By: Mike Harlos MD, CCFP(PC), FCFP

What is dehydration?

Dehydration is a condition that results from the excessive loss of water from the body. Diarrhea and vomiting are two of the most common causes of dehydration. Some medications can also reduce body water by increasing urine production. These drugs are called diuretics and are sometimes referred to as 'water pills'.

When people are nearing death, it is quite common for them to drink smaller and smaller amounts of fluid. Dehydration may occur even without being caused by any specific complication or medication. Many health care providers specializing in end-of-life care believe that people can be comfortable with small sips of fluid or ice chips, and may not experience thirst in the same way that healthy individuals do.

Causes of dehydration

Water is a vital component of the body. It plays a critical role in the proper functioning of the different body systems, such as the production of urine in order to remove toxins. There are many complex processes involved in maintaining the proper balance of body water. The body can sense how much fluid needs to be taken in to keep this balance, and the sensation of thirst is triggered when more fluids are needed.

Generally, dehydration is part of the normal process of the body shutting down at the end of progressive serious illness, and is a factor in the natural cycle of changes that occur as death nears.


What happens when people become dehydrated?

  • People become weak, and take in less fluid. They become even weaker, and tend to sleep more, resulting in even less fluid intake. This cycle continues over a matter of days or weeks, and is part of the dying process.
  • Because the mechanism that triggers the sensation of thirst is often weakened in advanced serious illness, people generally do not feel thirsty as long as the mouth is kept moist. So although dehydration is a common and natural part of the dying process, “dying of thirst” is not.
  • Normally, the kidneys try to save water when a person is dehydrated. Less urine is produced, and the urine becomes darker and more concentrated. If the body cannot spare enough water to allow the kidneys to remove toxins from the body, then the kidneys will start to fail and shut down.
  • The toxins, which are the normal by-products of the ongoing functioning of the body, will build up and contribute to the overall weakness and sleepiness of the person.


Sorting out symptoms

To determine possible causes of dehydration, the health care team will often ask questions, conduct a physical examination, or order some tests. This will help them to make decisions about how best to manage the dehydration.

Questions from the health care team

The medical team may ask some of the following questions in order to understand to what extent the patient is dehydrated, and what might possibly be causing it:

  • Has there been a change in the amount of fluid (water, juice, popsicles or ice chips) that the person is drinking?
    • If so, when did that change happen?
    • Is less fluid being taken in, or is there increased thirst and drinking?
  • If there have been difficulties drinking fluids, what are they related to?
    • Too weak to drink or suck from a straw?
    • Too sleepy to drink safely?
    • Can’t seem to swallow well. Just holds fluid in the mouth, or chokes and coughs when trying to swallow?
    • Tries to swallow, but everything seems to get stuck on the way down?
  • Is there nausea and/or vomiting?
  • Has the urine changed?
    • Less urine or more urine?
    • Has the colour changed (darker and more concentrated, or lighter)?
  • How have the bowels been functioning?
    • Is there diarrhea? Constipation?
    • Has there been any output at all… stool or gas?
    • Is there bloating?
    • Is there any pain or discomfort in the abdomen?
  • What medications are being taken?
    • Diuretics? (“water pills”, which can increase water loss)
    • Laxatives? (which can cause diarrhea)
    • Steroids? (such as dexamethasone, prednisone, which can cause blood sugar to rise, and which may result in increased urination and water loss)
    • Opioids? (may have by-products that build up when someone is dehydrated)
  • What are the effects of the person drinking less fluid?
    • Have there been any disagreements between the patient and family members about fluid intake?
    • Are there feelings of depression, sadness, or frustration because of the amount of fluids being taken in?
    • Sometimes family and friends are more concerned about this lack of fluid intake than the person who is experiencing it. How much concern does the patient have about not drinking much?

Physical examination

Certain physical clues (such as dry mouth) can help determine if dehydration is present, and how severe it is. Since dehydration can be caused by many different problems, the health care professional will usually do a general physical examination. The exam may provide some ideas about what could be causing the problems, and will help guide decisions about tests that may be needed.


Usually, blood tests are done to help confirm that dehydration is present, and to help assess how severe it is. Other tests may be considered, depending on what is suspected after asking questions and the physical examination.

