Dehydration happens when your body has lost so much fluid and electrolytes that there isn’t enough left for your body to function normally. (1) This common condition is easily addressed in most cases by simply drinking enough fluid to replenish your stores. But each year roughly half a million people in the United States end up in the hospital, primarily due to dehydration. Nearly 2 percent of them die at the hospital. (2) How does that happen, when the condition is so easy to correct? Read on to find out how the worst-case scenarios of dehydration develop, and what you and your healthcare team can do to help treat them.
When Is Dehydration Severe Enough That You Need to Seek Help?
To understand how bad dehydration can get, it’s important to understand the different stages you can go through, based on the amount of body weight lost to fluid depletion. You can lose 3 to 4 percent to dehydration without running into any problems other than not feeling in tip-top shape, says Alp Arkun, MD, an emergency medicine physician at the Kaiser Permanente Fontana Medical Center in Fontana, California. “Most people can absorb that loss without realizing it,” Dr. Arkun says. (3)
Typical scenarios that might cause fluid depletion include overexertion, especially in hot weather, which can lead to excessive sweating; illnesses that cause vomiting and diarrhea, such as the flu; and chronic illnesses, such as uncontrolled diabetes, which can cause excessive urination. (1)
If you lose more than 3 to 4 percent of your body weight to fluid loss, you’ll start having recognizable symptoms of dehydration. Arkun describes these stages:
Mild (5 to 6 Percent of Body Weight Loss)
This is when you will start to notice your thirst, and you may feel fatigue, dizziness, and headache. Your muscles may begin to cramp, brought on by a growing imbalance of electrolytes as you lose fluid. “We see that in people who run marathons and then drop out of the race because of bad, bad cramps. That’s what’s happening,” Arkun explains. Reaching for a drink such as plain water or a sports beverage with electrolytes, like sodium chloride (salt) and potassium, should address the problem.
6 Smart Tips for Staying Hydrated
Moderate (7 to 10 Percent Loss)
At this stage you will have symptoms you simply can’t ignore. The loss of fluid volume can lead to low blood pressure and greatly decreased urination. Your pulse may be racing and your skin has become so dry that it tents when you pinch it instead of springing back. A child who has these symptoms should receive fluid orally, if they can keep it down, and medical attention. If you’re dehydrated and vomiting, especially for more than four to five hours, you should visit the emergency room so your fluid loss doesn’t become severe. (3,4)
Severe (More Than 10 Percent Loss)
This stage can be life-threatening. “You can pass out,” says Arkun. “Because of electrolyte abnormalities, severely dehydrated people can have seizures and they can die.” Muscle spasms can intensify. “The worst thing that could happen, of course, is a spasm of your heart muscle. If that happens, it can put you into an arrhythmia [abnormal heartbeat] and kill you.” (3)
Bruce R. Tizes, MD, an emergency medicine specialist in Peridot, Arizona, says people in this state are at risk for injuries. “You can imagine if someone becomes severely dehydrated, they can fall down and bang their head.”
If fluid loss is severe enough, your heart can’t pump enough blood to your body, leading to hypovolemic shock. Symptoms include pale, cool, and clammy skin; a rapid heartbeat; and shallow breathing. (3,5) You must be taken to a hospital for emergency medical treatment when you are in this stage, typically for intravenous rehydration.
Once you have lost 15 to 25 percent of your total body weight to fluid depletion, death is likely to occur, Arkun says. But this stage is extremely rare and usually happens when someone can’t rehydrate themselves or get help from others.
How Is Severe Dehydration Treated in the ER?
If you or someone you know goes to the emergency room with a case of dehydration, doctors will carry out an examination, possibly have labs done, check your vitals, and analyze your medical history, if that info is available, to help identify the immediate and underlying causes. With severe cases, “we will give them saline [sodium chloride and water] solution, either very concentrated or not so, depending on what their lab results show,” says Dr. Tizes. (Arkun says a 9 percent saline solution is typical.)
The next steps are to administer medications to get fluid-depleting symptoms, such as vomiting and diarrhea, under control, Tizes says. Loperamide (Imodium) is a typical medication for diarrhea, with ondansetron (Zofran) often being used for nausea, he adds. “Then the other treatments all focus on the underlying disease or disorder. For instance, if you have hyperglycemia [elevated blood sugar] from diabetes, we might treat that; or if you have a bacterial gastroenteritis, then we might treat that.”
