Semaglutide Side Effects: What to Expect & How Long They Last
Also known by the brand names Ozempic® (for type 2 diabetes) and Wegovy® (for weight management), semaglutide is the active ingredient in these once-weekly injections. Although it’s generally safe for most people, semaglutide comes with possible side effects and risks.
What are they, and how long do semaglutide side effects last?
Whether you’re using Wegovy® for weight management or Ozempic® for treating type 2 diabetes, semaglutide might cause issues like nausea and constipation. In rare cases, it can increase the risk of serious medical conditions.
In this guide, we’ll discuss the most common side effects of semaglutide. We’ll also explore the rare but serious symptoms you may experience and share practical tips to keep symptoms to a minimum.
Common Semaglutide Side Effects
Semaglutide is a glucagon-like peptide-1 (GLP-1) receptor agonist. This means it mimics a hormone that helps you feel fuller for longer, slows stomach emptying, and prompts the pancreas to release insulin only when blood glucose is high.
Like other GLP-1 receptor agonists, semaglutide often causes nausea. Most people experience mild to moderate gastrointestinal (GI) issues when they first start GLP-1s, according to the Medicines and Healthcare products Regulatory Agency (MHRA).
The most common semaglutide side effects include:
Gastrointestinal issues. This includes nausea, vomiting, diarrhoea, constipation, and heartburn. GLP-1s delay gastric emptying, which can irritate the digestive system.
Fatigue. You might feel lethargic due to low blood sugar (glucose) levels, dehydration from vomiting, or not eating enough.
Muscle loss. If you’re in a calorie deficit, there’s a chance you might lose muscle rapidly — particularly if you’re not eating enough protein or engaging in resistance training.
“Ozempic face.” Losing subcutaneous fat can reveal lines or sagging in the face or other areas of the body. This is a normal consequence of any significant weight loss.
Change in menstrual patterns. Rapid weight loss can affect your menses.
Discomfort and bruising at the injection site. Weekly shots can result in redness or occasional bruising.
The good news is that you can manage and mitigate many of these side effects.
If you’re using the injectable form, you may also find it helpful to review how to inject semaglutide safely and correctly.
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How Long Do Semaglutide Side Effects Last?
There’s no specific timeline, but research has found that most GI issues peak in the first eight to 12 weeks and taper thereafter.
A review of studies conducted by Novo Nordisk (the manufacturer of Ozempic® and Wegovy®) found that gastrointestinal side effects can happen in the first eight to 12 weeks of treatment with Ozempic® and Rybelsus®.
Another review of studies by Novo Nordisk found that:
Nausea might last eight days or less for Ozempic® and Wegovy®
Diarrhoea may last about three days on Wegovy®
Constipation might last roughly 47 days on Wegovy®
What about semaglutide long-term side effects? If side effects remain troublesome beyond 12 weeks — or worsen suddenly — contact your GP (general practitioner) or private provider.
Muscle loss is a side effect that may take a bit longer to be noticeable. It won’t go away on its own, but you can avoid it by eating enough protein and engaging in strength training regularly.
Coping With Semaglutide Weight Loss Side Effects
Many home remedies and lifestyle adjustments can soothe the milder side effects of semaglutide.
Here’s what can help with nausea, vomiting, and other gastrointestinal issues:
Eat smaller, more frequent meals and stop eating when you feel comfortably full.
Sip fluids between — not during — meals. Aim for 1.5 to 2 litres of water daily.
Limit high‑fat or fried foods that worsen nausea.
Drink ginger or peppermint tea to reduce nausea.
Ask your prescriber about an anti‑nausea tablet such as ondansetron.
Try non-prescription treatments for vomiting and constipation.
Gradually increase fibre (wholegrains, veg, etc.) to combat constipation.
To cope with fatigue on semaglutide:
Ensure you’re eating enough calories. While semaglutide helps you lose weight because it’s an appetite suppressant, you still need to eat enough to carry out your basic bodily functions.
Drink enough fluids. Dehydration may make you feel tired.
Don’t overdo the training. While it’s important to exercise regularly, too much training — especially if you’re eating significantly less — can tire you out.
Get extra sleep if necessary. Your body may just be asking for extra rest. Take a nap or get to bed early if you need it.
To avoid muscle loss:
Eat enough protein. Your body needs protein to build and maintain muscle. Look for some high-protein recipes to get a few extra grams in every day.
Engage in strength training. Resistance training — anything that involves strength training or weights — can help you maintain muscle.
