Dehydration and Hydration


Laura Pole, RN, MSN, OCNS, BCCT Senior Researcher

Read more


Nancy Hepp, MS, BCCT Project Manager

Read more

Last updated April 22, 2021.


All of us need to stay hydrated every day—it’s essential to life and good health. Dehydration can cause a whole collection of health impacts:1

  • Increased frequency of headaches
  • Dizziness
  • Fatigue
  • Dry or flaky skin
  • Constipation
  • Difficulty swallowing
  • Reduced muscle strength, power and endurance
  • Mental status changes (impaired mood, concentration, attention and focus, reaction speed, short-term memory) and even delirium
  • High blood pressure
  • Kidney stones

Preventing dehydration is important to everyone, but especially for people with cancer. Hydration is widely recommended within both conventional and complementary approaches to cancer care.

Signs of Dehydration

Mild or moderate dehydration Severe dehydration
  • Thirst
  • A dry or sticky mouth or a swollen tongue
  • Fatigue or weakness
  • Irritability
  • Dizziness
  • Nausea and vomiting
  • Headaches
  • Constipation
  • Dry skin
  • Weight loss
  • Dark yellow urine or a decrease in urination
  • Extreme thirst
  • Low blood pressure
  • Fever
  • Rapid heartbeat
  • Lack of urination for more than eight hours
  • Sunken eyes
  • Inability to sweat
  • Inability to produce tears
  • Disorientation or confusion

Conditions That Can Cause Dehydration

  • Uncontrolled vomiting or diarrhea
  • Loss of appetite and changes to the way things taste, which may affect how much you eat and drink
  • Extended time in a hot environment
  • Vigorous exercise causing you to sweat

Hydration and Cancer

Highlighted Videos

Bladder Cancer Advocacy Network presents "Hydration during cancer treatment"

Dianne Zipursky Quale, Dr. Jill Hamilton Reeves, and BCCT Senior Research Laura Pole discuss eating healthy with bladder cancer, including hydrating.

People with cancer need to pay extra attention to staying well hydrated.

For people with cancer, dehydration may cause your treatment to be delayed until you can be rehydrated, so staying hydrated is an important consideration in  your treatment. Adequate hydration can also reduce some treatment side effects.

“Good hydration helps flush toxins out of the body and reduce treatment side effects, such as nausea, weakness, constipation and fatigue.”2

If you are having surgery, chemotherapy, radiation therapy and other treatments, you need to be extra attentive to your hydration:

  • Diuretics prescribed to treat high blood pressure and several chemotherapy drugs are designed to increase urination, so taking them may put you at increased risk of dehydration.
  • Some drugs can damage the kidneys and the bladder, and adequate hydration reduces the risk of that damage.
  • Toxic by-products of some drugs, as well as those released by dying cancer cells, need to be flushed from the body, and an adequate supply of liquids is crucial.
  • The surgical stress response as well as surgical complications can upset the balance of your fluids and electrolytes, so staying well hydrated both before and after surgery is important (being sure to follow your medical care team’s directions).
  • During treatments such as surgery and intravenous (IV) chemotherapy, IV fluids will hydrate you. But when the IVs are removed, you’re in charge of hydrating yourself.
  • If you have a fever or gastrointestinal problems such as nausea, vomiting, diarrhea, or difficulty swallowing, hydration is especially important.

Even if you are keeping up with your liquid intake goals, you may develop problems that cause you to lose more fluid than you’re able to take in, resulting in dehydration. Know what problems can cause dehydration, what to do if you have any of these problems, the signs of dehydration (above) and when to call your doctor.

Hydration and Surgery

Surgery, Gout and Hydration 

Recent surgery and dehydration are both risk factors for a gout attack. See advice on preventing and managing gout attacks:

While the recommendation formerly was to stop fluid intake several hours before surgery, updated guidance permits and even encourages clear liquids until two hours before surgery.

National anesthesia guidelines from the United Kingdom recommend drinking clear liquids until two hours before the start of anesthesia (but keeping a six-hour fast for solid food).3 Glucose-containing solutions before surgery show benefits:4

  • Decreased thirst, anxiety and hunger before surgery
  • Reduced loss of protein and muscle mass
  • Improved insulin resistance and nitrogen balance following surgery
  • Accelerated recovery and shorter hospital stay

Studies have found that hydration before surgery can decrease the perception of pain.5

More information on hydration and surgery:

How to Hydrate

Food, Water and Plastic Containers

Concern has arisen about the movement (leaching) of chemicals in plastic from dishes and containers into the foods and liquids they hold. Enough evidence is available to advise caution.

Read more

An ounce of prevention, and about 64 ounces of fluids every day goes a long way to prevent dehydration. A simple reminder is “Drink before you’re thirsty.” 

Here are some tried and true tips from on staying hydrated:6

  • Drink lots of fluids. 

Read more

  • Eat foods with high water content. 

Read more

  • Get help managing side effects.

Read more

  • Don't wait to drink. 

Read more

  • Avoid foods and drinks that may contribute to dehydration. 

Read more

Highlighted Video

A short video showing the water content of some fruits and vegetables.

More Tips

Additional tips on calculating and tracking your fluid intake if you’re having trouble staying hydrated:

Read more

Overhydration: What Happens if I Take in Too Much Liquid?

Everything in moderation, 
with a touch of consideration 
for what your body needs for adequate hydration.

It’s possible to take in more liquids than your body can handle, which can cause unpleasant and sometimes even serious problems. Normally, your kidneys can excrete up to one liter (about four cups) of total fluid per hour. Keep in mind you get fluid not just from what you drink but also from foods. It’s possible to exceed your kidneys’ capacity. If your kidneys are impaired at all, then you will become overhydrated even more quickly. 

Problems of overhydration:

  • Stomach discomfort from taking in more volume than it can handle
  • Swelling in your tissues (edema) and 
  • Fluid overload on your heart and lungs
  • Diluted electrolytes in blood, especially sodium (hyponatremia), can cause problems ranging from fatigue and weakness to confusion and—most seriously—convulsions.10

View All References

More Information

Enter your comments or questions below.

Comments (0)

Allowed tags: <b><i><br>Add a new comment: