Iris Oncology

Staying Hydrated During Cancer Care

Staying well hydrated during cancer treatment is extremely important, for both your ability to tolerate treatment and quality of life. About 60% of the body is water, which plays a critical role in many vital functions, including regulating heart rate, blood pressure, and body temperature, as well as transporting nutrients around the body and removing waste and toxins. Staying well hydrated requires taking deliberate steps to take in enough fluid to balance intake with losses over the day.   

When you’re fatigued, experiencing nausea, vomiting, diarrhea, or have a fever, staying on top of fluid needs can be challenging. Water may also taste “off,” and your thirst may be diminished, making it easier to drink less than the amount of fluid you need. Making the extra effort to drink enough can also reduce your need for additional IV fluids. 

Symptoms of Dehydration

Symptoms can include the following: 

  • Increased thirst 

  • Decreased urine output 

  • Dark yellow or amber-colored urine 

  • Dry skin, mouth, nose, and throat 

  • Increased heart rate 

  • Increased fatigue 

  • Confusion 

  • Fever  

Some of these symptoms may be due to other causes, so your symptoms should always be discussed with your clinical team. 

Estimating Fluid Needs

On average, at least 8-10 cups of fluid are recommended, though more may be needed to keep you well hydrated. A simple way to estimate your fluid needs for the day is to use this calculation: 

30 ml/kg of body weight 

To calculate kilograms (kg), divide your weight by 2.2. Then multiply that number by 30milliliters (ml) for a fluid goal of 2100 ml or 9 cups of fluid daily (1 cup = 240 ml). Using this calculation, you can see that different body sizes would need more fluid. 

What Counts as Fluid

Any liquids count except for alcohol. Small amounts of caffeinated beverages do count toward your fluid goal. Examples of fluids include the following: 

  • Water 

  • Seltzer 

  • Juice 

  • Sports/electrolyte drinks 

  • Soups 

  • Smoothies  

  • Protein shakes 

  • Ice cream 

  • Italian ice 

  • Popsicles and frozen juice bars 

  • Herbal/fruit teas 

Sometimes it’s easier to drink more if there’s a flavor to the liquids you choose. If you don’t like plain water, try a splash of lemon, lime, or other fruit juice. You can also infuse water with sliced fruits, berries, cucumbers, mint, basil, or ginger, and let it sit in the refrigerator for at least 2 hours. After 24 hours, strain the solids from the water and discard them.   

Fresh fruits and vegetables can also help you reach your hydration goals since they have a high-water content (averaging 80 – 95% water). 

Fluids with Electrolytes

During cancer treatment, you may experience electrolyte loss. Sodium and potassium are examples of electrolytes that can be depleted due to:  

  • Fluid losses 

  • Dehydration 

  • Vomiting 

  • Diarrhea 

  • Decreased oral intake 

  • Medications and treatments (diuretics, antibiotics, chemotherapy drugs, radiation therapy) 

The fluid highest in sodium is broth (400 – 800 mg per oz), and the highest in potassium is coconut water (400 – 500 mg per 8 oz).

This chart lists other examples of electrolyte-containing beverages:


Serving Size 

Sodium (mg) 

Potassium (mg)   

Liquid I.V. Hydration Multiplier 

1 stick 




20 oz bottle 



Nuun Sport Hydration 

1 tablet 



Pedialyte Advanced Care Plus 

1 (17 g) packet 



Ultima Replenisher 

1 scoop 




Make a Plan for Fluids

Plan to stay ahead of your hydration needs: 

  • Start early in the day so you have time to drink 8-10 (8oz) glasses of fluid daily.    

  • Experiment with both cold and hot liquids and frozen forms of fluids so you know how much you’ll need to rely on each to meet your needs. 

  • Check in with how you’re doing with fluids halfway through your day to see if you’re keeping up. 

  • Always keep a bottle of fluids with you and visible as a reminder to drink. 

  • To prevent waking up to urinate overnight, drink most of your fluids before the two hours before you go to bed. 

The Iris Care Team is available to support you. Our oncology registered dietitian and licensed nutritionists are here if you would like help meeting your nutritional needs. 

This article meets Iris standards for medical accuracy. It has been fact-checked by the Iris Clinical Editorial Board, our team of oncology experts who ensure that the content is evidence based and up to date. The Iris Clinical Editorial Board includes board-certified oncologists and pharmacists, psychologists, advanced practice providers, licensed clinical social workers, oncology-certified nurses, and dietitians.