Mounjaro fatigue: what to do if you're tired on tirzepatide

Simon Edward • 4 April 2025

Are you experiencing 'Mounjaro fatigue'? Learn why tirzepatide can cause tiredness and what to do about it.

Mounjaro (tirzepatide) helps you lose weight by affecting the hormones that control digestion, slowing the digestive processes down. It makes you feel full more quickly and keeps you full for longer, making it easier to eat less.

However, this can also lead to some unwanted Mounjaro side effects. Nausea, vomiting, diarrhoea, and lowered blood sugar are among the most common. These side effects usually get better with time.

Mounjaro's manufacturer, Eli Lilly, doesn't list tiredness among its official list of side effects. But that doesn't mean 'Mounjaro fatigue' is made up.

Some people certainly do feel tired after taking Mounjaro weight loss injections. The reason it's not listed is that it's not a direct result of the medication. Instead, fatigue can happen as a consequence of the side effects.

The feelings can range from simple tiredness to overwhelming fatigue. However, there are measures you can take that will help. Start practising good habits from the start and you'll limit the impact of the most common side effects. In turn, this can make experiencing fatigue less likely or, at least, make the fatigue less severe.

An important note for people living with type 2 diabetes

If you have type 2 diabetes and experience fatigue on Mounjaro, always check first for hypoglycaemia (low blood sugar).

Tips for avoiding Mounjaro fatigue

1. Hydrate

Have a bottle of water to hand so you can keep taking regular sips and avoid getting dehydrated. This is especially important if you're experiencing nausea, vomiting or diarrhoea.

Dehydration means there's not enough water in your body to run all its natural processes efficiently. This can soon cause tiredness and fatigue.

2. Keep your electrolytes balanced

Electrolytes are minerals your body needs, such as sodium, potassium, magnesium and calcium. They're critical for muscles to work properly, for energy production, and to hold water in tissues for later use. If electrolyte levels drop too low, tiredness and fatigue can follow.

This could happen if you're eating very little, perhaps because of nausea. Also, increased water consumption to manage dehydration can dilute the concentration of these essential minerals.

So, if you are hydrating well and still feeling fatigued, consider taking an electrolytes supplement. Your local pharmacist can offer suggestions. However, if you are taking another prescribed medication along with Mounjaro, check with your GP or SemaPen team before taking any supplements.

3. Eat a balanced diet

You should always aim to eat a balanced diet to make sure your body has the nutrients it needs to keep you healthy and alert. A good way to do this is to follow the NHS Eatwell Guide. This guide can help you choose what kinds of foods to eat and in what proportions.

Picture of a plate with balanced food groups.

If you're experiencing nausea while taking Mounjaro, try switching to six small, balanced eating episodes throughout the day instead of eating two large meals.

Increase activity

If you're tired, exercising may feel especially difficult. However, even 15 minutes of exercise – like taking a short, brisk walk – can actually give you more energy.

That's because it increases blood flow around the body, giving your muscles, heart and brain much-needed oxygen and nutrients. You'll also boost your metabolism, which helps your body convert calories into energy more quickly.

Moving more can start with simply getting up and walking around whenever you talk on the phone or text. For more practical help on how to gradually increase your activity levels, try the SemaPen app.

Improve your sleep quality

While your body is adjusting to Mounjaro, you may find your normal sleep patterns are disrupted by side effects, especially on medication day. This can be a common cause of Mounjaro fatigue.

Do your best to maintain a healthy sleep routine. This could mean going to bed at a set time each night, removing distractions from your environment and perhaps listening to gentle music or podcasts.

Exercise can help, too. Regular, moderate exercise releases melatonin – the hormone that regulates sleep-wake cycles. It also releases endorphins, serotonin and dopamine. These are your body's natural feel-good chemicals – they give you a sense of well-being, relax your muscles and calm anxiety.

All these contribute to you being able to settle more quickly and easily into sleep and more likely to stay asleep without interruption.

More practical tips for better sleep

Avoid alcohol at least three hours before bedtime. If you have alcohol in your bloodstream while you're asleep, it can disrupt your natural sleep cycles. This leads to fragmented, low-quality sleep with more wakings.

Avoid caffeine. As a stimulant, it can delay your dropping off to sleep, reduce the time you stay asleep and reduce the length of deep, slow-wave sleep. If you're trying to get a disrupted sleep pattern back on track, avoiding caffeine after lunch would be advisable.

What to do next

If your feelings of fatigue do not improve, see your GP, weight loss consultant or healthcare provider.

The specialist medical team at SemaPen is always ready to give practical tips and advice. Please feel free to contact us with any questions or queries. With more than 20 years' experience helping people manage their weight, we can give you the support you need to complete your weight loss journey.

Sources

1. Wang, F. & Boros, S. (2019) "The effect of physical activity on sleep quality: a systematic review" European Journal of Physiotherapy, 23(1) https://doi.org/10.1080/21679169.2019.1623314

2. Colrain, I.M et al. (2021) "Alcohol and the Sleeping Brain" Handbook of Clinical Neurology, 125:415–431 https://doi.org/10.1016/B978-0-444-62619-6.00024-0

3. Drake, C. et al. (2013) "Caffeine Effects on Sleep Taken 0, 3, or 6 Hours before Going to Bed" Journal of Clinical Sleep Medicine https://doi.org/10.5664/jcsm.3170

This article was reviewed by and approved by Alice Fletcher, Lead Bariatric Dietitian, on 3 April 2025.

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