Dehydration Headaches: Symptoms, Treatment, and Prevention

By Edo Paz, MD
Medically reviewed checkmarkMedically reviewed
April 10, 2021

Most people will suffer from a headache at some point in their life but luckily some common types of headaches, such as dehydration headaches, can be treated easily and avoided in the future. In this article, you will learn the symptoms of a dehydration headache, get tips on headache treatment, find out how long your dehydration headache will last, and learn when to speak to a doctor.

What Is Dehydration?

The old adage, “you are what you eat” could more accurately be said, “you are mostly what you drink.” About 60% of the average adult human body is made of water. Together with the right balance of electrolytes, water is therefore vital for our bodies to function properly.

Daily activities such as sweating and urinating cause the body to lose water. Usually, the amount of fluid lost is easily balanced through drinking or eating foods that contain lots of water. However, sometimes the body loses water faster than it can be replenished. This is especially true when you have symptoms like diarrhea and/or vomiting. When this happens, the body can become dehydrated. Mild dehydration happens when you lose up to 5% of your body weight through a loss of fluids. Moderate dehydration is when you lose between 6-10% of your body weight.

Check your symptoms for free

Talk with a doctor if necessary.

Start now

What Is a Dehydration Headache?

Dehydration headaches occur secondary to or as a complication of dehydration. Mild to moderate dehydration can cause headaches that can range from being relatively mild to severe headaches such as migraines.

Dehydration headaches may be caused by the brain temporarily contracting or shrinking due to the fluid loss. This action of the brain pulling away from the skull can potentially cause the pain of a dehydration headache. The volume of plasma in the blood vessels of the brain may also decrease since plasma has a high water component.

Dehydration headaches are relieved once the body is rehydrated and the brain returns to its normal size and state.

Causes of Dehydration Headaches

Dehydration can happen easily and for simple reasons. If you forget to drink enough water on a hot day, while exercising or during a hike, you could end up dehydrated. In some places, there may be no access to safe drinking water which can exacerbate the situation.

Other times, dehydration can occur because you’re sick. Even a relatively mild cold or sore throat can make you more susceptible to dehydration if you don’t feel like eating or drinking. Being sick with a fever can also worsen a situation where you are losing fluids and electrolytes through diarrhea and vomiting.

We lose fluid and electrolytes through four main ways:

  • Diarrhea: When you are sick and have severe acute diarrhea, this can cause a huge loss of water and electrolytes in a short amount of time.
  • Vomiting: Being sick and vomiting is also a way to lose fluid and electrolytes.
  • Sweating: When you are very active or are outside in hot weather, you sweat more and in turn lose more fluid. If the weather is humid, sweat can’t evaporate and cool you as quickly as normal, which causes your body to heat up and need even more fluids.
  • Urinating: Some conditions, such as undiagnosed or uncontrolled diabetes, can cause you to urinate more than normal. Similarly, certain medications, such as diuretics and some blood pressure medications, can also cause increased urination.

This loss of fluids and electrolytes can result in a dehydration headache.

Risk Factors for Dehydration

It is likely that everyone will experience at least mild dehydration at some point in their lives. Nevertheless, some people are at higher risk of getting dehydrated, including:

  • People with a chronic illness, such as diabetes or kidney disease, that causes increased urination
  • People who take medications that increase urine output
  • Infants and young children, because they are most likely to suffer from severe diarrhea and vomiting, have more frequent fevers and can’t always communicate their thirst
  • Older people who may struggle to conserve water and have a reduced sense of thirst

These factors can be further compounded by chronic disease and mobility problems that make it harder for them to get water for themselves such as people who:

  • Live in higher altitudes
  • Exercise and work outside
  • Live in hot climates

Dehydration Headache Symptoms

The pain from a dehydration headache can be located at the front, back, side, or all over the head. You will likely not feel facial pain or pressure, as you would with a sinus headache.

Dehydration can occur because thirst is not always a reliable early indicator of your body asking for water. In fact, there are many people, especially older adults, who don’t feel thirsty until they’re already dehydrated. Therefore, it is important to consciously drink more when you’re outside in hot weather or are sick rather than waiting until you feel thirsty.

