3 Day Water Fast: Benefits, Risks + Is It Safe?

Our nutrition coach gets into the pros and cons of a prolonged fast.

A 3-day water fast, also called a 72 hour fast, is an extreme version of water fasting that involves consuming only water for 72 hours or 3 full days.

Some people who practice water fasting permit non-caloric beverages like green tea, herbal tea, club soda, or very low-calorie beverages such as black coffee.

It is also common to supplement water with unsweetened electrolyte powders, tablets, or capsules during a 3 day water fast, although strict protocols only allow you to lick pure pink Himalayan salt to attain necessary sodium.

Water fasting for three days can sound overwhelming, if not impossible, if you have never done it before. However, proponents of 3 day water fasts attest that with a little preparation and mental grit, it’s not only worth it but not that hard to do once you try.

In this guide, we will discuss the benefits and risks of a 3 day water fast, what to expect while fasting, and if a 3 day water fast is safe.

An empty place setting and a clock.

Is 3 Day Water Fasting Safe?

A 24 hour water fast, or water fasting for a day or two, is not particularly uncommon, but longer fasts, such as a 72 hour fast, is fairly extreme and should only be done under medical supervision. 

Although studies suggest that prolonged fasting can be safe, water fasting for three days is often not recommended nor safe for some people, and there are usually healthier, less severe alternatives for body weight management and potential benefits for your health and well-being.1Finnell, J. S., Saul, B. C., Goldhamer, A. C., & Myers, T. R. (2018). Is fasting safe? A chart review of adverse events during medically supervised, water-only fasting. BMC Complementary and Alternative Medicine18(1). https://doi.org/10.1186/s12906-018-2136-6

‌These may include a shorter fast, an intermittent fasting diet, a well-balanced program of diet and workouts, etc. 

It’s highly recommended that you speak with a healthcare professional before embarking on a 3 day fast or any fasting period for that matter, and discuss potential safer alternatives to achieve health and wellness.2Wilhelmi de Toledo, F., Buchinger, A., Burggrabe, H., Hölz, G., Kuhn, C., Lischka, E., Lischka, N., Lützner, H., May, W., Ritzmann-Widderich, M., Stange, R., Wessel, A., Boschmann, M., Peper, E., & Michalsen, A. (2013). Fasting Therapy – an Expert Panel Update of the 2002 Consensus Guidelines. Forschende Komplementärmedizin / Research in Complementary Medicine20(6), 434–443. https://doi.org/10.1159/000357602

What Are The Potential Risks Of A 3 day Water Fast?

Three days of fasting may result in adverse health and metabolic changes such as dehydration, a loss of lean muscle mass, hyperuricemia, hyponatremia, protein sparing, sodium and potassium sparing, decreased serum calcium and magnesium levels, and acidic urine.3Ogłodek, E., & Pilis, Prof., W. (2021). Is Water-Only Fasting Safe? Global Advances in Health and Medicine10, 216495612110311. https://doi.org/10.1177/21649561211031178

‌Additionally, a 72 hour fast can lead to symptoms such as headaches, nausea, vomiting, constipation, the inability to regulate body temperature, muscle loss, lightheadedness, shakiness, poor healing, blurry vision, difficulty sleeping, mood instability, and adverse nutritional deficiencies.

A person smiling drinking water.

How To Do A 3 Day Water Fast

If you’ve never tried water fasting before and this is your first time, you’re probably wondering, “How do you do a 3 day water fast?”

This question seems simple enough, but it can actually be trying to pinpoint the answer to two distinct questions:

  • How do you do a 3 day water fast from a practical perspective? (i.e., what does water fasting entail, what can you eat, what do you have to do to prepare, etc.); and
  • How do you fast for 72 hours from a mental/hunger/discipline standpoint?

Let’s address both of these valid questions.

After you get the go-ahead from your healthcare provider, the next steps are to physically prepare your body and mentally and emotionally prepare your mind to fast for 72 hours. 

To physically prepare yourself for a 3 day water fast, it is advisable that you practice with shorter fasting intervals before you take on a full 72 hour fast.

Although this isn’t required, it can help your body get used to the physical sensations of not receiving any type of energy intake for an extended period of time.

An empty place setting.

For example, you might try a one day fast one week before your 72 hour water fast.

Or, you might try several days of 18/6 intermittent fasting (extending your overnight fast for a full 18 hours and then only allowing the consumption of food during a 6-hour window during the day) or a 20/4 intermittent fasting diet for a week.

