Does Mounjaro make you tired? How to manage fatigue

Mounjaro is an injectable prescription medication for type 2 diabetes and is commonly used off-label for chronic weight management. Clinical trials have shown Mounjaro’s efficacy in lowering blood sugar levels and weight due to its unique dual-acting GIP/GLP-1 receptor agonists.

Fatigue and tiredness are not listed as side effects of Mounjaro. However, some people report feelings of tiredness and low energy, which may impede ordinary activities and affect overall health.

There are multiple reasons why Mounjaro may cause fatigue. Mounjaro reduces your appetite and slows your digestion, which leads to reduced calorie intake and may cause fatigue. The medication can cause gastrointestinal-related side effects, which may result in fatigue as a result of dehydration. Some people may need time for their body to adjust to the medication. The adjustment period may lead to increased tiredness as the body adapts to changes in hormone levels and metabolism. As Mounjaro is used to lower blood sugar levels, some people may experience rapid drops in blood sugar that may cause fatigue, especially those taking other diabetes medications.

This article explains how Mounjaro works and possible reasons for its potential fatigue-related side effects. Keep reading to learn if Mounjaro causes tiredness and how to manage it for optimal blood sugar control and weight management.

What is Mounjaro?

Mounjaro (tirzepatide), produced by Eli Lilly Inc., is a GLP-1/GIP receptor agonist medication for adults with type 2 diabetes mellitus. It was approved by the U.S. Food and Drug Administration (FDA) in 2022. It is the first and only dual-acting glucose-dependent insulinotropic polypeptide (GIP) and glucagon-like peptide-1 (GLP-1) receptor agonist for treating type 2 diabetes.

Tirzepatide is an injectable medication administered under the skin once per week. It is combined with a diet and exercise regimen to help improve blood sugar control. Mounjaro works by lowering your blood sugar as it helps to increase insulin secretion and sensitivity in type 2 diabetes.

Mounjaro comes with a boxed warning (the most serious warning from the FDA) that the drug has caused both cancerous and non-cancerous thyroid tumors in mice and rats. It is contraindicated in people with a history or family history of thyroid tumors, including a thyroid cancer called medullary thyroid carcinoma (MTC). It is also contraindicated in patients with Multiple Endocrine Neoplasia syndrome type 2 (MEN 2).

Mounjaro should not be used by individuals with type 1 diabetes mellitus, those who have experienced a severe allergic reaction to Mounjaro or any of its ingredients, or patients with a personal or past medical history of pancreatitis.

Does Mounjaro make you tired?

Yes, Mounjaro can make you tired, despite fatigue not being officially listed as a side effect of Mounjaro in clinical trials.

While Mounjaro provides significant benefits for blood sugar control and weight management, many people report experiencing tiredness when using Mounjaro. The exact reasons why Mounjaro causes fatigue are still unknown.

It’s important to understand the relationship between Mounjaro and tiredness:

• Mechanism of action: Tirzepatide, the active ingredient in Mounjaro, is a dual GIP/GLP-1 receptor agonist. Mounjaro works by enhancing insulin secretion and lowering glucagon levels, which lowers blood sugar levels. It. also slows gastric emptying, increases satiety, and reduces calorie intake.
• Side effects: Clinical trials report common side effects that are often gastrointestinal-related, including nausea, vomiting and diarrhea. These side effects may indirectly lead to fatigue as a result of dehydration.

Keep reading to find out the possible reasons why Mounjaro might make you feel tired as a side effect of other side effects of the medication.

Why does Mounjaro cause fatigue?

Although there is no direct research that explains Mounjaro’s effects on chronic fatigue, there are several theories that may suggest why you might feel tired:

Appetite suppression and calorie deficit

Mounjaro’s dual-acting mechanism is effective at suppressing appetite and reducing calorie consumption. When consuming fewer calories, your body may not have enough fuel to function properly, resulting in feelings of tiredness or fatigue, especially if your body lacks the nutrients it needs to support energy levels.

Dehydration

Fatigue can also be a side effect of other potential side effects of Mounjaro, such as nausea, vomiting, and diarrhea. These gastrointestinal-related side effects may lead to dehydration because they cause your body to lose fluids and electrolyte imbalances which may manifest as fatigue. Dehydration can contribute to fatigue as your body will struggle to perform normal functions without adequate fluids.

