Does Lemon Water Break a Fast? [Full Details + Examples]

Does Lemon Water Break a Fast

Some people drink lemon water when water fasting because it has a nice flavor and very few calories.  It may also help control hunger. 

But does lemon water “break” a fast?  

The short answer is no.  In most situations, lemon water will not break your fast, and it’s probably worth using if it helps you get through the fast. 

On the other hand, you could miss out on some benefits of fasting if you drink lemon water, so whether it breaks your fast or not depends on your goals.

Keep reading and I’ll show you when lemon water is ok during a fast (with specific examples), and how to use it. 

Does Lemon Water Have Any Health Benefits?

Lemons are known for their high vitamin C content, and various antioxidants.

Lemon water will give you a splash of the same nutrients, but in smaller quantities (depending on how much lemon is in your water).

Like any fruit, you can also get some fiber if you eat it whole. But in this case we’re just squeezing out a little juice. So no fiber.

I couldn’t find evidence of other special health benefits from lemon water, despite various (likely unfounded) claims scattered across the internet. 🙂

Will Lemon Water (or Lemon Juice) Break a Fast?

To know if lemon water will “break your fast, you need to know a couple things:

  1. What nutrients does it contain?
  2. How do those affect your fasting goals?

What’s in Lemon Water?

A small lemon has about 16 calories and 5 grams of carbohydrates (from fruit sugar, called fructose).  Naturally, the energy content of lemon water depends on how much lemon you put in it.  

If you squeeze out the juice from ¼ of a lemon, you’d probably get about 4 cal and 1 gram of carbs.

Lemon Water nutrition facts

A very small lemon wedge, or slice (like the ones they use at restaurants) would only have about 1 cal, and basically no carbs. 

You’ll get even less sugar from the lemon if you don’t squeeze it, and just place it in the water instead.

Bottom line?

There’s not very much food energy in lemon water, but it varies depending on how much lemon you use, and how aggressively you squeeze out the juice.  

What About Lemon Juice? 

Lemon juice is what you squeeze directly out of the lemon, so it’s a lot more concentrated than lemon water.

One cup of lemon juice has over 60 calories and 20 grams of carbs, which is a bit too much for someone who’s fasting. 

Bottom line?

Lemon juice has a lot more sugar / carbs than lemon water, so don’t drink lemon juice by itself when you’re fasting. 

(Note:  If you want to try other things in your water as well, like honey or ginger, just look at the nutrition info for whatever you’re adding to make sure it doesn’t have more than a few calories or grams of carbs.) 

How does lemon water affect your fasting goals?

That depends on what your goals are, and how long you intend to fast.  

For the whole story, read on.  

Lemon Water and Short-term (Intermittent) Fasting

We’ll define short-term fasting as anything under 24 hours.

This includes what’s commonly called “intermittent” fasting, which is when someone eats all their food for the day within about 8-12 hours (instead of eating all day long, like most people do).

Some common goals of daily intermittent fasting include fat loss, blood sugar control, higher ketone levels, and bowel rest (among others).

Let’s see if lemon water is okay for each of these goals when intermittent fasting.

Lemon Water and Intermittent Fasting for Fat Loss

(Note:  I prefer the term “fat loss” rather than “weight loss”, since fat is what we’re trying to lose, not just weight.)

During a short (or long) fast, the body starts using its own fat stores for energy, since there’s no other energy coming in.

Lemon water has very little food energy (<5 cal & 1g of carbs per glass), so it won’t interfere much with fat loss.  

If you’re doing intermittent fasting for fat loss, lemon water is definitely okay, as long as you don’t overdo it.  

Limit yourself to about one whole lemon (or about 2-3 tbsp lemon juice) per day, and you should be fine. 

Lemon Water and Intermittent Fasting for Blood Sugar Control

When you fast, your blood sugar (or glucose) level tends to go down since you’re not taking in any sugar or other carbs.

fasting lowers blood sugar graph

Lemon water has very few carbs (~1g / glass), so it shouldn’t affect blood sugar levels much at all.

For example, when I drink bouillon (which has about 5 calories and 1 gram of carbs per serving, roughly the same as lemon water) during a fast, it doesn’t seem to have any noticeable effect on my blood sugar levels.  

I think if you’re doing daily intermittent fasting for blood sugar control, lemon water is definitely okay, as long as you don’t overdo it.

Lemon Water and Intermittent Fasting for Ketosis

Ketones are an alternative energy source your body makes when you’re not eating carbs, like when you’re fasting (no carbs) or eating a ketogenic diet (low carb, high fat).

Some people find that daily fasting helps increase their ketone levels more than if they just eat a ketogenic diet without fasting.

The carbs (~1g / glass) in lemon water are quite low, so they shouldn’t interfere very much with ketone production (aka ketosis) in your body.

To illustrate, a “strict” ketogenic diet can mean eating fewer than 20 grams of carbs per day,  which is about what’s in a medium-sized lemon.  So if you limit yourself to one lemon per day (or less), your ketone levels will probably stay high. 

I frequently use lemon in my tea when I’m fasting, and I haven’t noticed any change in my ketone levels from doing this.

So will lemon water take you out of ketosis?  As long as you don’t drink way too much, it shouldn’t be a problem.  

If higher ketone levels is your goal, lemon water is definitely okay.

Lemon Water and Short-term Fasting for Bowel Rest

Daily time-restricted eating (aka intermittent fasting) can be used for short-term bowel rest.  

For example, if you eat all your food within 8 hours every day, that leaves about 16 hours (out of 24) for your stomach and intestines to “rest”.

