Dry Fasting Causes Dehydration (And Why That’s A Good Thing!)

Does dry fasting dehydrate you? Yes, it does. But before you go, ‘I knew it! I’m gonna die!’ ‘She’s gonna die!’ ‘My doggy’s gonna die!’ just breathe for a moment and take this in… dry fasting could be the very thing that saves your life. 

Can dry fasting cause dehydration? Since you’re not hydrating your body externally, you can become dehydrated. Still, unless you’re dehydrated before dry fasting, this is not much cause for concern, as your body makes up for the lack of external water by producing its own water.

What is dehydration? 

Dehydration happens when your body loses more fluids than you take in, and the balance of minerals in your body gets thrown off, which upsets how your body works. 

Water makes up over 70% of your body and is vital for your body’s normal functioning. Without water, there is no life—water aids digestion, flushes out toxins, and lubricates your joints and eyes.

How much water should you drink? The Institute of Medicine (IOM) recommends 13 cups (3 liters) for men and 9 cups (2 liters) for women; however, the amount of water you should drink varies from person to person and depends on many factors, including climate, physical exercise or even diet. 

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Symptoms of dehydration 

The symptoms of dry fasting are somewhat similar because, during dry fasting, you’re definitely not having as much as you ordinarily would take into your body, which means, by definition, you’re dehydrated. This also means you could have some of the symptoms of mild dehydration. 

Some of the symptoms of mild dehydration:

  • Headaches
  • Bad breath 
  • Dizziness or light-headed 
  • Constipation
  • Feeling tired or lethargic 
  • Increased thirst 
  • Dry mouth, lips, and eyes 
  • Dry skin 
  • Decreased urination 

The most common symptoms of dry fasting are increased thirst, dry skin, and decreased urination. Symptoms can improve or change depending on the duration of your dry fast. 

These are the symptoms of severe dehydration: 

  • Low blood pressure 
  • Rapid heart rate 
  • Dark, strong-smelling pee
  • Rapid breathing 
  • Lack of sweat 
  • Shriveled skin 
  • Extreme thirst

If you have severe dehydration, pay attention to your body, and get medical attention immediately.

How does dehydration happen?

Dehydration happens more quickly in these instances: 

Chronic conditions 

People with chronic conditions, for instance, diabetes, need to pee more often and have fluctuating blood sugar levels, putting them at a higher risk of dehydration. This also applies if you’re taking diuretic medication. 

Vomiting / Diarrhoea 

Having food poisoning or a stomach infection could cause this and make you need to purge the liquid in your body, leaving you dehydrated. 

Being in the sun 

This can make you lose a lot of water, as your body sweats more and tries to make up to maintain its internal temperature. If you work outdoors—construction workers, mechanics, landscapers—then you could be more at risk. 

High temperatures 

Temperatures more than 38C such as outdoors or steam rooms and saunas can cause you to become dehydrated. 

Drinking too much alcohol 

Alcohol is a diuretic and causes you to pee very often—each shot of alcohol makes you pee an excess 120 ml of water—dehydrating you— which is why you get awful headaches when you have a hangover.

Too much exercise 

If you had a big workout and sweated a lot, like a long hike, or even a marathon, you could have lost a lot of water and become dehydrated. 


Short flights are not too much a concern, but long haul flights can be lead to severe dehydration.


If you’ve been diving, breathing in dry air, our more tries to make up for the dry air from your breathing apparatus by using more moisture. Excessive sweating in your suit could also cause you to become dehydrated. 

Mountain Climbing in High Altitudes 

The air in high altitudes can be very thin and low in oxygen, and moisture, which can cause your body to compensate with more water, leading you to become dehydrated. 

Now that you understand the potential situations where dehydration happens make sure you stay clear. If you are in this situation, you shouldn’t be dry fasting, so abort the mission! 

Why could dehydration during dry fasting save your life?

Dry fasting means taking in less water than you put out; therefore, by definition, you are dehydrated during a dry fast. However, your body is an intelligent organism and adapts to its environment. Otherwise, our caveman ancestors would not have survived harsh weather, where they had no access to food and water.

In periods without any water, total water deprivation, your body flips a switch and changes its metabolism. 

During a dry fast, your body senses that there isn’t enough water. It turns your body towards water conservation and creation, which it does through your fat cells. 

Their glucose stores run out in 24 hours for most people, although this depends on your nutrition, exercise, and body mass. Once glycogen has run out, your body uses fat for its supply of glycerol and fatty acids.

Some fatty acids are oxidized and converted into glycerol, which becomes glucose for your cells. Other fatty acids get converted into ketones. 

