Woman hugging a giant drop of water

Staying Hydrated on Chemo Days

Feeling more thirsty than usual on chemotherapy days is normal. It is important to pay attention to this sign from your body. But getting enough fluids can be tricky after chemo because of side effects like nausea and vomiting. Your body also may send signals other than thirst when it needs water.1

When your body has less fluid than it needs, you are dehydrated. Human bodies are two-thirds water, so it is important to replace water that is lost. Use these tips to understand how and why you need to stay hydrated on chemo days.1-3

The importance of hydration

Your cells and organs cannot function properly without enough water. Water supports many bodily activities, including:3

  • Regulating heart rate and blood pressure
  • Moving nutrients and oxygen to where they are needed
  • Protecting organs and tissues
  • Making saliva
  • Removing waste and toxins
  • Controlling body temperature

Your body naturally loses water from breathing, sweating, and going to the bathroom. You can lose even more fluids than normal when you are sick or undergoing medical treatments like chemotherapy. These lost fluids need to be replaced to prevent dehydration.3

Cancer treatments and dehydration

Cancer treatments that cause vomiting and/or diarrhea may place you at greater risk for dehydration. Chemotherapy, in particular, can cause people to lose extra fluids, but radiation therapy and surgery can also lead to fluid loss. Even simply having nausea without vomiting or diarrhea can prevent you from taking in enough fluids to maintain proper hydration.3

Dehydration symptoms

Dehydration can range from mild to severe. When you are mildly dehydrated, you may not feel parched. Signs of mild hydration include:3

  • Dark yellow urine
  • Decrease in urine output
  • Dry skin
  • Feeling tired or weak
  • Headache
  • Irritability
  • Nausea
  • Vomiting

Signs of severe dehydration include:3

  • Disorientation and confusion
  • Extreme thirst
  • Fever
  • Inability to make tears or sweat
  • Inability to urinate for more than 8 hours
  • Low blood pressure
  • Rapid heartbeat
  • Sunken eyes

Because chemotherapy can cause nausea and vomiting, it can cause dehydration. In turn, becoming dehydrated can worsen these side effects. If you or your loved one have signs of severe dehydration, seek urgent care immediately.

Diagnosing dehydration

If you seek care for suspected dehydration, your doctor will likely take your blood pressure and pulse. They may also collect blood and urine samples.3

The blood sample will show whether your kidneys are functioning well. It will also show your electrolyte levels. Electrolytes are minerals that occur naturally in your body and that have an electric charge. They are critical to certain metabolic processes, and they are thrown out of balance when you are dehydrated.3,4

The urine sample can help your doctor learn the cause of your dehydration. This can help rule out factors unrelated to your chemotherapy.3

What can you do to prevent dehydration from chemo?

Treatment for dehydration depends on its severity. If your dehydration is mild, it is best to drink small amounts of fluid frequently. If your dehydration is of medium severity, your doctor may recommend an oral rehydration solution. This will be used only if you can keep it down. If your dehydration is severe, you may be given fluids through a vein (IV).3

As a general rule, most people should drink 64 ounces of fluid each day. But this can vary based on your size or health conditions. Check with your doctor for your recommended intake, especially on chemo days.2

On days when you have chemo or any cancer treatment that can lead to nausea, vomiting, or diarrhea, try to be prepared. The best way to prevent dehydration due to chemotherapy is to take in extra fluids before your chemo is given.5

Staying hydrated on chemo days

But no matter how hydrated you are before your chemotherapy, monitor your fluid loss and intake after it. Try setting a timer to remind yourself to take sips throughout the day. Or ask your caregiver to give you gentle reminders to hydrate.2

Also, be aware that your preferences and taste tolerance may change after your chemotherapy appointment. Try to have a variety of fluid choices on hand. You may need to experiment to see what you can tolerate.2

Some ideas for fluid sources are:2

  • Ice cubes or ice chips
  • Flavored water
  • Sports drinks like Gatorade
  • Fruit or vegetable juices
  • Soup or broth
  • Sorbet
  • Ice cream
  • Popsicles
  • Nutritional drinks
  • Milkshakes
  • Milk
  • Decaffeinated soda
  • Decaffeinated tea or coffee

What are your special tips for staying hydrated on chemo days? We would love to hear from you in the comments. Your routine may help others find out what works for them.

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