For total bowel rest, you would want to avoid eating anything at all, and drink only water. 

So if your main goal is bowel rest, lemon water is not ideal.  

What’s the bottom line?

Unless you’re fasting specifically for bowel rest, drinking lemon water during short-term (intermittent) fasting is okay, as long as you don’t overdo it.

Intermittent Fasting with Lemon Water

Lemon Water and Extended Fasting

We’ll define extended fasting as anything over 24 hours.  This is also called “prolonged” fasting.  

Just like before, whether lemon water “breaks” a prolonged fast depends on your goals.  

Common goals of extended fasting include the same ones as daily time-restricted eating (fat loss, blood sugar control, etc), as well as others like autophagy or “resetting” the immune system, for example.

Can you still accomplish these goals if you drink lemon water during a long fast?

Let’s find out.  

Lemon water’s effects on Fat, Blood Sugar, and Ketones during a Prolonged Fast 

Just like with intermittent fasting, lemon water won’t significantly interfere with fat loss, blood sugar control, or ketone levels during a prolonged fast.

Mini self-experiment:  

On the second day of an extended fast (about 40 hours in), I drank one glass of lemon water (with about half a lemon, or roughly 8 cal and 2-3g carbs) to see the effect on my blood sugar level.

Results:   Before drinking the lemon water, my blood sugar was 79 (mg/dL).  30 minutes later it was 80.  30 minutes after that it was 73. 

So there was very little impact overall, and for some reason it went down at the end. 

It didn’t seem to affect my ketone levels much either (based on the urine test strips I’m currently using).

If your goals are fat loss, blood sugar control, or higher ketones, drinking lemon water during a long fast is definitely okay (as long as you don’t go crazy with it).

Does lemon water break autophagy during Extended Fasting?

Autophagy (Greek for “self-eating”) is a process in which your body starts recycling old, worn out proteins inside of your cells.  It’s like “spring cleaning” inside cells all over your body.

Fasting strongly stimulates autophagy (as does exercise).  

But there’s a catch.  

We haven’t done enough research to know if the small amounts of sugar and other nutrients in lemon water interfere with autophagy.

We can only make our best guess.

That’s why if your goal is to activate autophagy during a long fast, taking lemon water may be okay, but it’s probably better to avoid it if you can.

Lemon Water and Resetting the immune system during Extended Fasting

Extended fasting for about 5 days or longer kind of “resets” the immune system.  

What does this actually mean?

After several days of fasting, a lot of old immune cells get broken down and recycled.  Then they are rebuilt from your stem cells when you start eating again. 

This can be especially beneficial if you have an autoimmune disorder (when your immune system attacks your own body by accident) like multiple sclerosis or Crohn’s disease, for example.

There’s no human research that tells us if the nutrients in lemon water would interfere with this regeneration of the immune system.

Until we know more, it’s probably better to avoid lemon water (and other supplements) if your goal is to “reset” your immune system.

Bowel rest during Extended Fasting

Just like with daily fasting, if you’re doing extended fasting for bowel rest, it’s better to avoid lemon water (or any other supplements) if you can.

But it may still be beneficial for your gut even if you drink some lemon water. 

What’s the bottom line?

For most extended fasting benefits (including some not mentioned in this article), taking lemon water (or doing a “lemon water fast”) is just fine, as long as you don’t overdo it.

Try to avoid consuming more than about one whole lemon (or 2-3 tbsp lemon juice) per day.

If you’re doing a longer fast for autophagy or to “reset” the immune system, use lemon water sparingly, and only if needed.

If your goal is bowel rest, try drinking nothing but water if you can.

Extended Fasting with Lemon Water

How Do You Use Lemon Water For Fasting?

Let’s address a few common questions.

How much lemon water should you drink?  

If you’re just using lemon water (mostly water with a splash of lemon), you don’t need to worry that much about the amount.

If you start drinking lemon juice, you’ll have to be a lot more careful.  

It wouldn’t take much lemon juice to “break” a fast (by raising your blood sugar or lowering your ketone level for example).  

Try to limit yourself to no more than one lemon (or 2-3 tbsp lemon juice) per day.  

Will lemon water damage my teeth? 

Lemons have about five times as much citric acid as oranges, so there is some concern about harming your teeth if your lemon water is too concentrated or you drink it too often.

This article has some tips about preventing damage to your teeth from lemon water or juice.

When should you take lemon water while (intermittent) fasting?

That’s easy:  Whenever you feel like it.

The timing doesn’t really matter.

General Caveat:  The recommendations in this article apply to the vast majority of people, but everyone is different, so consider your individual health and circumstances.  It may take some trial-and-error to see what fasting supplements work the best for you. 


Some people like drinking lemon water during a fast, but whether it breaks your fast depends on how much you drink, and your fasting goals.

As with most other supplements (like apple cider vinegar, MCT oil, or stevia for example), it’s probably worth taking it if it helps you get through your fast.

Fasting is still very beneficial even if you drink lemon water or similar supplements.

(Lemon water is definitely a better option than artificial sweeteners like sucralose or aspartame!)

In the future, as you get more experience fasting, you may not feel the need to use “training wheels” like lemon water anymore.

So does lemon water break a fast? If you don’t overdo it, usually the answer is no.

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Hope it helps!

Ben Tanner, PA-C

Ben Tanner, PA-C

Ben has been practicing as a physician assistant (PA, or PA-C, similar to a doctor) in emergency medicine, urgent care, and family practice since 2014. Since 2016, he has developed an avid interest in various forms of fasting, using it to improve his own health while helping friends, family, and patients do the same.