Dehydration and Lack of Fluids

Everything in the body contains fluid (water). The human body must have a certain amount of liquid, and not having enough can be serious.

Fluid balance means that the body’s fluids are properly regulated and in the right places. Swelling is mostly caused by too much water in the body. (See Swelling.)

Dehydration is not having enough water in the body or not having enough fluid where it’s needed in the body. Keep in mind that fluid comes from both food and drink, so a person who isn’t eating must drink more to make up the difference.

What to look for

  • Dry mouth and lips
  • Thirst
  • Dizziness or weakness
  • Trouble swallowing dry food
  • Dry, sticky mouth that makes it hard to talk
  • Dry skin, skin that “tents” (stays up) when lightly pinched
  • A swollen, cracked, or dry tongue
  • Fever
  • Rapid weight loss (See Weight Changes)
  • Little or no urine
  • Constipation
  • Fatigue
  • Sunken eyeballs
  • Poor appetite and no thirst (Dehydrated people often feel less hungry and thirsty.)

What the patient can do

  • Drink fluids. Sometimes iced fluids are easier.
  • Remember that food contains fluid. Try to eat fruits, vegetables, soups, gelatins, Popsicles, and other moist foods.
  • Use lotion often to soften dry skin.
  • Try to get rid of the cause of dehydration, such as vomiting, diarrhea, or fever. (See these sections for information on these causes.)
  • Apply lubricant to lips to avoid painful cracking.
  • Fill a small cooler with juice boxes, bottled water, or other drinks and keep it next to you, if it’s tiring to get up.
  • Suck ice chips to relieve dry mouth if you can’t drink enough liquid.

What caregivers can do

  • Offer cold or cool liquids every hour or so.
  • Encourage the patient to eat small meals if they can.
  • Include moist foods, soups, and fruit smoothies (made with ice in a blender) as snacks.
  • Watch the urine output (pee) to see if it gets dark or the patient stops passing urine.
  • Check with the patient often to be sure they haven’t become confused.
  • Stand nearby when they get up, in case they get dizzy or faint.

Call the cancer team if the patient:

  • Can’t take in or hold down liquids
  • Has vomiting, diarrhea, or fever that last for more than 24 hours
  • Has urine that’s either very dark or only comes in a small amount, or if there’s no urine for 12 hours or more
  • Becomes dizzy or feels faint when standing up
  • Becomes confused or disoriented

The American Cancer Society medical and editorial content team
Our team is made up of doctors and master’s-prepared nurses with deep knowledge of cancer care as well as journalists, editors, and translators with extensive experience in medical writing.

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Last Medical Review: June 8, 2015 Last Revised: June 8, 2015

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