Some runners know a lot about the dangers of overhydration. They know how to avoid it, how to help others avoid it, how to recognize its symptoms, and what to do to treat it. Maybe they’ve even read Dr. Tracy Hoeg’s superb Running on Science column article, “Exercise-Associated Hyponatremia: The (Not So) Salty Truth.” But a lot of runners don’t know much about overhydration. Or what they think they know isn’t quite right. And severe overhydration, like severe dehydration, can have dangerous consequences.
Take the following 10-question quiz to see where you fall on hydration-genius spectrum. You’ll either confirm your expertise or you’ll learn something. Either way, you’ll finish feeling good about your ability to help others.
Overhydration (Hyponatremia) Quiz
Question 1. TRUE or FALSE: You can drink too much water during a run.
If you answered TRUE: Good job with an easy question! Move on to Question 2.
If you answered FALSE: Scroll down to the answers and read Answer 1.
Question 2. TRUE or FALSE: You can drink too much sports drink during a run.
If you answered TRUE: Nicely done! Move on to Question 3.
If you answered FALSE: Scroll down to the answers and read Answer 2.
Question 3. TRUE or FALSE: Salt supplements won’t prevent overhydration problems.
If you answered TRUE: Brilliant! Move on to Question 4.
If you answered FALSE: Scroll down to the answers and read Answer 3.
Question 4. TRUE or FALSE: Overhydration is common at marathons and ultramarathons.
If you answered TRUE: Superstar! Move on to Question 5.
If you answered FALSE: Scroll down to the answers and read Answer 4.
Question 5. TRUE or FALSE: You can tell that someone is overhydrated by looking at them.
If you answered TRUE: Scroll down to the answers and read Answer 5.
If you answered FALSE: You’re ultra-smart! Move on to Question 6.
Question 6. TRUE or FALSE: You can tell if someone is overhydrated by asking how much they’ve had to drink.
If you answered TRUE: Scroll down to the answers and read Answer 6.
If you answered FALSE: Your brain is huge! Move on to Question 7.
Question 7. TRUE or FALSE: You can tell if someone is overhydrated by asking how much they’ve peed.
If you answered TRUE: Scroll down to the answers and read Answer 7.
If you answered FALSE: Expert level! Move on to Question 8.
Question 8. It is difficult to distinguish between the symptoms of overhydration and dehydration.
If you answered TRUE: Scroll down to the answers and read Answer 8.
If you answered FALSE: Muy inteligente! Move on to Question 9.
Question 9. TRUE or FALSE: The treatment for overhydration is to stop drinking.
If you answered TRUE: Rock star! Move on to Question 10.
If you answered FALSE: Scroll down to the answers and read Answer 9.
Question 10. TRUE or FALSE: Overhydration is a much better name for being overhydrated than hyponatremia is.
If you answered TRUE: You are a genius! Tell your friends and then move on to the scenario. (Or read the answers and further confirm your brilliance before moving on to the scenario.)
If you answered FALSE: Scroll down to the answers and read Answer 10.
Overhydration Quiz Answers
Answer 1. It is definitely possible to drink too much water during a run. You’d think your kidneys would get rid of the excess fluid, but sometimes that doesn’t happen. Sometimes, a hormone is released that prevents you from peeing the excess fluid out. If you want to know more about how this hormone works and how exercise sometimes causes it to be released, read Dr. Tracy Hoeg’s, “Exercise-Associated Hyponatremia: The (Not So) Salty Truth.” (It’s so good!)
If you can’t pee off the excess fluid you’re taking in, it builds up. It dilutes your blood. Your cells swell. Ultimately, if you keep taking in too much fluid, your brain cells swell too. Seizures, coma, and even death can follow.
Answer 2. You can definitely overhydrate using sports drinks! Remember, they’re mostly water. The overhydration equation doesn’t change just because sports drinks contain electrolytes. If you drink too much fluid of any kind while you’re running, and a hormone gets released that prevents you from peeing the excess out, the fluid builds up. It dilutes your blood. Your cells swell. Ultimately, if you keep taking in too much fluid, your brain cells swell too. Seizures, coma, and even death can follow.
