How Much Water Do You Need to Survive: What happens without it?

You’ve probably heard that you should store a gallon of water per day for everyone in your house. That gallon of water is supposed to be for washing, cooking, and drinking but no one ever really talks about how much you actually need to drink to stay alive.

Based on research, the bare minimum that a human needs to survive is 1 liter a day, but experts suggest that you should be drinking 64 oz of water every day to maintain proper hydration. This amount increases if you live in extreme heat or cold and based on your activity level.

You should be trying to replace all of the water that you lose on a daily basis at a minimum.

How Much Water do you Need to Survive

We’re made up of about 60% water. Normally we get most of our water from drinking, but up to 20% of our water intake can come from the food we eat.

The human body uses water for a wide range of bodily functions. When we get dehydrated these functions either get severely reduced or stop completely. Losing enough water in the system eventually leads to death.

The body relies on water to do the following:

  • Regulating body temperature.
  • Removing waste from the system.
  • Cushion the brain, spinal cord, and joints.
  • Absorbing nutrients into the body.
  • Prevent certain medical conditions.

In order to keep the body functioning the general rule of thumb is to drink eight 8 oz glasses of water a day. This ends up being about 2 liters of water that you should be drinking on average.

There are many reasons why you could need to drink more than this. Bodyweight, activity level, age, and temperature can all change exactly how much water you need to take in.

How Much Water Should You Consume Based on Body Weight

Weight Ounces of Water Daily
100 pounds 67 ounces
110 pounds 74 ounces
120 pounds 80 ounces
130 pounds 87 ounces
140 pounds 94 ounces
150 pounds 100 ounces
160 pounds 107 ounces
170 pounds 114 ounces
180 pounds 121 ounces
190 pounds 127 ounces
200 pounds 134 ounces
210 pounds 141 ounces
220 pounds 148 ounces
230 pounds 154 ounces
240 pounds 161 ounces
250 pounds 168 ounces

In a survival situation, you should be drinking at least as much water as your body loses every day. This is right around a liter minimum if you’re just sitting around waiting for someone to rescue you. The lower you go below this number, the more dehydrated and unhealthy you’ll become.

Certain medical conditions common in survival situations (like vomiting and diarrhea) drastically increase the amount of water that you need to drink. These are life-threatening conditions! Don’t ignore them.

Rationing Water

When you start looking into when or how you should ration water, you’ll find all kinds of information out there.

Some people will tell you to drink everything that you have so your body can use the water. I mostly agree with this but only to a certain point. When the body is well hydrated it signals to the kidneys to produce more urine. You don’t want to reach this phase if you’re in a situation where you have limited water.

Drink what water you have until you’re reasonably hydrated (light yellow urine) and then try to stay around that level for as long as you can. Some rationing of water can help you preserve the water that you have, but you don’t want to allow your body to suffer the effects of severe dehydration until you just don’t have a choice.

What Happens as Your Body Loses Water?

Water loss has severe effects on the body. Some of them can happen in as little as an hour while others take longer to show up.

Losing water will cause the following to happen to the body:

  • Respiration will slow as the mucus in your lungs thickens.
  • The body will begin to overheat when there isn’t enough water to cool it through sweating.
  • The kidneys will have to work harder, eventually failing.
  • Loss of cognitive function will gradually increase stress levels and increase your heart rate.
  • The intestines will absorb as much water from your food as they can and lead to constipation.

Everyone wants to know what happens to your body when you don’t drink for 24, 48, or 72 hours. It’s difficult to say exactly how your body will react. A better way to measure the effects is by how much of your body weight you’ve lost in water weight.

% of Body Weight Lost Symptoms
2% Thirst
3% Severe Thirst, Absent-Mindedness, Loss of Appetite
4% Flushed Skin, Irritability, Increased Body Temperature, Exhaustion, Decrease in Urine
5% Headache, Feverish Feeling
8-10% Swaying, Convulsions
over 20% Kidney Failure, Death

How Can You Tell if You’re Dehydrated?

There are some pretty clear signs that the body gives us when we start getting dehydrated. The first one is thirst. We experience this pretty much every day and it’s a simple reminder that we’re beginning to get dehydrated. The symptoms after that get more severe as we become more dehydrated.

Signs of mild or moderate dehydration:

  • Thirst
  • Sticky or dry mouth
  • Not urinating very often
  • Dark yellow urine
  • Dry, cool skin
  • Headaches
  • Muscle cramps

Signs of more severe dehydration:

  • Very dark yellow urine
  • Not urinating
  • Dizziness
  • Rapid heartbeat
  • Rapid breathing
  • Sunken eyes
  • Sleepiness
  • Confusion
  • Loss of energy
  • Irritability
  • Loss of consciousness

Related Questions

Does bottled water go bad? Water never technically goes bad. As long as you have a way to filter it sufficiently, bottled water will remain usable forever. Just keep in mind that chemicals can leech into the water from the bottles and may not be removed with a filter.

How much water should I store for prepping? If you’re storing water for an emergency, you should have 1 gallon per person, per day. About half of that will go toward drinking and the other half will be for cleaning and cooking. In very hot or cold environments, you should store more than this.

What is the minimum amount of water to survive? The minimum amount of water that we need to continue to live is about 1 liter per day. This will replenish the water that the body loses through perspiration, breathing and other functions. If you’re active, this amount is going to increase a lot.

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