When your body loses more fluids than it takes in, dehydration and its many potentially serious consequences can follow. But keeping up with your fluid consumption and responding quickly to the first signs of trouble can help you avoid a dehydration headache, dizziness, and various cognitive problems, as well as the other health risks associated with dehydration.
“I tell patients even mild dehydration can cause cognitive, mood, and physical symptoms, which differ depending on age/sex/health status,” says Massachusetts General Hospital psychiatrist Simmie Foster, MD, PhD, whose research interests include the effects of extreme temperatures on the body, mind, and mood.
What Is a Dehydration Headache
A dehydration headache is a response to insufficient fluid intake. It can be an early symptom of dehydration when fluid losses occur through heat exposure, exercise, sauna use, illness, or simply inadequate fluid intake over the course of a day, Dr. Foster says.
You may be more sensitive to pain because dehydration has caused an electrolyte imbalance, which affects nerve signaling. A drop in fluid levels also may cause brain tissue to contract slightly, putting pressure on pain receptors in the membranes surrounding the brain.
What Does a Dehydration Headache Feel Like?
Dehydration headaches and tension-type headaches can feel very similar. Both are typically described as bilateral (on both sides of the head), non-throbbing, and mild to moderate in intensity. Dehydration headache symptoms can worsen with movement. Simply bending over, walking, shaking your head, or standing up quickly can intensify the pain.
“By contrast, classic tension-type headaches are generally not aggravated by routine activity. Dehydration headaches are also frequently accompanied by other signs of inadequate hydration, such as thirst, fatigue, irritability, difficulty concentrating, or lightheadedness.”
A dehydration headache is just one signal that you need to restore the fluid balance in your body. Other warning signs of dehydration include:
- Dry mouth and lips
- Lightheadedness
- Trouble concentrating
- Increased irritability
- Urine changes (darker urine or urinating less frequently)
Dr. Foster notes that in older adults, dehydration symptoms also may include confusion, sleepiness, worsening memory, and unsteadiness or falls. And while increased thirst is a common sign of dehydration—though you may be getting dehydrated well before you notice you’re thirsty—the thirst sensation can decline with age. “Older adults should not rely on thirst alone,” Dr. Foster says.
She adds that many studies show that dehydration’s clearest cognitive effects, when they occur, involve attention, executive function (ability to think and plan), motor coordination, short-term memory, and reaction time. “Dehydration can lead to increases in anxiety, irritability, fatigue, and depression, even earlier than the physical symptoms associated with dehydration, such as decreased urination, headache, lightheadedness,” Dr. Foster says. “In one study, for participants exposed to heat to induce mild dehydration, supplying fluid intake of as little as 300 milliliters—about 10 ounces or a little more than a cup—improved some of the cognitive and other symptoms.”
What Causes a Dehydration Headache?
Dehydration headache causes stem from insufficient fluid intake or excessive fluid loss. “A dehydration headache often develops after a clear period of fluid deficit,” Dr. Foster says. It can be as simple as not drinking enough fluids. Also, conditions and behaviors that lead to excess fluid loss can cause a dehydration headache. Sweating, spending time in the heat, and illness (especially if it includes vomiting and/or diarrhea) can also rob you of the fluids you need to stay properly hydrated.
“The brain is highly sensitive to changes in hydration because water balance affects blood volume, salt concentration, temperature regulation, and blood flow to the brain,” Dr. Foster explains.
A way to gauge that you have a dehydration headache and not a tension headache is how you respond to fluids. Dr. Foster explains that in a landmark study of water-deprivation headaches, most participants experienced substantial improvement or complete resolution within 30 minutes to three hours after drinking water. “That improvement with rehydration is something not typically seen with a primary tension headache,” she says. “From a practical standpoint, if someone develops a headache after prolonged heat exposure, a workout, a sauna session, travel, or a day when they’ve had little to drink, dehydration should be high on the list of possibilities. A simple trial of rehydration is often the quickest way to determine whether inadequate fluid intake is contributing to the symptoms.”
How to Treat a Dehydration Headache
Dehydration headache treatment involves the same strategies to address other dehydration symptoms. Start by drinking water slowly. Understand that you may need a couple of cups of water to feel better. If you’re dehydrated because you’ve been sweating a lot, try an electrolyte-packed sports drink, such as Gatorade. And if you are becoming dehydrated after vomiting or diarrhea, an oral rehydration solution, such as Pedialyte, may be best.
Over-the-counter pain relievers, such as ibuprofen or acetaminophen, might provide some dehydration headache relief. Just be sure you don’t have a health condition or take other medications that would make pain meds unsafe.
How Long Does a Dehydration Headache Last?
The duration of your headache will depend on the severity of your dehydration and how quickly you restore your fluid levels. If you start consuming fluids and become more hydrated, your dehydration headache could resolve in 30 minutes to an hour.
If you don’t start replenishing with fluids, your dehydration headache and other symptoms could linger. And if you’re drinking water, but your headache isn’t going away, you may need medical attention. Dehydration can land you in a hospital emergency room, where you’d be given fluids intravenously.
How to Prevent Dehydration Headaches
Of course, the best strategy is to avoid dehydration in the first place. The simplest way to lower your risk of dehydration is to make fluid intake routine. Drink with meals, keep water visible and easily accessible, add fluids after exercise or sauna/heat exposure, and increase intake during fever, vomiting, diarrhea, or hot weather, Dr. Foster recommends. Eating foods with high water content such as soups, fruit, vegetables, and yogurt are also helpful.
The National Academies of Sciences, Engineering, and Medicine recommend a daily intake of 3.7 liters of fluids (about 125 ounces) for healthy adult men and about 2.7 liters (around 91 ounces) for women. Those recommended amounts include beverages and foods with high water content. The recommendations are a little less for older men and women. And it’s especially important for people with health issues such as heart failure, kidney disease, and low sodium problems to get specific guidance, as those conditions often demand fluid restrictions.
Dehydration can sneak up on you, so be mindful of things like thirst, feeling flushed, and changes in urine color. If your urine is darker than normal, it could be a sign that you need to hydrate.
You should also be mindful of circumstances that can lead to dehydration. In hot weather, take breaks to cool off and rehydrate. If you are exerting yourself with exercise or other physical activity, keep drinking fluids. It’s better to drink smaller amounts of fluids frequently rather than a large amount at once, especially for older adults.
And if a dehydration headache or other symptom develops, stop what you’re doing and get into a cool location, if possible, and slowly drink more fluids—consider drinking an oral hydration solution (designed specifically for rehydration, not a sports drink which may have excess sugar). If you feel faint or experience a rapid heart rate or rapid, shallow breathing, call 911. Severe dehydration is a life-threatening medical emergency, but it’s one that can often be avoided by prioritizing your fluid intake.
When to See a Doctor
If a dehydration headache doesn’t improve, even with your hydration efforts, see a doctor or visit a local urgent care center. If you experience confusion or other severe dehydration symptoms, such as fainting or vomiting, seek emergency medical attention immediately.
Like any medical issue that comes on suddenly, a dehydration headache and other dehydration symptoms should be taken seriously. They indicate an underlying health problem that should be evaluated and treated, if necessary.
