Hydration on Ozempic, Wegovy or Zepbound: How Much Water and Warning Signs

On semaglutide (Ozempic, Wegovy) or tirzepatide (Zepbound, Mounjaro) there’s no special amount of water you need to drink. As a general reference, the US National Academies found that adequately hydrated women take in about 2.7 liters (91 fl oz) of total water a day and men about 3.7 liters (125 fl oz), from drinks and food combined; Europe’s food safety agency (EFSA) sets lower references of 2.0 and 2.5 liters. What changes on these medications is that you eat less and, with nausea, vomiting or diarrhea, you lose more fluid. The US labels warn that this can lead to dehydration and kidney injury. Sipping through the day and leaning on water-rich foods usually helps. Call your prescriber if you can’t keep fluids down, haven’t urinated in 8 hours or feel dizzy every time you stand up.

I built this guide from the US prescribing information and Medication Guides for Wegovy, Zepbound and Ozempic, the water references from the National Academies and EFSA, the 2025 joint advisory on nutrition and GLP-1 therapy from four US medical and nutrition societies, and the dehydration pages of MedlinePlus and the UK’s NHS. Ozempic and Mounjaro are the type 2 diabetes versions of the same two molecules. The full eating plan is in my guide to what to eat on GLP-1 medications.

What the labels say about dehydration

All three US labels carry the same warning, “Acute Kidney Injury Due to Volume Depletion” (section 5.5 of Wegovy, 5.3 of Zepbound, 5.6 of Ozempic). The Wegovy label puts it this way: there have been postmarketing reports of acute kidney injury, in some cases requiring hemodialysis; most occurred in patients whose nausea, vomiting or diarrhea led to dehydration. The labels ask prescribers to monitor kidney function in patients with those symptoms, especially while the dose is being started and escalated.

How often did it happen in the trials?

• Wegovy: acute kidney injury in 7 adults on Wegovy (0.4 cases per 100 patient-years) versus 4 on placebo (0.2), some linked to digestive side effects or dehydration. The label adds that the risk of kidney adverse reactions was higher in adults with a history of kidney impairment and showed up more often during dose titration.
• Zepbound: acute kidney injury in 0.5% of patients on Zepbound versus 0.2% on placebo, in the two main weight-management trials.

The Medication Guides for all three put it in plain language:

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.

They also tell you to call your healthcare provider right away if nausea, vomiting or diarrhea doesn’t go away. The EU prescribing information for Mounjaro adds a nuance the US label doesn’t spell out: precautions against fluid depletion and electrolyte disturbances matter especially in older people. How many people get nausea, vomiting or diarrhea, and for how long, is in my guide to GLP-1 nausea and what to eat.

How much water you need: US and European references

Both references count total water: plain water, every other drink and the water in food. They’re population references, not a personal quota.

Adults	National Academies (US)	EFSA (Europe)
Women	2.7 L (91 fl oz)	2.0 L (68 fl oz, about 8½ cups)
Men	3.7 L (125 fl oz)	2.5 L (85 fl oz, about 10½ cups)
Share from drinks	About 80%	70% to 80%
Share from food	About 20%	20% to 30%

The National Academies figures describe what adequately hydrated Americans actually take in, and people who are very active or live in hot climates may need more. EFSA set its figures in 2010 with European data. Applying EFSA’s percentages, which is my own arithmetic, a woman would get 1.4 to 1.6 L (47 to 54 fl oz) from drinks and 0.4 to 0.6 L (14 to 20 fl oz) from food; a man, 1.75 to 2.0 L (59 to 68 fl oz) and 0.5 to 0.75 L (17 to 25 fl oz). EFSA applies the same values to older adults, and explains that per calorie they need more water, because the kidneys concentrate urine less well with age.

The hydration calculator (in Spanish; it works in liters) shows the EFSA reference by sex, pregnancy or breastfeeding.

A simple check from the NHS: drink enough during the day that your urine is a clear pale yellow.

