Ozempic Side Effects UK: What to Expect

Published on: April 12, 2026

Medically reviewed by

Ashis Tandukar

Superintendent Pharmacist · Reg: GPhC No. 2084170

You've read the patient information leaflet. You've scrolled through Reddit threads at midnight. And you're still not entirely sure what to actually expect from Ozempic — or when something is worth worrying about.

You're not alone. It's one of the most common questions we hear: what will this feel like, and is what I'm feeling normal?

What Ozempic actually does in your body

Ozempic contains semaglutide, a synthetic version of a hormone called GLP-1 that your gut produces naturally after eating. It does three things simultaneously: it tells your pancreas to release more insulin when blood sugar rises, it dials down the glucose your liver pumps out between meals, and it slows how quickly food leaves your stomach.

That last part — the slower gastric emptying — is what causes most of the side effects people notice. Your digestive system isn't used to working at this new pace, and it takes time to adjust.

Semaglutide also acts on appetite centres in the brain, which is why many people notice reduced hunger and what's sometimes called food noise quietening down. That's not really a side effect, though most patients would call it a welcome one.

Common Ozempic side effects

These are the ones that show up most often in clinical trials and in practice. They're not inevitable — plenty of people sail through without much trouble — but they're worth knowing about.

Nausea

This is the big one. In the SUSTAIN 1 trial, around 24% of people taking 1 mg of semaglutide reported nausea. It tends to appear in the first week or two after starting or stepping up a dose, then gradually fades.

What patients actually describe varies quite a lot. For some, it's a low-grade queasiness that comes and goes. For others, it's more like that heavy, full feeling after a big meal — except they haven't eaten much at all.

What helps:

• Eat smaller portions, more often. Three large meals a day is likely to make things worse.
• Bland, low-fat foods (toast, rice, plain crackers) tend to sit better than rich or greasy options.
• Sip water or ginger tea throughout the day rather than drinking large amounts in one go.
• Take your injection just before bed — some people find they sleep through the worst of it.
• Fresh air genuinely helps. A short walk after eating can settle things.

Diarrhoea

Reported by roughly 11% of people at the 1 mg dose. It's usually mild and intermittent rather than severe, and it tends to improve as your body adapts.

Staying hydrated matters here — not just for comfort, but because dehydration on semaglutide can affect kidney function. Aim for at least 1.5–2 litres of water a day. Increasing soluble fibre (oat bran, cooked vegetables, peeled fruit) can help firm things up. Avoid artificial sweeteners, which can make diarrhoea worse.

Vomiting

Less common than nausea but follows the same pattern: worst in the first few weeks, then settles. If you're vomiting more than once a day or can't keep fluids down, contact your prescriber. Persistent vomiting increases your risk of dehydration and electrolyte imbalance.

Constipation

Somewhat counterintuitively, some people get the opposite problem. Slower gastric emptying means slower transit through the entire digestive tract. Drinking enough water, eating fibre-rich foods, and staying physically active all help. If it persists, a pharmacist can recommend an appropriate over-the-counter option.

Stomach pain and bloating

A general sense of abdominal discomfort — cramping, bloating, feeling overly full — is fairly common in the early weeks. Eating slowly, chewing thoroughly, and avoiding carbonated drinks can all make a difference. If the pain is severe or doesn't improve, it needs medical attention (more on that below).

Uncommon side effects

These affect roughly 1–10% of people and are worth knowing about, even if most people won't experience them.

Taste changes

Some people notice food tastes different — often described as metallic or slightly dulled. This is usually temporary and resolves within a few weeks. It's not harmful, but it can be disconcerting.

Injection site reactions

Redness, itching, or a small lump at the injection site happens occasionally. Rotating your injection site each week (alternating between stomach, thigh, and upper arm) helps prevent this. If a reaction is spreading or getting worse, show it to your pharmacist or GP.

Dizziness and fatigue

Particularly if you're eating significantly less than before or if blood sugar drops lower than usual. This is more common in people who also take insulin or sulphonylureas — the combination increases hypoglycaemia risk. Your prescriber should adjust those other medications when you start Ozempic.

Acid reflux and heartburn

Slowed gastric emptying can push stomach acid upwards. Avoiding eating within 2–3 hours of lying down, reducing spicy and acidic foods, and raising the head of your bed slightly can all help. If you're already taking a proton pump inhibitor and reflux worsens, speak to your doctor.

Increased heart rate

A small rise in resting heart rate (2–4 beats per minute on average) has been observed in clinical trials. It's generally not clinically significant, but if you notice palpitations or your heart rate consistently exceeds your normal range by more than 10–15 bpm, mention it to your prescriber.

Serious side effects — rare, but important

These are uncommon, but you need to recognise them because they require prompt action.

Pancreatitis

Inflammation of the pancreas has been reported in people taking GLP-1 medications, though research hasn't conclusively established whether semaglutide directly causes it. The risk is very low, but it's serious when it happens.

Seek urgent medical attention if you experience:

• Severe, persistent stomach pain that may radiate to your back
• Pain that worsens after eating
• Nausea and vomiting that won't settle
• A tender, swollen abdomen

This isn't something to "wait out." If you recognise these symptoms, stop your injection and contact your GP or go to A&E.

Gallbladder problems

Gallstones and gallbladder inflammation (cholecystitis) have been reported more frequently in people taking semaglutide than in those on placebo. Rapid weight loss of any kind increases gallstone risk — it's not necessarily unique to the medication.

