GLP-1s and Fatigue: Why You Feel Tired and How to Bounce Back

By helitra·October 31, 2026·8 min read

When you’re ready to start taking a GLP-1 medication for obesity or diabetes, you might feel excited, energized, and ready for action. But until your body adjusts to the medication, you might find yourself dealing with an unexpected sensation: fatigue.

“Fatigue is common in people on a GLP-1,” says Yuval Pinto, MD, an obesity and family medicine doctor at Johns Hopkins Medicine in Baltimore.

Researchers are still learning about why some people feel drained of energy when taking GLP-1 medications like semaglutide (Wegovy, Ozempic), tirzepatide (Mounjaro, Zepbound), and orforglipron (Foundayo).

Meanwhile, physicians and registered dietitian nutritionists have advice to share about how people experiencing fatigue on a GLP-1 can bounce back, both physically and mentally.

How Many People on GLP-1 Experience Fatigue?

Research on GLP-1s has identified numerous side effects. While gastrointestinal problems like nausea and constipation get most of the attention, fatigue is also an issue for many people.

In clinical trials, about 11 percent of adults taking Wegovy reported fatigue or weakness, compared with 5 percent of those on a placebo. Among people taking Zepbound, 5 to 7 percent reported fatigue, depending on the dose, compared with 3 percent on a placebo.

In real-world scenarios, fatigue appears to affect even more people on GLP-1s – at least according to a recent social media analysis. Researchers utilized artificial intelligence (AI) to review more than 410,000 Reddit posts from people taking semaglutide or tirzepatide.

They found that about 1 in 6 users mentioned fatigue, making it the second most common GLP-1 complaint after nausea.

Why Does GLP-1 Use Cause Fatigue?

There are many reasons why GLP-1s might sap energy. “Undereating can cause fatigue, dehydration can cause fatigue, and nutritional inadequacies can cause fatigue,” Dr. Pinto says.

Those factors and others can add up.

Eating Too Little

“A significant part of feeling fatigued often comes from eating much less than you used to – and in some cases, not eating enough,” Pinto says.

You typically take in fewer calories on a GLP-1, he explains. GLP-1s cause food to move more slowly through the stomach, so you feel full and stop eating sooner.

The calories in food aren’t just a number you count when you’re trying to lose weight; they’re your body’s fuel. A calorie is a measure of energy, and without an adequate amount you’ll feel fatigued, both physically and mentally.

Dehydration

Dehydration has a strong link to fatigue.

GLP-1s can cause dehydration for several reasons. Research has shown that GLP-1s can weaken thirst and hunger cues in the brain, causing you to drink less.

Dehydration on a GLP-1 can also happen because you’re eating less. The American Academy of Nutrition and Dietetics estimates that a person gets about 20 percent of the hydration they need from food.

Nutritional Gaps

Poor nutrition can contribute to fatigue. Eating less because of a GLP-1’s effects can mean missing out on protein, healthy fats, carbs, and the vitamins and minerals in vegetables, says Pinto.

People with obesity already tend to have low vitamin D, which can play a role in fatigue, he notes. Additional vitamin D deficiency from GLP-1 use can worsen tiredness.

Thyroid Changes

If you take thyroid medication, losing a lot of weight (whether or not you’re on a GLP-1) can throw your levels out of balance and leave you fatigued, says Pinto.

Thyroid medication doses are based partly on your weight and may require adjustment over time to keep levels normal.

Effect of Diabetes and Some Diabetes Medications

Fatigue is a common symptom of diabetes, and it can get worse when your body is adjusting to eating less due to GLP-1 use, says Pinto.

People who take insulin or a sulfonylurea, a type of diabetes medicine, may find that GLP-1s contribute to low blood sugar, worsening fatigue.

When Does GLP-1 Fatigue Start and How Long Does It Last?

For many people, fatigue hits hardest during the period of fastest weight loss as the body adjusts to running on less fuel, says Pinto.

“I see a lot of people with fatigue after they’ve lost 20, 25, 35 percent of their weight. It typically stays for about two or three months, and then they’re not fatigued anymore, because the body has adjusted,” he says.

“It’s almost like a thermostat: When you open a window, the air conditioner needs time to adjust, but eventually it brings the temperature back to normal,” says Pinto. In the same way, your body needs time to get used to eating less, he adds.

“If fatigue lingers well beyond that adjustment period, other causes are worth exploring,” says Pinto. Fatigue is very common in the general population, and it often doesn’t have anything to do with food intake or weight loss, he adds.

How to Boost Energy and Beat Fatigue While on GLP-1s

Fatigue rarely comes down to one cause that can be fixed, so it often takes a few changes to feel better, says Pinto.

