Mounjaro tiredness and fatigue: Causes, how long it lasts, and what helps

Yes, tiredness is a common side effect of Mounjaro and can affect up to 1 in 10 people.

Fatigue can be caused by a number of reasons when starting or adjusting to Mounjaro. It is reported as a common side effect, but it can be indirectly caused by other side effects of Mounjaro like:

• stomach ache and/or nausea – which can stop you from getting quality sleep
• dehydration – as a result of gastrointestinal side effects like stomach ache, nausea and vomiting
• lowered appetite – meaning you eat less calories and in turn have lower energy levels
• reduced blood sugar levels – this can make you feel sluggish, disrupt sleep and make you less alert
• changes to metabolism – this usually affects sleep as you increase a dose or when you first start treatment
• hypothalamus impact – this part of the brain works to regulate your appetite on Mounjaro, however it also works to regulate your sleep cycle

A study has found that GLP-1 medications like Mounjaro can increase energy expenditure in many ways. This means Mounjaro makes your body burn fat faster than you create it, leading you to feeling more tired.

Tiredness is usually experienced during the first few days or weeks of taking Mounjaro and when the dose is increased. This happens because your body is adjusting to the changes caused by Mounjaro, such as decreased calorie intake and fluctuating blood sugar levels.

Mounjaro may cause some initial, temporary tiredness, but as you lose weight over time during treatment, this will also help with tiredness. As you start to lose more weight, there is less strain on your body, and your overall energy levels will increase.

Losing weight has a positive effect on your sleep long-term, with studies showing that people with moderate to severe obstructive sleep apnoea can see a reduction of up to 63% in sleep apnoea events per hour.

If you are experiencing fatigue while taking Mounjaro, you can boost your energy levels and reduce your tiredness by:

Eating well

A great way to keep your energy levels up is to eat nutritious meals regularly. Even though Mounjaro reduces your appetite, we encourage eating smaller, nutrient-dense meals and healthy snacks more often, which can help you to increase your energy levels.

Staying hydrated

Gastrointestinal side effects of Mounjaro, such as feeling sick (nausea), being sick (vomiting), or diarrhea, can dehydrate you, which can make you feel tired.

Staying well hydrated throughout the day can help reduce feelings of fatigue. We recommend drinking at least 1.2 to 1.5 litres which is 6-8 glasses of water a day when using GLP-1 medications like Mounjaro. This can increase the effectiveness of your treatment and minimise side effects like tiredness.

Exercising

Exercising regularly can help to improve your energy levels. Even a short, gentle walk can boost your energy and support overall wellbeing. More frequent exercise can lead to more benefits.

It is recommended by the NHS to do around 150 minutes of moderate-intensity aerobic exercise a week, which includes activities such as cycling or fast walking.

However, if you are not very active, you should start with small amounts of exercise and build up gradually. Low-impact, gentle exercises include:

• yoga
• weight-lifting
• pilates
• swimming
• walking

Any form of regular exercise will be good for tiredness and weight loss, including local gym classes or team sports. It is important to take part in exercise that makes you feel comfortable and confident.

Reducing stress

Stress can play a major role in feeling tired as it uses up a lot of energy. Keeping your stress levels down can help to improve feelings of fatigue. You can help manage stress by:

• practicing mindfulness
• spending time with friends
• doing activities you enjoy, such as reading or listening to music
• doing yoga or tai chi

If you feel stress on a regular basis and it begins to affect your day-to-day life, speak to your local GP. They may recommend Talking Therapies to help you manage your stress, like Cognitive Behavioural Therapy (CBT).

Lowering caffeine intake

Caffeine is a stimulant that makes you feel more awake. However, it can also disrupt your sleep rhythms and reduce total sleep time by 45 minutes. Avoiding or limiting your caffeine intake in the evenings can help to improve your sleep. Products that contain caffeine include:

• coffee
• tea
• energy drinks
• fizzy drinks

Avoiding alcohol

Alcohol can help you to fall asleep more quickly, but you will not sleep as deeply as you normally would and will feel more tired when you wake up. Cutting down on alcohol before bed can help to improve your sleep quality and have more energy.

You can find out more information on the impact of alcohol during your treatment in our guide: Mounjaro and Alcohol.

You should speak to a doctor about Mounjaro fatigue if it lasts more than a few weeks or has a severe impact on your daily life. You should also speak with your doctor if you experience fatigue along with:

• severe dizziness
• persistent vomiting
• low blood sugar symptoms (sweating, confusion, and intense hunger)

Can Mounjaro cause extreme tiredness?

Yes, Mounjaro can cause extreme tiredness for some people. It is a common side effect and is reported to affect 1 in 10 people.

Why do I feel exhausted after my Mounjaro injection?

You may feel tired after taking your Mounjaro injection, as your body is experiencing a sudden drop in calories and blood sugar levels, as well as changes in metabolism. These can lead to lower energy levels and increased tiredness.

Does fatigue get worse with higher Mounjaro doses?

Yes, fatigue can get worse when you increase to a higher dose of Mounjaro, as increasing the dose can make common side effects more intense. However, fatigue is often a temporary side effect and should improve as the body adjusts.

Can Mounjaro affect my sleep?

Yes, Mounjaro can affect your sleep. Tiredness is often an indirect effect of Mounjaro caused by a number of other side effects impacting your energy levels.