An Indiana mom of two died after her family says she developed water toxicity from drinking too much water.Devon Miller told WRTV Indianapolis that his sister Ashley Summers was on a boat with her husband and two daughters and felt like she was dehydrated. The 35-year-old reportedly complained of having a headache and feeling lightheaded. So, she drank a lot of water in a short period of time.“Someone said she drank four bottles of water in 20 minutes,” Miller said. “I mean, an average water bottle is like 16 ounces, so that was 64 ounces that she drank in a span of 20 minutes. That’s half a gallon. That’s what you’re supposed to drink in a whole day.”Summers went home after her boating trip but passed out in her garage — and never regained consciousness. She was taken to the hospital where she died from what the family was told was water toxicity. “It was a shock to all of us. When they first started talking about water toxicity. It was like, this is a thing?” Miller said. While it doesn’t happen often, doctors say that water toxicity is real. Here’s what you need to know about this scary — and sometimes fatal — condition.What is water toxicity?Water toxicity actually goes by several names — hyponatremia, water intoxication, water poisoning, and overhydration. The big challenge with water toxicity is its impact on levels of sodium, one of your body’s key electrolytes, said Dr. Russ Kino, an emergency medicine physician and medical director of the Weingart Foundation Emergency Department at Providence Saint John’s Health Center in Santa Monica, Calif. Sodium helps your nerves, muscles, and other body tissues work properly, and it’s important for maintaining your blood pressure, the U.S. National Library of Medicine explains. What are the symptoms of water toxicity?“If you drink too much water too rapidly, you dilute the electrolytes in your blood and, in particular, the sodium,” Kino said. “That leads to the movement of water into cells in your brain, and your brain swells up.” This swelling can cause “major problem” with your brain, he said. That can lead to a slew of potential symptoms, the Cleveland Clinic says, including: Muscle cramps or weakness Nausea and vomiting Low energy Headache Altered mental statusIn severe cases, water toxicity can lead to seizures, coma, and death, said Dr. Edward W. Boyer, an emergency medicine physician specializing in medical toxicology, at The Ohio State University Wexner Medical Center.How much water does it take to cause toxicity?This is a little tricky to figure out. “There’s no rule of thumb, other than listen to your body,” Boyer said. “If you’re not thirsty, you usually don’t need to drink more fluids.”The U.S. National Academies of Sciences, Engineering, and Medicine recommends that women aim to take in 11.5 cups of fluids from food and water a day and that men should strive for 15.5 cups. However, you may need to take in a little more than usual if it’s a hot day or if you’re sweating a lot, Boyer said.Boyer continues that factors like your body size, whether you tend to sweat a lot, the level of activity you’re doing, and humidity levels can all be variables. “But your body is pretty good at telling you when you need more water—you’ll get thirsty,” he said. Kino stresses the importance of listening to your body. “Be mindful of how much you’re drinking and drink until you’re satisfied,” he said. “Then stop. Don’t try to overcompensate.”What causes water toxicity?Water toxicity is usually caused by taking in too much water, Kino said. However, the Cleveland Clinic points out that, less commonly, you can lose too much sodium from your body, leading to hyponatremia. Those causes can include: Taking diuretics. These can increase the amount of sodium you pee out. Drinking too much alcohol. This can cause you to pee more and lose fluid from throwing up. Having untreated diarrhea. This may lead to dehydration and lowered sodium levels. Using certain medications. Some drugs like selective serotonin reuptake inhibitors (SSRIs) and carbamazepine (Tegretol) raise your risk of hyponatremia.Boyer stresses that people shouldn’t be scared to drink water for fear of getting water toxicity. “It’s a pretty rare event,” he said. Still, Kino said it’s a good idea to be aware that this can happen. “Your thirst is a good guide—pay attention to it,” he said.