Staying Hydrated on a GLP-1: Water, Electrolytes and Habits

Drinking enough sounds simple until you're eating much less and nothing sounds good. Here is what official health sources say about how much fluid adults need, why smaller meals can mean less water, the signs of dehydration, and small habits that make sipping easier. None of it replaces advice from your own prescriber.

How much water do you need each day?

There is no single number for everyone. In its report on water and electrolytes, the National Academies found that women who appear to be adequately hydrated take in an average of about 2.7 liters (91 ounces) of total water a day, and men about 3.7 liters (125 ounces). Total water means drinks plus the water in food. About 80% of it came from drinking water and other beverages.

The same report said most healthy people meet their daily needs by letting thirst be their guide, and that caffeinated drinks can count toward hydration as much as non-caffeinated ones. It also noted that prolonged physical activity and heat raise your needs.

MedlinePlus, from the National Library of Medicine, adds a few useful points:

• There is no specific recommendation for how much water you should drink. Needs vary with sex, weight, age, activity level and medical conditions.
• Drinking fluids when you feel thirsty and having beverages with meals should give you enough water to stay hydrated.
• Thirst may change as you get older, so it matters to take in fluids throughout the day.
• Alcohol does not add to the body's water, because it is a diuretic.

The CDC notes that your body needs more water in hot climates, when you are more active, and when you have a fever, diarrhea or vomiting. If you have a heart, liver or kidney condition, or a doctor has given you a fluid limit, ask them what amount is right for you.

Why can eating less mean taking in less water?

Because food is part of your water intake. The National Academies put food at about 20% of total water, and Cleveland Clinic notes that “almost everything on your plate contains some water.” If your meals are much smaller than they used to be, the water that came with them shrinks too. Your drinks may need to cover more of the gap.

Some foods carry a lot more water than others. According to Cleveland Clinic:

MedlinePlus also counts soup, milk, tea, coffee and juices as sources of water. A small bowl of soup or a few pieces of watermelon can be an easy add on a low-appetite day. If protein is the harder part for you, see how to get enough protein when you're barely hungry.

Can GLP-1 side effects lead to dehydration?

They can, and the official labels say so. The Wegovy Medication Guide, the patient leaflet that comes with the medicine, says: “Diarrhea, nausea, and vomiting may cause a loss of fluids (dehydration) which may cause kidney problems. It is important for you to drink fluids to help reduce your chance of dehydration.”

The prescribing information for Wegovy and for Zepbound both describe postmarketing reports of acute kidney injury, in some cases requiring dialysis. Most of those reports involved people whose nausea, vomiting or diarrhea led to dehydration. Both labels ask doctors to monitor kidney function in people with these side effects, especially when a dose is started or increased, and to advise patients to take precautions to avoid fluid depletion.

If you cannot keep fluids down, or if nausea, vomiting or diarrhea does not go away, contact your prescriber right away. That is what the Wegovy Medication Guide tells patients to do, and the Zepbound prescribing information asks doctors to tell patients to promptly report persistent nausea, vomiting and diarrhea. Don't wait it out.

What are the signs of dehydration?

MedlinePlus lists these symptoms.

Mild to moderate dehydration

• Thirst
• Dry or sticky mouth
• Not urinating much
• Darker yellow urine
• Dry, cool skin
• Headache
• Muscle cramps

Severe dehydration

• Not urinating, or very dark yellow or amber-colored urine
• Dry, shriveled skin
• Irritability or confusion
• Dizziness or lightheadedness
• Rapid heartbeat or rapid breathing
• Sunken eyes
• Listlessness
• Shock, unconsciousness or delirium

MedlinePlus says to call 911 or your local emergency number if a person loses consciousness, has any other change in alertness such as confusion or seizures, has a fever over 102°F (38.8°C), shows symptoms of heatstroke such as a rapid pulse or rapid breathing, or does not improve or gets worse despite treatment. It also says that if you think you may become dehydrated, call your provider.

What are electrolytes, in plain terms?

Electrolytes are minerals that carry an electric charge when they dissolve in water or body fluids, including blood, according to MedlinePlus. The main ones are sodium, potassium, chloride, calcium, magnesium, phosphate and bicarbonate. They help balance the amount of water in your body, move nutrients into your cells and wastes out, support your muscles and nerves, and keep your heart rhythm and blood pressure steady.

You get electrolytes from the foods you eat and the fluids you drink. Levels can drift too high or too low when the amount of water in your body changes. MedlinePlus lists severe vomiting or diarrhea, heavy sweating and drinking too much water among the common causes.

For dehydration, MedlinePlus suggests sipping water or sucking on ice cubes, and drinking water or sports drinks that contain electrolytes. It also says not to take salt tablets, because they can cause serious complications. Whether you need an electrolyte drink, how often and what kind is a good question for your prescriber, especially if you have a heart or kidney condition or have been told to watch your sodium.

What simple habits make drinking easier?

• Use a marked bottle. The CDC suggests carrying a reusable water bottle. Draw or tape a few time marks on the side, like 10 a.m., 1 p.m. and 4 p.m., so you can see your progress at a glance.
• Sip through the day. Small, regular sips can feel easier than a big glass all at once, and MedlinePlus stresses taking in fluids throughout the day.
• Add flavor without much sugar. The CDC suggests adding a wedge of lime or lemon. Cucumber slices or a few berries work the same way. MedlinePlus advises choosing water over sweetened drinks, which can add too many calories.
• Keep it cold. The CDC suggests freezing water in freezer-safe bottles for ice-cold water all day.
• Eat some of your water. Put a food from the table above on your plate once or twice a day.
• Pair it with things you already do. A glass when you wake up, one with each meal or snack, one at each break. MedlinePlus says drinking when you are thirsty and having beverages with meals should keep you hydrated.
• Plan for heat, exercise and travel. The CDC and the National Academies both say heat and activity raise your needs. For the airport side of a trip, see traveling with a GLP-1 pen.

Holiday season adds its own challenge, since alcohol does not count toward your fluids. Our guide to holiday parties on a GLP-1 has more on that.

Next Size Club members get a monthly comfort kit with hydration items, snacks and small comfort things, alongside a capsule of everyday basics in their current size. You can see how it works on the membership page. Next Size Club does not give medical advice, so for anything about your medication or your fluid needs, your prescriber is the person to ask.