Chemotherapy and Dehydration

Chemotherapy is a common treatment for different types of cancer. While it kills cancer cells, it can also kill healthy cells. This treatment can cause side effects that can lead to dehydration.

Dehydration happens when your body loses more fluids than it takes in and when you don't take in enough fluid. Understanding why and how chemotherapy (chemo) can make you dehydrated is key. It’s also important to know how to stay hydrated during treatment. Severe dehydration can be life-threatening, but there are ways to help prevent it.

How does chemo cause dehydration?

Chemo can cause dehydration in a few ways:

• Peeing more. Some medicines make you pee a lot, which means you’re losing more fluid than usual.

• Diarrhea. Some chemo medicines give you diarrhea or watery, loose stool. This makes you lose more fluid than normal.

• Vomiting. Many cancer treatments can make you feel ill or throw up. When you throw up, you’re getting rid of everything in your stomach, including water.

• Mouth sores. If your chemo medicine gives you sores in your mouth, it might be painful to eat or drink. As a result, you may drink less than your body needs.

• Less appetite. If your medicine is making you feel sick, giving you diarrhea, or decreasing your appetite, you may not want to eat or drink. That can make it hard to get enough water.

How do you know if you're dehydrated?

Watch for these signs that you may be dehydrated and tell your healthcare provider:

• Dark yellow pee

• Dizziness

• Dry or sticky mouth

• Dry skin

• Feeling abnormally tired or weak

• Feeling very thirsty

• Sweating or peeing less than normal

• Weight loss

• Headaches

• Low blood pressure

• Fast heart rate

How can you prevent dehydration?

To make sure you stay hydrated during cancer treatment, here are some things you can do:

• Talk with your provider about any treatment side effects. They can help treat possible causes of dehydration, such as nausea, diarrhea, or mouth sores.

• Drink lots of fluids, including at least 8 glasses (64 ounces) of water each day, unless advised otherwise by your healthcare team. Keep a log of how much fluid you drink in a day.

• Don't have drinks with caffeine and alcohol. They can make you lose more fluids. Instead, choose water, herbal tea, or other drinks without caffeine or alcohol.

• Eat foods that have lots of water. Try watermelon, cucumber, oranges, or lettuce.

• Sip slowly. If you can't drink a lot of water at once, take small sips throughout the day. You can also suck on ice chips.

• If you feel sick and can’t drink enough, your healthcare provider might recommend special drinks that can help replace the water and minerals you’re losing. Talk with your provider before starting any new supplements.

• Check your pee. It should be a pale yellow or straw-like color. If it’s darker, you might be dehydrated.

Everyone’s water needs are different. Things like age, your general health, and the medicines you’re taking can affect how much water you need.

Dehydration can make you feel worse during cancer treatment. By following your provider’s advice and these tips, you can cut your risk of dehydration.

When to call your healthcare provider

Call your healthcare provider right away if you:

• Can't drink or keep fluids down

• Have vomiting or diarrhea that lasts for more than 24 hours

• Have dark pee or make only a small amount of pee

• Feel dizzy or faint

• Are confused or disoriented

• Have low blood pressure and a fast heart rate

• Have extreme thirst

• Can't sweat or produce tears

• Have a fever