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Hydration and Cancer

During cancer treatment, it is very important that you stay hydrated. Water is needed for regulating your temperature and for removing wastes and toxins. The human body is made up of about 60% water. Every organ is dependent upon water for optimal functioning. Water and other fluids help you chew and swallow food to release the nutrients and often improves digestion. Even mild dehydration can cause some of the following symptoms: fatigue, dry mouth, lightheadedness, headaches, irritability, constipation and nausea.

What does dehydration mean?

  • Dehydration is a condition caused by excessive loss of body fluids. It occurs when your output of fluid exceeds fluid intake.
  • Infections, high fever, bleeding, or even something as simple as not drinking enough fluids can lead to dehydration.
  • Side effects of treatment such as vomiting or diarrhea can lead to dehydration.
  • Electrolytes, such as potassium and sodium, are present in the blood. When these electrolytes are too high or too low, confusion, disorientation, and other symptoms can occur.

What are signs that I am not drinking enough?

  • Dry mouth
  • Dry skin
  • Dry eyes
  • Little or no urine output
  • Low blood pressure
  • Dark, strong-smelling urine
  • Fatigue
  • Skin that ‘tents’ when pinched
  • Fever

Staying hydrated:

How much fluid you need daily to stay hydrated depends on your age, sex, and health status. Ask your healthcare team for a daily fluid intake goal to meet your needs. For example, cancer patients in treatment may need more fluids than a person not in cancer treatment.

In general, the “8 X 8 rule” is a good place to start. Aim to drink 8, 8 ounce glasses of caffeine-free fluid a day. Drinks that contain caffeine contribute to fluid loss so opt for decaffeinated or caffeine-free options. Here are more tips to stay hydrated:

  • If you develop a fever, diarrhea, or vomiting, you will need to increase your fluid intake to replace fluids. Drink 1 cup of fluid after each bout of vomiting or diarrhea.
  • Drink fluids throughout the day instead of waiting to drink when you feel thirsty.
  • Keep a glass, cup, or bottle of water in sight at all times. It is much more likely that you will drink fluids when they are within reach.
  • Keep track of the fluids you drink to make sure you are getting enough fluids.
  • Everyone is unique. If you have edema (retaining fluid), other medical conditions (heart or kidney disease), or are receiving pallative care, your fluid goals may be less. Ask your healthcare provider for specific water goals per day.
  • Food contains some fluid. Only foods that are liquid at room temperature should be counted toward your goal of “8 X 8.” The following are foods and beverages that can be counted toward your fluid goal:

8 X 8 Goal Friendly Foods



soup and broth, gelatin, ice cream, fruit ice, popsicles, sorbets,watermellon, clear-liquid nutritional beverages water, milk, decaf coffee*, decaf tea*, fruit or vegetable juice, decaf soda*, sports drinks, liquid nutrition supplements, hot chocolate, milkshakes, ice cubes, and ice chips

* Drinks that contain caffeine contribute to fluid loss. Use decaffeinated versions of these drinks instead.

What if I don’t like plain water?

Try sparkling waters, flavored waters, adding berries or slices of lemon, orgranes, cucumbers, or lime, or mixing water with a splash of 100% fruit juice or peppermint.

How do I measure my fluid intake?

One easy way to track fluid intake is to find a reusable water bottle or tumbler with the measurements in fluid ounces (fl oz.) marked on the side of the bottle.

One cup is equal to 8 fluid ounces. A glass that holds 8 fluid ounces of liquid is roughly the size of a baseball. It may not always be possible to keep track of your exact fluid intake, but you can estimate using this visual cue.

Bottled and canned drinks include the number of fluid ounces it contains on the label. You can also use the chart below for reference. Remember measurements can vary in size depending on the brand of the product or if the glass or cup is a specialty size.


Amount of Liquid

Small drinking glass  8 fluid ounces
Can of soda 12 fluid ounces
Coffee mug 8-12 fluid ounces
Shot glass 1.5 fluid ounces
Plastic water bottle (8 inches) 16.9 fluid ounces
Juice box 4.23-6.75 fluid ounces
Starbucks® Tall coffee 12 fluid ounces
McDonald’s small drink 16 fluid ounces

What if I have severe vomiting and can’t keep fluids down?

Try sucking on ice cubes and ice chips, and taking small sips of fluids frequently. This will be better tolerated than drinking large amounts at one time. If you are vomiting for 24 hours or more, contact your healthcare provider.