Why does Wegovy make you feel tired?
Researchers haven’t fully established exactly why Wegovy causes fatigue, as this specific side effect hasn’t been extensively studied yet.
However, clinical evidence and patient experiences point to two main mechanisms that likely contribute to feeling more tired than usual while taking Wegovy:
| Fatigue Mechanism |
How it Works |
Signs You’re Experiencing This |
| Very low calorie intake |
Wegovy significantly reduces appetite, potentially leading to insufficient energy intake to maintain normal activity levels |
Feeling weak, lightheaded, having difficulty concentrating, or noticing increased tiredness after minimal activity |
| Effects on brain’s sleep/wake cycle |
Semaglutide interacts with the hypothalamus, which controls both appetite and our internal body clock |
Feeling tired despite adequate sleep, changes in sleep patterns, or difficulty waking up in the morning |
“What many patients don’t realise is that the dramatic appetite reduction from Wegovy can lead to consuming fewer calories than their body needs for normal energy levels. In our experience, we often see energy levels improve when patients focus on nutritional quality rather than just eating less.”
– Dr. Rachel Hall, Principal Doctor at Second Nature
Our research at Second Nature shows that fatigue typically follows a predictable pattern:
- Weeks 1-4: Nearly half of patients (44%) report increased tiredness
- Weeks 5-8: Fatigue significantly improves, with only 22% still reporting tiredness
- Beyond week 12: Most patients return to normal energy levels as the body adapts
For some patients, tiredness can persist longer, particularly if they’re not consuming adequate nutrition or have underlying issues like poor sleep habits or nutrient deficiencies.
How low calorie intake leads to fatigue on Wegovy
The most common reason for feeling tired on Wegovy is simply not eating enough. Semaglutide (the drug in Wegovy) can dramatically reduce hunger, sometimes to the point where you have almost no desire to eat.
When your calorie intake drops too low, your body responds by conserving energy. This survival mechanism prioritises essential functions like heart and brain activity while reducing energy available for physical activity and alertness.
Signs you might not be eating enough on Wegovy:
- Feeling dizzy or lightheaded when standing up
- Difficulty concentrating or brain fog
- Feeling cold more often than usual
- Extreme fatigue after minimal activity
- Mood changes including irritability
- Hair loss or brittle nails
Practical strategies to ensure adequate nutrition:
1. Prioritise protein at every meal
Protein requires less volume than other nutrients while providing essential amino acids your body needs for energy and muscle maintenance.
- Aim for 20-30g protein per meal (roughly the size of your palm or 25% of your plate)
- Good options: Greek yoghurt, eggs, chicken, fish, tofu, lean red meat
- Consider protein smoothies if you’re struggling to eat enough protein in your main meals
2. Eat by the clock, not by hunger
Because Wegovy can lower hunger, relying on appetite to guide eating can lead to inadequate intake.
- Schedule three consistent meals daily
- Set alarms if you tend to forget eating
- Eat something even when not hungry
- Consider more frequent, smaller meals if that’s easier
- Eat protein-rich snacks, like 2 boiled eggs, between meals
3. Focus on nutrient-dense foods
When eating less volume, the nutritional quality of what you do eat becomes even more important.
- Choose foods rich in vitamins and minerals, like red meat, green leafy vegetables, eggs, fish, and dairy
- Include healthy fats like olive oil, nuts, and avocado
- Ensure adequate iron intake through red meat, leafy greens, or supplements if recommended by your doctor
Key points:
- Eating too little on Wegovy forces your body to conserve energy, causing fatigue
- Schedule regular meals rather than waiting for hunger signals
- Prioritise protein and nutrient-dense foods to get more nutrition with less volume
- Consider tracking your food intake temporarily if fatigue persists
How Wegovy affects your sleep/wake cycle
The second way Wegovy may cause fatigue involves its effects on your brain’s internal clock. Semaglutide works by targeting the hypothalamus; the same brain region that regulates your sleep/wake cycle.
Recent research suggests GLP-1 medications like Wegovy may unintentionally disrupt your circadian rhythm, the 24-hour biological cycle that determines when you feel alert or sleepy.
A study in rats found that liraglutide (a similar GLP-1 medication) reduced wakefulness and altered sleep patterns. While human studies are limited, many patients report changes in their sleep quality and patterns when starting Wegovy.
