When someone asks me how to stay hydrated, my short answer is to drink electrolyte water to thirst. That’s the golden rule of hydration, and it would make a sweet bumper sticker (for hydration nerds like me, anyway). I’ll give you my longer answer and the science behind it today, but first, let me explain the golden rule.
The thirst part is crucial. Your thirst system is designed to optimize fluid intake; listening to it and drinking to thirst, not beyond, works for most folks to stay hydrated (the exceptions being older age and some medical conditions, which can disrupt the thirst mechanism). Hydrating this way simultaneously prevents dehydration and overhydration, allowing you to feel and perform your best.
The other part is electrolytes. Electrolytes like sodium, potassium, and magnesium support the balance of water in the body that keeps your cells, organs, and the circulatory system functioning. Beyond that, they also support energy production, cellular communication, and bone health. When you get enough electrolytes, you feel the difference. A few years back, bumping up my electrolytes made me feel about 20 years younger on the jiu-jitsu mat. Nobody mistook me for a 25-year-old (dang!), but I sure felt like one.
Follow these principles, and you’ll be hydrating like a pro. Keep reading to geek out on fluid balance, how much water to drink, the science of electrolytes, and hydration strategies.
What Does It Mean To Be Hydrated?
We throw around the word “hydration” a lot, so let’s define it to get on the same page. Hydration means maintaining fluid balance in the body. To get a picture of how this works, think of your body as a vehicle for water molecules. Water enters the body when you drink it or eat food containing water (like cucumbers and watermelon). Water exits the body through urine, sweat, breathing, and feces. A key goal of healthy hydration is to keep the gains and losses roughly equivalent, avoiding too little or too much water in the body.
Much of this fluid balancing system is automatic. Thirst regulates water inputs, while the brain, kidneys, and hormones (like vasopressin) regulate water outputs. Your body constantly strives to balance the two sides of the water ledger. An optimal balance keeps your blood flowing, brain floating, sweat glands sweating, and more.
Electrolytes such as sodium, potassium, and magnesium also influence fluid balance, and your body seeks to balance their inputs and outputs, too. For example, if you don’t consume enough sodium, your body secretes sodium retention hormones like aldosterone and norepinephrine (these hormones may explain why salt restriction brings side effects like elevated baseline heart rate that are detrimental to long-term heart health). As with fluids, your body is trying to balance the electrolyte ledger.
To summarize, staying hydrated is a matter of getting enough fluids and electrolytes so the inputs and outputs stay roughly balanced. Let’s talk about how to calibrate fluid inputs.
How Much Water Should You Drink?
To stay hydrated, you should consume enough liquid to replace the water exiting your body, thus maintaining fluid balance. The best way to accomplish this goal is to drink to thirst.
Thirst is a well-calibrated mechanism. Receptors in your brain continuously monitor your blood’s volume and sodium concentration. Low blood volume and high blood sodium are signs of insufficient water in the body — both alert the receptors to trigger thirst. Then you drink, fluid balance is restored, and thirst fades.
Two things can go wrong if you don’t drink to thirst:
- If you don’t drink enough, you don’t replace the fluids you’re losing (dehydration)
- If you drink too much, you can overwhelm the body with too much fluid (overhydration)
Let’s review each of these hydration problems.
#1: Losing too much fluid (dehydration)
Dehydration means net water loss from the body. You become dehydrated if you lose more water than you consume — from, say, sweating without adequately rehydrating.
The most common dehydration symptoms include headaches, fatigue, muscle cramps, weakness, dry mouth, dark urine, and decreased urinary volume. Being dehydrated also makes your heart work harder during activity, impairing exercise performance. Read our performance hydration article to explore this topic.
Generally, people who drink to thirst avoid dehydration. Athletes may become temporarily dehydrated during and after training, but drinking to thirst eventually restores the balance. An exception is older adults. These folks can have impaired thirst mechanisms and more difficulty accessing fluids, so they may want to sip electrolyte water throughout the day. Learn more here.
#2: Gaining too much fluid (overhydration)
Drinking to thirst doesn’t just prevent dehydration. It also prevents overhydration, or consuming too much water. Overhydration dilutes blood sodium levels, making it harder for sodium to support life-sustaining functions (like cellular communication).
Many overhydration symptoms — headache, fatigue, muscle cramps, weakness — overlap with dehydration symptoms, so diagnosis can be tricky. Elite endurance athletes often hydrate to prevent dehydration while ignoring the perils of overhydration. The mix-up can be dangerous and, in rare but extreme cases, fatal (this is a speculative piece, but it’s possible the martial arts icon Bruce Lee may have died from over consumption of water, underconsumption of electrolytes).
But most cases aren’t extreme. Most folks who drink plain water to replace sweat loss feel “off” or “low energy” throughout the day. I’ve been there! Drinking to thirst partly solves this overhydration problem, but you must also replace electrolytes.
Why You Need Electrolytes for Hydration (Especially Sodium)
Electrolytes are the other component of healthy hydration, playing an important role in helping balance those fluid gains and losses.
Sodium is an essential mineral for regulating fluid balance outside cells. Sodium lends volume to blood plasma, which helps maintain the blood pressure that allows blood to circulate and nourish tissues.
Sodium also primes the sodium-potassium pump, a protein in every animal cell that helps nerve impulses fire and allows cells to communicate with each other (this communication allows us to think, move, and breathe). Learn more about the pump here.
The electrolyte potassium complements sodium’s role, supporting the sodium-potassium pump, and also regulating fluids inside cells, which helps cells maintain their volume and function properly. Learn more about potassium here.
Magnesium is another electrolyte that indirectly affects fluid balance by helping regulate heart contraction, which of course moves blood throughout the body. It also supports over 300 enzymatic reactions. Learn more about magnesium here.
But if you have to pick one electrolyte for hydration, pick sodium. That’s the primary electrolyte lost through sweat and the most important to include in rehydration fluids. Read our guides on sweat rate and sweat sodium concentration to learn more about replacing sweat losses from exercise, or check out our Sodium Intake Calculator for some quick math. The simple rule, though, is to drink salty fluids to thirst.
Tips for Staying Hydrated
Now that we’ve covered the two halves of hydration (water and electrolytes), let’s review practical tips to keep your hydration system running smoothly.
#1: Drink to thirst
I know you get it by now: Drink to thirst! Drinking to thirst (and not beyond) keeps your fluids balanced, preventing dehydration and overhydration.
#2: Get enough electrolytes through diet
Aim for science-backed daily ranges of 4–6 grams of sodium, 3.5–5 grams of potassium, and 400–600 mg of magnesium through diet and other sources. We have a whole guide to electrolyte-rich foods to help you hit those targets, and this article explains what influences electrolyte needs.
#3: Enjoy electrolyte drinks
While diet is the first place to start with filling in electrolyte deficiencies, it can be difficult to consume enough sodium, potassium, and magnesium solely through food and the salt shaker. That’s where electrolyte drinks can help fill in the gaps.
Sodium is the electrolyte that can be most lacking in a whole foods diet. That’s why we designed LMNT Drink Mix and LMNT Sparkling to deliver 1 gram of sodium in each stick pack and can, in addition to 200 mg of potassium and 60 mg of magnesium.
Before signing off, let’s repeat the hydration mantra: Drink electrolyte water to thirst. You’ll feel the difference when you get your fluid balance right. Stay Salty and hydrated, everyone.
