Can You Drink Water (and Lemon Water) While Fasting?

In 30 seconds

Yes. Still or sparkling water does not break a fast. A 12-month trial encouraged plenty of it; drinking enough is part of fasting safely. Lemon water depends on how strict you are: a slice adds a little energy, while juice and coconut water end the fast.

• Still and sparkling water fit the whole fasting window; one long trial actively encouraged water.
• A slice of lemon or lime makes water easier to drink, but it isn't strictly zero-energy.
• Fruit juice, smoothies, coconut water and sugary drinks contain sugar and end the fast.
• Pale-yellow urine is a practical sign that you're drinking enough.

Does water break a fast?

No. The fasting trials behind this guide define the fast by caloric intake, and water has none. In one long trial, researchers didn’t just allow water during the fast; they asked participants to drink plenty of it.

In a 12-month randomized trial of eating only between noon and 8 p.m., participants were encouraged to drink plenty of water during the 16-hour fasting window.Source 11

In the 12-week TREAT trial, participants in the time-restricted group were told to completely abstain from caloric intake outside their noon-to-8 p.m. eating window.Source 22

What about lemon water?

It depends on how strict you are. The sources here don’t back lemon as a fasting booster; what it does is make water more appealing, which helps if you struggle to drink enough. A slice adds a trace of energy, and honey or sugar turn it into a sweet drink.

NHS guidance suggests sparkling water or a slice of lemon or lime for people who dislike plain water, and advises limiting fruit juice and smoothies to one small 150 ml glass a day with a meal because they are high in sugar.Source 33

How much water do you need?

There’s no fasting-specific number. Food normally supplies part of your fluid, so a long fast can quietly lower your intake. Start from general guidance and adjust for heat, exercise and how you feel.

NHS guidance suggests aiming for clear pale-yellow urine and about 6 to 8 cups or glasses of fluid a day, and more when pregnant or breastfeeding, in a hot environment, physically active for long periods, or ill.Source 33

These fluid targets come from general NHS guidance for everyday life. The fasting trial cited here encouraged water but did not test amounts, so treat the numbers as a starting point, not a fasting rule.Source 33Source 11

Signs of dehydration while fasting

Frequently asked questions

For warning signs and a fuller plan, see hydration during intermittent fasting.

Talk to a qualified health professional before fasting if you are pregnant or breastfeeding, under 18, living with or recovering from an eating disorder, have diabetes, take insulin or a medicine affected by meal timing, are an older adult, or are acutely ill. Do not change the dose or timing of any medicine without your clinician. See Blimbi’s safety guide.

Related guides

• What Can You Drink While Fasting?

  Water, black coffee and plain tea fit a zero-calorie fast; diet soda adds little or no energy. See what you can drink while fasting and what ends a fast.

• Can You Drink Coffee While Fasting?

  Yes, if it's black: a 12-month trial allowed black coffee while fasting. See which additions end a fast, how much caffeine is too much and when to stop.

• Can You Drink Tea While Fasting? Green, Black and Herbal

  Yes: plain black, green and herbal tea add essentially no energy while fasting. See which additions end the fast and how much caffeine tea adds.

• Vitamins and Supplements While Fasting: Do They Break It?

  Taking vitamins and supplements while fasting: sugary gummies and protein powders end a strict fast, plain tablets are a grey area. Magnesium, creatine and medicines.

• Electrolytes and Dehydration During Intermittent Fasting

  Do you need electrolytes during intermittent fasting? Not for an ordinary fast, per official sources. Learn the dehydration signs to watch and when to end a fast.

Frequently asked questions

Can you drink water while fasting?

Yes. Water, still or sparkling, has no energy, so it does not break a fast, and a 12-month fasting trial encouraged participants to drink plenty of it during the fasting window.Source 11

Does sparkling water break a fast?

No. Plain sparkling water has no energy, so it fits a zero-calorie fast, and NHS guidance suggests it for people who find plain water hard to drink. Flavoured versions with sugar or juice add energy and end the fast, so check the label.Source 33Source 11

Does lemon water break a fast?

Only on a strict fast. A slice of lemon or lime adds a trace of energy, so if you follow a strict zero-calorie fast, plain water is the simpler choice. Otherwise it's a common way to make water easier to drink, and NHS guidance suggests it. Skip the honey or sugar.Source 33

Does coconut water break a fast?

Yes. Coconut water contains natural sugars and energy, and fasting trials such as TREAT asked participants to avoid all caloric intake outside the eating window. Save it for your eating window.Source 22

How much water should I drink while fasting?

There is no fasting-specific number. As a general guide, NHS advice suggests about 6 to 8 cups or glasses of fluid a day and pale-yellow urine, with more in hot weather, during exercise, illness, pregnancy or breastfeeding.Source 33

Sources

1. 1

   Time-Restricted Eating Without Calorie Counting for Weight Loss in a Racially Diverse Population: A Randomized Controlled TrialShuhao Lin et al. American College of Physicians, July 1, 2023.DOI: 10.7326/M23-0052 · PMID: 37364268Human randomized trial

2. 2

   Effects of Time-Restricted Eating on Weight Loss and Other Metabolic Parameters in Women and Men With Overweight and Obesity: The TREAT Randomized Clinical TrialDylan A. Lowe et al. American Medical Association (AMA), November 1, 2020.DOI: 10.1001/jamainternmed.2020.4153 · PMID: 32986097Human randomized trial

3. 3

   Water, drinks and hydrationNHS. NHS, May 17, 2023.Official guidance

4. 4

   DehydrationNHS. NHS, May 1, 2026.Official guidance

5. 5

   Fasting Safely with DiabetesMartin M. Grajower. National Institute of Diabetes and Digestive and Kidney Diseases, August 26, 2020.Official guidance