One hallmark of dehydration is the dreaded dehydration headache. When you have a dehydration headache, it means your body has lost too much water. The solution seems obvious. Just wrap your lips around the nearest water spigot and let it rip! Right?
Wrong. As with most health-related things, it’s not that simple. Dehydration is just one star in a vast galaxy of headache causes. Maybe you’re not dehydrated. It could be sleep deprivation, hypoglycemia, sodium deficiency, or the side effects of a supplement or medication.
But even if dehydration is the cause of your headache, you shouldn’t be cavalier with your rehydration strategy. If you glug too much plain water, you may fix one problem but cause another. For example, you may cause an acute sodium imbalance.
If you follow my work, you know I worry more about exercise-associated low blood sodium (hyponatremia) than about dehydration. Unlike dehydration, low sodium is routinely fatal to elite endurance athletes—a population routinely encouraged to drink plain water beyond thirst.
Sadly, hyponatremic people are often treated as dehydrated people because the symptoms (including headache) are similar. And since drinking more water dilutes blood sodium levels (the leading cause of exercise-associated hyponatremia), the results of this mix-up can be tragic.
Later, I’ll share a hydration strategy to remedy your dehydration headache while also preventing blood sodium dilution issues. I’ll also dive deeper into the causes of headaches, the dangers of overhydration, and the importance of electrolytes. First, though, let’s get synced up on dehydration.
To be dehydrated is to have lost water from your body. Dehydration typically begins at a 1% loss of total body water, though it generally isn’t considered “severe” until the losses exceed 5%.
Along with headaches, the most common dehydration symptoms are dark urine, low urine volume, thirst, dry skin and lips, fatigue, muscle cramps, constipation, nausea, dizziness, fainting, rapid heartbeat, low blood pressure, and impaired mood. For me, the critical dehydration indicators are thirst and urine. If you’re thirsty and peeing amber, you probably need more fluids. The other symptoms are less specific.
It’s helpful to lump the causes of dehydration into two main buckets:
- Inadequate fluid intake
- Excessive fluid losses
The first cause is rare among healthy adults. Why? Because healthy adults tend to have a working thirst mechanism and 24/7 access to fluids. When you get thirsty, the water bottle is never far away.
Older folks aren’t always so lucky. Mobility issues, medications, and impaired thirst regulation largely explain the higher dehydration rates in older people. When it’s more difficult to get to your water source and you don’t regularly feel thirsty, it’s less likely that you’re drinking sufficient water.
The second bucket (heavy fluid losses) includes causes like:
- Excess sweating due to climate, activity, or skin issues
- Urinary water losses due to diuretic drugs, kidney disease, high blood sugar (hyperglycemia), Addison’s disease, and other conditions
- Diarrhea, vomiting, laxatives, and other GI-related water losses
- Respiratory fluid losses from asthma or COPD
With that background established, let’s double-click on headaches.
Is Dehydration Causing Your Headache?
The headache is a frustrating and nonspecific symptom. It can be challenging to pinpoint its cause, especially while your head is throbbing and you have work due.
Yes, it could be dehydration. But if you’re not thirsty and your urine is light in color and relatively transparent, it’s probably something else.
What else could it be? Well, how long do you have? I could write my next book on possible headache causes, but since I value spending time with my lovely family, this list will have to do.
Possible Headache Causes
- Medication or supplement side effects
- Lack of sleep
- Low blood sugar
- Brain inflammation from infection, head injury, or other conditions
- Electrolyte disturbances (especially low sodium)
- And many more
As you can see, determining the cause of your headache may take some sleuthing. Now, let’s move forward assuming that you’ve ruled out those causes and determined that dehydration is to blame.
The popular recommendation is to guzzle fluids like a thirsty lion at a watering hole. Just fix the dehydration as fast as possible, right? But there are consequences to this “one-size-fits-all” approach to rehydration.
The Danger of Overhydration
When you drink plain water beyond thirst, you dilute blood sodium levels. Dilute them far enough, and you’ll develop a dangerous low sodium condition called hyponatremia.
The symptoms of hyponatremia include headache, fatigue, cramps, confusion, brain damage, seizures, and occasionally death. What’s the most common lifestyle-related cause of low serum sodium? Overhydration.
The problem lies with aggressive rehydration strategies propagated by organizations like the American College of Sports Medicine (ACSM). The ACSM tells athletes to drink not to thirst, but on a set schedule to prevent water loss.
