Ozempic (semaglutide) has gained considerable attention for its effectiveness in managing type 2 diabetes and promoting weight loss. However, like all medications, it carries potential disadvantages that warrant careful consideration. Understanding the cons of taking Ozempic—from common gastrointestinal side effects to serious complications such as pancreatitis and diabetic retinopathy—is essential for informed decision-making. This article examines the drawbacks, contraindications, and practical limitations of Ozempic, helping patients and clinicians weigh these concerns against therapeutic benefits within the context of comprehensive diabetes management and UK clinical guidance.

What Is Ozempic and How Does It Work?

Ozempic (semaglutide) is a prescription medication licensed in the UK for the treatment of type 2 diabetes mellitus in adults. It belongs to a class of drugs called glucagon-like peptide-1 (GLP-1) receptor agonists, which mimic the action of a naturally occurring hormone that regulates blood glucose levels and appetite.

The medication works through several complementary mechanisms. Primarily, semaglutide stimulates insulin secretion from pancreatic beta cells in a glucose-dependent manner, meaning it only triggers insulin release when blood sugar levels are elevated. This reduces the risk of hypoglycaemia compared to some other diabetes medications, though this risk increases when combined with insulin or sulfonylureas. Simultaneously, Ozempic suppresses glucagon secretion—a hormone that raises blood glucose—thereby preventing excessive glucose production by the liver. Additionally, it slows gastric emptying, which moderates the rate at which nutrients enter the bloodstream after meals.

Ozempic is administered as a once-weekly subcutaneous injection, typically into the abdomen, thigh, or upper arm. The dosing schedule begins with 0.25 mg weekly for four weeks (a non-therapeutic dose intended to improve tolerability), then increases to 0.5 mg weekly. Depending on glycaemic control and tolerability, the dose may be further increased to 1 mg weekly after at least four weeks, with a maximum licensed dose of 2 mg weekly available if needed.

Whilst Ozempic has demonstrated efficacy in improving glycaemic control and promoting weight loss, it is important to understand that like all medications, it carries potential disadvantages and risks that must be carefully considered before initiation and throughout treatment. It's worth noting that Ozempic is specifically licensed for type 2 diabetes, while Wegovy (semaglutide 2.4 mg) is the licensed product for weight management in the UK.

Common Side Effects of Ozempic

The most frequently reported adverse effects of Ozempic are gastrointestinal in nature, affecting a substantial proportion of patients, particularly during dose escalation. These include nausea, vomiting, diarrhoea, abdominal pain, and constipation. Clinical trial data suggest that nausea occurs in approximately 15–20% of patients, though severity varies considerably between individuals. These symptoms typically emerge or intensify when the dose is increased and often diminish over several weeks as the body adapts to the medication.

For some patients, however, gastrointestinal side effects persist and can significantly impact quality of life and treatment adherence. Persistent nausea may affect nutritional intake and daily functioning, whilst severe or prolonged vomiting and diarrhoea can lead to dehydration and electrolyte disturbances. Patients should be advised to maintain adequate fluid intake and contact their GP if symptoms become severe or unmanageable.

Injection site reactions represent another common concern, with patients occasionally experiencing redness, itching, or discomfort at the injection site. Rotating injection sites and ensuring proper injection technique can help minimise these reactions. Additionally, some individuals report experiencing fatigue, dizziness, or headaches, particularly during the initial weeks of treatment.

Appetite suppression, whilst therapeutically beneficial for weight management, can be experienced as an unwanted effect by some patients, potentially leading to inadequate nutritional intake if not monitored appropriately. Some patients have reported altered taste perception and increased burping or flatulence, though these effects are less commonly observed.

Hypoglycaemia is an important consideration, particularly when Ozempic is used in combination with insulin or sulfonylureas. Dose reductions of these medications may be necessary when starting semaglutide to prevent low blood sugar episodes.

It is worth noting that the gradual dose escalation protocol recommended in the Ozempic SmPC is specifically designed to improve tolerability and reduce the incidence and severity of these common side effects. Patients experiencing persistent or troublesome symptoms should discuss these with their healthcare provider rather than discontinuing treatment abruptly, as dose adjustment or symptomatic management strategies may be effective.

Serious Risks and Complications Associated with Ozempic

Beyond common side effects, Ozempic carries several serious potential risks that require careful consideration and monitoring. One of the most significant concerns is the risk of pancreatitis (inflammation of the pancreas). Whilst the absolute risk remains relatively low, GLP-1 receptor agonists as a class have been associated with acute pancreatitis in post-marketing surveillance. Patients should be counselled to seek immediate medical attention if they experience severe, persistent abdominal pain that may radiate to the back, particularly if accompanied by nausea and vomiting. Semaglutide should be discontinued if pancreatitis is suspected.

Animal studies demonstrated an increased incidence of thyroid C-cell tumours in rodents exposed to semaglutide, though the relevance to humans is unclear. Patients should be advised to report any symptoms suggestive of thyroid tumours, such as a lump in the neck, persistent hoarseness, difficulty swallowing, or shortness of breath.

Diabetic retinopathy complications have been observed in clinical trials, particularly in patients with pre-existing diabetic eye disease who experience rapid improvements in glycaemic control. The SUSTAIN-6 trial reported a higher incidence of retinopathy complications in the semaglutide group compared to placebo. Patients with a history of diabetic retinopathy should undergo careful ophthalmological monitoring, and rapid glycaemic improvements should be managed cautiously.