If your body is not accustomed to any type of fasting or intermittent caloric restriction, it can be quite jarring to suddenly have a complete absence of calories coming in. 

Engaging in “mini” fasts will improve your ability to burn fat and use ketones for energy (ketosis), such as on the keto diet (which will occur after prolonged fasting), making your longer water fast more comfortable.

Whether or not you decide to try shorter fasts to prepare your body, it’s a good idea to be deliberate in your food and beverage choices in the 48 to 72 hours before you begin your water fast.

A variety of herbal teas.

Eliminate alcohol, soda, excessive caffeine, and processed foods high in sugar, salt, hydrogenated oils, and artificial sweeteners, as these can trigger appetite.

Instead, focus on eating nourishing, unprocessed foods such as vegetables, fruits, complex carbs like whole grains, lean proteins, nuts, seeds, eggs, and fermented foods like yogurt, kefir, sauerkraut, kimchi, and tempeh.

It’s also wise to resist the urge to “stock up“ or overeat with a big meal heading into a 72 hour water fast.

Binging can throw your insulin and blood sugar levels haywire and can also compromise some of the potential weight loss and health benefits of water fasting that you’re ultimately aiming for.

From the very first day of your 3 day water fast begins, you will only drink water (and potentially herbal tea or black coffee if you choose) for a full 72 hours.

You cannot eat any caloric food or beverages, and most people avoid all artificial sweeteners as well.

In terms of the second question about how to mentally do a 3 day water fast, control your cravings, and manage your hunger, it helps to come up with a few strategies you can employ when things get tough.

There’s no “secret” or magic solution that will make fasting for 72 hours feel easy.

However, some people find things like mindfulness meditation, journaling, praying, taking walks, playing golf, listening to audiobooks and podcasts, or doing needle crafts can be a good way to ground themselves when they feel overwhelmed with cravings.

It’s important to state that if you experience any type of concerning symptoms or side effects, you should consult your doctor immediately.

Holding a cup of coffee.

What to Expect With a 3 Day Water Fast

There are a variety of different benefits that can potentially be enjoyed by occasionally doing prolonged fasts or engaging in intermittent fasting with more regularity. 

Some of the reported benefits of fasting include the following:

Pouring a glass of water.

While this list of benefits of fasting is impressive, many of these benefits are achievable with more conservative approaches to fasting as opposed to long-term fasting, such as intermittent fasting diets and periodic 24-hour water fasts. 

You might not need to do a full 3 day water fast to achieve the results you are looking for, so it often makes sense to review your options and get professional medical advice from your healthcare provider.

Along with the benefits of a 3 day water fast, there are some downsides as we mentioned above. Not fueling your body can result in feeling tired and make you feel weak, dizzy or even nauseous.

With that said, some people who do occasional 3 day water fasting find that it’s a powerful physical and mental reset that helps them feel much more vibrant, focused, and healthy.

The response to prolonged fasting is quite individual, so work with a healthcare provider and a dietitian you trust, and be open to experimenting to find what works best for you.

It’s important to consider any existing health conditions, such as an eating disorder, when considering a fast.

If you are cleared to try fasting, start with a short-term 24-hour water fast. Check out our guide here.

A person meditating during a 3 day fast.


