Can Mounjaro Make You Tired?

Tirzepatide, sold under the brand name Mounjaro, has become one of the most talked-about medications in recent years for its effectiveness in managing type 2 diabetes and aiding weight loss. As more people begin using Mounjaro, questions about its side effects have become more frequent. One particular concern that stands out among users is fatigue. But can Mounjaro make you tired, or is there more to the story?

In this article, we’ll explore what the science says, how common this side effect is, what real patients are experiencing, and how you can manage or reduce tiredness if it happens to you.

What Is Mounjaro and How Does It Work?

Mounjaro (tirzepatide) is a once-weekly injectable medication approved by the FDA for type 2 diabetes. It’s usually used as a second-line treatment if other diabetes medications aren’t enough. You take it once per week using a subcutaneous injection (under the skin), and the dose is increased slowly over time.

In the SURPASS-5 study:

• • People taking 5 mg/week had a 2.11% drop in HbA1c (a marker of blood sugar control)
  • At 15 mg/week, the drop was 2.34%
  • Weight loss ranged from 5.4 kg (around 12 lbs) to 10.5 kg (about 23 lbs), depending on the dose

What makes Mounjaro unique is that it activates two different hormone receptors – the GIP receptor and the GLP-1 receptor. These receptors help control blood sugar and appetite, so Mounjaro is considered the first of its kind, a dual GIP/GLP-1 receptor agonist, also called a “twincretin.”

Mounjaro helps your body manage blood sugar in several ways:

• • It boosts insulin release both right after eating (first-phase) and later on (second-phase), but only when your blood sugar is high.

• • It also lowers glucagon, a hormone that raises blood sugar. At 15 mg, it can reduce fasting glucagon by 28% and post-meal glucagon (AUC) by 43% compared to no change with placebo.

Like other GLP-1 drugs, Mounjaro also makes you feel full, slows down digestion, and helps with weight loss.

Can Mounjaro Make You Tired?

Fatigue isn’t listed as a common side effect in the prescribing information reviewed by the FDA, but some people still report feeling unusually tired. In the SURMOUNT-4 weight-loss trial, participants were asked to share their experiences through online interviews.

About 62% said they had more energy while using tirzepatide. They described feeling less sluggish and more active overall. But a few had different experiences. One person mentioned feeling more tired, which they linked to eating fewer calories. Four others said they felt fatigue as a side effect of tirzepatide.

In general, most people felt an energy boost, but a small number reported tiredness, either from the drug itself or from dietary changes.

Why Does Mounjaro Make You Tired?

Several biological and behavioral factors may contribute:

Blood Sugar Changes

Mounjaro helps lower blood sugar levels. While this is its main purpose, rapid changes in glucose can sometimes lead to symptoms that mimic fatigue.

When your body senses low blood sugar, it sees it as an emergency. To fix it, your body releases adrenaline and cortisol. These are stress hormones that try to raise your glucose levels quickly. This fight-or-flight response can make you feel jittery at first, but once it’s over, it often leaves you feeling exhausted and drained, similar to a post-stress crash.

The brain is especially sensitive to low glucose. Without enough fuel, mental functions like concentration, memory, and alertness start to fade. This mental fog often shows up as sleepiness or mental fatigue.

Your muscles also rely on glucose to keep going. Without it, even simple movements may feel heavy or sluggish, contributing to that overall tired, run-down feeling.

Low blood sugar was more common when Mounjaro was taken together with a sulfonylurea, a type of diabetes medication. In a clinical trial that lasted up to 104 weeks, the following was observed in people using both medications:

Even if blood sugar doesn’t technically fall into hypoglycemic range, these fluctuations can create a feeling of sluggishness.

On the other hand, when blood sugar stays too high, your body struggles to use it properly for energy. The sugar stays in your bloodstream instead of reaching your muscles and organs. This means your cells aren’t getting the energy they need, making you feel tired.

Appetite Suppression

Reduced appetite can cause a drop in calorie intake, especially during the early phases of weight loss. In clinical trials, up to 11% of participants reported having less appetite.

