Will Mounjaro make you tired?

In this article:

• Mounjaro fatigue
• Why does it cause fatigue?
• Mounjaro-related fatigue vs. other causes
• Managing fatigue
• When to be concerned

In this article

• Mounjaro fatigue
• Why does it cause fatigue?
• Mounjaro-related fatigue vs. other causes
• Managing fatigue
• When to be concerned

Mounjaro (tirzepatide) is a once-weekly subcutaneous injection prescribed to help adults with Type 2 diabetes manage blood sugar, alongside diet and exercise, similar to other GLP-1 medications like semaglutide. It works by mimicking the action of two hormones, GLP-1 and GIP, which affect appetite, digestion, and glucose regulation. Zepbound is a weight loss medication containing the same active ingredient, which is approved for the treatment of obesity or weight-related conditions, such as obstructive sleep apnea (OSA).

Because tirzepatide affects metabolism and blood sugar levels, some people report feeling unusually tired after starting Mounjaro or increasing to higher doses. Fatigue may be linked to reduced calorie intake, shifts in blood glucose, or the body adjusting to the medication. In some cases, tiredness may also be related to an underlying medical condition rather than the drug itself.

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Can Mounjaro make you tired?

“Fatigue is a common side effect of taking Mounjaro for diabetes and Zepbound for weight loss,” says Mir Ali, MD, bariatric surgeon and medical director of MemorialCare Surgical Weight Loss Center at Orange Coast Medical Center. The incidence and duration vary widely, but fatigue is more common among those losing weight, he says. Dr. Ali notes that fatigue or tiredness often occurs alongside weight loss, whether it is due to surgery, medication, or dietary changes. 

According to clinical trials, other common Mounjaro side effects include:

• Nausea
• Diarrhea or constipation
• Indigestion
• Abdominal pain
• Decreased appetite
• Injection site reactions

Serious side effects that warrant immediate medical advice include:

• Severe allergic reactions
• Pancreatitis (inflammation of the pancreas)
• Hypoglycemia (low blood sugar)
• Acute kidney injury
• Vision changes
• Gallbladder problems
• Severe stomach pain

Although it’s not known if Mounjaro causes thyroid cancer in humans, animal studies have shown an increased risk of certain types of thyroid cancer. People with symptoms of thyroid cancer, such as trouble breathing or swallowing, a lump in the neck, or hoarseness, should seek medical attention.

Does Mounjaro fatigue go away?

“Fatigue associated with Mounjaro is often temporary and may resolve as the body adjusts to the medication,” says Shopana Ganpath, MD, an internist with IntraCare Health Center in Grapevine, Texas.

Dr. Ganpath explains that many people report that Mounjaro side effects, including tiredness, are most pronounced during the initial weeks of treatment and gradually diminish over time.

However, for some individuals, fatigue may persist, particularly when other factors, such as dietary changes or underlying health conditions, are contributing.

Why might Mounjaro cause fatigue?

Dr. Ganpath explains that fatigue after taking Mounjaro may occur due to the following reasons:

Blood sugar fluctuations

Mounjaro changes how your body releases insulin and glucagon (another hormone that raises blood sugar). As your body adjusts to the medication, this can sometimes cause short periods of low blood sugar, also known as hypoglycemia. When that happens, you may feel tired, lightheaded, dizzy, or weak.

Gastrointestinal effects

Mounjaro makes food move more slowly through your digestive system, a process known as delayed gastric emptying. This can decrease appetite and make you want to eat less, resulting in lower energy levels from reduced calorie intake. Hydration with water and electrolytes can help manage side effects such as constipation and dehydration.

Nutritional deficiencies

Dr. Ali notes that fatigue may also result from anemia or other nutritional deficiencies caused by Mounjaro-induced appetite loss, which may prevent adequate intake of protein, healthy fats, or whole grains.

Distinguishing Mounjaro fatigue from other causes

It’s also possible that the fatigue you experience while on Mounjaro is not a result of the medication but rather due to other factors like lifestyle, underlying health conditions, and other treatments.

For instance, other medical conditions like insomnia and obstructive sleep apnea (OSA) can cause you to experience fatigue, tiredness, or low energy. If you are prescribed Mounjaro (or Zepbound, which is also FDA-approved for moderate to severe OSA in adults with obesity), you may still occasionally experience these symptoms. Other lifestyle habits, such as sleep, diet, physical activity, and mental health, can affect your energy levels and lead to fatigue.  

But how can you tell if the fatigue is caused by Mounjaro or by some other factors? Dr. Ganpath provides the following tips to help you differentiate the two:

• Timing: Mounjaro-related fatigue often occurs shortly after starting the medication or increasing the dose. If fatigue coincides with these changes, it is likely drug-related.
• Associated symptoms: Tiredness caused by Mounjaro may be accompanied by other possible side effects, including nausea, dizziness, and mild hypoglycemia. If these symptoms are present, they may point to the medication as the cause of your fatigue.
• Duration: In many cases, fatigue associated with Mounjaro resolves as the body adapts to the medication.
• Lifestyle factors: Consider whether fatigue could be related to poor sleep, stress, or dietary changes. For example, reduced caloric intake due to appetite suppression may contribute to tiredness.
• Other medications: Discuss any other medications you take with a healthcare provider, as some, such as antihistamines, are known to cause fatigue.  
  

Dr. Ganpath recommends keeping a symptom diary to help you track when fatigue occurs, its severity, and any accompanying symptoms. “This information can be invaluable for identifying patterns and determining the cause,” she says.

Managing Mounjaro-related fatigue

The following recommendations may help manage this side effect: 

• Make dietary adjustments. Dr. Ali advises that you first ensure that you are consuming an adequate, balanced diet, including sufficient protein. “Lack of protein may increase muscle loss, which can contribute to fatigue,” he says. 
• Move your body more. Lifestyle changes, such as exercise, may help boost energy. Dr. Ali notes that regular exercise (including walking) has the added benefit of minimizing muscle loss, another potential side effect.
• Maintain a regular, healthy sleep schedule. Ensure you get at least seven hours of sleep each night. 
• Focus on hydration. Dehydration worsens fatigue and other side effects of Mounjaro.

When to be concerned

Fatigue may seem like a mild side effect, but it can disrupt your daily life. If you experience persistent tiredness that does not improve after a few weeks, seek medical advice from your healthcare team. You might need a dose adjustment or additional tests.