  • 1
    Finnell, J. S., Saul, B. C., Goldhamer, A. C., & Myers, T. R. (2018). Is fasting safe? A chart review of adverse events during medically supervised, water-only fasting. BMC Complementary and Alternative Medicine18(1). https://doi.org/10.1186/s12906-018-2136-6
  • 2
    Wilhelmi de Toledo, F., Buchinger, A., Burggrabe, H., Hölz, G., Kuhn, C., Lischka, E., Lischka, N., Lützner, H., May, W., Ritzmann-Widderich, M., Stange, R., Wessel, A., Boschmann, M., Peper, E., & Michalsen, A. (2013). Fasting Therapy – an Expert Panel Update of the 2002 Consensus Guidelines. Forschende Komplementärmedizin / Research in Complementary Medicine20(6), 434–443. https://doi.org/10.1159/000357602
  • 3
    Ogłodek, E., & Pilis, Prof., W. (2021). Is Water-Only Fasting Safe? Global Advances in Health and Medicine10, 216495612110311. https://doi.org/10.1177/21649561211031178
  • 4
    Tinsley, G. M., & La Bounty, P. M. (2015). Effects of intermittent fasting on body composition and clinical health markers in humans. Nutrition Reviews73(10), 661–674. https://doi.org/10.1093/nutrit/nuv041
  • 5
    Johnson, J. B., Summer, W., Cutler, R. G., Martin, B., Hyun, D.-H., Dixit, V. D., Pearson, M., Nassar, M., Tellejohan, R., Maudsley, S., Carlson, O., John, S., Laub, D. R., & Mattson, M. P. (2007). Alternate day calorie restriction improves clinical findings and reduces markers of oxidative stress and inflammation in overweight adults with moderate asthma. Free Radical Biology and Medicine42(5), 665–674. https://doi.org/10.1016/j.freeradbiomed.2006.12.005
  • 6
    Hoddy, K. K., Gibbons, C., Kroeger, C. M., Trepanowski, J. F., Barnosky, A., Bhutani, S., Gabel, K., Finlayson, G., & Varady, K. A. (2016). Changes in hunger and fullness in relation to gut peptides before and after 8 weeks of alternate day fasting. Clinical Nutrition35(6), 1380–1385. https://doi.org/10.1016/j.clnu.2016.03.011
  • 7
    Bhutani, S., Klempel, M. C., Berger, R. A., & Varady, K. A. (2010). Improvements in Coronary Heart Disease Risk Indicators by Alternate-Day Fasting Involve Adipose Tissue Modulations. Obesity18(11), 2152–2159. https://doi.org/10.1038/oby.2010.54
  • 8
    Bagherniya, M., Butler, A. E., Barreto, G. E., & Sahebkar, A. (2018). The effect of fasting or calorie restriction on autophagy induction: A review of the literature. Ageing Research Reviews47, 183–197. https://doi.org/10.1016/j.arr.2018.08.004
  • 9
    Home Page: The American Journal of Clinical Nutrition. (n.d.). Ajcn.nutrition.org. https://ajcn.nutrition.org/
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Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

24 thoughts on “3 Day Water Fast: Benefits, Risks + Is It Safe?”

  1. Very helpful. I decided to do a three-day yesterday with one exception. I had a small orange yesterday morning and had two slivers of honeydew this morning. I’ll probably do two more slivers tomorrow. It helps with any symptoms of deprivation and keeps the digestion system and motabolism active. Stay as active as you can during the fast, but tack naps when you feel the need. I’m also drinking a vitamin / mineral / electrolyte mix to keep the micro-nutrients coming. Fasting also helps to shrink the stomach so you don’t feel as hungry. I’m near 70 and about 40 pounds overweight and decided I’m just too darned fat. Almost through day two and doing even better (had a rare slight headache) than day one. Treat it like an adventure with no comprimises.

    • Even1/4 of an orange will release significant amounts of insulin. Within a half-hour, your ketones (if you have any) will plummet to zero. Instead of moving from a metabolic state where you are breaking down and releasing fat from fat cells, you are moving into reverse. It’s so simple. Measure w/ meter, blood glucose (BG) and with a meter ketones.

      Let’s say your BG is 100, and your ketones are 0.6 (a sort of average, overweight young person’s numbers). Eat one single “wedge” of orange. Wait one hour, remeasure. You’ll see BG up to 120, and ketones down to probably zero.

      Worse, dropping your ketones just took away the one tool to offset cravings/hunger. Now you are more hungry. Fast enough to increase ketones to 1.4 or ^ and *poof* NO hunger. That is the magic of ketones.

      Sadly, you are not on any fast. Keep it up and in your own words: you’ll be “too darned fat.”

    • Autophagy and detoxification *may stop if you eat sugar. Either you are in the mode where your body uses body fat and damaged cells for amino acids as fuel or you aren’t. So once you put anything in your stomach, autophagy (using damaged cells) and using fat cells where toxins are likely stored (detox) will probably stop. However, this experience will help you next time if you want to fast because it does help you to adjust to the overall experience. A water is just that, a water fast. In my perosnal opinion, even coffee or green tea will confuse the system into thinking it is in food ingesting mode. I too drank something on mine (green tea) BUT if there are no calories, it only slows things down. There are amino acids in green tea and coffee but somehow people still gain benefit (better without those though) but sugar and amino acids (in oranges) could stop everything. If you can get bloodwork before and after that is a great way to see if any benefits came from the fast itself.

    • Take it with a tablespoon of fat is enough in your stomach – fruit is not necessary. And you could add tspn of ACV to a glass of water with the fat/butter and the medication with no upset to the stomach plus the ACV helps with the headache as well.

