Feeling unusually tired whilst taking GLP-1 medications such as semaglutide (Ozempic, Wegovy) or liraglutide (Victoza, Saxenda) is a common concern that affects daily life for many patients. These medications, prescribed for type 2 diabetes and weight management, work by slowing gastric emptying and reducing appetite, which can lead to fatigue through reduced caloric intake, nutritional imbalances, and metabolic adjustments. Understanding why tiredness occurs and how to manage it effectively can help you maintain energy levels whilst benefiting from treatment. This article explores the causes of GLP-1-related fatigue and provides practical strategies to address it.

Why GLP-1 Medications Can Cause Tiredness

Glucagon-like peptide-1 (GLP-1) receptor agonists are increasingly prescribed medications for type 2 diabetes and weight management, including semaglutide (Ozempic, Wegovy) and liraglutide (Victoza, Saxenda). While these medications offer significant therapeutic benefits, fatigue is a side effect that some people experience, which can affect daily functioning and quality of life.

The relationship between GLP-1 medications and tiredness likely involves several factors. These medications work by mimicking the natural GLP-1 hormone, which slows gastric emptying, reduces appetite, and influences insulin secretion. These effects on your body's food processing and energy regulation may contribute to feelings of tiredness, particularly during the initial treatment period.

Several practical factors may explain fatigue during GLP-1 therapy:

• Reduced food intake due to appetite suppression can lead to lower energy consumption

• Gastrointestinal side effects like nausea can be physically draining

• Adaptation to metabolic changes as your body adjusts to the medication

For people with diabetes who take insulin or sulfonylureas (like gliclazide) alongside GLP-1 medications, low blood glucose (hypoglycaemia) may cause fatigue. This is less common when GLP-1 medications are used alone.

It's important to note that there is considerable individual variation in how people respond to GLP-1 therapy. Some patients experience minimal fatigue, while others find it significantly impacts their daily activities, particularly when starting treatment or following dose increases.

Common Causes of Fatigue During GLP-1 Treatment

Understanding the specific factors contributing to tiredness can help you and your healthcare team address the issue effectively. Reduced caloric intake is perhaps the most significant contributor. GLP-1 medications substantially decrease appetite, and many patients inadvertently consume far fewer calories than their body requires for optimal energy levels. This caloric deficit, while beneficial for weight loss, can leave you feeling persistently tired and lacking motivation.

Nutritional imbalances may develop when food intake drops dramatically. When eating less, it can be challenging to get all the nutrients your body needs, including:

• Protein – essential for maintaining muscle mass during weight loss

• Iron – necessary for oxygen transport and preventing anaemia

• Vitamin D – important for muscle function and overall wellbeing

• B vitamins – crucial for energy production (note that vitamin B12 deficiency is particularly associated with metformin, which is often taken alongside GLP-1 medications)

Dehydration is another frequently overlooked cause. The nausea some patients experience may discourage fluid intake, and reduced eating often means reduced drinking too. Even mild dehydration can cause significant fatigue, headaches, and difficulty concentrating.

Gastrointestinal side effects such as nausea, vomiting, and diarrhoea are common with GLP-1 therapy and can be physically draining. These symptoms may disrupt sleep quality and contribute to daytime tiredness. Furthermore, blood glucose fluctuations may cause fatigue, particularly if you take insulin or sulfonylureas alongside your GLP-1 medication.

Other conditions common in people with obesity or diabetes can also contribute to fatigue, including sleep apnoea, thyroid disorders, and depression. These should be considered if tiredness persists despite managing GLP-1-related factors.

How Long Does Tiredness Last on GLP-1 Medications?

The duration of fatigue associated with GLP-1 medications varies considerably between individuals, but there are recognisable patterns that can help set realistic expectations. Many people report feeling most tired during the initial weeks of treatment, particularly during the dose titration phase when the medication is being gradually increased to therapeutic levels.

For many people, fatigue begins to improve as the body adapts to the medication's effects. This adaptation period often occurs over several weeks to months, during which metabolic adjustments stabilise and patients often develop strategies to manage their reduced appetite more effectively. Many patients report improved energy levels once they reach a stable maintenance dose and establish consistent eating patterns.

However, it is important to recognise that some individuals experience persistent fatigue that continues beyond the initial adjustment period. This may indicate underlying issues such as nutritional imbalances, inadequate caloric intake, or other medical conditions that require investigation. There is no evidence suggesting that GLP-1 medications cause permanent or irreversible fatigue, and most cases are manageable with appropriate interventions.

