight too quickly or not getting all the nutrients you need through your diet could be causing your hair loss. Your body may respond by slowing down non-essential processes, like hair growth.
This type of hair loss (called telogen effluvium) is temporary. It should improve when you start eating a nutrient-rich diet. Make sure your diet is healthy and balanced and that you’re eating enough food. Aim for steady weight loss of 1-2 lb per week.
Some users have reported that Wegovy causes vaginal dryness.
Vaginal dryness is not an official side effect of the medication. And there’s no evidence that medication causes it. But it’s possible that changes caused by Wegovy can impact vaginal health.
Changes in your hormone levels cause vaginal dryness. Certain things, like the menopause, breastfeeding and taking some medications, can impact your hormones – leading to vaginal dryness. Rapid weight loss or dietary changes can also influence hormone levels.
It could also be a side effect of side effects. Some stomach-related side effects, like vomiting, diarrhoea, constipation, can also impact the gut. This can lead to vaginal dryness.
Uncommon side effects
(which may affect up to 1 in 100 people) are:
Most patients experience common side effects when they start using Wegovy and when they increase their dose. But you should feel them less as your body adapts to the dose.
Wegovy reaches peak concentration two to three days after injecting it. So you might find side effects get worse when it reaches these levels.
How long side effects last will vary from person to person. In many cases, they’ll improve as your body gets used to the medication.
Most people notice they settle down within a few days of starting Wegovy or moving to a higher dose.
But in rarer cases, your body might not build that tolerance. That means with each injection, as the drug builds up in your system, side effects could get worse. If that happens, reach out to your Wegovy provider for advice.
It can help to understand how long Wegovy stays in your system. You can get a better idea of when side effects will be at their worst and when to expect them to improve.
Wegovy has a half-life of seven days. So the amount of semaglutide (the active ingredient) halves in your body in one week. That’s why it’s a once-weekly injection – so it stays at a steady level in your body.
The medication stays in your system for around five to seven weeks after your last dose.
The best strategy will depend on the specific side effect. Different methods can help you lessen different types of discomfort.
However, for a lot of the common side effects, you can reduce them by:
We recommend you make dietary and lifestyle changes to manage heartburn. Here are a few things you can reduce irritation and improve comfort:
If lifestyle changes alone aren’t helping, medications can help. We’d usually recommend a treatment like Nexium. It offers protective support for your stomach and is available in 14-day courses for longer-term relief.
However, for faster-acting, short-term relief, Tums, Rolaids, Gaviscon, and Rennies can help. These treatments, called antacids, work by neutralising stomach acid. Most local pharmacies stock these over the counter. Your local pharmacist can advise on the most suitable option for you.
If your acid reflux persists or worsens, get in contact with us or your GP for further advice.
When managing symptoms of diarrhoea, these small steps you can make a big difference:
Over-the-counter medications such as loperamide (Imodium) can also help manage symptoms. However, only use this medication for a short period. If diarrhoea symptoms don’t improve, or get worse, contact us or your GP for advice.
Nausea is a common side effect of the medication – and it should eventually pass. But there are a few steps you can take to stop feeling sick on Wegovy:
If you’re still feeling nauseous, you could also try anti-sickness medication. However, this should only be a short-term solution. Please let us know if you’re struggling with nausea. Our team can advise you on suitable anti-nausea medication and offer advice tailored to you.
On Wegovy, we encourage you to eat a healthy diet. This means adding more whole foods to your diet: fruits, veg, whole grains, lean meat and healthy fats. But what about foods to avoid on the medication?
You don’t need to follow strict diet rules or cut out favourites completely. Burgers, pizza and ice cream can still be part of a healthy, balanced diet. But mindful eating is important here. When you pay attention to how you feel when you eat, you’ll find some foods may worsen side effects.
Foods that may make side effects worse include:
Up to 1 in 10 people using weight loss injections, like Wegovy, report injection site reactions. Patients might experience redness, bruising, itching and swelling. In most cases, these symptoms subside as your body adjusts to the medication.
However, there are some ways to manage these reactions. Here’s what can help:
If the reaction gets worse, spreads, becomes more painful, stop using the medication. Seek medical advice from your GP, NHS 111 or A&E.
Like all medications, Wegovy has some serious side effects. They’re not common, but it’s important you know what they are and recognise the symptoms.
The uncommon serious side effects, which may affect up to 1 in 100 people, are:
If you experience any of these symptoms, seek urgent medical attention.
The rare side effects of Wegovy, which may affect up to 1 in 1,000 people, are:
Wegovy also comes with a risk of a severe form of constipation. Additional symptoms include stomach ache, bloating and vomiting. While rare, experts don’t know exactly how often this side effect occurs.
