Dehydration and Rehydration, by Dr. Marc

One of the great killers in the third world is dehydration from diarrhea and dysentery, due to contaminated water. This is particularly dangerous with respect to the elderly and children.
As your readers are likely aware, having the ability to filter or purify drinking water is critical. Having a high volume and high-capacity water filter can go a long way toward preventing diarrhea and dysentery, with its associated dehydration.
I very much recommend, based upon personal experience, water filters including the Katadyn endurance series and the Sawyer inline series.  Both of these vendors have extremely long lived, large volume and quality filters for drinking water. They have the capacity to filter many thousands of gallons of drinking water and they are appropriate for North America.
Please note that travel to Africa and other areas where the water is contaminated with viruses should entail the use of a water purifier, not a filter, which often has an iodine element. These have lesser volume capacity by necessity, but the water is treated for viruses.  As you know, there are additional options to purify water including UV sterilization, boiling, and so on.
One critically important thing to know is how to treat dehydration from dysentery.  Because dysentery often occurs remote from medical care and IV hydration, the world health organization created an oral rehydration solution. This has been shown to reduce the mortality from dehydration associated with dysentery by as much as 93% .
It behooves readers to learn how to make this solution and how to administer it. The following quote from Wikipedia is informative:

 “The formula for the current WHO oral rehydration solution (also known as low-osmolar ORS or reduced-osmolarity ORS) is 2.6 grams (0.092 oz) salt (NaCl), 2.9 grams (0.10 oz) trisodium citrate dihydrate (C6H5Na3O7⋅2H2O), 1.5 grams (0.053 oz) potassium chloride (KCl), 13.5 grams (0.48 oz) anhydrous glucose (C6H12O6) per litre of fluid.[15] This is 44 mmol salt, 10 mmol trisodium citrate dihydrate, 20 mmol potassium chloride, and 75 mmol anhydrous glucose per litre. This would have a total osmolarity of (44×2 + 10×4 + 20×2 + 75) = 243 mOsm/L.

A basic oral rehydration therapy solution can also be prepared when packets of oral rehydration salts are not available. It can be made using 6 level teaspoons (25.2 grams) of sugar and 0.5 teaspoon (2.9 grams) of salt in 1 litre of water.[16][17] The molar ratio of sugar to salt should be 1:1 and the solution should not be hyperosmolar.[18] The Rehydration Project states, “Making the mixture a little diluted (with more than 1 litre of clean water) is not harmful.”[19]

WHO/UNICEF guidelines suggest ORT should begin at the first sign of diarrhea in order to prevent dehydration.[32][33] Babies may be given ORS with a dropper or a syringe. Infants under two may be given a teaspoon of ORS fluid every one to two minutes. Older children and adults should take frequent sips from a cup, with a recommended intake of 200-400 ml of solution after every loose [bowel] movement.[1] WHO recommends giving children under two a quarter- to a half-cup of fluid following each loose bowel movement and older children a half- to a full cup. If the person vomits, the caretaker should wait 5–10 minutes and then resume giving ORS.[20](Section 4.2) ORS may be given by aid workers or health care workers in refugee camps, health clinics and hospital settings.[34] Mothers should remain with their children and be taught how to give ORS. This will help to prepare them to give ORT at home in the future. Breastfeeding should be continued throughout ORT.[20]

I strongly encourage your readers to do a little online research into how to treat dysentery, and how to mitigate the dangerous effects of dehydration, through the appropriate administration of oral rehydration solution.


  1. In my pack med kit is also includes electrolytes, metronidzole, azithromycin (Z-Pack), Imodium a-d. (Metronadzole = Flagyl.) Although I would use a life straw water filter, or a Katadyn pump, and would boil water if there were dead bodies in the water, or a known virus in the area, having diarrhea on the trail would be life threating, as water may not be easily accessed during some parts of the journey. The backpacker is usually somewhat dehydrated during some parts of the day, and dysentery would make travel away from a water source a dangerous prospect. Being just one quart too low, a person can feel the weakness, and delirium of dehydration. This combination meds during WROL would be priceless, as it could keep one on the trail, or get them back on the trail sooner rather than latter, and to the safety of their destination. A side effect could be more diarrhea, yet it would be a necessary part of the process, the cure. Shigella, cholera, and protozoa are common water borne causes of diarrhea and dysentery.

    I ain’t no doctor, so the reader is on their own here. Do your own research. I highly recommend getting a signed copy of Dr. Alton’s Antibiotics and Infectious Diseases. It is a easy read. See what it can do for you. Or pick up a Merck Manual, or PDR, and then get Dr. Alton’s book. I have a pile of medical books for reference, bot cheap at the thrift store.



  2. Great article Dr. Marc! I appreciate you covering this topic, as dehydration can kill or disable as quickly as any factor can during WTSHTF/ if we turn into a third world country overnight.

    In addition to the filters you recommended, I also like the Berkey water filters…especially the large units for homestead drinking if your well, city water connection, or other water source is at risk of contamination. While not portable, they would work well in a kitchen.

    Dr Marc, your recipe for hydration was great. Balanced solutions of water, salt/electrolytes, and sugar is key to retaining the water…just ask the folks at Gatorade who have made billions figuring this out for athletes.

    Speaking of Gatorade, since it’s available right now in our first-world economy, I recommend keeping this constantly stocked at your home for everyday hydration as well as long-term preparedness supplies.

    Rectal Hydration may be necessary in a situation where the patient (human or potentially an animal I suppose) cannot take oral medications/fluids due to excessive hydration or other factors, and when an IV hydration therapy isn’t an option. Here is a link to one scientific article about it. If you look at the text boxes on the right hand side, it provides some simple step-by-step instructions that even a lay person could use. Rectal hydration is used in the third world often because it is much easier/cheaper than an IV to make and administer by non-medical folks to children who are severely dehydrated. We were taught about it in medical school to demonstrate the physiology of how the large intestine cells work to absorb water, and also as a backup plan for rehydration therapy for those of us who intended to do medical mission trips during our careers.

    (I would provide age/weight-appropriate doses of the fluids Dr. Marc recommended, but just give it rectally when necessary.)

    Here are some supplies on Amazon you could purchase in order to provide this therapy; they may be worth stocking up on:

    1a.) Foley Catheters (normally used in a bladder cath situation, but they can be placed rectally and the balloon inflated gently until it seals against the bowel wall:

    1b.) or you can use these as an alternative, but there is no balloon in the tip to get a good seal:

    2.) These syringes are useful for both inflating/deflating the Foley catheter balloon, but also for administering oral medication doses to kiddos, such as pediatric tylenol or ibuprofen.

    3.) And finally, these syringes are useful in delivering all the fluids through the catheter into the bowel:

    So, to summarize this purchase, you would need either 1a or 1b, plus 2 and 3. Please do the math and get matching numbers (some quantities are much different than others), so that you have as many functional sets as possible. You might also want some K-Y type lubricating gel and some gloves.

    Lastly, for those readers who have medical training placing IV catheters, if you can obtain a stock of IV fluid bags, IV tubing, and angiocath IV needles, these are all extremely useful in fluid replacement therapy for dehydration.

  3. Thanks for this article and the comments.

    I purchased (stored for emergency) boxes of Medi-Lyte electrolyte supplement, which have 50 packets of 2 tabs per packet.

    Listed ingredients: Calcium (from 27.0 calcium carbonate) 10.8 mg, Potassium (from 80 mg potassium chloride) 40 mg, Magnesium (from 20 mg magnesium oxide) 12 mg.

    Any suggestions of administration and dosage would be welcomed. Please advise.

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