Signs of dehydration include thirst, dizziness, dry mouth, headache, fatigue, sunken eyes, lack of tears, low urine output, and dark-colored urine. Accompanying signs and symptoms may include hypotension, increased heart rate, weakness, anxiety, and mood changes.

Blood sugar fluctuations

While Mounjaro is effective in managing blood sugar levels, some people may experience blood sugar fluctuations, especially when starting the medication or taking Mounjaro with other diabetes medications.

A rapid drop in blood sugar levels can lead to hypoglycemia, a dangerous health condition that is associated with fatigue, weakness, and dizziness.

Gut reactions

The gastrointestinal-related side effects of Mounjaro such as diarrhea and vomiting may also affect the integrity of your gut lining, causing inflammation, ulceration, and malabsorption of nutrients. This may result in nutrient deficiencies such as vitamin B12 and iron deficiencies, and less energy in your body, manifesting as fatigue. Signs of nutrient deficiencies include fatigue, muscle weakness, mouth ulcers, diarrhea, restlessness, dry skin, and weight loss.

The good bacteria in your gut, called probiotics, could also become affected. An imbalance in your gut microbiome could hinder nutrient absorption, pH balance, and energy, resulting in fatigue.

Your gut also produces the neurotransmitter, serotonin, which helps regulate your mood and sleep. An offset in your serotonin levels could lead to poor mood, sleep and digestion, contributing to decreased energy and fatigue.

Sleep disruption

Mounjaro’s effect on the brain may disrupt normal sleep patterns, leading to fatigue. Tirzepatide may affect your hypothalamus which is responsible for your appetite regulation and also plays a key role in regulating the sleep-wake cycle. More research is needed to establish tirzepatide’s influence on the hypothalamus.

A research study in rats reported that another GLP-1 medication with similar effects to tirzepatide, Saxenda (liraglutide), lowered wakefulness and modified the rat’s sleep patterns. This study suggests a possible link between GLP-1 medications and energy levels. However, this is an animal study and it isn’t certain if the same effects are present in humans.

Mounjaro may cause nocturnal hypoglycemia (low blood sugar levels during the night) due to your reduced calorie consumption during the day because of its appetite suppression and delayed gastric emptying. This may also be due to your exercise regimen, as burning more calories than consumed could further contribute to low blood sugar in your body.

Nocturnal hypoglycemia may cause poor mood, anxiety, restless sleep and worsen your fatigue. If Mounjaro is used with other diabetes medications, this could further exacerbate your sleep and fatigue.

Hormonal changes

When you start taking Mounjaro, your body needs time to adjust to the medication to adapt to the hormonal changes. During this adjustment period, your body may experience hormonal changes and imbalances can occur, which may lead to feelings of fatigue as your body gets used to the medication.

Your body will eventually adjust to the medication, the hormonal fluctuations will stabilize, and your fatigue will improve.

Mounjaro fatigue: How long does it last?

It has not been scientifically established that Mounjaro causes fatigue. Therefore, a set timeline for fatigue improvement has not been established. More long-term clinical trials are needed to understand the role of Mounjaro and its fatigue-related side effects.

As explained in this article, it is believed that Mounjaro-induced fatigue is related to other potential side effects of the medication and its mechanism of action. You should expect fatigue to improve as your body gets used to the medication and the other side effects subside over time.

The timeframe of Mounjaro’s gastrointestinal-related side effects varies by person. Various factors may contribute to side effects such as your health status, other medical conditions, other medications, dosage strength, diet, and duration of treatment.

Generally, when starting Mounjaro or increasing to higher doses, there may be an increase in side effects and fatigue due to your body needing time to adjust. This adjustment period may take a few days for feelings of fatigue to improve but individual response can vary.

Managing fatigue while on Mounjaro

Healthy dietary and lifestyle adjustments are essential in managing side effects and fatigue while on Mounjaro. These lifestyle changes could support the effectiveness of your treatment and help reduce side effects or feelings of fatigue.

Ongoing monitoring of your blood sugar levels may aid in reducing your blood sugar and hormonal fluctuations that induce fatigue. This may also help with adherence to your medication.