Why it’s easier to fall short on a GLP-1

You eat less, and food carries water. The 2025 advisory reports reductions in energy intake of 16% to 39% on these drugs. If a fifth or more of your daily water arrives with meals, eating much less takes some of it away. Eating very little isn’t the goal: if eating has become a struggle or a source of anxiety, talk to your prescriber or a registered dietitian. MedlinePlus describes eating disorders as serious mental health conditions and stresses that getting help matters.

You drink less and lose more. MedlinePlus explains that people drink too little when they don’t feel like eating or drinking or are nauseated, and that vomiting and diarrhea drain fluid.

The consequences. The 2025 advisory warns that dehydration from severe nausea, vomiting or diarrhea can cause acute kidney injury, with or without existing kidney disease, and palpitations. It asks that people with kidney problems, or at risk of them, get advice and monitoring. Drinking too little can also make constipation on GLP-1 medications worse.

What counts as fluid

For both references, every drink counts, and so does the water in food. The NHS spells it out: water, lower-fat milk and sugar-free drinks, including tea and coffee, all count toward your daily intake. The National Academies say the same of caffeinated drinks. A 250 g (about 1 cup) glass of nonfat milk brings 226.0 g (7.6 fl oz) of water, and 125 g (about ½ cup) of plain whole-milk yogurt, 109.9 g. Soups add up too: MedlinePlus lists clear soups among foods with a lot of water.

Two caveats. If you’re vomiting or already dehydrated, the NHS advises avoiding caffeinated drinks and alcohol, and MedlinePlus suggests avoiding carbonated drinks when you’re nauseated. And because of the sugar, the NHS limits fruit juice to one small glass of 150 ml (about 5 fl oz) a day. Alcohol works against you: the NHS lists drinking too much of it among the causes of dehydration.

12 foods with the most water per serving

These are the 12 solid foods in our database tagged “Hydrating” (85 g of water or more per 100 g, or 3.5 oz) that bring the most water per usual serving. I’ve left drinks out.

Food	Serving	Water per 100 g	Water in the serving	Energy in the serving
Watermelon	200 g (7.1 oz)	91.4 g	182.8 g (6.2 fl oz)	60 kcal
Honeydew melon	200 g (7.1 oz)	89.8 g	179.6 g (6.1 fl oz)	72 kcal
Orange	180 g (6.3 oz, one large)	86.8 g	156.2 g (5.3 fl oz)	85 kcal
Apple, with skin	180 g (6.3 oz, one medium)	85.6 g	154.1 g (5.2 fl oz)	94 kcal
Zucchini, raw	150 g (5.3 oz)	94.8 g	142.2 g (4.8 fl oz)	26 kcal
Tomato, raw	150 g (5.3 oz, one medium)	94.5 g	141.8 g (4.8 fl oz)	27 kcal
Nopales, cooked	150 g (5.3 oz)	94.3 g	141.5 g (4.8 fl oz)	23 kcal
Pumpkin, cooked	150 g (5.3 oz)	93.7 g	140.6 g (4.8 fl oz)	30 kcal
Chayote, cooked	150 g (5.3 oz)	93.4 g	140.1 g (4.7 fl oz)	36 kcal
Swiss chard, cooked	150 g (5.3 oz)	92.6 g	138.9 g (4.7 fl oz)	30 kcal
Eggplant, raw	150 g (5.3 oz)	92.3 g	138.5 g (4.7 fl oz)	38 kcal
Cauliflower, raw	150 g (5.3 oz)	92.1 g	138.2 g (4.7 fl oz)	38 kcal

Data: USDA FoodData Central, as listed on each food page. Servings are a guide, not a recommendation. Cucumber has more water per 100 g than any of them, 95.2 g, but its usual serving is 100 g, so it doesn’t make the cut.