Common sleep changes reported on Wegovy:
- Difficulty falling asleep despite feeling tired
- Waking during the night
- Vivid dreams or nightmares
- Morning grogginess that’s difficult to shake off
- Changes in preferred sleep timing (going to bed earlier/later than usual)
Evidence-based strategies to improve sleep on Wegovy:
1. Regulate your light exposure
Light is the primary signal that regulates your internal clock.
- Get bright light exposure within 30-60 minutes of waking
- Spend at least 10-15 minutes outdoors in morning daylight
- Reduce bright and blue light exposure 2-3 hours before bed
- Use night mode on devices and consider blue-light blocking glasses in the evening
2. Maintain consistent sleep/wake times
Regularity reinforces your body’s natural rhythm.
- Go to bed and wake up at the same time daily, even weekends
- Aim for 7-9 hours of sleep (individual needs vary)
- Avoid compensating for fatigue with excessive time in bed
3. Create an optimal sleep environment
Your sleeping space significantly impacts sleep quality.
- Keep your bedroom cool (16-18°C is ideal)
- Ensure the room is as dark as possible
- Reduce noise or use white noise if needed
- Reserve your bed for sleep and intimacy only
4. Monitor caffeine and timing of meals
- Avoid caffeine after 12pm
- Try to finish eating 2-3 hours before bedtime
- Consider a small protein-rich snack before bed if hunger disrupts sleep
Key points:
- Wegovy may affect your internal body clock by interacting with the hypothalamus
- Morning daylight exposure helps reset your circadian rhythm
- Consistent sleep/wake times are crucial for energy regulation
- Sleep disruption typically improves as your body adjusts to the medication
Other ways of managing Wegovy fatigue
Beyond addressing nutrition and sleep, several additional approaches can help manage fatigue while your body adjusts to Wegovy.
Movement and exercise
While it may seem counterintuitive to exercise when tired, appropriate physical activity can actually boost energy levels.
- Start with gentle movement: Walking, stretching, or light yoga
- Time activity: Exercise when your energy naturally peaks
- Build gradually: Start with 5-10 minutes and increase slowly
- Consider strength training: Even brief sessions help maintain muscle mass during weight loss
- Avoid high-intensity exercise during periods of extreme fatigue
Hydration
Dehydration can worsen fatigue, and Wegovy may affect your fluid and electrolyte balance.
- Aim for at least 2 litres of water daily
- Include electrolyte-rich foods like bananas, yoghurt, nuts, seeds, and leafy greens
- Reduce alcohol consumption, which can worsen dehydration and fatigue
Stress management
Chronic stress depletes energy and can compound medication-related fatigue.
- Practice brief relaxation techniques (even 2-3 minutes can help)
- Try box breathing: inhale for 4 counts, hold for 4, exhale for 4, hold for 4
- Consider a mindfulness app or practice
- Reduce commitments temporarily if possible
- Communicate with family/colleagues about your temporary energy limitations
Timing your Wegovy injection
Some patients find that when they administer their injection affects their energy patterns.
- If fatigue is worse in the days immediately following injection, consider Friday evening administration so the lowest energy days fall on weekends
- Track your energy levels daily to identify patterns
- Discuss with your healthcare provider before changing your injection schedule
Key points:
- Light movement can paradoxically increase energy levels when feeling tired
- Proper hydration and electrolyte balance are essential for combating fatigue
- Stress management techniques can preserve limited energy
- Strategic timing of your Wegovy injection may help manage predictable energy dips
When to be concerned about fatigue on Wegovy
While tiredness is common and typically improves with time, certain symptoms warrant medical attention.
| Normal fatigue on Wegovy |
Concerning fatigue symptoms |
| Gradual onset of tiredness |
Sudden, severe fatigue that doesn’t improve with rest |
| Improved energy after eating or resting |
Extreme weakness or inability to perform daily activities |
| Tiredness that improves over time |
Progressively worsening fatigue beyond 8-12 weeks |
| Mild dizziness when standing quickly |
Fainting or severe dizziness |
| Some difficulty concentrating |
Confusion, disorientation, or memory problems |
| Manageable tiredness during the day |
Fatigue accompanied by yellowing skin, dark urine, or right upper abdominal pain |
Potential medical causes of excessive fatigue:
- Thyroid dysfunction: Wegovy may rarely affect thyroid function
- Anaemia: Reduced food intake may lead to iron or B12 deficiency
- Dehydration: Particularly if experiencing diarrhoea or vomiting
- Hypoglycaemia: Low blood sugar, more common if taking diabetes medications
- Medication interactions: Wegovy may interact with other medications
Key points:
- Normal Wegovy fatigue gradually improves and doesn’t severely impact daily functioning
- Consult your healthcare provider if fatigue is severe, worsening, or accompanied by other concerning symptoms
- Simple blood tests can identify underlying medical causes of excessive fatigue
- Dose adjustments may be necessary if fatigue significantly impacts quality of life
Frequently asked questions about Wegovy and tiredness
How long does Wegovy fatigue last?