Chronic dehydration symptoms include:


How to Get Rid of a Dehydration Headache

Since dehydration is the root cause of your headache, it is important to rehydrate as well as relieve the pain. Therefore, to treat the dehydration you should:

  • Drink more water by sipping small amounts frequently until symptoms subside
  • Drink a rehydration solution which is scientifically formulated to contain a balance of glucose and electrolytes to help your body rapidly rehydrate. These solutions are formulated based on the World Health Organization criteria for effective rehydration and are more effective than sports drinks, which often contain sugar and artificial colors and flavors.
  • Rest in a cool environment so that you can rehydrate without sweating

To treat the pain and get fast relief, you can take over-the-counter medications such as acetaminophen or ibuprofen.

Prevent Dehydration Headaches

Prevention is the best treatment for a dehydration headache. The simple act of remembering to drink enough water can allow you to avoid unpleasant headaches and any medical interventions. So plan ahead and make sure you have water with you and drink it in your everyday routine. This is especially important if you’re overweight, live in a warm climate, or are at a higher altitude. Make sure you hydrate in advance of any sporting or active event and see if you can avoid being outside during the hottest times of the day. Taking this proactive approach to prevention before you feel thirst is the best way to reduce the likelihood of suffering from a dehydration headache. Medical research has shown that drinking sufficiently can at least reduce the intensity and duration of dehydration headaches.

Some useful tips for ensuring that your body gets sufficient fluids include:

  • Drink enough water consistently throughout the day so that you never feel thirsty. Here is an online calculator you can use to see how much water you need to drink each day. It is calculated based on your weight and the amount of time you exercise.
  • Drink enough water so that your urine is light yellow or clear. Most people urinate between 6-8 times a day. However, if you’re drinking plenty, it’s not abnormal to go as many as 10 times a day.
  • Make sure you are drinking water or non-alcoholic drinks to hydrate. Drinking excessive amounts of alcohol can cause ‘alcohol dehydration’. This is because alcohol can reduce the body’s production of an antidiuretic hormone which acts to reabsorb water. If there is less of this hormone, more fluid than normal is lost from the body through increased urination.
  • Increase your water intake through eating more fresh fruit and vegetables. For tips on healthy eating, read more here.

Check your symptoms for free

Talk with a doctor if necessary.

Start now

How Long Does a Dehydration Headache Last?

Drinking water should make you feel better within about half an hour, although for some people it may take as long as three hours.

If you have a dehydration headache for days and it’s not relieved by drinking more water, it is time to talk to a doctor.

When to See a Doctor

If your dehydration is severe, you can’t keep fluids down, or your headache does not subside, home remedies may not be enough and you will need to seek medical help.

You or your companions will know your dehydration is severe if you are experiencing further symptoms, such as:

  • Lack of sweating
  • Sunken eyes
  • Fever
  • Delirium/confusion
  • Unconsciousness
  • Shriveled skin

These symptoms can lead to serious complications.

You should also talk to a doctor if you have dehydration headaches occurring more than occasionally, just to rule out other underlying causes.

How K Health Can Help

Did you know you can access online urgent care with K Health?

Check your symptoms, explore conditions and treatments, and if needed, text with a healthcare provider in minutes. 

K Health’s AI-powered app is based on 20 years of clinical data.

K Health articles are all written and reviewed by MDs, PhDs, NPs, or PharmDs and are for informational purposes only. This information does not constitute and should not be relied on for professional medical advice. Always talk to your doctor about the risks and benefits of any treatment.

Edo Paz, MD

Edo Paz is the VP of Medical at K Health. Dr. Paz has two degrees in chemistry from Harvard and earned his medical degree from Columbia University. He did his medical training in internal medicine and cardiology at New York-Presbyterian. In addition to his work at K Health, Dr. Paz is a cardiologist at White Plains Hospital, part of the Montefiore Health System. 

Close button

Have a headache? Talk to a doctor with K Health and find relief.

Start Now