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, or 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 extra effort to drink enough can also reduce your need for additional IV fluids. 

Symptoms of Dehydration 

Symptoms of dehydration 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 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, particularly if you’re a larger person.  One simple way to estimate fluid needs for the day is to use this calculation: 30-35 ml/kg of body weight 

To calculate kilograms (kg), divide your weight by 2.2 – for example, a 154# person weighs 70 kg.  Then multiply that number by 30 and 35 milliliters (ml) for a fluid goal of 2100 - 2450 ml, or 8-10 cups of fluid daily (1 cup + 250 ml).  Using this calculation, you can see that someone who is larger would need significantly more fluid. 

What Counts as Fluid 

Fortunately, except for alcohol, all fluids count (including small amounts of caffeinated beverages). 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 

• Diet soda 

• Regular (in moderation) and decaffeinated coffee and tea 

• Herbal/fruit teas 

People tend to drink more if there’s flavor to what they’re drinking, so if you don’t like plain water flavor it up with a splash of lemon, lime, or other fruit juice. You can also infuse water with flavor by adding sliced fruits, berries, cucumbers, mint, ginger, or other appealing tastes to a container of water and letting it sit in the refrigerator for at least 2 hours. After 24 hours, strain the solids from the water and discard.   

On average, fruits and vegetables are also about 80 – 95% water so will also contribute to hydration if eaten regularly. 

Electrolyte-Containing Beverages 

During cancer treatment some situations can create electrolyte imbalances in sodium and potassium making it necessary to include some electrolyte-containing beverages in your routine.  Causes of these imbalances include the following: 

• Fluid losses 

• Dehydration 

• Vomiting 

• Diarrhea 

• Decreased oral intake 

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

The fluid highest in sodium is broth (400-800 mg per oz), and highest in potassium is coconut water (400 – 500 mg per 8 oz).  Check out this chart for more examples of electrolyte beverages. 

Please note: although powders may recommend to mix each serving with 16 ounces of water, for comparison all information is provided per 8 oz serving.  

Make a Plan for Fluids 

Preventing dehydration is always best, so make a 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 falling behind. 

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

• If you don’t want to be waking up a lot to urinate at night, wrap up most of your fluids within two hours of going to bed.