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A cautionary tale about advice to ‘drink plenty of fluids’ when sick

Drinking too much water can lead to abnormally low levels of sodium in the body.

The idea that adults must drink eight 8-ounce glasses of water a day to stay hydrated — and therefore healthy — has been thoroughly debunked.

What scientists now recommend is that we drink fluids (preferably water) primarily when we’re feeling thirsty, and that we pay particular attention to satisfying that thirst when it’s hot and humid and/or when we’re exercising strenuously.

But, as the experts also stress, we shouldn’t overdo it. That’s because drinking too much water (overhydrating) can lead to abnormally low levels of sodium in the body. Cells, including those in the brain, may then begin to swell with water — a potentially life-threating condition known as hyponatremia.

Symptoms of hyponatremia include headache, nausea, vomiting, fatigue, disorientation and difficulty speaking. If left untreated, seizures, coma and death may occur.

A 2013 study estimated that about 2 percent of Americans develop hyponatremia during any given year, and that 11 percent of those people die from complications related to the condition.

Most of those cases of hyponatremia are not caused by drinking water too much water, but by an existing heart or kidney problem that makes it difficult for the body to excrete fluids. But recent research has shown that the condition also occurs with surprising frequency among athletes, particularly those involved in endurance sports.

In a 2002 study, for example, 13 percent of 488 Boston Marathon runners were found to have hyponatremia after the race, and 0.6 percent of the runners had severe cases of it.

Others at risk

Last week, two British doctors extended concerns about drinking too much water to people who are feeling unwell. Writing in the journal BMJ Case Reports, they say that doctors may need to add some caveats to the standard advice they give to patients ill with a viral or other infection to “drink plenty of fluids” and “keep well hydrated.”

One patient who followed that advice too vigorously had to be hospitalized as a result, they explain.

That patient was a 59-year-old woman who showed up at the emergency department of the King’s College Hospital in London with a urinary tract infection (UTI). She had no history of other illnesses and took no regular medications. 

The emergency department doctors prescribed the woman antibiotics and pain medication, but noticed a deterioration of her symptoms.

“She became progressively shaky and muddled,” write Dr. Laura Christine Lee and Dr. Maryann Noronha. “She vomited several times, and was tremulous and exhibited significant speech difficulties.” 

The mystery solved

The doctors became worried that the woman was experiencing a stroke. But then the woman’s partner told them an important bit of information:

Her partner described that the patient had woken up that Sunday morning with dysuria [pain while urinating] and lower abdominal pain, which she had attributed to her recurrent UTI. Throughout the day she had consumed several litres of water based on medical advise she recalled from previous similar episodes.

Suspecting hypernatremia, the doctors ordered blood tests, which quickly revealed that the woman’s sodium level was significantly below the normal range. They admitted her to the hospital and restricted her fluid intake. The following morning, her blood tests were normal and she felt improved. She was sent home — with instructions, presumably, not to overdo it with her water consumption.

‘A paucity of evidence’

As Lee and Noronha emphasize, cases of hypernatremia in people with normal kidney function are rare but not unknown.

“This [case] mirrors a previous case report in which a young, previously healthy female drank excessive amounts of water during an episode of uncomplicated gastroenteritis, resulting in acute hyponatraemia and death,” they write (with the British spelling of the condition).

Lee and Noronha suggest that the medical community needs to do more research in order to “qualify our oft-given advice to drink more fluids.” 

“There is a paucity of evidence behind the advice to ‘drink plenty of fluids’ in the management of mild infective illness,” they conclude. “This needs to be addressed, especially considering the significant morbidity and mortality of acute hyponatraemia.”

FMI: You can read the case report in full on the BMJ Case Reports website.

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Comments (9)

  1. Submitted by Susan Lesch on 12/05/2016 - 10:12 am.


    Ms. Perry, would you please write a similar article about the advice to “walk 10,000 steps” every day? As near as I can tell, that count is arbitrary, just like doctors’ advice to drink 8 glasses of water every day. I guess based on an Asian habit of rounding up a big unknown number to “ten thousand”, “a million.”

    Here are two starters:


  2. Submitted by Emily Sojourn on 12/05/2016 - 11:41 am.

    Almost a non-story

    Of course this story is relevant to the 2% of the population for whom this condition applies but I still have to wonder if near non-stories like this are almost as bad as fake news.