Many marathoners who follow this strategy find themselves in a lethargic daze as they stagger across the finish line. They’ve sapped their sodium levels by slugging plain water every few miles. Read Waterlogged by Tim Noakes for an illuminating tour of this problem.
Preventing dehydration shouldn’t be the goal anyway. A little exercise-induced dehydration is healthy and normal. Dehydrated athletes, it’s been shown, perform similarly to hydrated peers, and they stop exercising at lower body temperatures. Contrary to popular belief, dehydration does NOT cause heatstroke.
It makes sense through the evolutionary lens. Do you think our ancestors always had water on long treks through the hot plains? How would they carry it? Maybe in a bison bladder if they were lucky enough to have one, but more commonly, they just endured temporary dehydration.
Fortunately, we don’t have to go thirsty. We can replace fluids as needed, but we should be careful to replace electrolytes too.
Electrolytes and Fluid Balance
Your body is about 60% water weight, but that doesn’t mean water is all you need to stay hydrated. You also need electrolytes.
Electrolytes are minerals that can carry a charge in your body. These minerals also help regulate water distribution in your blood, organs, and other tissues. Maintaining this system (called fluid balance) is the goal of healthy hydration.
The electrolytes sodium and potassium are essential for fluid balance. Sodium regulates fluid outside cells, and potassium regulates fluid inside cells. Both are important for hydration, but I’ll be focusing on sodium today because:
- You lose significant sodium through sweat.
- Overhydration with plain water dilutes sodium (not potassium) levels.
- Low sodium can cause headaches. (Just like dehydration!)
- Most health-conscious people are super skinny on sodium.
That’s right. If you eat a whole foods diet with plenty of greens, you’re probably getting a decent hit of potassium. Beyond the salt shaker, however, that same diet provides very little sodium.
If you’re keto or low-carb, you REALLY need more sodium. Carb restriction suppresses the hormone insulin, increasing urinary sodium losses. The truth is, “keto flu” is usually a case of “low sodium flu.”
And a dehydration headache is often a low sodium headache. Let’s talk about solutions now.
Dehydration Headache Remedies
If you have a headache, the first step is to figure out the cause. Let’s assume your urine is dark and your thirst is raging—both signs of a dehydration headache. What should you do?
#1: Drink to thirst
Thirst is the lynchpin of your fluid balancing system. Let’s geek out on how it works.
When your blood volume drops due to dehydration, sensory molecules called osmoreceptors detect the problem. The osmoreceptors then relay the message to your brain (specifically, the hypothalamus), making you thirsty. Then you take a drink, restore fluid balance, and thirst dissipates.
As you’ll recall, drinking beyond thirst can lead to hyponatremia. Drinking to thirst prevents this unfortunate condition while ALSO preventing most cases of dehydration.
#2: Stay salty
Are you getting enough salt? If you eat a whole foods diet, you probably aren’t.
Without sodium from processed foods, hitting 4–6 grams of sodium per day takes effort. Why 4–6 grams? Because that’s what most people need to meet baseline needs, plus it’s correlated with the lowest risk of heart problems in high-risk patients. Conversely, the FDA’s 2.3-gram limit is correlated with higher blood pressure and more heart problems. For the sake of our health, we need to get this one right.
For reference, 4–6 grams of sodium equals 2–3 teaspoons of salt. That’s why I recommend liberal salt shaking.
#3: Drink electrolyte water
I also recommend consuming electrolytes (especially sodium) with your water. When you drink electrolyte water, you consume fluids and electrolytes simultaneously. It’s a neat little solution to both dehydration and overhydration.
Speaking of electrolyte water, I have to mention LMNT, my tasty sugar-free electrolyte drink mix. Unlike other brands, LMNT contains enough sodium to move the dial. (A whole gram per stick.) This noticeable difference—noticeable in performance, mood, energy, and fewer symptoms—is why pro athletes from Bradley Beal (NBA) to team USA Weightlifting now use LMNT to stay hydrated.
I’ll conclude with my golden rule of hydration. The rule contains within it the most practical hydration info in the fewest possible words. And the rule is…
Drink electrolyte water to thirst.
Follow that rule and you’ll be in good shape to prevent and treat the dreaded dehydration headache. In fact, you’ll likely be able to feel the headache melt away when you give your body what it needs. Try it out and let me know what you think. Stay hydrated, Stay Salty, and thanks for reading.