Arkun says the most severe cases that he sees in the emergency room tend to involve people who are isolated and already have health problems or infirmities that prevent them from getting help quickly.
“There was an elderly person who lived by themselves in a trailer. They fell down and just stayed there. They were not within reach of a phone, did not have any neighbors within earshot, and stayed on the ground for maybe two or three days. What made it worse was that they had been in a hot trailer, so they were suffering from heat injuries as well as dehydration. So they were brought into the emergency room in pretty bad shape. They were dehydrated to the point where their kidneys had shut down and their potassium level was sky-high and actually causing [heart] arrhythmias. We had to take pretty quick action in order to reverse the effects of that high potassium levels on their heart.”
Even at such an advanced level of dehydration, proper treatment can help reverse such negative health effects. “After they were admitted to the hospital they had to undergo dialysis in the short term, but over [a] period of time of slowly rehydrating and getting their kidneys functioning again, they were discharged from the hospital. Within a few weeks of that, they were able to discontinue dialysis.”
Who Is at the Highest Risk of Developing Severe Dehydration?
As Arkun says, people who are isolated and cannot get help are especially vulnerable to dehydration that escalates to a severe stage. So are:
Infants and Children Youngsters can’t tell you if they are thirsty or get a drink for themselves. Furthermore, children and infants lose a higher proportion of their body fluid to fever, and they are more likely to have severe diarrhea and vomiting. (3)
Older People As we age, our body’s fluid reserve decreases, as does the thirst drive. “The elderly are our biggest population of patients who come in with major dehydration issues without realizing what is happening to them,” notes Arkun.
Medications that increase urination, as well as health conditions that prevent someone from self-hydrating are also vulnerabilities. (5) Dementia is one such health condition. “Some of the medications that patients might take to slow down the progress of their disease or to reduce their symptoms can sometimes interfere with the thirst drive,” explains Sanjey Gupta, MD, the chairman of emergency medicine at South Shore University Hospital in Bay Shore, New York. “Depending on how advanced the dementia is … it can get so bad that you forget how to take care of yourself, and you can forget to eat and drink.”
People With Chronic Health Conditions People with diseases that can make them urinate more often, such as uncontrolled diabetes or kidney disease, are at a higher risk of severe dehydration. High blood pressure medications and diuretics can also increase urination. (5,6)
People With Infections Any infection, such as the flu, that causes you to lose fluid through urination, vomiting, or diarrhea can escalate quickly. (4,7)
Anyone Who Lacks Access to Clean Drinking Water Losing fluid can compromise your body’s ability to cool off and can lead to heat illness — particularly when a person has a fever or the weather is hot. A person who is poor may lack access to water or a place to cool off, notes Dr. Gupta.
People Who Work or Exercise Outdoors Especially when it’s hot and humid and your sweat can’t cool you off as well as it normally can, your risk of dehydration and heat illness rises. The pressure to keep working or win an athletic competition can lead you to ignore warning signs of the earlier stages of dehydration. (5)
But, Arkun says, the symptoms of dehydration usually cause people to rehydrate or seek help before they get to the severe stage. “Thankfully, most of the people we get coming into the emergency room are more in the 5 percent [of body weight lost to dehydration] range because their bodies tell them, I can’t do it anymore.”
After they have been rehydrated and given medications to address symptoms such as nausea or diarrhea, he says, “9 times out of 10, they’ll feel well and can go home in a couple of hours.”
Editorial Sources and Fact-Checking
- Dehydration. MedlinePlus. August 10, 2021.
- Kim S. Preventable Hospitalizations of Dehydration: Implications of Inadequate Primary Health Care in the United States. Annals of Epidemiology. September 2007.
- Dehydration. Encyclopedia.com. August 13, 2018.
- Do You Know When to Visit the Hospital for Vomiting? Cleveland Clinic. March 8, 2021.
- Hypovolemic Shock. MedlinePlus. September 23, 2019.
- How to Manage Your Diabetes in Extreme Summer Heat. Cleveland Clinic. July 21, 2020.
- The Flu: Caring for Someone Sick at Home [PDF]. Centers for Disease Control and Prevention. December 2010.