    The headline: “A cautionary tale about advice to ‘drink plenty of fluids’ when sick” hooks us in by implying that we might be doing something wrong when trying to get well from a virus. What we actually read is a story about a tiny population of people who make choices 98% of us don’t. The possible short-term result: a wasted 2-3 minutes of reading. The possible long-term result: another contributor to the fear-and-paranoia culture that sees danger around every corner.

    I’m not implying this issue is totally irrelevant. I have heard of one person in my entire life who over-hydrated and had to see a doctor, but aren’t there stories that effect a few more people that we could be writing about? Or, if we choose to write about things like this, could the headlines be a little bit less deceptive?

    • Submitted by Jason Goray on 12/05/2016 - 12:03 pm.

      If accurate, it’s a huge issue.

      If this story is accurate and 2%/year get the issue and 11% of those die, that’s about 700,000 deaths per year which would be more than heart disease or cancer.

      I question the accuracy, but if it turns out to be correct, then this is as big of a deal as cancer or heart disease (which also don’t kill the vast majority of us in any given year)

  3. Submitted by Jason Goray on 12/05/2016 - 11:54 am.

    One in 455 dies?

    Can these numbers be right?

    If “2 percent of Americans develop hyponatremia during any given year, and that 11 percent of those people die from complications related to the condition”, then by my calculator, that’s one in 455 Americans dying every year from hyponatremia related conditions.

    Can that possibly be correct?

    • Submitted by Jason Goray on 12/05/2016 - 12:01 pm.


      Again, looking at it, if 2% of Americans have the issue per year and 11% of those die from complications relating to it, that makes about 700,000 dead Americans per year.

      By way of comparison, we get a bit under 600k/year from cancer, 93k/year from alzheimers, and 76k/year from diabetes.

      If these numbers _are_ accurate, this is a huge issue but I find them a bit hard to believe.

  4. Submitted by Pat Berg on 12/05/2016 - 12:13 pm.

    There’s quite a gulf . . . .

    There’s quite a gulf between “several litres” and 64 ounces (eight 8-oz glasses of water). The recommendation for 64 ounces is just shy of 2 liters. But your article – from the very first line – is implying danger at the 64 ounce level.

    After suffering a kidney stone and being told to start drinking 64 ounces of water a day, I stifled my initial gasp and did the calculation and determined that an 8 ounce glass (not that much, really) upon rising and every 2 hours thereafter would get me to that goal by around 8pm, thereby permitting me to make it through the night without the need for bathroom breaks.

    I’m a person who sometimes went an entire day drinking maybe a glass of water, and not a lot of liquids besides. I’m just not a thirsty person. Yet I developed that kidney stone. So clearly, following the dictates of my thirst (or lack thereof) was far from adequate.

    Now that I’m drinking that 8 ounces every two hours (Not that much. Really.) I’m realizing how far overboard I went at those times in the past when I tried to “drink more water”. Without measuring, I WAY overdid it. And I bet a lot of other people do the same thing.

    For the people who developed serious health problems from drinking too much water, I’d like to see an actual, factual measured amount of how much they were really drinking. Because I’m pretty darn sure it was far in excess of 64 ounces (and possibly not distributed over the course of a day).

  5. Submitted by chuck holtman on 12/05/2016 - 01:27 pm.


    I’m switching to beer.

  6. Submitted by Susan Perry on 12/05/2016 - 01:49 pm.

    A clarification

    As I thought today’s post made clear (but apparently it didn’t), most cases of hyponatremia are caused by an underlying health condition, such as heart failure, that makes it difficult for the body to excrete water. But athletes and others (including people who are overly enthusiastic about following the “drink more fluids” advice when ill) can also develop hyponatremia if they load up on too much water (or other fluids). How much is too much? That will, of course, depend on the individual. So, this is a cautionary tale. That’s all. By the way, a BMJ reporter wrote an interesting article several years ago about the central role that the sports drink industry has played in developing the “science of hydration” and sports. http://www.bmj.com/content/345/bmj.e4737

    • Submitted by Pat Berg on 12/06/2016 - 07:06 am.

      You bet it wasn’t clear!

      Six paragraphs down before you even mentioned the contribution of underlying health conditions’ role in most cases of hyponatremia after you’d already spent several paragraphs talking about the perils of following the previous “8 x 8” guidelines and how you should just let your body’s thirst be your guide.

      Then you go right back to “the perils of too much water” while – apparently – citing anecdotes of people who were drinking WAY too much water – probably FAR in excess of “8 x 8”, although your post never actually makes this clear.

      A poorly constructed post, indeed!

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