Ozempic (semaglutide) is a glucagon-like peptide-1 (GLP-1) receptor agonist licensed in the UK for treating type 2 diabetes mellitus. Whilst gastrointestinal side effects such as nausea and diarrhoea are well documented, some patients report experiencing fatigue during treatment. Does Ozempic cause fatigue directly, or might tiredness arise from indirect mechanisms such as reduced caloric intake, hypoglycaemia, or dehydration? Understanding the relationship between Ozempic and fatigue is essential for patients and healthcare professionals to ensure safe, effective diabetes management. This article examines the evidence, explores potential causes, and provides practical guidance on managing tiredness whilst taking Ozempic.

Understanding Ozempic and Its Common Side Effects

Ozempic (semaglutide) is a glucagon-like peptide-1 (GLP-1) receptor agonist licensed in the UK for the treatment of type 2 diabetes mellitus only, not for weight management. Administered as a once-weekly subcutaneous injection, it works by mimicking the action of the naturally occurring hormone GLP-1, which plays a crucial role in glucose regulation. The medication enhances insulin secretion in response to elevated blood glucose levels, suppresses inappropriate glucagon release, and slows gastric emptying, thereby improving glycaemic control.

As with any medication, Ozempic is associated with a range of side effects, the most commonly reported being gastrointestinal in nature. These include nausea, vomiting, diarrhoea, abdominal pain, and constipation, which typically occur during the initial weeks of treatment or following dose escalation. According to the Summary of Product Characteristics (SmPC) approved by the Medicines and Healthcare products Regulatory Agency (MHRA), these effects are usually mild to moderate in severity and tend to diminish over time as the body adjusts to the medication.

Other recognised adverse effects include injection site reactions, decreased appetite (which contributes to the weight loss often observed with this medication), and hypoglycaemia—particularly when Ozempic is used in combination with insulin or sulphonylureas (the risk is much lower when used alone). Gastrointestinal side effects may lead to dehydration in some patients, which can affect kidney function.

Less common but more serious potential risks include pancreatitis, diabetic retinopathy complications (particularly in those with pre-existing retinopathy who may experience early worsening), and gallbladder disorders. Understanding the full spectrum of possible side effects is essential for both patients and healthcare professionals to ensure appropriate monitoring and timely intervention when necessary. Patients should be counselled about what to expect when starting Ozempic and encouraged to report any concerning symptoms to their GP or diabetes specialist nurse.

Does Ozempic Cause Fatigue? What the Evidence Shows

Fatigue is not a commonly reported adverse reaction in clinical trials of Ozempic. In product information, fatigue or asthenia (weakness) is reported at low frequency where listed. The pivotal SUSTAIN clinical trial programme, which evaluated the efficacy and safety of semaglutide in thousands of patients with type 2 diabetes, did not identify fatigue as a frequent or significant adverse event. However, this does not mean that patients never experience tiredness whilst taking the medication.

In post-marketing surveillance and patient forums, some individuals have reported feeling unusually tired or lacking energy after starting Ozempic. These anecdotal reports warrant consideration, even though they have not been systematically validated in large-scale studies. It is important to distinguish between fatigue as a direct pharmacological effect of the drug and tiredness that may arise from indirect mechanisms related to how Ozempic affects the body.

The European Medicines Agency (EMA) and MHRA continue to monitor adverse event reports for all GLP-1 receptor agonists, including semaglutide. Healthcare professionals and patients are encouraged to report any suspected adverse reactions through the MHRA Yellow Card Scheme (via yellowcard.mhra.gov.uk or the Yellow Card app), which helps regulatory authorities identify previously unrecognised safety signals.

For patients concerned about fatigue, it is essential to have an open conversation with their healthcare provider. A thorough assessment can help determine whether the tiredness is related to the medication itself, the underlying diabetes, or other contributing factors such as lifestyle, diet, or concurrent health conditions.

Why Fatigue May Occur When Taking Ozempic

Although fatigue is not among the most common side effects of Ozempic, several indirect mechanisms may explain why some patients feel tired during treatment. Understanding these potential contributors is crucial for appropriate management and reassurance.

Reduced caloric intake and nutritional changes are among the most plausible explanations. Ozempic significantly reduces appetite and promotes early satiety by slowing gastric emptying and acting on appetite centres in the brain. Whilst this effect is therapeutically beneficial for glycaemic control, it can lead to an unintentional reduction in energy intake. If patients are not consuming adequate calories, carbohydrates, or essential nutrients, they may experience fatigue, weakness, or lethargy. This is particularly relevant during the initial weeks of treatment when appetite suppression is most pronounced.

Hypoglycaemia (low blood glucose) is another important consideration, especially in patients taking Ozempic alongside other glucose-lowering medications such as insulin or sulphonylureas. As noted in the SmPC warnings, symptoms of hypoglycaemia include tiredness, dizziness, confusion, and sweating. Even mild, unrecognised episodes can contribute to persistent fatigue. Regular blood glucose monitoring is essential to identify and address this issue.

Gastrointestinal side effects such as nausea, vomiting, and diarrhoea can lead to dehydration and electrolyte imbalances, both of which are well-recognised causes of fatigue. The SmPC specifically warns about the risk of dehydration with Ozempic. Additionally, the physical discomfort associated with these symptoms may disrupt sleep quality, further contributing to daytime tiredness.

