Preventing Dehydration During Cancer Treatment

Author: OncoLink Team
Last Reviewed: February 01, 2024

Dehydration is when there is not enough fluid in your body. Dehydration can be mild or very serious. Water makes up about 66% of your body. Proper hydration helps keep your body at the right temperature, deliver nutrients to your cells, fight infections, and helps to remove waste and toxins.

You should drink/eat 64 ounces of fluid a day unless you are told otherwise by your provider. If you have a heart condition you may be told to drink less. In some cases, the amount of fluid you should have in a day depends on your weight. If you have a fever, diarrhea, or vomiting you will need more fluids to replace the ones that are lost.

Symptoms of Dehydration

Dehydration can cause:

  • Fatigue.
  • Dry mouth.
  • Feeling light-headed.
  • Headaches.
  • Irritability.
  • Constipation.
  • Nausea.

What can I do to prevent dehydration?

You can track how much fluid you are taking in. This will help you figure out if you need to increase your fluid intake or find other ways to prevent dehydration. See the end of the article for conversions to help you track your fluids.

There are a few ways you can help prevent dehydration:

  • If it is very hot out, stay indoors.
  • If you are doing activities that cause sweat, make sure you drink extra fluids.
  • Protect your skin from sunburn. Sunburn can increase your body temperature and cause dehydration.
  • Wear loose, comfortable clothing during warmer times.
  • Eat food and drinks that contain sources of fluid. Foods that are liquid at room temperature can be counted toward your daily fluid goal:
    • Water (carbonated, still, or flavored). You can add fruit slices or juice to add taste.
    • Milk, flavored milk, and hot chocolate.
    • Decaffeinated coffee, tea, and soda. Caffeine can cause fluid loss.
    • Fruit or vegetable juice.
    • Sports drinks.
    • Soup, broth, stew.
    • Gelatin.
    • Ice cream, milkshakes, water ice, popsicles, and sorbets.
    • Nutritional supplements, such as Boost or Ensure.
    • Ice cubes and ice chips.

If you are having nausea, vomiting, or taste changes, try sucking on ice cubes and ice chips, and taking small sips of fluids often. These little bits of fluid can help you stay hydrated.

When to Contact Your Care Team

Even when doing your best, you may still become dehydrated. To manage dehydration, your care provider may suggest IV fluids. If you have any of the following symptoms of severe dehydration, contact your care team right away:

  • Feeling very thirsty or thirst that doesn't stop when you drink.
  • Less frequent urination.
  • Dark-colored urine.
  • A loss of more than 5% of body weight within one week.
  • Muscle cramps.
  • Lightheadedness.
  • Feeling more fatigued than normal.

If you are having trouble taking in as much fluid as you should, or you are having trouble staying hydrated, talk with your care team. 

Conversions to Help You Track Fluid Intake

  • 1 quart = 4 cups = 32 ounces = 960ml
  • 1 pint = 2 cups = 16 ounces = 480 ml
  • 1 cup = 8 ounces = 240 ml
  • 1/2 cup = 4 ounces = 120 ml
  • 1/4 cup = 2 ounces = 60 ml


Medline Plus. Dehydration.

NHS Inform. Dehydration. 2023. 

Reber, E. et al. 2019. Management of Dehydration in Patients Suffering Swallowing Difficulties. Journal of Clinical Medicine.

Scripps Health. 6 Simple Ways to Stay Hydrated. 2019.

VNS Health. Preventing Dehydration.


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