An example: 150 g (5.3 oz) of cooked pumpkin and a 180 g orange add up to 296.8 g (about 10 fl oz) of water. The full list is under hydrating foods (in Spanish), and you can combine that tag with other filters in the filling foods finder. If bloating bothers you, note that cauliflower also carries our “bloating risk” tag.

How to spread fluids through the day

I haven’t found trials that test a drinking schedule on GLP-1 medications. This table gathers general advice, with no personal amounts.

When	What to try	Where it comes from
When you get up	A few sips of water or herbal tea with a small breakfast	2025 advisory: a small breakfast with enough fluids
Every 3 to 4 hours	A small meal with its drink	2025 advisory
Between meals	Regular sips; if drinking with your plate fills you up, move some fluid here	NHS: drink regularly through the day
With nausea	Start with small sips and build up; cold water or ice chips	NHS and MedlinePlus
With vomiting or diarrhea	Drink more than usual and ask a pharmacist about an oral rehydration solution	NHS
Heat or exercise	Drink more	NHS, MedlinePlus and the National Academies

The symptom diary (in Spanish) has a box for 250 ml (about 1 cup) glasses of water and other fluids, next to vomiting and diarrhea. A few days of notes help at your next appointment.

If you have heart failure or kidney disease, your doctor sets the number. According to MedlinePlus, with heart failure you may need to limit fluids and salt. With chronic kidney disease, especially advanced or on dialysis, your care team tells you how much to drink, and water-rich foods such as soups, melons and tomatoes count within that limit. Check with your doctor before drinking more than you’ve been told.

Electrolyte drinks: when, and with what care

Electrolytes are minerals such as sodium and potassium that you lose when you vomit or have diarrhea. The NHS explains that if you’re losing a lot of fluid that way, you need to put back the sugar, salts and minerals, and that a pharmacist can recommend an oral rehydration solution: powders you mix with water. MedlinePlus also mentions sports drinks that contain electrolytes.

Three precautions:

• Ask which one suits you. The NHS advises asking your pharmacist which rehydration solution is right for you.
• Don’t take salt tablets. MedlinePlus warns they can cause serious complications.
• With heart or kidney disease, check first. You may have limits on salt or potassium, according to MedlinePlus.

Signs of dehydration

The NHS lists these symptoms in adults:

• Feeling thirsty.
• Headache and feeling light-headed.
• Dark yellow, strong-smelling urine.
• Peeing less often than usual.
• Feeling dizzy.
• Feeling tired.
• A dry mouth, lips and tongue.
• Sunken eyes.

MedlinePlus adds dry, cool skin and muscle cramps.

When to get medical help

Severe stomach pain that won’t go away has its own warning signs, covered in my nausea guide. And don’t change or delay a dose on your own: that’s your prescriber’s call.

Frequently asked questions

Do I need to drink more water on Ozempic, Wegovy or Zepbound?

The labels don’t set an amount; they say drinking fluids helps reduce your chance of dehydration. General references: about 2.7 L (91 fl oz) of total water a day for women and 3.7 L (125 fl oz) for men (National Academies), or 2.0 L and 2.5 L (EFSA).

Do coffee and tea count?

Yes. Both the NHS and the National Academies count them. If you’re dehydrated or vomiting, the NHS advises avoiding caffeine.

How do I know if I’m drinking enough?

The NHS suggests checking the color of your urine: it should be a clear pale yellow.

Are sports drinks OK?

MedlinePlus mentions them as an option with electrolytes; the NHS suggests asking a pharmacist about an oral rehydration solution. With heart or kidney disease, check with your doctor first.

Can dehydration damage the kidneys?

Yes. The US labels report acute kidney injury, mostly in people dehydrated by nausea, vomiting or diarrhea. If you already have a kidney problem, tell your doctor.

What if nausea won’t let me drink?

Try small sips of cold water, ice chips or water-rich foods such as watermelon or clear soup. If you can’t keep fluids down, call your prescriber. More ideas in my guide to GLP-1 nausea and what to eat.