Finally, it is important to consider that uncontrolled diabetes itself is a common cause of fatigue. Patients who are newly diagnosed or whose diabetes has been poorly controlled may attribute their tiredness to the medication when, in fact, it reflects the underlying metabolic disturbance. Other medical conditions such as anaemia, thyroid disease, vitamin B12 or folate deficiency, and kidney disease commonly contribute to fatigue and should be assessed if symptoms persist. As glycaemic control improves with Ozempic treatment, many patients actually report increased energy levels over time.

Managing Fatigue While on Ozempic Treatment

If you are experiencing fatigue whilst taking Ozempic, there are several practical strategies that may help alleviate this symptom whilst continuing to benefit from the medication's therapeutic effects.

Ensure adequate nutritional intake: Despite reduced appetite, it is important to consume balanced, nutrient-dense meals that provide sufficient energy. Focus on:

• Complex carbohydrates such as wholegrain bread, brown rice, and oats for sustained energy release

• Lean proteins including chicken, fish, eggs, and legumes to support muscle function and satiety

• Healthy fats from sources like avocados, nuts, and olive oil

• Plenty of fruits and vegetables to ensure adequate vitamin and mineral intake

Eating smaller, more frequent meals may be better tolerated than large portions, particularly if you are experiencing nausea or early satiety. The NHS Eatwell Guide provides helpful information on balanced nutrition for people with diabetes.

Monitor blood glucose levels regularly: If you are taking other diabetes medications alongside Ozempic, work with your healthcare team to adjust doses as needed to prevent hypoglycaemia. NICE guidance (NG28) recommends careful titration of insulin or sulphonylureas when adding GLP-1 receptor agonists like Ozempic. Keep a glucose meter accessible and check your levels if you feel unusually tired or unwell. Carry fast-acting carbohydrates (such as glucose tablets or fruit juice) to treat low blood sugar promptly.

Stay well hydrated: Dehydration can significantly contribute to fatigue. Aim for at least 6–8 glasses of water daily, and increase this if you are experiencing vomiting or diarrhoea. Oral rehydration solutions may be helpful if gastrointestinal symptoms are persistent. Seek medical advice if you are unable to maintain adequate fluid intake due to persistent vomiting or diarrhoea.

Prioritise sleep and rest: Establish a regular sleep routine, aiming for 7–9 hours of quality sleep per night. Good sleep hygiene practices—such as avoiding screens before bedtime, keeping your bedroom cool and dark, and maintaining consistent sleep and wake times—can improve restorative sleep.

Engage in regular physical activity: Whilst it may seem counterintuitive, moderate exercise can actually boost energy levels and reduce fatigue. Activities such as walking, swimming, or cycling for 30 minutes most days of the week are recommended for people with type 2 diabetes and can improve overall wellbeing.

When to Seek Medical Advice About Fatigue

Whilst mild tiredness during the initial adjustment period to Ozempic may be manageable with lifestyle modifications, certain situations warrant prompt medical attention. It is important to recognise when fatigue may signal a more serious underlying issue.

Contact your GP or diabetes specialist nurse if:

• Fatigue is severe, persistent, or worsening despite adequate rest and nutrition

• You experience symptoms of hypoglycaemia such as confusion, sweating, trembling, or rapid heartbeat

• Fatigue is accompanied by unexplained weight loss beyond what is expected with Ozempic treatment

• You develop signs of dehydration including dark urine, dizziness, or reduced urine output

• You notice yellowing of the skin or eyes (jaundice), which could indicate liver or gallbladder problems

• You experience new or worsening vision changes, floaters, or blurred vision, which may relate to diabetic retinopathy complications

• Fatigue is associated with severe abdominal pain, particularly if radiating to the back, which may suggest pancreatitis

Seek urgent medical care (call 111 or attend A&E) for:

• Severe, persistent abdominal pain

• Inability to keep fluids down due to vomiting

• Significant visual changes

Call 999 immediately for:

• Chest pain

• Severe shortness of breath

• Palpitations with dizziness or fainting

Your healthcare provider may wish to perform investigations to rule out other causes of fatigue, such as:

• Blood tests to check full blood count (for anaemia), thyroid function, vitamin B12 and folate levels, kidney and liver function, and electrolytes

• HbA1c measurement to assess overall glycaemic control

• Review of all medications to identify potential drug interactions or cumulative side effects

According to NICE guidance (NG28) on type 2 diabetes management, regular monitoring and medication review are essential components of safe prescribing. Your healthcare team can adjust your Ozempic dose, modify concurrent medications, or explore alternative treatment options if side effects are significantly impacting your quality of life. Never stop taking Ozempic without consulting your doctor, as abrupt discontinuation may lead to deterioration in glycaemic control.

If you suspect your fatigue or any other symptoms might be related to Ozempic, you can report this directly to the MHRA through the Yellow Card Scheme at yellowcard.mhra.gov.uk or via the Yellow Card app. Open communication with your healthcare provider ensures that any concerns about fatigue are addressed appropriately whilst maintaining effective diabetes management.

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