Hydration and Electrolytes: The Science Behind Balance and Performance

• Hydration is about balance. Your body works best when water intake equals output. Adequate hydration keeps your cells happy and all your organs functioning.
• Electrolytes are crucial for our health but adding them into our beverages is context-dependent.
• One size doesn’t fit all for water needs. The “8 glasses a day” rule is an oversimplification. Factors like exercise, climate, body size, and diet mean your optimal intake could be quite different from someone else’s.
• Understanding hydration and electrolytes can help you make smarter choices about your fluid intake and maintain electrolyte balance year-round.

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Staying hydrated is essential for life—our bodies are mostly water, and we can only survive a few days without it (Popkin et al., 2011). Yet there’s a lot of confusion about how much water we really need, what dehydration actually means, and whether we really need those fancy electrolyte drinks. Especially with the hot summer season upon us, it's important to break down the biology behind hydration and electrolytes in an accessible way. We’ll explain what hydration and dehydration mean for your body, what electrolytes like sodium and potassium do, and when electrolyte-enhanced beverages might (or might not) be helpful.

Hydration vs. dehydration: keeping the water balance

Hydration simply means having enough water in your body for it to function properly. In physiology, hydration status is essentially a balance between water input and output—what we consume through drinks and food versus what we lose through urine, sweat, breathing, etc. (Rebelo-Marquez et al., 2024). When this balance is maintained, cells and organs operate optimally. This hydration and electrolyte balance is critical for physical and mental performance.

Water makes up about 60% of the average adult’s body weight, and it’s vital for things like regulating body temperature, digesting food, transporting nutrients, and cushioning joints (Shaheen et al., 2018). In other words, being well-hydrated helps your body run smoothly.

Dehydration occurs when your body is losing more water than it takes in. In practical terms, dehydration is a drop in your total body water content, which can result from losing fluid (i.e., through sweating, diarrhea, or urine) without adequate replacement, generally not drinking enough, or a combination of the two (Taylor & Tripathi, 2025; Beck et al., 2021). Common signs of dehydration include dry mouth, fatigue, headaches, and poor concentration.

Even mild dehydration can have effects. Losing as little as 1–2% of your body weight in water (for a 150 lb person, that’s about 3-6 cups of water loss) may impair mood, concentration, and physical performance (Gopinathan et al., 1988; Adan, 2012; Magee et al., 2016). If you’ve ever felt tired or had trouble focusing on a hot day before you remembered to drink water, that could’ve been why.

More significant dehydration (e.g. >3–4% body weight lost) can lead to thirst, dry mouth, headache, dizziness, and reduced exercise capacity. In extreme cases, it causes low blood pressure or confusion. But in everyday life, mild dehydration is much more common.

Think of dehydration as an imbalance—your body’s water tank is getting low, and that impacts how everything functions. Maintaining hydration and electrolyte balance helps prevent these common symptoms.

It's worth noting that your body tries hard to avoid this imbalance. We have built-in safeguards like thirst (your brain’s way of nudging you to drink) and hormones that regulate urine output. For example, when you’re dehydrated, your pituitary gland releases antidiuretic hormone (ADH), telling your kidneys to conserve water (Taylor and Tripathi, 2025). That’s why your urine gets darker and more concentrated when you’re not drinking enough. These mechanisms are effective—but not perfect, especially if water loss is rapid or you ignore thirst.

What are electrolytes and why do they matter?

We can’t talk about hydration without talking about electrolytes. You’ve probably seen those electrolyte drink mixes that claim to hydrate you better than water. So, what are electrolytes and do we need them to supplement our water?

Electrolytes are minerals in your body that carry an electric charge, including sodium, potassium, chloride, magnesium, and calcium. They’re essential for life, helping muscles contract, your heart beat, and nerves send signals. We get them from food and drink, and our bodies work hard to keep them in balance, especially during physical activity.

Here’s what the key electrolytes do (Shrimanker and Bhattarai, 2023):

Do we need electrolyte drinks to stay hydrated?

The short answer is: it depends.