Answer 3. Salt supplements won’t prevent overhydration problems. Overhydration is a fluid-intake problem, not a salt-loss problem. You dilute your blood when you drink too much and you’re not able to pee out the excess. There’s the same amount of salt in your blood when you’re overhydrated as when you’re not; the salt’s just not as concentrated. Taking a sodium-tab to treat drinking too much water is like dumping a packet of salt in a freshwater lake and hoping for salt water. Sodium supplements won’t prevent or fix overhydration.
Answer 4. Mild and moderate overhydration is very common at marathons and ultramarathons. Here are three reasons why:
- Many runners believe they can’t trust how thirsty they feel to let them know how much and when to drink. They’ve been told they should drink a certain amount of fluid every hour. But how much fluid you need every hour depends on a lot of factors including your body size and the outside temperature. Drop the schedule and drink when you’re thirsty.
- The symptoms of overhydration are often confused with dehydration. Headache, weakness, and fatigue are common symptoms of mild and moderate overhydration. If you complain of these symptoms, your pacer, your crew, and the aid-station volunteers will usually assume you’re dehydrated. They’ll insist you drink more. You’ll probably figure they’re right and comply.
- It usually takes athletes four or more hours of exercise and consistent fluid intake to become overhydrated. That’s pretty much a description of what we’re doing during all ultras and a lot of trail marathons too. We’re set up to become overhydrated if we drink beyond our thirst.
Answer 5. No, you can’t tell whether someone is overhydrated by looking at them. You can’t tell whether they’re dehydrated either. Your skin is an unreliable diagnostic tool for all kinds of medical and environmental emergencies. Swelling and bloating is common with overhydration, but you won’t be able to look at someone and see that. You’ll have to ask questions to try to figure out whether a runner is overhydrated, “Do you feel bloated or swollen? Do your clothes feel tight? Does your watch band feel tight?” This symptom is not always present.
Answer 6. You usually can’t tell if a runner has had too much to drink simply by asking how much they’ve drunk. That’s because ‘too much fluid’ varies from person to person depending on body size, exertion level, and temperature. What’s too much fluid for me, a 100-pound female, is likely different than your ‘too much.’ And what’s too much fluid for me in Texas when it’s 90 degrees Fahrenheit is different than what’s too much for me in the mountains when it’s 40 degrees Fahrenheit. Sometimes, it’s quite clear when fluid intake is excessive. Other times, that number is just one piece of the puzzle. It’s important note how long the runner has been drinking that much fluid. It usually takes more than four hours of excessive drinking to become overhydrated.
Answer 7. You can’t rely on urine output to determine whether someone is overhydrated. Remember, overhydration is a problem because your kidneys can’t get rid of the excess fluid. You might not pee at all when you’re overhydrated, or you might just pee a little bit. Sounds a lot like dehydration, doesn’t it?
Answer 8. It’s actually easy to distinguish overhydration from dehydration. You can simply ask, “Are you thirsty?” If a runner is thirsty, they’re dehydrated. If they’re not thirsty, it’s something else. If they’re not thirsty and have the following symptoms, then they are likely overhydrated:
- A history of heavy water intake usually over four or more hours
- Headache
- Unusual weakness or fatigue
- Swelling and bloating
- Nausea and/or vomiting
Answer 9. The treatment for mild and moderate overhydration is to stop drinking. That’s it. You caused the problem by drinking too much. You can fix the problem by not drinking any more. Eventually your kidneys will kick in and get rid of the excess fluid.
If a runner is confused or has a decreased level of consciousness with a history of prolonged water intake, they need to be taken to a hospital as quickly as possible. Their brain is swelling, and they need an IV of highly concentrated saline solution to draw the fluid out of their brain.