Most people notice significant improvement in energy levels after 4-8 weeks. In our research, the percentage of patients reporting fatigue dropped from 44% at week 4 to 22% by week 8. For most people, energy levels return to normal or near-normal by 12 weeks as the body adjusts to the medication.
Is tiredness on Wegovy dangerous?
Typical Wegovy-related fatigue is not dangerous, though it can be uncomfortable and disruptive. However, extreme fatigue, especially when accompanied by other symptoms like severe dizziness, confusion, or jaundice, should be evaluated by a healthcare provider. Monitoring your symptoms and communicating with your healthcare team is important.
What can I take for energy while on Wegovy?
R
ather than turning to supplements, focus on nutrition, hydration, and sleep quality first. Ensure adequate protein intake, stay well-hydrated, and maintain consistent sleep patterns.
If fatigue persists, speak with your healthcare provider about testing for deficiencies in iron, vitamin B12, or vitamin D, which can be supplemented if levels are low. Caffeine can help temporarily but may disrupt sleep if consumed later in the day.
Does everyone get tired on Wegovy?
No, not everyone experiences fatigue. Our research shows about 44% of patients report increased tiredness in the first month, meaning more than half don’t experience this side effect significantly. Individual responses vary based on factors like starting weight, dose, dietary habits, and overall health status.
Can I exercise if I’m tired on Wegovy?
Yes, but it’s important to adjust your expectations and approach. Light to moderate activity like walking, gentle yoga, or brief strength training can actually improve energy levels, while intense exercise might temporarily worsen fatigue.
Listen to your body, start with short sessions (5-10 minutes), and gradually increase as your energy improves.
Will fatigue affect my ability to work while on Wegovy?
Most people can continue working normally while adjusting to Wegovy, though you might need to make temporary accommodations.
Consider scheduling your injection on Friday so initial side effects occur over the weekend, prioritise rest during off-hours, and implement the energy management strategies discussed in this article.
If fatigue significantly impacts your work, discuss dose adjustments with your healthcare provider.
Take home message
Feeling tired is a common side effect of Wegovy, affecting nearly half of patients in the first month of treatment. The good news is that this fatigue typically improves significantly by week 8 as your body adjusts to the medication.
Two main mechanisms likely cause Wegovy-related tiredness: dramatically reduced calorie intake and effects on the brain areas controlling both appetite and sleep cycles. Understanding these mechanisms helps you take effective steps to manage fatigue.
Key strategies for combating Wegovy fatigue include maintaining adequate nutrition despite reduced appetite, optimising your sleep environment and schedule, staying properly hydrated, and incorporating gentle physical activity into your routine.
Remember that while tiredness is expected, severe or worsening fatigue should prompt a conversation with your healthcare provider, as it may indicate an underlying issue that needs addressing.
By implementing the practical approaches outlined in this article, most people can effectively manage energy levels while still benefiting from Wegovy’s powerful weight loss effects.
Second Nature's Mounjaro programme
Second Nature provides Mounjaro as part of our Mounjaro weight-loss programme
Why choose Second Nature over other medication providers, assuming you’re eligible?
Because peace of mind matters.
We’ve had the privilege of working with the NHS for over eight years, helping people across the UK take meaningful steps toward a healthier, happier life.
Our programmes are designed to meet people where they are, whether that means support with weight loss through compassionate one-to-one health coaching, or access to the latest weight-loss medications (like Mounjaro) delivered alongside expert care from a multidisciplinary team of doctors, psychologists, dietitians, and personal trainers.
At the heart of everything we do is a simple belief: real, lasting change comes from building better habits, not relying on quick fixes. We’re here to support that change every step of the way.
With over a decade of experience, thousands of lives changed, and a long-standing record of delivering programmes used by the NHS, we believe we're the UK’s most trusted weight-loss programme.
We hope to offer you something invaluable: peace of mind, and the support you need to take that first step.