Stay hydrated

Proper hydration is important to maintain energy levels and overall health. Drink plenty of water throughout the day to stay hydrated.

Approximately 3 liters of water per day is recommended. Electrolyte-rich beverages such as energy drinks or mineral water may help replenish your body’s fluid. Other healthy hydration options include soups, milk, and yogurt.

Strategies for managing nausea include not having beverages with meals but having them approximately 30 minutes before or after meals. Ingesting ginger-infused drinks approximately 30 minutes after taking Mounjaro may help with gastrointestinal-related symptoms. Ingesting whole foods such as fresh fruit and vegetables is recommended as these are hydrating foods that may eliminate fatigue.

Healthy diet

A nutrient-enriched, balanced diet is highly recommended to improve your gut health and energy levels. Meals that contain adequate calories include complex carbohydrates (e.g. brown rice), lean protein (e.g. skinless poultry), and healthy fats (e.g. olive oil). High-fiber foods such as whole grains are also recommended.

You should also consume foods high in vitamins, minerals, and electrolytes such as leafy green vegetables, bananas, potatoes, avocados, fortified cereals, and dairy products. Superfoods, such as berries, are enriched with antioxidants and recommended to reduce fatigue. You should avoid sugary, spicy, fatty, overly processed foods and additives.

Portion control is essential. Your carbohydrate intake should be approximately 60% of your daily calories and your protein intake should be approximately 20% of your daily calories. There is no standard calorie target while using Mounjaro.

The recommended dietary allowance (RDA) or daily calorie count is in the reference range of approximately 2000-2500 kcal for adults, depending on your gender and level of activity, and differs among diabetes patients. According to the American Diabetes Association (2025), a 500–750 kcal/day energy deficit is recommended to achieve significant weight loss with lifestyle adjustment programs in adults.

You should have small and frequent meals throughout the day. Try chewing your food slowly and maintaining an upright posture for approximately 2 hours after meals.

Increase physical activity

Exercise is recommended for increasing energy levels and supporting weight management. Regular physical activity, such as moderate-intensity and stretching exercises, is strongly recommended to enhance your body’s movement, energy flow, and mood.

Aim for at least 30 minutes of moderate exercise for most days of the week, and have at least 1 session of moderate-intensity training (e.g. aerobic exercise) per week. Avoid high-intensity training as it may result in muscle damage and fatigue. Muscle-strengthening exercises are good for boosting your energy. Daily brisk walking is also recommended for aiding your metabolism and energy.

Your body needs time to adjust to the medication. Gradually increase the intensity of your physical activities to avoid fatigue.

Optimize your sleep

Having good quality sleep is strongly recommended as this allows your body’s energy to be replenished, enabling you to combat fatigue. Quality sleep also helps reduce stress and promotes a better mood, which directly helps with fatigue. It is recommended to get approximately 8 hours of quality sleep each night.

While caffeine can provide a temporary energy boost, consuming it later in the day can negatively interfere with your sleep. Avoiding screen time close to bedtime may also help with quality sleep.

Alternative therapies such as relaxation techniques may also aid in improving your sleep. By adopting a regular sleep schedule, going to sleep at the same time every night and waking up at the same time every morning, your body should get the rest it needs.

Stress reduction

Self-care management strategies may help to alleviate your stress. These strategies include relaxation techniques such as meditation, progressive muscle relaxation, autogenic training, and mindfulness practices. Cognitive behavioral therapy may also help you cope with stress and combat fatigue.

Leisure time and socializing are important in reducing stress and fatigue. Receiving health coaching may help motivate you to stay focused, guiding you with tools to sustain a healthy lifestyle.

Supplements and medications

You should consult your doctor to help you manage your underlying health condition(s), side effects, and fatigue. Your doctor can recommend appropriate interventions, including over-the-counter supplementation to support your body with essential vitamins and minerals e.g. vitamin B complex, vitamin D, iron, and calcium.

Your physician may prescribe anti-nausea and anti-emetic medications to help with nausea.

Alternative therapies

Complementary medicine offers alternative relaxation techniques that may help you with fatigue. These include acupuncture, massage therapy, breathing exercises, yoga, and aromatherapy. These interventions, conducted regularly, may help improve your circulation, energy circuit, stress levels, and sleep, potentially reducing your fatigue.