Answer 10. Overhydration is a much better name for being overhydrated than hyponatremia is. Overhydration communicates both the problem and the solution. You drank too much. Stop drinking. Hyponatremia makes you think you’re dealing with a salt-loss problem. The word literally breaks down like this: ‘hypo’ = low, ‘natr’ = sodium, and ‘emia’ = blood. ‘Low salt in the blood.’ But remember, you haven’t lost salt. You’ve just diluted your blood by taking on too much water. It’s a relative salt loss. You don’t need more salt. You need to stop adding water.
Image: Semi-Rad/Brendan Leonard
Overhydration Scenario
You’re running Run the Red 120k in Wyoming. The course is gorgeous and the temperatures are in the low 70s Fahrenheit (low 20s Celsius). Gels upset your stomach during your last race, so this time, you’re planning to use a sports drink for your calories. You put 100 calories of drink mix in each of your 500-milliliter hydration flasks. Your plan is to take in 200 calories per hour. You’ve trained through the summer down in San Antonio, Texas (95 to 100 Fahrenheit or 35 to 38 Celsius) using this method, with great success.
Six hours into the race, you’ve got a mild headache, you’re nauseated, your fingers are swollen, and your watch feels tight on your wrist. Your shorts are also tight at the waist. You feel wrecked. You make it to the mile-30 aid station and share your woes with your crew.
Your crew thinks you’re dehydrated. Before they give you anything to drink, what can they ask to be sure you’re actually dehydrated?
They should ask, “Are you thirsty?”
You are not, so it’s not dehydration that’s causing you to feel so rotten.
What combination of questions could your crew ask to help them determine whether you’re overhydrated?
- “How much have you been drinking every hour?”
- “Have you urinated?”
- “Do you feel bloated or swollen? Do your clothes feel tight?”
You answer:
- You’ve been drinking one liter/hour for the past six hours.
- You have not urinated since you started running.
- Yes, your hands and wrists are swollen. Your shorts feel tight around the waist.
You’re showing classic signs and symptoms of mild to moderate overhydration.
Signs and Symptoms of Mild/Moderate Overhydration
- History of heavy water intake usually over four or more hours
- Headache
- Unusual weakness and fatigue
- Swelling and bloating
- Nausea and/or vomiting
Your friends tell you need to stop drinking until you start peeing again. They load you up with a peanut butter and jelly sandwich for calories and tell you they’ll meet you at the next aid station in seven miles.
You try to eat the peanut butter and jelly sandwich, but you just can’t stomach it. After a mile, you decide to go back to using the calories in your hydration flasks. By the time you get to the next aid station, you’re clearly disoriented. You’re convinced you’re at the finish line and you’re talking about getting into your car to get back to the Lander Bar.
Mental-status changes (confusion, disorientation, combativeness, or unconsciousness) signal how severe your overhydration is. Your brain is swelling. You need medical attention immediately.
Your crew asks for help from the aid-station volunteers. They’ve all taken a Wilderness First Aid class and know that severe overhydration (hyponatremia) like this requires rapid evacuation.
At the hospital, they carefully restrict fluids while adding salt to draw the fluid from your brain. You make a full recovery and are released later that day. You vow to return to Wyoming’s Red Desert next year.
Overhydration Key Take-Home Points
- Cause: Drinking too much fluid
- Treatment: Stop drinking
- Prevention: Use thirst to guide hydration
[Author’s Note: Learn more about caring for overhydration and other wilderness first-aid skills with a two-day NOLS course. Thank you to Tod Schimelpfenig, NOLS Wilderness Medicine’s Curriculum Director and author of NOLS Wilderness Medicine, for his guidance and oversight of this series. Thanks also to graphic artist Brendan Leonard, the trail and ultrarunner of Semi-Rad fame, for his graphics collaboration in this article series.]
Call for Comments (from Meghan)
- Were you taught at some point in the past to drink a certain amount of fluids per hour during long runs and races? Now that scientific understanding of hydration and overhydration has evolved and the recommendation is for us to drink only when we are thirsty, have you shifted your fluid intake? Does it work for you to drink when you are thirsty and stop when you aren’t?
- Have you experienced or seen symptoms of mild to moderate overhydration? What were the circumstances in which they came about?
