Dehydration on a GLP-1 Is a Real Risk — Here’s How to Make Sure You’re Drinking Enough

If you’re on a GLP-1 medication for obesity or diabetes, you may experience common side effects like nausea, vomiting, diarrhea, or constipation. When these problems occur they’re hard to overlook.

“Many patients do not realize that dehydration is a GLP-1 side effect, but obesity medicine physicians are routinely screening for dehydration at follow-up visits,” says Reema Dbouk, MD, assistant professor of medicine at Emory University in Atlanta and a spokesperson for The Obesity Society.

For people on medications like semaglutide (Ozempic, Wegovy), tirzepatide (Mounjaro, Zepbound), and orforglipron (Foundayo), experts say it’s vital to have strategies in place to prevent dehydration, which can pose serious health risks.

GLP-1s raise dehydration risk for a few possible reasons. One is the very mechanism that makes these medications effective in the first place.

“Some individuals on GLP-1s may reduce fluid intake because these medications delay gastric emptying, and patients may feel too full to drink more,” says Marie Hiett, RD, a registered dietitian at Tufts Medicine Weight + Wellness—Stoneham in Massachusetts.

If the food you do eat is lacking in nutrients, it may also be low in water content, says Amy Rothberg, MD, professor of medicine in the division of metabolism, endocrinology, and diabetes at the University of Michigan in Ann Arbor and director of Rewind, a virtual weight management and diabetes treatment program.

“If you’re eating more foods like Doritos as opposed to fruits and vegetables, you may not be getting a lot of water from that type of diet,” she says.

Over time, not taking in enough fluid can have a serious negative impact on health.

• Constipation risk increases. With inadequate water in the body, stools can become dry and hard and difficult to pass. “Hydration helps soften your stool,” says Katherine Zeratsky, RD, a registered dietitian-nutritionist at Mayo Clinic in Rochester, Minnesota. “You want to keep substances that are moving through the digestive tract soft, and then you can more easily have a comfortable bowel movement.”
• Overall digestive health suffers. Beyond constipation, insufficient fluid can cause a host of other digestive tract problems, including bloating, gut discomfort, poor nutrient absorption, an unhealthy balance of bacteria in the gut microbiome, and reduced saliva production.

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• Kidney function can be damaged. Dehydration forces kidneys to work harder to filter waste, raising the risk of acute kidney injury, kidney stones, and chronic kidney disease.

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Ultimately, the entire body can be affected by a lack of hydration, according to Hiett. “Dehydration impacts all organ systems in the body and if left untreated can lead to cardiovascular disease, neurological dysfunction, kidney failure, gastrointestinal damage, generalized muscle cramps and weakness, and in severe cases, death,” she says.

• Dry mouth or tongue
• Urinating less than usual
• Lethargy
• Fatigue
• Dry skin
• Decreased skin turgor (skin that doesn’t become taut again after being pulled up and released)
• Muscle weakness
• Lightheadedness
• Headache
• Lack of focus (“brain fog”)
• Darkening of urine

Signs of extreme dehydration include

• Sunken eyes
• Lack of tears
• Low blood pressure
• Fast resting heart beat
• Unconsciousness

“Signs that you are sufficiently hydrated include infrequent thirst, light yellow urine, and good energy levels,” says Hiett. Also, skin on the back of your hand should snap back after it’s pulled.

• Seltzer
• Herbal tea
• Skim milk
• Coconut water
• Electrolyte or sports drinks (especially after vigorous exercise when the body needs to rebalance both mineral and fluid levels)
• Soups and bone broth
• Vegetables and fruits with high water content, such as cucumbers, iceberg lettuce, tomatoes, spinach, strawberries, and watermelon

• Beer, wine, and liquor
• Sodas
• Coffee
• Sweetened fruit juices
• Certain energy drinks

The following tips can help you stay sufficiently hydrated on a GLP-1:

• Keep a water bottle on hand so you can easily take sips throughout the day.
• Set timers on your phone to remind yourself to take a few sips of water, even if you’re not feeling thirsty.
• Take in small amounts of fluid slowly — this can be easier on the digestive system than drinking a lot of liquid at once.
• Eat more highly hydrating foods.
• Drink and eat at separate times to avoid overfilling the stomach.

“While on a GLP-1, hydration needs to become intentional, not passive,” says Priya Jaisinghani, MD, an endocrinologist and obesity medicine specialist at NYU Langone in New York City. “Staying ahead of hydration is essential for preventing side effects and supporting overall health.”