In the wilderness yesterday I ran out of water and did not think I could hike out safely at my level of hydration. Lacking a treatment method, I drank 1.5 liters of water directly out of a small, swampy creek.

I understand that the risk of getting sick really comes down to chance, and that it might be weeks before any illness manifests itself. Being back in civilization, is there anything I can do now to ward off a potential symptomatic infection?

  • 18
    Probably too late now but if this comes up again it might be helpful to capture a sample of the untreated water for later analysis/culture. Commented Jun 3, 2021 at 15:59
  • 6
    Yes, and it might also be advisable to drink a lot less than 1.5l Commented Jun 5, 2021 at 3:21
  • 4
    @RobbieGoodwin that depends how long the OP had been going without water, or expected to. It's probably better to drink more from one suspect creek than less from each of several (even if there are several)
    – Chris H
    Commented Jun 7, 2021 at 9:08
  • 1
    How was this resolved? Did you get giardia Peter?
    – Justin
    Commented Jun 29, 2022 at 20:25
  • @Justin I didn't! Answer updated. Commented Jul 11, 2022 at 18:31

8 Answers 8


This is nothing to worry about. Visiting the doctor won't accomplish anything if you don't have any symptoms of illness.

In the case of giardia, which is the organism that is the biggest worry in popular perception, there's about a 25% chance that you already had it in your gut and were just asymptomatic. People often acquire it when changing diapers. Wilderness-acquired cases are extremely rare, and there is little definitive documentation that they even occur at all. It has a long incubation period, and even if you did have a wilderness-acquired case, there would probably not be enough of it to detect in a stool sample at this early date. It resolves itself and does not require treatment except possibly for symptoms (immodium).

There are other disease-causing organisms besides giardia that you could have conceivably picked up, but speculating about all the hypotheticals is pointless if you don't have any symptoms.

  • 6
    I know an old NOLS instructor. In the 80's they (like many of us) used iodine to treat water. He led so many trips that he got iodine poisoning (it is toxic). He stopped treating his personal water at all, and worked for years in heavily traveled backcountry areas without issues.
    – Jon Custer
    Commented Jun 3, 2021 at 16:44
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    I suggest that you add that the OP see a doc as soon as symptoms appear. One of my friends in college, her husband & two of their friends acquired giardia, in all liklihood from drinking from a stream in New Hampshire, years ago. Two of them got very sick and one had to drop out of school. This was so many years ago that giardia was thought not to be present at all in the US. The lady who left school was eventually diagnosed by specialist in tropical medicine, who met her parents at a cocktail party. Symptoms can ramp up quickly, and for giardia can come & go & repeat & repeat.
    – ab2
    Commented Jun 3, 2021 at 17:57
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    While this is a comforting answer, I'd appreciate some sources for the statistics/perspective. I've taken WFA courses from different institutions that do not agree with each other about the subject. Commented Jun 3, 2021 at 20:46
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    I think it's more than conceivable that you could pick up something that gives you a less or more severe case of the runs. If this happened I wouldn't panic if the symptoms were restricted to an urgent need to go to the toilet at frequent intervals, and if it resolved naturally in a day or two I'd not worry any further. (Basically, this is evidence of warfare between your gut biota and an intruder. Your gut biota usually win).
    – nigel222
    Commented Jun 4, 2021 at 10:50
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    @JonCuster: I wouldn't be surprised if one can build up immunity by encountering iodine-killed bacteria and end up not needing the iodine later. These days I carry iodine neutralizer tablets as well.
    – Joshua
    Commented Jun 5, 2021 at 17:58

The best thing you can do to both ward off illness, and catch any illness so it can be treated early, is to schedule an appointment with your doctor, soon. When you request the appointment, make sure you mention drinking untreated creek water as the reason for the appointment. That will give your doctor time to look up references to the appropriate information they will need to advise you. Follow their advice.

Prior to seeing your doctor, practice good self care. Get your regular 8 hours of sleep a night, stay well hydrated, eat a reasonably balanced diet, get a little bit of exercise every day, and stay sober. Basically, do the things you would do to try to stay healthy if you thought you might have a cold coming on right before a big vacation and you really don't want to get sick and have to cancel.

Also, practice good hand-washing hygiene, especially around using the bathroom and preparing food for others. Some water-borne illnesses such as cholera are caused by exposure to waste in the water (either human or animal), and can be spread by preparing food with poorly washed hands. Again, it's nothing very special, just being diligent about actually doing the good habits that we all know we should do but sometimes get lazy about.

  • 6
    +1 And buy some Immodium.
    – ab2
    Commented Jun 3, 2021 at 3:24
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    “That will give your doctor time to look up references to the appropriate information they will need to advise you” - doctors don’t have access to information that is unavailable to others. This answer could be improved by adding some references to medical literature on what the treatment options are generally prescribed. This way OP has a list of suggestions when they go for a visit rather than being dismissed with “come back when you have symptoms”. Many doctors are quite busy and won’t bother doing deep research without serious symptoms being present. Commented Jun 3, 2021 at 19:40
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    Going to the doctor without any symptoms is pointless. This isn't House MD. There isn't some team of specialists just waiting to jump on your case and try all kinds of complicated diagnoses... Unless you are a head of state maybe, or have bottomless pockets to pay for soothing your hypochondria. ;)
    – fgysin
    Commented Jun 4, 2021 at 5:23
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    @fgysinreinstateMonica Absolutely in concurral with that, with a minor nitpick; hypochondria is when you misinterpret a non-specific symptoms to be of far greater importance. Head-ache -> brain tumor. Nosophobia is the word you want, the fear of having a disease but without any symptoms. Often called medical student's disease ;)
    – Stian
    Commented Jun 4, 2021 at 10:28
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    @AndrewMorton there's a time and a place for both approaches (and plenty of contra-indications and cautions for loperamide). If at home and able to rest, ORS can be enough; if out in the wilds or trying to get home, with limited toilet facilities, clean water, and even handwashing options, suppression may be the best option, despite the likely internal discomfort. I looked for evidence of it prolonging the course, but that doesn't appear to be the case (hard to test for though); I suspect this is because the bad stuff still works its way through to where it's less bad
    – Chris H
    Commented Jun 22, 2021 at 14:18

For what it's worth, I had a previously scheduled appointment with my primary-care physician a few days after the incident. One of his interests/specialties is remote and wilderness medicine.