Have Small, Balanced Meals

Some people may find that a little food helps fight fatigue. “Eating four or five smaller meals (150 to 400 calories at a time) throughout the day with lean protein, vegetables, fruit, and whole grains, along with adequate hydration, are strategies to try to overcome fatigue and low energy,” says Susan Swafford, MPH, RD, clinical dietitian at the Duke Lifestyle and Weight Management Center in Durham, North Carolina.

While Pinto doesn’t recommend eating when you’re not hungry, he does suggest planning ahead and noticing whether your energy improves when you eat regularly. “Try to predict hunger and tackle it with small amounts of food,” he says.

Make Every Bite Count

When you’re on a GLP-1, the goal is to get enough nutrients from a smaller amount of food, so choose a variety of minimally processed foods that are rich in nutrients.

Smoothies or protein drinks made with fruit, vegetables, and unsweetened milk or yogurt, as well as cottage cheese and soups, can provide needed nutrients and might appeal to you more than heavier foods.

Prioritize Protein

Over time, protein deficiency can lead to muscle loss; this can show up as fatigue, among other symptoms.

Protein is especially important to protect muscles during periods of rapid weight loss, which can include muscle loss.

Most people need about 70 to 100 grams (g) of protein a day, but the body can absorb only about 20 to 30 g at a time, so spread it over at least three meals, says Swafford.

“Many people we meet [who are taking GLP-1s] are only eating one or two meals per day, and they are often in danger of not consuming enough protein,” she says.

Add Strength Training and Other Physical Activity

Strength training to protect muscles is important for people losing weight on GLP-1s, says Swafford.

In studies, “Only when people ate adequate protein and engaged in strength training regularly was muscle wasting prevented,” she says.

Any kind of movement is also going to help increase your energy levels versus spending most of your day sitting. “Go out for a walk in the sun. You’re probably going to feel better,” says Pinto.

Stay Hydrated

Drinking until your urine is almost clear is a good rule of thumb for adequate hydration, unless vitamins are tinting it, says Swafford.

Most people need at least 48 ounces (oz) of fluid a day, and taller people may need 80 to 100 oz; a reusable water bottle makes it easier to keep track, she says.

Save electrolyte drinks for heavy sweating, workouts longer than an hour, or recovery from vomiting or diarrhea, says Swafford.

Protect Your Sleep

Poor sleep can leave you fatigued, so protecting your sleep schedule is critical.

If you have a sleep disorder like obstructive sleep apnea, which results in repeated awakenings during the night, talk to your doctor about treatment.

Weight loss often can help improve obstructive sleep apnea symptoms, and Zepbound has received approval by the U.S. Food and Drug Administration (FDA) for this disorder.

Consider a GLP-1 Dose Adjustment

If you’re unable to take in enough calories to prevent fatigue, it’s possible your GLP-1 dose is too high.

“If your appetite seems too low, then it may be good to discuss a lower dose of the GLP-1 medication with your doctor,” says Swafford. Never change your dose on your own.

When to Talk to Your Doctor

Pinto says to contact your healthcare provider if your fatigue:

Is so severe that you can’t get out of bed or you fall asleep while driving
Comes with an extreme loss of appetite
Comes with thoughts of suicide
Comes with very long or heavy menstrual periods or blood in the toilet

“If [fatigue] is consistent, getting worse, and debilitating, see your doctor for a workup,” says Pinto.

The Takeaway

Fatigue is a common complaint on GLP-1 medications, often tied to eating much less and losing weight quickly, and for many people it eases within a few months.
Small, balanced meals with enough protein, plenty of fluids, strength training, and good sleep can help you get your energy back.
Talk with your doctor if fatigue is severe, keeps getting worse, or comes with warning signs because you may need blood work or a change in your dose.

EDITORIAL SOURCES

Everyday Health follows strict sourcing guidelines to ensure the accuracy of its content, outlined in our editorial policy. We use only trustworthy sources, including peer-reviewed studies, board-certified medical experts, patients with lived experience, and information from top institutions.

Resources

Wegovy (Semaglutide) Prescribing Information. DailyMed. June 18, 2026.
Zepbound (Tirzepatide) Prescribing Information. DailyMed. August 28, 2026.
Sehgal NKR et al. Self-Reported Side Effects of Semaglutide and Tirzepatide in Online Communities. Nature Health. August 2026.
Kommu S et al. Semaglutide. StatPearls. February 11, 2024.
Counting Calories: Get Back to Weight-Loss Basics. Mayo Clinic. September 5, 2024.
Mozaffarian D et al. Nutritional Priorities to Support GLP-1 Therapy for Obesity: A Joint Advisory From the American College of Lifestyle Medicine, the American Society for Nutrition, the Obesity Medicine Association, and the Obesity Society. Obesity Pillars. September 2025.

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