Adopting alternative therapies should be considered as part of a holistic approach integrated with your Mounjaro comprehensive treatment. Your doctor can advise you accordingly.

When to seek medical attention

You should consult your physician if you experience fatigue which lasts longer than a couple of weeks or a low-grade fever. Urgent medical attention is needed in case of persistent fatigue, which may be debilitating and life-threatening.

A lack of improvement in self-management strategies due to fatigue may include procrastination and emotional imbalance. Your medical professional may help you prioritize your tasks. Therapy and life coaching may also support your self-management strategies.

You should discuss with your doctor about any comorbidities that you may have and potential drug interactions. If adverse effects persist despite lifestyle changes, your doctor may need to prescribe other medications or adjust your dose.

Other factors that may cause fatigue

Underlying health conditions such as anemia, hypothyroidism (underactive thyroid), heart and lung disease, chronic fatigue syndrome, chronic kidney disease, immunosuppression, and mental illnesses can affect your body’s energy, which may cause fatigue.

Infections such as the flu and COVID-19 may also cause fatigue. Unhealthy lifestyle behavior including an unhealthy diet, low-quality sleep, sedentary lifestyle or lack of exercise, substance use, and excess caffeine may also cause fatigue. Life challenges, hormonal imbalances, other medication or conditions, burnout, allergies and aging may also cause fatigue.

Common side effects of Mounjaro

The most common side effects of Mounjaro include:

• Gastrointestinal-related issues such as nausea, diarrhea, decreased appetite, vomiting, constipation, indigestion, heartburn and abdominal pain (stomach pain)
• Dizziness
• Injection site reactions, itching, and rash

Your doctor or pharmacist can provide medical advice on managing these side effects.

Rare and serious side effects of Mounjaro include pancreatitis (inflammation of the pancreas), severe abdominal pain, hypoglycemia, serious allergic reactions, kidney problems, diabetic retinopathy complications, and gallbladder problems.

Mounjaro and fatigue: FAQs

How long does fatigue last on Mounjaro?

It’s unknown how long fatigue may last as it isn’t a listed side effect of the medication. The duration of Mounjaro side effects varies among individuals. The fatigue may be related to the mechanism of action or other side effects of the drug. In general, fatigue should improve over time as your body gets used to the medication and the other side effects subside over time.

In general, mild side effects may last for a few days to a couple of weeks as your body adjusts to Mounjaro. Severe side effects may persist for longer.

Can Mounjaro cause chronic tiredness?

Yes, Mounjaro may cause chronic tiredness. However, chronic tiredness is not listed in clinical trials as an adverse effect. Chronic tiredness is defined as tiredness for more than 6 months. Mounjaro has a dual-action mechanism and potential gastrointestinal-related side effects that may cause Mounjaro weight loss fatigue.

Are there ways to prevent fatigue while taking Mounjaro?

Yes, there are lifestyle modifications you can make such as eating a balanced, nutrient-enhanced diet, proper hydration, regular exercise, good sleeping routine, self-management strategies, counseling, alternative therapy, and appropriate dietary supplementation as a holistic approach.

You should avoid substance use. Additionally, ongoing monitoring of your blood sugar levels and overall health may aid in reducing your blood glucose fluctuations that induce fatigue.

Should I stop taking Mounjaro if I feel tired?

No, you should consult your doctor first. Tiredness has not been officially listed as an adverse effect of Mounjaro, therefore it should not be severe and does not warrant you to discontinue your medication. Your doctor can advise you about the potential root causes of your tiredness. They may have to adjust your dose or prescribe another medication related to your tiredness.

Bottom line

Mounjaro, is a dual-acting GIP/ GLP-1 receptor agonist used for type 2 diabetes and off-label for weight management in people with obesity and overweight.

Although fatigue is not a listed side effect of Mounjaro, many people report feeling tired while using the medication. It’s important to understand the potential reasons for this, which can include Mounjaro’s mechanism of action that causes appetite suppression or other side effects like vomiting, diarrhea, and nausea, all of which may cause dehydration and lead to fatigue.

If you experience persistent fatigue, speak with your healthcare provider as they can help you address the underlying cause of fatigue which may include lifestyle changes or other medications.