  2. I am at hour 38, started at 8pm Tuesday evening and it is now 10am Thursday. I had some hunger pains and growling stomach yesterday but today I feel fine. Stomach is empty and not expecting food so it stopped complaining.

    I’m drinking half my weight in ounces of water with some Himalayan salt. Aside from missing the comfort and ritual of eating meals I am feeling ok.

  3. I’m doing a Christian 3 day fast with only water. I’m at 48hrs. There have been moments where I wanted to give in and eat, but I prayed a lot and focused on other things. Music, doing household chores, reading, and taking a semi-long shower helped a lot. I personally feel like this has helped me with my faith and trust God with this fast. I recommend it, but be sure to stay hydrated and keep yourself busy.

  4. on day 2, feeling fine, I am intermittent faster, and once a year I do a 10-day cleanse, so my body doesn’t typically get shocked when I try these things. Have had black coffee in the AM, 1 cup instead of my usual 2, and water throughout, although I haven’t done the sea salt, I will when I get home, see how that goes. I have been particularly abusive to my body this summer eating and drinking alcohol, and recently hurt my back so haven’t been able to go to the gym, so hoping this will be a nice little reset.

  5. i started a 24 hour fast. i had no issues so i extended to a two day fast. i am now at 42 hours and think i might go for the third day. It has been so much easier than i thought it would be. i am going to add some Himalayan salt. i am a bit worried about electrolytes. So far i have not had any symptoms except a headache which i had before the fast started. No change in intensity. So, i think i will push it to three days.

  6. These stories sound so inspiring! I just started my fast I haven’t had anything but water, tea, and coffee (black) so far. Started around 9pm last night 08/14/2023, hoping I can feel better and re-charged and just overall healthier after all this. This is my first time fasting so I’m pretty excited! Any suggestions or advice would be greatly appreciated. Are vitamins ok to take during a fast such as iron, magnesium, etc…?

  7. Doing a Christian fast on my 3rd day of my water fast. On the 3rd morning I drank coffee and feeling much better… but have been experiencing lack of sleep on the 2nd day but that has help with meditating and prayer of the word of God. Not feeling tired. It’s been a great fast. I intend to fast once in a week so I feel good about this 3 days fast I took.

  8. This is my second time doing this 72 hour fast. The first time, one month ago, made me feel so good that I decided to do it again. Felt a little shaky early this morning (3rd morning) but after a glass of water and a cup of black coffee I feel great. Even did some exercise, Tia Chi, and a little gardening.

  9. Hello it is been 28 hours since I started my 3 days fasting, feel bit tired but didnt have any hunger issue yet. i just had lt bit of salt one hour ago, and water all day long. hope to see what will effect in my health and will keep you posted.

    • Good for you… but this article is somewhat alarmist and misleading. EG, you won’t lose any lean muscle mass, that’s just none sense, and the statement “a 72 hour fast is fairly extreme and should only be done under the guidance and supervision of a medical professional.” Way over the top fear mongering. Humans are well evolved to tolerate intermittent periods of fasting. Eating three meals a day isn’t evolutionarily normal.

  10. I thought the same thing, I’m on day 2 and came across this article and thought maybe I should quit? I feel totally fine. Only water, no salt or anything. I don’t want to lose muscle mass just want to clean out my body and reset. All the comments encouraged me to finish the 3 days. Thanks Y’all!

  11. I’ve done the 3 day water fast about 6 weeks ago and it made me feel great once it was done. I used no salts or electrolytes and I had no issues. Had a little bit of lightheadedness on my workouts and when I went for a lake swim. I am now going to do a 4 day fast starting this Sunday as it feels like the benefits of the three day are gone now. I did talk to my doctor about the 4 day and said he wouldn’t sign off on anyone doing it but I was OK to try if I wanted. Wish me luck!!

    • They never sign off on anything that is not studied as a drug is studied. It is the oldest most true form of medicine. That is the funny part. I have been damaged in so many ways by tested drugs but a 3 day fast mostly was an amazing boost to my system.

  12. Currently on day 2 of the 3-day water fast.
    Feeling a little low on energy and lightheaded but I’ve done this before and felt pretty good afterwards.
    Following this:
    Day 1 – only water and electrolytes (sugar free propel), black coffee
    Day 2 – 1-2 cups of bone broth, water and electrolytes (sugar free propel), black coffee
    Day 3 – 1-2 cups of bone broth, water and electrolytes


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