Managing dehydration

The topic of dehydration and its management is one of the more controversial issues in palliative care.

  • Some consider dehydration a normal part of the dying process that should be left to run its natural course, and that treating dehydration only serves to prolong dying.
  • Others may view dehydration as an easily treatable condition, whose correction may improve alertness, communication and interaction with loved ones, and general well-being.
  • Still others consider it unethical to withhold fluids, even if it means that fluids must be given by administering fluids continuously into a vein (intravenous) or under the skin (hypodermoclysis) in a person who is near death.

There are different reasons for these conflicting approaches to dehydration:

  • There is no clear and strong scientific evidence to guide an overall approach to dehydration in the palliative care setting.
  • Cultural, religious, and ethical/moral considerations may influence the views of patients, families, and health care providers about whether withholding fluids is ever appropriate.

As with most decisions about care in advanced illness, each situation should be approached individually, reviewing the wishes of the patient and family, the overall goals of care, the scientific evidence for different treatment choices, and potential burdens and benefits of the existing options.

When treating dehydration may help

There are specific circumstances in which treating dehydration has the potential to significantly improve quality of life and overall well-being.

  • Confusion (delirium)
    Dehydration can result in a build-up of toxins and medications when there is not enough water to help the kidneys remove them from the bloodstream. This can result in delirium, which is upsetting and difficult for everyone involved. Giving fluids may allow increased alertness and more clear thinking, and improved ability to interact with others.
  • Opioid side effects
    Opioid medications can build up in the body, particularly when someone is dehydrated. This can result in delirium, and irritation of the nervous system which may cause muscle twitching and possibly seizures. Giving fluids sometimes helps the kidneys clear these medications.
  • Nausea, vomiting and diarrhea
    These digestion problems can often be helped once the cause of the symptom is found and treated, but in the meantime, the symptoms may lead to dehydration. Dehydration often makes nausea and vomiting worse, resulting in a cycle of further dehydration. When the health care team is trying to reverse the problem that is causing nausea, vomiting or diarrhea, giving fluids by infusion intravenously or under the skin should be considered early.
  • High calcium levels in the blood
    Sometimes cancer causes a high level of calcium in the bloodstream, which results in increased sleepiness and confusion. High levels of calcium can eventually be fatal. There are times where, through discussion with the patient and/or family of all factors involved, a decision is made to not treat the high calcium. However, if treatment is chosen, administering fluids is an important part of the management of high calcium.

TIP: Let your health care team know if you are experiencing nausea, vomiting or diarrhea. Early treatment of these symptoms can help to reduce the severity of dehydration.

When the benefits of treating dehydration are unclear

There are a couple of situations where the evidence is not clear as to whether fluids are helpful or harmful.

  • Thirst
    It is not clear from studies whether dehydration in people with advanced illness causes thirst. In those who are unconscious, it is very unlikely that a sensation of thirst can be felt. In people who are awake but unable to drink, it is generally thought that maintaining a moist mouth with vigilant mouth care is the most effective approach to relieving thirst. However if this is not effective, it is reasonable to try administering fluid into a vein intravenously or under the skin.
  • Congestion in the lungs when death is near (“death rattle”)
    Some health care providers may feel uncomfortable administering fluids when congestion is present. They may argue that fluids will only worsen the build-up of secretions in the lungs. However, there is no strong evidence to support this concern. The secretions are the result of pooled collections of mucus rather than water, except in the circumstance of heart failure. There are times when such secretions can be quite substantial even though no fluids have been given for many days.

Some families (and health care providers) feel that it is never ethical to withhold fluids, or perhaps doing so is not consistent with their faith. These concerns may be very strongly held. Heath care teams involved in decision-making have every reason to respect differing points of view on this question, as there is not sufficient evidence that administering fluids worsens congestion.
See alsoHealth Care Directives

What you can do

When someone who is dying is drinking poorly and becoming dehydrated, family and friends often feel helpless and want to “fix” the problem by improving the person’s fluid intake. We hope the sick person will feel better, get better, and even live longer as a result of drinking more.

However, towards the end of serious illness, it is quite common for people to drink smaller and smaller amounts of fluid. Dehydration may occur even without being caused by any specific complication or medication. Many health care providers specializing in end-of-life care believe that people can be comfortable with small sips of fluid or ice chips, and may not experience thirst in the same way that healthy individuals do.