His advice was that in the absence of symptoms there is nothing to do but wait. There is no way to preempt symptomatic infection after exposure, but if symptoms develop they should be reported as soon as possible for treatment.

For what it's also worth, I did not contract any symptomatic illness (or known asymptomatic illness) from this episode.

  • Thanks for coming back and keeping us updated, that will be a help for future worried people.
    – Willeke
    Commented Jul 11, 2022 at 19:34

At the time, yes.

Don't eat anything when you drink the water.

This will reduce the likelihood and severity of food poisoning.

The ingested water will have its pH rapidly reduced which will kill some pathogens. if you have food in the stomach as well this will happen more slowly. Also, a bolus of food is more likely to protect and transport pathogens. Particularly don't eat fatty/oily foods.

I did spend time looking up my microbiology books, but cannot find an exact ref. I was taught this in one of my four microbiology subjects.


Many years ago, I was in a similar situation. When I returned to civilization I went to see a medical doctor.

If I recall correctly, the doctor ordered one or two tests in which I was required to collect a small amount of my stool and place it in a cup for analysis. My memory of the experience has faded, but I think the cup was filled with some sort of liquid to help preserve the stool sample. There might have also been a test that had me smear a tiny amount of stool onto a card for lab analysis.

The doctor also had some blood (serum) tests performed at a lab to establish a baseline for my health. The doctor then performed the same tests several weeks later to see if anything had changed.

As a courtesy to others, I did not share food/drinks/kisses with anyone until we had determined that my health was not affected by drinking the non-potable water.

After that experience, I have always packed extra water, and when appropriate, a water filter.


I am a retired university professor in Public Health, especially in simple remedies. My Korean wife and I have traveled into 30 countries giving seminars. The one friend of travelers is charcoal, either powder or tablets. It is one of the best stomach remedies to protect from water or food in foreign situations. A couple of cards of Activated Charcoal carried in the pocket or backpack are very useful in any situation with suspect food or water. A couple tablespoons of Charcoal Powder in warm water or 8 tablets with a glass of warm water are a good remedy or preventive. If you are infected, then you might have to repeat it 2-3 times in a day.

Of course sometimes you contact something really bad and you have to get to the hospital or MD. Iodine drops can be useful, too, but you can develop an iodine sensitivity if overdoing the drops. Charcoal never does anything but help you, except in one way - It can adsorb some of your vitamins and, if you don't have enough fiber in your diet = constipation. Like a rock!

  • Comments are not for extended discussion; this conversation has been moved to chat.
    – Rory Alsop
    Commented Jun 7, 2021 at 16:33
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    Please provide citations for the claims in your post, as they could be potentially dangerous
    – Rory Alsop
    Commented Jun 7, 2021 at 16:37

There's not much you can do now about untreated water you already drank. At this point I wouldnt' worry unless I became symptomatic.

Although it's smart to carry enough drinking water or have a method of treating backcountry water, it was a good call to take a reasonable chance on drinking untreated water when the alternative was a dangerous level of severe hydration. Odds are you'll be fine this one time.

There are about 1 million giardia cases in the United States per year (1 out of 300 people.) It is not true that "about 25% of people already have it in their gut." (1 out of 4)

Despite claims to the contrary, there is plentiful evidence that a significant number of people get sick from giardia and other pathogens from drinking from lakes, streams and springs. Most giardia cases are from water.


I have drank from springs, rivers, and lakes all untreated and in retrospect, it was not smart and I was unaware of the dangers; I turned out fine the doctor said the brain ameba probably starved.

To answer the question directly

"What should I do if I am worried after ingesting untreated water?"


Write down the time and date you ingested it. The course of treatment if something happens will all be responding to that timestamp, and you can mostly determine what is causing an illness by knowing when symptoms started.

There is a risk of disease-causing microbes or parasites, with parasites normally being much worse.

You should start feeling symptoms if something is wrong in 1 hour to 3 days for illness from disease-causing microbes.

Here is what the CDC says for drinking water risks:

Health effects of consuming water with disease-causing microbes. Most life-threatening waterborne diseases caused by microbes (such as typhoid fever or cholera) are rare in the United States today. The more common illnesses caused by viruses, bacteria, and parasites can result in stomach pain, vomiting, diarrhea, headache, fever, and kidney failure. Infectious diseases such as hepatitis can also occur. Hepatitis may be severe in people with weakened immune systems (e.g., infants and the elderly) and sometimes fatal in people with severely compromised immune systems (e.g., cancer and AIDS patients). CDC Water Safty Information

If you start to feel any of those symptoms you should contact your doctor, explain your issue from the water, note the time and date, and get on an anti-biotic.


Don't sweat it, your body is capable of fighting off a lot of things, now is not a great time to educate yourself about rat-lung-worm. Make sure to document how you feel, take your own temperature, and eat some leafy greens and filtered water.

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