What Are the Signs of Severe Dehydration? How to Know If You Need to Go to the ER
Key takeaways:
Severe dehydration can cause damage to your kidneys, heart, and brain. Serious cases can become a medical emergency.
You should go to the ER if you’re having signs of severe dehydration, such as confusion, fainting, dark urine, or no urine.
In the ER, the medical team will evaluate you to see if you need IV fluids. Many people, especially children, will be able to rehydrate using an oral rehydration solution.
Table of contents
It’s normal to get dehydrated every now and then. You might find yourself feeling dizzy while recovering from a stomach bug. Or you may feel lightheaded after exercising on a hot day. But sometimes, it can be hard to tell how dehydrated you are.
When dehydration becomes severe, it can cause serious health problems. It can even lead to shock and organ failure. So how can you tell when dehydration is severe? And when should you go to the ER for dehydration? We’ll break it down here.
What are the symptoms of severe dehydration?
Many people have a general sense if they are dehydrated based on how much fluid they’re drinking and the color of their urine.
Symptoms of severe dehydration can be different depending on your age and general health. In the next section, we go into more detail about how to know if you are dehydrated. But in general, someone with dehydration might experience:
Dizziness
Confusion or grogginess
Exhaustion
Sunken eyes
Dry, cracked skin
Extreme thirst
Dark urine, or low amount of urine
You can’t always tell exactly how dehydrated someone is from their symptoms alone. For example, a young and healthy person with food poisoning might feel dizzy, but only be mildly dehydrated. And on the other hand, an older adult in a hot climate might have few symptoms and be at risk for kidney damage if they are not drinking enough fluids.
How to rehydrate fast: If you’re recovering from dehydration at home, these drinks provide the right mix of fluids and electrolytes to help you rehydrate fast.
What does a dehydration headache feel like? If you’re wondering if your headache could be from dehydration, people explain what theirs feel like.
Caregiver tips: It can be hard to help older adults stay dehydrated. Some experienced caregivers chime in with tips that can help.
Quiz: Should I go to urgent care or the ER?
When should you go to the ER for dehydration?
You should go to the ER if you think you or someone else is showing signs of severe dehydration. The symptoms of severe dehydration can be different depending on your age.
Adults
Young, healthy adults usually experience more noticeable symptoms with severe dehydration than older adults.
Symptoms of severe dehydration in adults include:
Extreme lightheadedness
Fainting, especially when going from sitting to standing
Dark urine
Muscle cramps
Nausea that won’t go away
Increased heart rate (over 100 beats per minute)
Read more like this
Explore these related articles, suggested for readers like you.
Older adults
The signs of dehydration in older adults (over 65 years old) may be more subtle. As people age, their thirst mechanism tends to be weaker. So, they’re more likely to get dehydrated from lack of drinking fluids. And older adults are more likely to have chronic medical conditions. This makes them more vulnerable to the effects of dehydration.
Older adults can experience all the same symptoms as young adults. But they may also experience milder symptoms, even when dehydration is severe. Older adults might also notice:
Confusion
Sunken eyes
Increased lethargy
General weakness
Extremely dry skin or cracked lips
A lower blood pressure than their baseline
Children
The most common cause of severe dehydration in children is vomiting and diarrhea. So, it’s especially important to watch for any symptoms of dehydration if your child has a stomach bug. Signs of severe dehydration in children can include:
Confusion or changes in mental status
Exhaustion
Cold, clammy hands and feet
Fast heart rate
Inability to drink fluids by mouth (because of persistent vomiting)
Very dark pee or not peeing
Infants and babies
Infants won’t be able to tell you they’re thirsty or complain if they have a headache. So, it’s even more important to know what to watch for with your baby. You should go to the ER if your infant is experiencing symptoms like:
Fewer wet diapers (fewer than three wet diapers in 24 hours)
Constant crying
Appearing more sleepy than usual
Fast breathing
Crying with no tears
Dry cracked lips
A sunken soft spot on the top of their head
It’s important to remember that wet diapers are a very good indicator of hydration. If your baby still has regular wet diapers every few hours, they are unlikely to be severely dehydrated. If you are unsure what to do, don’t hesitate to reach out to your child’s pediatrician for guidance about your next best steps.
What causes severe dehydration?
Dehydration happens when you lose more fluids than you take in. Severe dehydration means that your body doesn’t have enough water to function properly. And this puts your organs at risk for becoming damaged. This is even more concerning if you have a condition that makes it hard to drink fluids to recover.
Severe dehydration can be caused by:
Vomiting or diarrhea: Either of these can cause you to lose a lot of fluid in a short amount of time. And if vomiting or diarrhea persist, it can be hard to drink enough fluid to make up for what your body is losing.
Heat: You lose more fluids through your sweat, when it’s hot out. This makes you more prone to dehydration. And depending on the circumstances, severe dehydration can happen without obvious sweating.
