Feeling Off? Dehydration Might Be the Hidden Cause
Fatigue, brain fog, and mood swings? You might just be dehydrated. Learn the subtle signs of dehydration and how staying hydrated supports overall health and well-being.
By Kim Sheffield-ChangAug. 7 2025, Published 11:35 a.m. ET
Feeling off? It might be dehydration
There’s a reason why you see colorful, trendy water bottles everywhere: Water is good for your body. But did you know it might also be the key to your emotional balance?
It’s easy to blame a bad mood on stress, lack of sleep, or having just a “weird day.” But there’s one common culprit that often flies under the radar: dehydration. It can cause irritability, fatigue, anxiety, and even foggy thinking. What’s worse, most of the time, people don’t even realize it’s happening.
It doesn’t take extreme heat or strenuous exercise to get dehydrated, either. Small drops in your body’s hydration levels can start to affect how you feel and how you think. Vivian Chung Easton, a mental health clinician at Blueprint, a therapist-enablement technology platform takes a closer look at what’s actually happening in your mind and body when you’re dehydrated and what changes you can make to your routine to meet your hydration goals.
Your Brain Runs on Water
Water is essential for your brain to function properly. In fact, your brain is made up of about 80% water, so even slight dehydration can throw that delicate system out of balance. That means things like mood regulation, memory, focus, and even decision-making can take a hit.
A study published in the “American College of Sports Medicine Health and Fitness Journal” found that a mere 1–2% drop in hydration is enough to cause declines in attention, short-term memory, and mood. And research from the University of Connecticut linked dehydration to increased tension, anxiety, and fatigue—feelings many chalk up to a bad night’s sleep or a long day. In short, your brain doesn’t just like water, it needs it to help you stay emotionally steady and mentally sharp.
The Subtle Signs You’re Underhydrated (That’s Not Thirst)
One of the trickiest things about dehydration is that you might not even feel thirsty when it starts. Thirst, it turns out, is a “lagging indicator” – which just means that your body is already running low on fluids by the time that signal kicks in. In the meantime, you might notice more subtle things like:
- Afternoon mood crashes
- Trouble concentrating
- Anxiety that feels “baseless”
- Headaches that come and go
- Feeling tired even after a full night’s sleep
According to a report in the “British Journal of Nutrition”, mood disturbances can show up before you feel any physical thirst. That means what feels like a rough emotional patch may just be your brain quietly asking for a glass of water.
Why You’re More Likely to Be Dehydrated in the Summer
If you’re feeling “off” this time of year, hydration could be an even bigger factor. Summer brings warmer temperatures, more time outdoors, and – for many people – less routine. Whether you’re traveling, adjusting to back-to-school season, or simply sweating more than usual, it’s easier than ever to fall behind on fluids. Here’s why:
- Heat = sweat loss: You lose more fluids (and electrolytes) in the summer, especially in humid conditions.
- Busy schedules = fewer cues: When your day looks different—due to vacation, back-to-school, or packed afternoons—you may forget to drink water altogether.
- Travel disrupts routines: Airport travel, road trips, and long days out can mean fewer breaks to drink water—and more reliance on dehydrating options like coffee or soda.
The result? Dehydration becomes a silent contributor to both physical fatigue and mental fog.
Busting Hydration Myths That Might Be Holding You Back
You don’t need to carry a gallon jug or obsess over water trackers to stay hydrated, but it’s important to examine some of the misconceptions around keeping your hydration levels up. Here’s a look at several common hydration myths that may be making it harder for you to stay consistent:
- “Coffee dehydrates you.”
Not exactly. While caffeine has a mild diuretic effect, moderate coffee intake still counts toward your fluid intake. - “Only plain water counts.”
Not quite – high-water foods like cucumbers, watermelon, and soups do contribute, as do drinks like herbal tea and milk. - “I drink when I’m thirsty, so I’m fine.”
Actually, thirst shows up late in the game—by then, you’re already a bit dehydrated. - “Everyone needs 8 glasses a day.”
That’s an outdated rule. Your needs vary depending on your activity level, body size, and even the climate you live in.
Bottom line: hydration doesn’t have to be rigid—but it does need to be intentional.
How to Drink More Water Without Thinking About It
So, what’s the easiest way to get and stay hydrated, whether water or electrolyte drinks, especially if you’re not in the habit?
You don’t need to overhaul your day. Mental health clinician Vivian Chung Easton shared a few low-effort tweaks that can help you stay hydrated consistently, without needing to count ounces or set timers. Try these simple strategies:
- Habit stacking: It takes about 21 days to form a habit – each time you repeat a behavior, you reinforce the neural pathway, which makes the behavior feel more automatic. For adding water or electrolyte drinks into your existing routine, pair your new hydration habit with something you already do – like having a glass right before your morning coffee, or with every meal. The key is consistency so that your brain has a better chance of making hydrating alongside your existing habits stick.
- Use visual cues: As the old saying goes, “out of sight, out of mind,” but that logic can be flipped to keep something on your mind – and in this case, water or hydration drinks like coconut water. Keep a glass in sight (perhaps by your laptop, nightstand, or toothbrush) as a reminder to hydrate throughout the day.
- Eat your electrolytes and minerals: Load up on fruits and vegetables that naturally are more water-dense to hydrate you and full of minerals your body needs.
- Set low-pressure goals: Set yourself up for success with realistic goals. Instead of aiming for drinking 10 glasses of water daily right away, just try adding one more glass than usual and work your way up from there.
- Upgrade the experience: If plain water bores you, try chilled, flavored, or sparkling options to keep it interesting.
It’s not about perfection—it’s about consistency. Think of water as something you give your body and mind throughout the day, like charging a battery.
Your Mood Might Just Need a Refill
When you’re not feeling like yourself, it’s easy to assume the worst: that something’s wrong, or that you need to push through. But sometimes, the answer is as simple as a little more water.
Paying attention to your body’s early signs, like headaches, irritability, and brain fog, can help you take better care of yourself without overthinking it. And while staying hydrated won’t solve everything, it’s a strong (and simple) foundation for both mental clarity and emotional resilience.
So next time you’re feeling off, take a moment to ask: Have I had enough water today? Your brain – and your mood – will thank you.
This story was produced by Blueprint and reviewed and distributed by Stacker.