Dose increases can trigger temporary recurrence of tiredness, even in patients who had previously adapted well. Each time the dose increases, your body must readjust, potentially causing a brief return of fatigue symptoms. If tiredness persists or worsens over time rather than improving, this warrants discussion with your GP or diabetes specialist, as it may indicate the need for dose adjustment or additional investigation to exclude other causes of fatigue.

Managing Fatigue While Taking GLP-1 Medications

Practical strategies can significantly reduce tiredness and improve your quality of life while taking GLP-1 medications. Optimising nutritional intake is paramount, even when appetite is suppressed. Focus on nutrient-dense foods that provide maximum nutritional value in smaller portions:

• Lean proteins (chicken, fish, eggs, legumes) to maintain muscle mass and provide sustained energy

• Complex carbohydrates (wholegrains, oats, sweet potatoes) for steady glucose release

• Healthy fats (avocado, nuts, olive oil) for hormone production and vitamin absorption

• Colourful vegetables and fruits for essential vitamins, minerals, and fibre

Consider eating smaller, more frequent meals throughout the day rather than three large meals. This approach can help maintain steady energy levels and makes adequate nutrition more achievable when appetite is reduced. Many patients find that consuming protein with each meal helps sustain energy and prevents muscle loss during weight reduction.

Hydration deserves particular attention. The NHS recommends 6–8 cups or glasses of fluid daily, including water, lower-fat milk, sugar-free drinks, and tea or coffee. Adequate hydration supports all bodily functions and can dramatically improve energy levels. Consider setting reminders if you're not feeling naturally thirsty.

Physical activity, while challenging when tired, can paradoxically improve energy levels. Start with gentle exercise such as short walks, gradually increasing duration and intensity as tolerated. Regular movement improves sleep quality, enhances mood, and supports metabolic health. The NHS recommends at least 150 minutes of moderate-intensity activity weekly, but any movement is beneficial when starting from a fatigued baseline.

Sleep hygiene is crucial. Establish consistent sleep and wake times, create a relaxing bedtime routine, and ensure your bedroom is dark, quiet, and cool. Poor sleep quality compounds medication-related fatigue and hinders your body's ability to adapt to treatment.

If you take insulin or sulfonylureas alongside your GLP-1 medication, discuss with your healthcare team whether these doses need adjustment as your eating patterns change, to avoid low blood glucose levels that can worsen fatigue.

When to Speak to Your GP About GLP-1 Side Effects

While mild to moderate fatigue is common during GLP-1 treatment, certain situations require prompt medical attention. Contact your GP or diabetes specialist if you experience:

• Severe or worsening fatigue that significantly impairs daily functioning or persists despite self-management strategies

• Signs of dehydration including dark urine, dizziness, rapid heartbeat, or confusion

• Symptoms suggesting hypoglycaemia (low blood glucose) such as shakiness, sweating, confusion, or palpitations, particularly if you take insulin or sulfonylureas

• Persistent nausea or vomiting preventing adequate food or fluid intake

• Unintentional, rapid, or concerning weight loss, or inability to maintain adequate nutrition

• Symptoms of nutritional deficiency including pale skin, shortness of breath, tingling in hands or feet, or muscle weakness

Seek urgent medical attention if you develop:

• Severe, persistent abdominal pain (with or without vomiting) – may indicate pancreatitis

• Right upper abdominal pain, fever, or yellowing of skin/eyes – possible gallbladder problems

• Severe dehydration or significantly reduced urination – risk of kidney problems

• Signs of allergic reaction such as rash, swelling, or difficulty breathing

Your GP may recommend blood tests to assess for anaemia, thyroid function, kidney function, and other causes of fatigue based on your symptoms. If nutritional deficiencies are identified, supplementation may be prescribed.

In some cases, dose adjustment may be appropriate. Your healthcare team can reduce the dose temporarily or slow the titration schedule to allow better adaptation. Alternatively, switching to a different GLP-1 medication may be considered if side effects are intolerable, as individual responses vary between agents.

Do not stop taking your GLP-1 medication without medical advice, as this may affect your diabetes control or weight management goals. Your healthcare team can work with you to find strategies that maximise therapeutic benefits while minimising side effects.

You can report suspected side effects to medicines via the Yellow Card Scheme at yellowcard.mhra.gov.uk or search for MHRA Yellow Card in the Google Play or Apple App Store.

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