If you’re eating too little or skipping meals because of Mounjaro’s appetite-suppressing effects, you might start to feel low on energy.

In one study, people with type 2 diabetes who took tirzepatide 15 mg once a week ate 348 fewer calories during a freely chosen lunch. This reduction was linked to lower appetite, feeling fuller, and a decreased interest in eating. These changes may explain some of the weight loss observed during treatment.

Digestive Side Effects

Many people experience gastrointestinal side effects when starting Mounjaro. These may include nausea, vomiting, diarrhea, and constipation.

These symptoms, especially if persistent, can lead to:

• • Reduced blood volume – When you’re dehydrated, the amount of fluid in your blood drops. This makes it harder for your heart to pump oxygen and nutrients to your tissues. As a result, your muscles and brain don’t get the fuel they need, which can make you feel sluggish or weak.

• • Drop in blood pressure – Lower fluid levels can lead to a drop in blood pressure. This can reduce blood flow to the brain, causing dizziness, lightheadedness, or fatigue, especially when standing up.

• • Electrolyte imbalance – Water loss often comes with a loss of important electrolytes like sodium, potassium, and magnesium. These help your muscles and nerves function properly. When they’re off balance, your body may feel tired, crampy, or mentally foggy.

• • Brain function slows down – Your brain is around 75% water. Even mild dehydration can impair concentration, memory, and mood, leading to mental fatigue or that “tired but wired” feeling.

• • Sleep gets disrupted – Being dehydrated can increase your heart rate, raise your core temperature, and even cause leg cramps at night. These factors can make it harder to get restful sleep and leave you feeling tired the next day.

Even mild fluid loss can trigger fatigue, so staying well-hydrated while on Mounjaro is important.

Mental Health Issues

Mounjaro’s clinical trials did not show a high rate of psychiatric side effects like depression, anxiety, or suicidal thoughts. These were not flagged as common adverse events during FDA review or pivotal studies like SURPASS trials.

However, post-marketing reports have raised concerns. Some users have experienced mood changes, anxiety, or suicidal thoughts, prompting regulatory bodies like the European Medicines Agency (EMA) to investigate the entire GLP-1 class (which includes Mounjaro, Ozempic, and Wegovy).

In their analysis, they found 31,444 reports of GLP-1 side effects, and only 1.18% (372 reports) involved psychiatric side effects. Among those:

• • Depression (187 cases)
  • Anxiety (144 cases)
  • Suicidal thoughts (73 cases)

If Mounjaro triggers mood changes, this emotional shift can indirectly lead to fatigue. Even mild depressive symptoms, such as low motivation, sadness, or mental fog, can cause persistent exhaustion, sleep disturbances, or a feeling of being “drained,” regardless of how much rest you get.

Dose Titration Effects

Fatigue tends to spike during dose increases. Mounjaro is often started at 2.5 mg and increased every 4 weeks until a maintenance dose is reached. Each new dose can stress the body slightly, leading to temporary fatigue as your system adjusts.

One Mounjaro user shared on Reddit that they began experiencing moderate fatigue and low energy after increasing their dose from 2.5 mg to 5 mg. While they had no side effects on the lower dose and successfully lost around 10 to 12 pounds in the first month, the higher dose brought noticeable tiredness throughout the week.

Other users responded with similar experiences. Many said they felt fine on 2.5 mg but became exhausted on 5 mg or higher doses, with some describing it as “almost unbearable.” Several users noted that the fatigue improved after a few days or weeks, while others had to return to a lower dose or take breaks due to persistent exhaustion.

Tips to Manage and Reduce Fatigue

If you’re feeling more tired than usual while taking Mounjaro, the following strategies might help:

Maintain a Balanced Diet & Stay Active

Even if you’re eating less, prioritize nutrient-dense foods to maintain energy. Focus on:

• • Complex carbohydrates (whole grains, legumes) to provide a steady release of energy.