While hydration needs vary based on activity, sweat rate, diet, and health status, we lose some electrolytes through normal daily functions like urination. These losses increase more significantly during bouts of diarrhea or vomiting. The most common way we can lose electrolytes, however, is through sweating. Let’s take sodium as an example. Generally, when you sweat, you lose more water than salt—but the exact composition of your sweat varies. Factors like how much you’re sweating, your diet, and how acclimated to the heat you are all play a role, and these differ widely from person to person (Orrú et al., 2018). The intensity of your workout will affect this, too.

To replenish sodium after physical exertion, The American College of Sports Medicine recommends a drink with 0.5–0.7 grams of sodium per liter of water for workouts over 1 hour (or 300-600mg of sodium per hour of exercise) (Convertino et al., 1996).

For reference, many of the electrolyte drink mixes are at or above the 1 gram per liter if mixed according to the stick pack. So, unless you're participating in especially intense and long duration exercise at particularly high temperatures, it’s unlikely that you will require that level of sodium replenishment.

Your body does a great job of balancing electrolytes through diet and kidney function. For most healthy people, eating a balanced diet provides plenty of electrolytes, and any excess is filtered out by the kidneys to maintain the right levels. Problems like electrolyte imbalance can arise when you lose electrolytes and water but you only replace the water at rapid rates.

So, let’s get back to the main question. Sports drinks and electrolyte-enhanced beverages are marketed as the key to optimal hydration, but are they really needed for the average person? The nuanced answer: usually no, but sometimes yes. It depends on context. To put it simply: if your activity is short or moderate, plain water is likely sufficient. If you’re doing high-intensity exercise for a prolonged period of time, losing fluids from illness or extreme temperature, then consider fluids with electrolytes. And even then, while sports drinks and electrolyte packs are convenient, they’re also often overkill; you don’t necessarily need a high-end product to solve this problem. Some people make their own DIY electrolyte drink (a pinch of salt and a bit of sugar or juice in water), and maybe eat a banana (for potassium) along with water. The important part is getting some salts and sugars in when you’ve lost a lot. But for a normal day at the office or a 60-minute gym session, regular water and a balanced diet will more than handle your electrolyte and hydration needs.

The truth about the “8 glasses a day” rule

We’ve all been given the advice to drink 8 glasses of water a day. But this popular rule—also called the "8x8 rule" (eight 8-ounce glasses)—is more a guideline than a fact. Research shows that a one-size-fits-all number doesn’t make sense because hydration needs vary a lot from person to person and day to day.

A 2022 study published in the journal Science measured daily water turnover (how much water people use and replace per day) in over 5,000 individuals worldwide and found that needs ranged from ~1 liter to nearly 6 liters per day—even up to 10 liters in extreme cases (Yamada et al., 2022). Why such a huge range? Because hydration needs depend on a lot of factors, including:

So, how much water should you drink?

The bottom line is that hydration needs are individualized. The best approach is to listen to your body and adjust based on environmental conditions, sweat rate, and your level of physical activity. Your thirst mechanism kicks in before you’re seriously dehydrated—it’s your body’s natural prompt to drink more. If you pay attention to signs like dark urine or dry mouth, you’re likely meeting your daily hydration needs. But as with everything, balance is key. While it’s much more rare, overhydration (too much water) can cause problems too, so don’t go overboard!

Rather than counting cups obsessively, it’s better to understand the factors that change your fluid needs and adjust accordingly—drink more on hot or active days, and don’t worry if you drink a bit less on a day spent mostly indoors. Science and years of research back this nuanced view: one size does not fit all.

Quick pause while we take a sip of water

Ah, much better!

Staying well-hydrated is about maintaining the right fluid and electrolyte balance for your body’s needs. It’s not complicated—drink when you’re thirsty, more when it’s hot or you’re active, and make sure to replenish electrolytes during extreme sweat or sickness. By applying hydration science and listening to your body, you can stay ahead of dehydration and perform at your best.

Quick tip: You should carry a water bottle if it helps remind you to sip throughout the day, and include water-rich fruits and veggies in your diet.

By understanding the science of hydration, electrolytes, and listening to your body’s signals, you can keep your system in balance and better support your health—no magic number of water bottles per day required. Stay hydrated, stay healthy, and if this blog hasn’t convinced you yet, here’s a gentle reminder to go fill up that water bottle!

This article is for informational purposes only and does not constitute medical advice. The information contained herein is not a substitute for and should never be relied upon for professional medical advice.