Talk to the health care team

When discussing concerns about fluid intake with your health care team, it may be helpful to consider these questions:

  • Who is actually concerned? Often the person who is ill is less concerned about fluid intake than family and friends. The wishes and goals of the patient should direct the approach to care.
  • What do you think the patient would want?
  • What will happen with and without fluids being given?
  • What can be done to ensure comfort and relief of the sensation of thirst, no matter which choice is made?
  • Are there safety concerns about swallowing? Your health care team may be able to suggest ways to help swallowing to reduce the risk of aspiration into the lungs (“going down the wrong way”).
  • How complicated and burdensome will it be to treat dehydration? For example, would transfer to hospital from home be required?
  • What is the evidence that giving fluids will help the problem at hand or achieve the goals of care?

If possible, the best approach to drinking is to let the person with the illness make the decisions about what to drink, when to drink or whether to drink at all.

Family members are sometimes asked to decide whether or not fluids should be given to a loved one who is dying, can no longer swallow, and cannot direct the health care team in what to do. This decision is made even more difficult if there is no health care directive, and if the wishes of the patient to guide the decision are unknown.

This can be a very challenging and distressing situation, as it may feel that the choice is between letting death occur without doing anything – not even giving a drop of water and perhaps prolonging the dying. Neither seems like a good option.

There is actually no evidence that giving fluids to a person who is imminently dying will prolong the dying process. If family members are unsure about the decision to give fluids, it is usually best to lean towards giving rather than withholding; there seems to be less likelihood of looking back with regret for what might have been done.

Make taking fluids easier

  • Offer people fluids they enjoy – water, juice, jello, popsicles or ice chips. Avoid juices high in acid, such as orange juice, as they may irritate the mouth.
  • Have a variety of fluids available. People may change their fluid preferences often.
  • Offer a straw for drinking. One advantage of drinking from a straw is that straws are less likely to cause choking than cups, as they can more easily deliver small amounts.
  • Do not give fluids to people who are not able to swallow safely.
  • Do not force someone to drink.
  • Offer small, frequent sips of fluid rather than a whole cup at one time.
  • When someone is too weak to swallow, provide mouth care to keep the person’s mouth moist and comfortable.

Care for the mouth

Some people will be able to brush teeth, floss, and rinse their mouth as normal.

See also: Care of the Mouth

How often should the mouth be checked for dryness?
Mouth care should be done at least three or four times a day, or even every hour or two if the mouth is very dry. People taking medication under the tongue should have their mouths moistened frequently; otherwise, the medication may not be properly absorbed.

Other factors that may contribute to dry mouth
Sometimes people are only able to breathe comfortably through the mouth. These people may find that their mouths are especially dry. Certain medications can also be very drying to the mouth.

What your health care team can do

Giving fluids (rehydration or sometimes simply hydration)

The health care team will consider several different options for giving fluids:

  • By mouth
    Oral rehydration can be effective if fluids can be swallowed and ‘kept down’. Giving frequent sips of water or a commercial preparation such as Gatorade®, Powerade®, or Pedialyte® can maintain hydration. Generally, the goal is to drink one to two litres per day but it is important not to ‘force fluids’ if a person does not feel like taking them.

  • Intravenous
    Fluids can be given through a small plastic catheter placed into a vein. This is the most common route of fluid administration in hospitals if the oral route is not used. This option may or may not be available in other settings (for example at home, in a hospice or personal care home).
  • Under the skin (subcutaneous)
    Using small needles known as butterfly needles, or, preferably, using small plastic catheters placed under the skin, fluids are administered by continuous infusion into the tissues under the skin, which are then absorbed into the rest of the body. This method is called hypodermoclysis, (or simply clysis). This method can be useful when it is difficult to find veins for intravenous infusions and may be more readily available in settings outside of the hospital.

Care when fluids are not given

Health care providers have noted that patients can be very comfortable even if they drink very little fluid. These people may experience a dry mouth, or the occasional feeling of thirst. However, such symptoms are usually easily managed with sips of fluid, ice chips, and regular mouth care.

Content reviewed May 2019

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