When ketones build up in your body, it means you’re in ketosis, and your body is only burning fat for fuel—and by this point, you usually don’t feel thirsty because your body is making its own metabolic water!

The process is broken down into this: Dehydration causes the hypothalamus in your brain to release ADH, an anti-diuretic hormone. ADH stimulates the kidneys to release lipase, breaking down the fat stores in your liver to release glucose and fatty acids. 

Glucose becomes a source of fuel for your body and starts feeding the cells of your body. Fatty acids become ketones that become fuel for your heart, brain, and muscles. 

Meanwhile, free fatty acids circulating your bloodstream go straight into all of your cells. Inside the mitochondria, the cell’s powerhouse, the fatty acids get broken down into Hydrogen (H) molecules. The (H)ydrogen molecules combine with the (O)xygen molecules that enter your body (through every breath you take) and make H20!

So each and every of your body’s 37 trillion cells is making its own water!

There’s another source of water for your body, though, and this happens through a process called autophagy. 

Dry fasting triggers a spike in autophagy, or ‘self-eating, a metabolic process that consumes all the unwanted, weak, old, damaged, and malfunctioning organelles, proteins, and cells in your body, to get more proteins to be repurposed and repair your body’s cells. 


The source of this unwanted cellular material includes old skin, skin tags, cysts, tumors, and pathogenic cells, which, when they break down, release more water into your system. Cells are made up of 60% water, which adds to how your body gets water internally.

There is limited research on dry fasting, but this pioneering 5-day dry fasting study done in 2013 by the Institute for Social Medicine, Epidemiology, and Health Economics in Germany found that even after 5 days, none of the 10 participants showed any signs of dehydration.

However, some did report a controllable feeling of thirst. The 2013 study also could not explain the apparent ‘insensible water loss’ during the dry fast, as the patients showed increasing urine discharge over 5 days. 

Interestingly, autophagy became more widely understood by the medical community only in 2016, when Japanese Scientist Yoshinori Ohsumi won the Nobel prize for medicine and physiology for his study on the subject. 

Your body is fully capable of making water for itself, and not just a tiny bit of water—it can make up to 1 liter of water a day. This 1989 study done in Malaysia during Ramadan, which is intermittent dry fasting of about 12–14 hours, shows that the urine production and water content in your body remain the same during the entire period of dry fasting. 

This is why most people feel more thirsty on the first day (or 24 hours) of their dry fast, but not so much after, because your body is getting metabolic water!

As a plus, while you’re making this water, your body is getting an internal housekeeping job.

It’s getting healthier and healthier, as it eats away all the useless and sometimes dangerous cells (cancer cells are simply malfunctioning cells that have multiplied), which is why dry fasting could save your life! 

For more on the incredible powers of dry fasting to get fitter, healthier and age backwards, sign up for my new video course, 25 Again! The Dry Fasting Lifestyle For A Younger, Slimmer You

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***Disclaimer: I am not a doctor/ physician, and although I have a bachelor’s degree in Biomedical Science, I cannot and do not hold myself to be a medical professional (“Medical Provider”). This article does not contain medical /health advice. The medical/ health information here is for general and educational purposes only. It is my opinion, based on my research and personal experience, and not a substitute for professional advice by your health care provider. Please consult with a professional before acting on the information here, and do not disregard medical advice or delay seeking medical attention because of anything you read in this article. THE USE OR RELIANCE OF ANY OF THE INFORMATION ON THIS WEBSITE IS SOLELY AT YOUR OWN RISK.***


  1. Papagiannopoulos IA, Sideris VI, Boschmann M, Koutsoni OS, Dotsika EN. Anthropometric, hemodynamic, metabolic, and renal responses during 5 days of food and water deprivation. Forsch Komplementmed. 2013;20(6):427-433. doi:10.1159/000357718
  2. Levine B, Klionsky DJ. Autophagy wins the 2016 Nobel Prize in Physiology or Medicine: Breakthroughs in baker’s yeast fuel advances in biomedical research. Proc Natl Acad Sci U S A. 2017;114(2):201-205. doi:10.1073/pnas.1619876114
  3. Cheah, S., Ch’Ng, S., Husain, R., & Duncan, M. (1990). Effects of fasting during Ramadan on urinary excretion in Malaysian Muslims. British Journal of Nutrition, 63(2), 329-337. doi:10.1079/BJN19900119
  4. Dunning, August. The Phoenix Protocol Dry Fasting for Rapid Healing and Radical Life Extension: Functional Immortality. August Dunning , 2020. 
  5. Filonov, Sergey. 20 Questions & Answers About Dry Fasting . Translated by Vera Giovanna Bani , Siberika , 2019.