By Michael J. Critelli | MakeUsWell Newsletter, 

Recently, I had my routine periodic dental checkup here in Naples, FL. The technician told me that I appeared to have a “dry mouth,” and needed to refine the fluids I was ingesting. My physician advised me to increase the amount of electrolytes in my water or to increase them in some other way. This was a real eye opener for me, as it might be for others.

For decades, we’ve been told a simple rule of thumb for hydration: drink eight 8-ounce glasses of water a day. The familiar “64 ounces” guideline is easy to remember and generally helpful. But like many health slogans, it oversimplifies a more complex physiological reality—especially for people living or working in hot and humid environments like Florida.

In these conditions, hydration isn’t just about replacing water. It’s about replacing what we lose when we sweat. And that includes electrolytes.

What Happens When We Sweat

Sweating is the body’s primary cooling mechanism. As sweat evaporates from the skin, it carries heat away, helping regulate core body temperature. But sweat isn’t just water. It contains electrolytes—primarily sodium, along with potassium, chloride, and smaller amounts of magnesium and calcium.

In mild conditions, electrolyte losses are modest. But in high heat and humidity, even in more temperate climates, sweat rates can increase dramatically. In summers in tropical or subtropical climates, it’s not uncommon to lose a liter or more of sweat per hour during outdoor activity. Over the course of a day, that can translate into substantial electrolyte depletion.

If we replace those losses with plain water alone, we dilute the remaining electrolytes in the bloodstream. That imbalance can impair normal physiological function, even if total fluid intake appears adequate.

What Electrolytes Actually Do

Electrolytes are minerals that carry an electric charge. They play essential roles in:

• Regulating fluid balance inside and outside cells
• Supporting muscle contraction, including the heart
• Enabling nerve signaling
• Maintaining stable blood pressure

Sodium, in particular, helps the body retain the fluid we drink. Without enough sodium, water passes through more quickly, increasing urine output and reducing effective hydration.

This is why athletes, outdoor workers, and people exposed to sustained heat often feel weak, dizzy, fatigued, or mentally foggy even when they are “drinking plenty of water.”

The Limits of the 64-Ounce Rule

The 64-ounce guideline was never meant to be a universal prescription. It does not account for:

• Body size and muscle mass
• Physical activity level
• Environmental temperature and humidity
• Sweat rate
• Individual variation in electrolyte loss

In hot, humid climates, hydration needs increase—not just in volume, but in composition. Drinking more water without addressing electrolyte loss can be inefficient or even counterproductive.

This is particularly relevant for older adults, who often have a diminished thirst response, and for people taking medications that affect fluid balance.

Florida and other Tropical Climates: A Special Case for Hydration

Florida’s climate, along with other tropical climates in which we might spend significant time, creates a perfect storm for electrolyte imbalance. High temperatures increase sweat production, while high humidity reduces evaporation efficiency. The body sweats more to achieve the same cooling effect, accelerating fluid and electrolyte loss.

People who spend time outdoors, walking, tennis (my primary outdoor sport), golfing, gardening, working, or exercising, may unknowingly enter a cycle of chronic mild dehydration or electrolyte deficiency. The symptoms are often subtle: fatigue, headaches, muscle cramps, irritability, or reduced exercise tolerance. These are easy to attribute to “just the heat,” but hydration composition is often part of the story.

When Electrolytes Make Sense

Electrolyte supplementation isn’t necessary for every glass of water or for sedentary days in air-conditioned environments. But it can be beneficial when:

• You are sweating heavily for prolonged periods
• You are outdoors in heat and humidity
• You engage in endurance exercise or physical labor
• You experience frequent muscle cramps or fatigue in the heat
• You drink large volumes of water and still feel under-hydrated

Electrolytes can come from lightly salted foods, broths, or purpose-designed hydration mixes. The goal is balance, not excess sugar, not megadoses of minerals, and not replacing all water intake with sports drinks.

A More Nuanced Hydration Message

A better public health message might be:

“Drink enough fluids to stay hydrated—and replace electrolytes when heat, humidity, or physical activity increase your losses.”

This framing respects human physiology and environmental context. It acknowledges that hydration is dynamic, not static. And it helps people avoid the false reassurance that simply hitting a water quota guarantees optimal hydration.

The Bottom Line

Water is essential. But in hot and humid environments like Florida, water alone may not be enough. Electrolytes help the body use the water we drink, maintain fluid balance, and support normal muscle and nerve function.

The old 64-ounce rule isn’t wrong—it’s just incomplete. As our understanding of hydration deepens, so should our guidance. In the heat, smarter hydration means thinking not only about how much we drink, but about what we’re replacing when we sweat.