Weight Changes

Weight changes during cancer treatment are common. There are a number of causes for weight loss, including:

Causes for weight gain include:

  • Less activity
  • Eating more
  • Retaining water
  • Certain medicines

Quick weight loss is often a sign of dehydration, which can be serious. Weight changes of more than 5 pounds in a week should be reported to your cancer team. A decrease in weight over time may affect the patient’s ability to function, and make them weak and unable to perform daily activities. An increase in weight over time may suggest a serious health condition, such as diabetes or high blood pressure. You may be able to tell if you gain or lose 5 pounds in a week by the way you feel or the way your clothes fit, or you can weigh yourself on a scale every few days.

What to look for

  • Weight loss of 5 pounds or more in a week or less
  • Dry skin
  • Fatigue, weakness
  • Feeling very thirsty
  • Dizziness
  • Clothes or rings are too big


  • Weight gain of 5 pounds or more in a week or less
  • Swollen ankles
  • Shortness of breath
  • Feeling puffy or bloated
  • Tight shoes, clothes, or rings

What the patient can do

If you have lost weight

  • Be sure to drink enough water and other liquids. 
  • Drink extra high-protein and high-calorie fluids between meals.
  • Eat high-protein foods. You may also try liquid food supplements.
  • Ask about meeting with a dietitian.

If you have gained weight

  • Ask if you need to limit fluid if your ankles are swollen.
  • Limit your salt intake.
  • Limit high-calorie foods.
  • Ask about meeting with a dietitian.

What caregivers can do

  • Weigh the patient at the same time every day and write it down along with the date. A good time is in the morning before eating or drinking.
  • Talk to the cancer team if the patient’s weight loss or weight gain concerns you.
  • Watch the patient for other symptoms.

Call the cancer team if the patient:

  • Loses or gains more than 5 pounds in a week
  • Has shortness of breath
  • Feels dizzy or becomes confused

The American Cancer Society medical and editorial content team

Our team is made up of doctors and oncology certified 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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