Some medications, supplements, and substances may interact with Wegovy or make side effects worse. And some patients may have health conditions that make Wegovy unsuitable for them (called a contraindication).
Some drugs and substances react with other drugs and change how they work. Clinicians call this an interaction, and it means some medications make Wegovy unsuitable.
There aren’t any direct drug-drug interactions. However, Wegovy slows down the stomach. So it may affect how some medications are absorbed – especially when you increase your dose.
This is particularly relevant for antibiotics and drugs with a low therapeutic index, like warfarin or insulin. In low therapeutic index drugs, there is a narrow margin between an effective dose and a dose that’s either harmful or ineffective. So even very small changes in absorption or blood levels can cause serious issues.
Side effects like diarrhoea or vomiting can also affect how well your body absorbs medication. If you’re vomiting, your body may not absorb the drug at all. Dehydration can also concentrate drugs in your system, increasing the risk of side effects. So, if you’re on medication and have persistent diarrhoea or vomiting, please consult us for support.
If you’re taking any medication, please let us know on your assessment form.
Not everyone is suitable for Wegovy. You cannot use Wegovy if you:
You might have heard there is a connection between Wegovy and cancer.
One animal study has suggested a possible link between GLP-1 medication and thyroid cancer. The study found that GLP-1 receptor activation caused thyroid tumours in rodents.
Researchers have not found this effect in humans. However, as a precaution, we don’t recommend Wegovy for those who’ve had some thyroid cancers. Or those who have a family history of thyroid cancer. This includes medullary thyroid cancer or multiple endocrine neoplasia syndrome type 2 (MEN2).
Clinical evidence shows no concerns regarding the safety of using Wegovy long-term.
We recommend staying on the treatment for as long as it’s beneficial. Staying on the medication during the maintenance phase of your journey will help you build sustainable habits. This will make it easier for you to manage your weight if you choose to stop taking the medication.
We won’t stop prescribing you the medication when you reach your goal weight. Our clinicians will continue to prescribe it to you – as long as you’re still benefiting from it.
Yes. Wegovy is safe. The UK’s medicines regulator approved it as a weight loss medication in 2021. Since it launched in the UK in 2023, thousands of people have used it to safely manage their weight.
The UK regulator has also approved Wegovy as a preventative treatment for patients with heart disease. A recent study found it cut the risk in repeat heart events, like stroke and heart attack, in overweight and obese patients.
Like all medicines, Wegovy has risks as well as benefits. You do risk serious side effects, although these are less common.
While Wegovy is safe for most people, it is not safe for everyone. Patients with certain health conditions will not be able to use Wegovy. That’s why your provider must carry out a comprehensive assessment before prescribing it. And it’s crucial you’re honest about your medical history.
Before you start Wegovy, your prescriber will look at your medical history and health profile. They will advise if it’s safe for you to use. They’ll also let you know what side effects you can expect on the medication.
If you experience any side effects on Wegovy, let your clinician know. They might alter your dosage or give you advice to help you feel more comfortable.
And if you have any concerns at all about your side effects, contact your prescriber. They’ll be able to provide you with support or alleviate any concerns. At Simple, we’re here for you throughout your journey. Call us on 0141 774 5023 if you need support.
Package leaflet: Information for the patient Wegovy FlexTouch. (n.d.). Available at: https://www.medicines.org.uk/emc/files/pil.13800.pdf
www.wegovy.com. (n.d.). Wegovy® Side Effects | Wegovy® (semaglutide) Injection 2.4 mg. [online] Available at: https://www.wegovy.com/taking-wegovy/side-effects.html
Hansen, M.S., Wölfel, E.M., Jeromdesella, S., Møller, J.-J.K., Ejersted, C., Jørgensen, N.R., Eastell, R., Hansen, S.G. and Frost, M. (2024). Once-weekly semaglutide versus placebo in adults with increased fracture risk: a randomised, double-blinded, two-centre, phase 2 trial. eClinicalMedicine, 72, p.102624. doi: https://doi.org/10.1016/j.eclinm.2024.102624
Lau, D.C.W., Batterham, R.L. and le Roux, C.W. (2022). Pharmacological profile of once-weekly injectable semaglutide for chronic weight management. Expert Review of Clinical Pharmacology, 15(3), pp.251–268. doi: https://doi.org/10.1080/17512433.2022.2070473
Copyright © 2013 - 2025 Simple Online Pharmacy Ltd. All rights reserved.
Data security and protection policies available by request.
