“If you’re thirsty, you’re already dehydrated” is a thought many people have as they fill up their water bottles or purchase a drink at the store ― but is it true?
No, not really, experts say. “The science shows that we start to get thirsty when we’ve lost 1 to 2% of our body water,” said Dr. Nate Wood, the director of culinary medicine at the Yale School of Medicine in Connecticut. Losing this amount of water generally doesn’t come with big health issues and can be easily fixed by drinking some fluids.
When it comes to dehydration, it becomes a problem when someone loses about 8% of their body’s water, said Dr. Philip Skiba, an associate professor and the medical director of Jefferson Health Sports Medicine in Philadelphia — not when they lose 1% or 2%. Early thirst cues are just your body cluing you into the fact that you could use some fluids.
Dr. Jordan Hilgefort, a sports medicine and family medicine doctor at the University of Louisville Health in Kentucky, agreed. Thirst is “maybe not necessarily a marker of dehydration, but perhaps is more aptly said as an early warning sign of impending dehydration.”
As we lose water, it’s only natural for our bodies to tell us to have more fluids, according to Wood. “But the body is really smart, and it would be really dumb if its thirst mechanism only kicked in after we were dehydrated,” Wood said.
The actual signs of dehydration include dry mouth, dry skin and lightheadedness.
While being thirsty isn’t a sign of dehydration, there are other red flags. According to Hilgefort, dry mouth, dry lips and dry skin are all signs of slight dehydration.
“When you think about things like dizziness, lightheadedness — those are big ones that start to come on when you can get pretty significantly dehydrated,” Hilgefort said. This is also true of headache and fatigue.
You can also look at the color of your urine. “It does give us a good way to gauge how well-hydrated you are and how much fluid intake you have or need to have,” Hilgefort said, noting that pale yellow urine is a sign of good hydration.
But if you do notice dry lips or darker urine than usual, don’t panic. “Being a little dehydrated is not a big deal, because you drink water and you have some Gatorade or whatever, and you get better,” Skiba said.
Once you drink some water and the sensation of thirst goes away “that’s a good gauge that, ‘Hey, I’ve at least started to drink and replete my fluid stores,’” Hilgefort explained.
Getting dehydrated repeatedly can lead to serious complications if it’s not handled.
Getting slightly dehydrated here and there likely won’t cause you many problems as long as you drink fluids to remedy the problem. However, if you repeatedly get dehydrated you could experience health consequences.
“The big thing that I think about with patients is chronic kidney dysfunction. Not just in the sense of how well the kidneys are working, but even in putting you at higher risk for things like kidney stones or urinary tract infections,” Hilgefort said.
On the other hand, drinking too much water can lead to kidney problems, too.
“Your kidneys, in particular, work to keep the blood sodium in a very, very tight range, because if it goes too high or too low, bad stuff starts happening,” Skiba said. This includes headaches and seizures. This is pretty rare, but can be seen in marathon runners, he said.
To keep a healthy amount of water in your system, it’s important to listen to your thirst cues; drink when you’re thirsty and stop when you’re not.
Hydration is important for our body’s most essential functions.
“Water is extremely important in the body. It’s used in metabolic processes, which keeps our cells functioning really, really well,” Wood said.
It also helps keep our blood pressure in a healthy range and ensures our organs get the fluid, nutrients and oxygen they need, he added. “Having an adequate amount of water in the body is really important for temperature regulation, too,” Wood said. Without it, heat stroke can happen.
Exactly how much water you need to drink each day depends on your body, climate, activity level and health conditions, all three doctors told HuffPost.
You’re probably familiar with the advice that says you should drink eight glasses of water, 8 ounces each, every day. This is a good place to start, according to Wood, but isn’t a hard-and-fast rule for everyone.
You may find you require a little less or a little more. “You can basically just drink every time you get thirsty. I think that’s a pretty reasonable thing to do,” Wood said. You can also use the color of your urine as a hydration clue.
For some people, a visit to the doctor can help determine how much fluid you should be drinking. Heart failure patients can’t have as much water as those without the condition, Hilgefort said, and athletes require more fluids than those who don’t exercise. More, being overly thirsty can be an early sign of conditions like diabetes, Skiba noted.
Feeling thirsty is a sign your body is doing what it needs to ensure you have the right amount of fluid in your system; feeling thirsty isn’t a reason to panic about your water consumption for the day.
Bottom line: “When you get thirsty, you’re not yet dehydrated, but if you ignore those thirst cues for a couple of hours, then you probably will start to feel the effects of true dehydration,” Wood said.