• • Lean proteins (chicken, fish, eggs, tofu) to support muscle health and metabolism.

• • Healthy fats (avocados, nuts, olive oil) to promote brain function and long-lasting energy.

• • Iron-rich foods (spinach, red meat, lentils) to prevent anemia-related fatigue.

• • Aim for at least 8-10 cups of water per day to avoid dehydration. Even mild dehydration (as little as a 1-2% drop in body water) can impair cognitive function and energy levels.

Regular physical activity also helps by increasing circulation, improving sleep, and enhancing mood through endorphin release. Studies suggest that just 30 minutes of moderate exercise, 5 days a week, can significantly boost energy. Incorporate activities such as walking, yoga, and strength training into your daily routine.

Improve Your Sleeping Habits

To improve sleep quality:

Manage Gastrointestinal Issues

Try eating smaller, more frequent meals throughout the day. This can ease the strain on your stomach and help prevent bloating. It’s also a good idea to avoid high-fat or greasy foods, as they tend to slow digestion and may worsen symptoms like nausea or indigestion.

Staying hydrated is important, especially if you’re dealing with vomiting or diarrhea. In these cases, water alone might not be enough. Electrolyte-rich options like coconut water, diluted sports drinks, or oral rehydration solutions can help replace lost fluids and minerals.

If you’re feeling nauseated, sipping on ginger or peppermint tea may provide relief. Both are supported by research for their ability to ease nausea and promote better digestion.

Adjust Your Dose

If you find that fatigue isn’t going away and starts affecting your daily life, it could mean your dose of Mounjaro is too strong for your body. Higher doses may suppress your appetite for too long, cause dehydration, or lead to ongoing stomach issues, any of which can leave you feeling worn out and low on energy.

Check for Underlying Health Conditions

Fatigue isn’t always caused by Mounjaro alone. Other common health conditions can contribute to low energy levels. If you’re experiencing persistent exhaustion, consider getting tested for:

• • Iron deficiency or anemia
  • Thyroid disorders
  • Vitamin B12 or D deficiency
  • Obstructive sleep apnea (OSA)

OSA, in particular, is highly prevalent in individuals with type 2 diabetes, with an even higher occurrence in those with uncontrolled blood sugar levels.

Zepbound Is Now FDA-approved for OSA!

Did you know? Zepbound, another tirzepatide-based drug, isn’t just for weight loss, it’s FDA-approved for treating obstructive sleep apnea (OSA) in people with obesity. Early findings also suggest that Zepbound may improve sleep quality, likely due to weight reduction and better airway function.

Take Care of Your Mental Health

Mindfulness and meditation offer a simple but effective way to reduce stress. Just 10 minutes a day of deep breathing, quiet reflection, or guided relaxation can help lower stress hormones and clear your mind. It also helps to carve out time for things that make you feel good.

When you’re dealing with fatigue, tending to your mental health is just as important as addressing the physical side. Both work hand in hand to help you feel more balanced and energized.

When Should You Be Concerned?

Most fatigue linked to Mounjaro is mild and short-lived. However, consult your healthcare provider if you experience:

• • Sudden or severe tiredness
  • Weakness that interferes with daily activities
  • Dizziness or lightheadedness
  • Shortness of breath
  • Persistent vomiting or diarrhea
  • Unintentional weight loss or malnutrition

These symptoms could indicate a more serious issue, whether it’s related to blood sugar, dehydration, or another underlying cause.

Wrap-up

Fatigue is not among the most commonly reported side effects of Mounjaro in clinical trials, but real-world experiences tell a more nuanced story. Many users, especially those new to the medication or increasing their dose, report feeling tired or drained. Several potential causes, such as blood sugar changes, low food intake, sleep disruption, and digestive side effects, could be contributing.

To manage fatigue, eat balanced meals, stay hydrated, get regular exercise, and improve your sleep habits. If tiredness doesn’t improve or gets worse, talk to your doctor. It could mean your dose needs adjusting or that another condition is contributing to your symptoms.

Frequently Asked Questions