Vigorous exercise: The more intense your exercise is, the more fluids you lose. Fluid loss is even more of a concern if you exercise vigorously on a hot day. This leaves you at an even higher risk for severe dehydration.
Not drinking enough: For most people, dehydration will trigger their natural thirst drive. But some people — like babies and people older than 65 years — have a weaker thirst instinct. This is part of the reason they are at high risk for severe dehydration.
Medications: Certain medications can lead to dehydration. For example, diuretics make you pee more. And laxatives can make you lose more fluids from your intestines.
Medical conditions: Some health conditions — like kidney disease and diabetes — can sometimes make you urinate more often.
Can you rehydrate without an IV?
People often assume that if they go to the ER for dehydration, they will need to receive intravenous (IV) fluids. This is when fluids are given through a needle placed in the vein. But not everyone who goes to the ER for dehydration will need IV fluids.
Healthcare professionals in the ER can determine if you need IV fluids by:
Assessing your vital signs: Dehydration can affect your vital signs. People who are severely dehydrated may have a higher heart rate and lower blood pressure.
Doing a physical exam: They will look for things like dry or elastic skin, poor circulation in your hands and feet, and general mental status.
Performing blood tests: An electrolyte panel is the best way to assess your overall hydration.
Monitoring symptoms: Someone who is actively vomiting will be more likely to need IV fluids, since drinking fluids isn’t a good option.
But if your dehydration seems mild or moderate, the ER physician may start by offering you an oral rehydration solution. This involves drinking a liquid that has a good balance of sugar and electrolytes — it’s not purely water. Oral rehydration treatments are especially helpful for children. And it spares them needing an IV placement.
How can you treat dehydration at home?
If you think you might be dehydrated, but aren’t yet showing signs of severe dehydration, you can try to hydrate at home. There are several ways to do this:
Make your own oral rehydration solution: Making a homemade rehydration solution is especially helpful if you are dehydrated from vomiting or diarrhea.
Drink frequent, small sips of fluid: If you have been vomiting, your stomach might not tolerate large amounts of fluid, all at once. Instead, start small and drink frequently.
Drink all kinds of fluids: Remember that you’re not limited to water. You can rehydrate with fluids like soup broth, juice, coconut water, tea, or milk. In fact, these types of fluids are often more helpful in replenishing your electrolytes.
Eat hydrating foods: Eating water-rich foods like watermelon or grapes can help you rehydrate faster. Popsicles are also a great option, especially for kids. And soup is another great way to hydrate with extra nutrients and electrolytes.
How can you prevent dehydration?
You can prevent dehydration by making sure that you drink enough fluids for your body. While that might sound easy, you might not notice subtle signs your body needs more fluids. To prevent dehydration, you should:
Drink regularly rather than waiting until you are really thirsty.
Drink more than usual when you’re exercising, feeling sick, or in hot weather.
Eat hydrating foods.
Notice if your urine is darker than usual, and start drinking more fluids.
Frequently asked questions
It can take anywhere from hours to days to recover from dehydration. It depends on what caused the dehydration, and its severity. Recovering from mild dehydration typically takes 2 to 3 hours after fluid replacement. Recovery from moderate dehydration can take a full day or more. And recovery from more severe dehydration can take several days.
If someone passes out from dehydration, you should call 911 or take them to the nearest ER. Fainting isn’t always a medical emergency, and doesn’t necessarily mean someone has severe dehydration. It can also just happen from a small drop in blood pressure when someone stands up. But to be safe, it’s best to get medical help if someone is dehydrated and passes out. Especially if they don’t immediately regain consciousness.
The bottom line
While dehydration is common, severe dehydration can be harmful to your body. That’s why it’s important to know when to go to the ER for dehydration. Pay attention to certain symptoms — like confusion or dark urine — that can mean your dehydration is becoming severe. If you go to the ER, it doesn’t mean that you’ll definitely need IV fluids. But it does mean that you’ll be in the best of hands to figure out what treatment your body needs.
Why trust our experts?
References
Aghsaeifard, Z., et al. (2022). Understanding the use of oral rehydration therapy: A narrative review from clinical practice to main recommendations. Health Science Reports.
Canavan, A., et al. (2009). Diagnosis and management of dehydration in children. American Family Physician.
Carlton, A., et al. (2015). The effects of fluid loss on physical performance: A critical review. Journal of Sport and Health Science.
Daley, S. F., et al. (2024). Pediatric dehydration. StatPearls.
Kenney, W. L., et al. (2001). Influence of age on thirst and fluid intake. Medicine & Science in Sports and Exercise.
Li, S., et al. (2023). Hydration status in older adults: Current knowledge and future challenges. Nutrients.
Taylor, K., et al. (2025). Adult dehydration. StatPearls.