Additionally, there have been reports of acute kidney injury, often in the context of severe gastrointestinal side effects leading to dehydration. Patients with pre-existing renal impairment require particularly careful monitoring. Gallbladder-related problems, including cholelithiasis (gallstones) and cholecystitis (gallbladder inflammation), have also been reported more frequently in patients taking GLP-1 receptor agonists, likely related to rapid weight loss.

The MHRA has issued a Drug Safety Update highlighting the risk of diabetic ketoacidosis (DKA) when insulin is rapidly reduced or discontinued when starting GLP-1 receptor agonists. Insulin dose adjustments should be made gradually and with careful monitoring of blood glucose levels.

There have been some post-marketing reports suggesting concerns regarding gastroparesis (delayed gastric emptying), though further research is needed to establish causality and prevalence. Patients should report persistent digestive symptoms to their healthcare provider.

Patients are encouraged to report any suspected side effects to the MHRA Yellow Card Scheme (yellowcard.mhra.gov.uk or via the Yellow Card app).

Who Should Avoid Taking Ozempic?

Ozempic is contraindicated in patients with hypersensitivity to semaglutide or any of the excipients in the formulation.

The medication is not licensed for use in type 1 diabetes mellitus or for the treatment of diabetic ketoacidosis. It should not be used in patients under 18 years of age, as safety and efficacy have not been established in paediatric populations. Ozempic should not be used during pregnancy or breastfeeding. Women of childbearing potential should use effective contraception during treatment and discontinue semaglutide at least two months before a planned pregnancy, as animal studies have shown potential reproductive toxicity.

Certain patient groups require particular caution and specialist input before initiation. Ozempic is not recommended in patients with severe gastrointestinal disease, including severe gastroparesis, as it may worsen symptoms. Patients with a history of pancreatitis should be carefully evaluated, as the risk-benefit profile may be unfavourable.

There is limited clinical experience in patients with severe renal impairment (eGFR <15 mL/min/1.73m²) or end-stage renal disease. While no dose adjustment is required based on renal function, careful monitoring is advised, particularly if significant gastrointestinal adverse effects occur that could lead to dehydration. Similarly, no dose adjustment is required for hepatic impairment, though experience in severe hepatic impairment is limited.

Patients with proliferative diabetic retinopathy or diabetic maculopathy should be monitored closely due to the potential for complications with rapid glycaemic improvement. Those with a history of severe hypoglycaemia or hypoglycaemia unawareness, particularly if taking concomitant insulin or sulfonylureas, require careful dose adjustment of these medications to prevent hypoglycaemic episodes.

Elderly patients (≥75 years) have limited clinical trial experience, and initiation should be considered carefully, balancing potential benefits against increased vulnerability to adverse effects such as dehydration and renal impairment. Additionally, patients with significant cardiovascular disease should be assessed individually, though cardiovascular outcome trials have generally shown benefit rather than harm in this population.

Patients taking warfarin or other coumarin anticoagulants should have their INR monitored when starting semaglutide, as there may be an interaction affecting anticoagulant activity.

Weighing the Disadvantages Against the Benefits

When considering Ozempic therapy, both patients and clinicians must engage in shared decision-making that carefully balances potential disadvantages against therapeutic benefits. For individuals with type 2 diabetes and inadequate glycaemic control despite lifestyle modifications and first-line therapies, Ozempic offers substantial advantages, including significant HbA1c reductions (typically 1.0–1.5% or more), potential cardiovascular benefits as demonstrated in the SUSTAIN-6 trial, and clinically meaningful weight loss.

However, the disadvantages outlined above—particularly gastrointestinal side effects, injection requirements, cost implications, and serious but rare complications—represent genuine concerns that may outweigh benefits for certain individuals. Patient-specific factors must guide decision-making: someone with a history of pancreatitis or significant gastrointestinal disease may be better suited to alternative therapies, whilst a patient with established cardiovascular disease and obesity may derive particular benefit despite tolerating mild nausea.

The practical burden of weekly injections, whilst less frequent than daily medications, may be unacceptable to some patients, particularly those with needle phobia or dexterity limitations. Additionally, the significant cost of Ozempic—which is available on the NHS for type 2 diabetes according to local formularies but has experienced supply constraints—represents a practical disadvantage that may limit access.

It is crucial to emphasise that Ozempic is not a standalone solution and must be integrated within comprehensive diabetes management including dietary modification, physical activity, and regular monitoring. The medication's appetite-suppressing effects, whilst beneficial for weight management, require nutritional vigilance to ensure adequate protein and micronutrient intake.

According to NICE guidance (NG28), GLP-1 receptor agonists like Ozempic should be considered as part of intensified therapy when glycaemic targets are not achieved with other medications, and continued only if demonstrating beneficial metabolic response (HbA1c reduction ≥11 mmol/mol [≥1.0%] and weight loss ≥3% at six months). This evidence-based approach ensures that patients experiencing disadvantages without corresponding benefits can be transitioned to more suitable alternatives. Regular review, open communication about side effects, and realistic expectation-setting remain fundamental to optimising outcomes whilst minimising the disadvantages associated with Ozempic therapy.

Frequently Asked Questions