Warning signs include pain in the upper right part of your abdomen, nausea, fever, and yellowing of the skin or eyes. These need same-day medical assessment.

Diabetic retinopathy complications

This applies specifically to people with existing type 2 diabetes who already have some degree of diabetic eye disease. Rapid improvements in blood sugar control can sometimes worsen retinopathy in the short term — a study in Nature found up to 10% of people with no previous history developed retinopathy complications while taking semaglutide.

If you have diabetes and notice any vision changes — blurring, floaters, dark patches — contact your eye clinic or GP promptly. Regular diabetic eye screening is especially important while on treatment.

Severe allergic reactions

Anaphylaxis is extremely rare but possible with any injectable medication. Signs include swelling of the face, lips, tongue, or throat, difficulty breathing, severe rash, and feeling faint. Call 999 immediately.

What about Ozempic feet?

You might have come across this term on social media. "Ozempic feet" isn't a medical condition caused by the drug itself — it describes changes to the appearance of your feet (wrinkling, loose skin, reduced padding) that happen because of rapid fat loss.

When you lose a significant amount of weight quickly, the fat pads on the soles of your feet thin out. This can make walking on hard surfaces less comfortable and give your feet a more aged appearance. It's a cosmetic and mechanical issue, not a pharmacological one.

Wearing well-cushioned shoes, using gel insoles, and moisturising regularly can help. The same phenomenon can cause what's sometimes called Ozempic face — loss of facial volume that leads to a gaunt appearance. Both tend to improve as your skin adapts over time.

Ozempic side effects by dose

One of the most useful things to understand is that side effects aren't random — they follow a pattern tied to your dose schedule.

The key principle: each time you step up, expect a possible return of mild GI symptoms for 1–3 weeks. If side effects at any dose are still significant after 4–6 weeks, your prescriber may hold you at that dose longer or step you back down.

How Ozempic side effects compare to other GLP-1 medications

If you're considering weight loss medication more broadly, it helps to know that all GLP-1 receptor agonists share a similar side effect profile. The differences are in degree rather than kind.

Ozempic and Wegovy contain the same active ingredient at different doses and for different licensed indications. Mounjaro (tirzepatide) works on two gut hormones rather than one, and some trial data suggest slightly lower rates of nausea — though direct comparisons are limited. We've covered Wegovy side effects in a separate guide if you'd like to compare.

When to contact your doctor

Most Ozempic side effects don't need medical intervention. But some do. Here's a straightforward framework:

See your GP or prescriber within a few days if:

• Side effects haven't improved after 4–6 weeks on the same dose
• You're losing weight faster than expected (more than 1 kg per week consistently)
• You notice persistent changes in your vision
• You feel dizzy or lightheaded regularly
• You develop injection site reactions that spread or don't heal

Seek urgent medical attention (same day or A&E) if:

• Severe, persistent abdominal pain — especially if it radiates to your back
• You can't keep any fluids down for more than 24 hours
• Signs of an allergic reaction (facial swelling, difficulty breathing, widespread rash)
• Yellowing of your skin or the whites of your eyes
• Significant, sudden changes in vision

Call 999 if:

• Symptoms of anaphylaxis (throat swelling, severe difficulty breathing, feeling faint)

How to reduce Ozempic side effects

There's no guaranteed way to avoid them entirely, but these strategies make a measurable difference:

Follow the titration schedule. It exists for a reason. Skipping the 0.25 mg phase or jumping doses doubles your chances of significant nausea. Four weeks minimum at each step.

Eat smaller meals, more often. Your stomach is emptying more slowly now. Large portions overwhelm it. Five small meals tends to work better than three large ones.

Stay hydrated. At least 1.5–2 litres of water daily. Dehydration makes every GI side effect worse and puts extra strain on your kidneys.

Cut back on high-fat and greasy foods. They're harder to digest at baseline, and semaglutide makes that even more true. This doesn't mean a restrictive diet — just lean towards lighter options in the early weeks.

Limit alcohol. It irritates the stomach lining and can amplify nausea. You don't necessarily need to stop entirely, but less is better while your body adjusts.

Keep a brief food diary. Patterns emerge quickly. Some people find specific trigger foods (dairy, spicy dishes, artificial sweeteners) that are easy to avoid once identified.

Ozempic side effects in men vs women

The evidence here is still emerging, but there are signals worth noting. A study published in Nature found that women taking GLP-1 medications were roughly eight times more likely to report headaches and four times more likely to experience vomiting compared to men.

This doesn't mean men won't experience these side effects — just that the reported rates differ. Hormonal differences, body composition, and differences in gastric motility may all play a role. The management approach is the same regardless of sex.

Who should not take Ozempic

Ozempic isn't suitable for everyone. You should not take it if you:

• Have a personal or family history of medullary thyroid carcinoma (MTC) or Multiple Endocrine Neoplasia syndrome type 2 (MEN 2)
• Are allergic to semaglutide or any ingredient in Ozempic
• Have type 1 diabetes or diabetic ketoacidosis
• Are pregnant, planning to become pregnant, or breastfeeding — semaglutide should be stopped at least two months before a planned pregnancy

You'll also need to tell your prescriber about any history of pancreatitis, kidney disease, diabetic retinopathy, or gastroparesis. And if you're booked for surgery under general anaesthetic, your surgical team needs to know you're taking Ozempic, as it affects gastric emptying.

This article is for informational purposes only and does not constitute medical advice. Always consult with a qualified healthcare professional before starting any treatment.