Take those rest days. Allow time to recover after training. This gives your body a chance to build muscle.
If you’re still struggling with specific side effects, consider making a follow-up appointment with your GP or prescribing care provider.
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Rare But Serious Risks of Semaglutide
There are a few uncommon but serious side effects of semaglutide injections. These include:
Hypoglycaemia (low blood sugar)
Pancreatitis (inflammation of the pancreas)
Gallbladder problems
Kidney injury or other kidney problems
Diabetic retinopathy progression (for those with diabetes)
Non-arteritic anterior ischemic optic neuropathy (NAION) — optic nerve damage
Medullary thyroid carcinoma (only observed in rodent studies)
Allergic reactions
Seek immediate medical care if you have the symptoms of an allergic reaction — like a rash, itching, swelling in the face or throat, or difficulty breathing. Call 999 if these symptoms are severe.
You should also seek immediate medical advice if you’re experiencing:
Signs of low blood sugar, like shakiness, sweating, lightheadedness, and hunger
Severe stomach pain
Yellowing of the skin or eyes (jaundice)
Difficulty urinating accompanied by swelling in the legs or ankles
Sudden vision loss or blurring in one eye
Persistent hoarseness or difficulty swallowing
Please report all serious side effects of semaglutide medicine via the MHRA Yellow Card scheme.
Another note: If you’re scheduled for surgery or any procedure requiring general anaesthesia, tell your healthcare team and anaesthetist you’re taking semaglutide. GLP-1 medications slow stomach emptying, which can increase the risk of stomach contents entering your airways during anaesthesia.
Who Should Not Take Semaglutide?
Most adults tolerate semaglutide well, but it isn’t right for everyone. Certain people may have an increased risk of experiencing adverse events with semaglutide.
You should not start — or should pause — semaglutide if you:
Are pregnant, trying to conceive, or breastfeeding. GLP‑1s haven’t been proven safe for pregnant people, developing foetuses, or nursing babies.
Have a personal or family history of medullary thyroid cancer (MTC) or multiple endocrine neoplasia syndrome type 2 (MEN 2). Thyroid tumours were seen in rodent studies, although they haven’t been observed in human clinical trials.
Currently use another GLP‑1 or dual GIP/GLP‑1 medication, like liraglutide or tirzepatide. Combining these medicines increases your risk of side effects.
Have active pancreatitis or a history of recurrent pancreatitis. Semaglutide may worsen the condition.
Live with severe gastroparesis or inflammatory bowel disease (e.g., Crohn’s). Slower stomach emptying can worsen GI symptoms.
Have proliferative diabetic retinopathy that’s not well‑controlled. Rapid glucose shifts or weight changes may aggravate eye damage.
Have end‑stage kidney disease or need dialysis. Close specialist supervision is required if semaglutide is considered.
Always discuss your full medical history and current medicines with a healthcare provider before starting semaglutide. If semaglutide isn’t suitable for you, a different medication may be recommended.
If you’re thinking about starting treatment, you can also learn more about how to get semaglutide through private care or the NHS.
How Long Should You Stay on Semaglutide?
Semaglutide is intended for long-term use to sustain blood sugar levels or weight control. If you stop suddenly, you might regain weight.
However, if you’re finding the side effects intolerable, a healthcare professional may be able to prescribe a different weight loss medication. They might also advise you to reduce your dosage or move to a maintenance dose for long-term weight management.
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In Summary: Semaglutide Side Effects U.K.
Semaglutide is generally safe to use for weight loss and type 2 diabetes. But like all medicines, it can cause a number of uncomfortable side effects.
Here’s what to remember about semaglutide side effects:
Nausea, diarrhoea, and constipation are the most common semaglutide side‑effects. They usually settle within eight to 12 weeks.
Serious events like pancreatitis are rare. Tell your GP about any persistent or severe symptoms.
Lifestyle adjustments (smaller meals, hydration, protein, resistance training) and anti‑nausea meds can make semaglutide treatment more comfortable.
Semaglutide’s side effects can be difficult to deal with — but the long-term health benefits of weight loss are significant for people with a high body mass index (BMI). Losing just five percent of your body weight can help prevent certain weight-related health conditions, like heart disease. For this reason, the benefits may outweigh the risks.
To help you cope with the side effects, Hers U.K. allows you to message your care team about dose adjustments and symptom advice. You can do a free assessment to see if semaglutide or another MHRA‑licensed weight loss medicine fits your health goals.
This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice. Always talk to your GP about the risks and benefits of any treatment.