Guide · Oct 21, 2026

Does Lemon Water Break a Fast?

A squeeze of fresh lemon adds about 1 to 3 calories, per USDA data. Here's when lemon water fits a fast, when it doesn't, and what to check on labels.

By the Ping Diet editorial team · Last updated Oct 21, 2026

Short answer: For most intermittent fasting, no. A squeeze of fresh lemon in a glass of water adds about 1 to 3 calories and well under half a gram of sugar, based on USDA FoodData Central [1]. The exceptions are a strict water-only fast, a fasting blood test, and lemon drinks made with honey or sugar.

In PingDiet terms, a glass of water with a lemon wedge isn't a Ping. A Ping is an eating event, and a few calories of juice don't get you there. Lemonade, or lemon water with a spoonful of honey, is a different drink, and the numbers below show why.

Who should skip fasting: Johns Hopkins Medicine says intermittent fasting isn't for children and teens under 18, people who are pregnant or breastfeeding, people with type 1 diabetes who take insulin, or anyone with a history of eating disorders, and that everyone should check with a doctor before starting [5]. This page is general information, not medical advice.

How many calories are in lemon water?

Very few, as long as it's just water and lemon. USDA lists raw lemon juice at 22 calories per 100 grams [1]. A wedge only gives up about 6 grams of juice, and a tablespoon is about 15 grams, so the totals stay tiny.

What goes in the glass	Calories	Sugars	Breaks most fasts?
1 lemon wedge, squeezed (6 g)	~1	0.1 g	No
Fresh juice, 1 tbsp (15 g)	~3	0.4 g	No
Bottled juice, 1 tbsp (15 g)	~3	0.2 g	No
Juice of 1 whole lemon (48 g)	~11	1.2 g	Barely
Honey, 1 tbsp (21 g)	~64	17.2 g	Yes
Lemonade, 8 fl oz (from concentrate)	~99	24.7 g	Yes

We calculated these from the USDA FoodData Central entries for raw lemon juice, bottled lemon juice, honey and lemonade made from frozen concentrate (SR Legacy data) [1][2][3][4]. The water itself adds nothing.

The jump is easy to see. One tablespoon of honey has about 20 times the calories of a tablespoon of lemon juice. That's the line between a flavored glass of water and a snack.

Does it depend on why you're fasting?

Yes, and that's the honest answer to the question. "Breaks a fast" means different things depending on your rules.

Intermittent fasting or time-restricted eating. Johns Hopkins lists water and zero-calorie drinks such as black coffee and tea as fine during the fasting hours [5]. Lemon water isn't zero, but a squeeze sits at about the same level as the 2 or so calories in a cup of black coffee, which our coffee guide covers in detail. By the numbers, a wedge of lemon in water lands in the same place.

A strict zero-calorie rule. If your rule is nothing but zero-calorie drinks, then lemon water is out. That's a fine rule to have. Just know it's your rule, not a measured line where something in your body switches off.

A fasting blood test. Here the answer is a clear no. MedlinePlus, from the National Library of Medicine, says fasting for a blood test means nothing but plain water, and it specifically says to avoid lemon-flavored water [6]. Follow the instructions your provider gives you.

A religious fast. Follow the rules of your tradition. This page doesn't cover those.

Does lemon water spike insulin?

We couldn't find a controlled study that measured insulin after plain lemon water during a fast, so we won't guess. Plenty of websites make confident claims either way without citing anything.

What we can tell you is what's in it. A tablespoon of fresh lemon juice has about 1 gram of carbohydrate and 0.4 grams of sugar, according to USDA [1]. Honey and lemonade are a different story: they bring 17 to 25 grams of sugar per serving [3][4].

The same goes for autophagy, the cell clean-up process that fasting gets linked to online. We found no human study that measured it after lemon water. Claims that a squeeze of lemon stops it or boosts it are guesses.

What about bottled lemon drinks, flavor drops and lemon seltzer?

Read the Nutrition Facts panel, because the word "lemon" on the front tells you nothing. Some lemon-flavored waters are sweetened with sugar. Others use sucralose or stevia and list zero calories.

One thing to know about that zero: FDA rules let a Nutrition Facts label round anything under 5 calories per serving down to zero [7]. For a drink you have once a day, that hardly matters. If you sip several servings across a long fast, the numbers can add up.

If a drink lists sugar, it's a Ping. If you're unsure, paste the panel into our label checker, which reads Nutrition Facts as well as Supplement Facts and lays out the serving size and amounts.

Is lemon water hard on your teeth?

It can be if you sip it all day. The American Dental Association notes that citrus flavorings such as lemon add acid to drinks, and that acidic drinks can wear on tooth enamel over time [8].

The ADA's tips are simple [8]:

Drink it rather than swishing or holding it in your mouth.
Use a straw if you like.
Rinse with plain water afterward.
Wait about an hour after acidic drinks before you brush.

A tall glass of water with a slice of lemon dropped in, splashing on a white background

Photo: Adonyi Gábor, Pexels

How to make lemon water that fits your fast

Use a wedge or a tablespoon of juice. That keeps you around 1 to 3 calories a glass [1].
Bottled juice is fine. A tablespoon of bottled lemon juice comes out about the same as fresh [2].
Leave out honey and sugar. Save the honey-lemon drink for your eating window.
Make a pitcher. A few slices in a jug of cold water flavors your whole morning, so you're not reaching for a sweet drink.
Hot or cold doesn't matter. Warm water with lemon has the same calories as cold.

On a long fasting day, plain water is still the main drink. If you fast longer than a day or sweat a lot, our guide to electrolytes while fasting covers sodium and potassium.

Where lemon water fits in a fasting day

Lemon water works best as a tool for the stretch when you'd usually snack. A glass mid-morning on a 16:8 schedule, or in the late afternoon on OMAD, gives you something with flavor without adding a Ping.

If you're still picking a schedule, our 16:8 vs 18:6 vs OMAD comparison lays out the trade-offs, and the eating window calculator works out your hours for any start time. For more drinks and add-ins, see the full What Breaks a Fast section.

Top photo: Julia Zolotova, Pexels

Sources

Frequently asked questions

Does lemon water break a fast?

Not for most intermittent fasting. A squeeze of fresh lemon adds about 1 to 3 calories, according to USDA FoodData Central. It does break a strict water-only fast or a fasting blood test, and honey or sugar turns it into a snack.

Does lemon water spike insulin?

We found no controlled study that measured insulin after plain lemon water during a fast. A tablespoon of fresh lemon juice has about 1 gram of carbohydrate and 0.4 grams of sugar, according to USDA.

Can I drink lemon water before a fasting blood test?

No. MedlinePlus says to drink only plain water before a fasting blood test and to avoid lemon-flavored water. Follow the instructions your provider gives you.

Does lemon water with honey break a fast?

Yes. One tablespoon of honey has about 64 calories and 17 grams of sugar, according to USDA. Save it for your eating window.

What can I drink in the morning while intermittent fasting?

Johns Hopkins Medicine lists water and zero-calorie drinks such as black coffee and tea. Water with a squeeze of lemon isn't zero, but it adds only about 1 to 3 calories, according to USDA FoodData Central.

Does bottled lemon juice break a fast?

Not for most fasts. A tablespoon of bottled lemon juice has about 3 calories in USDA data, about the same as fresh juice.