Dehydration Symptoms During Chemotherapy

How to recognize when you're deydrated

Recognizing the signs and symptoms of dehydration is essential for a cancer patient going through chemotherapy. Vomiting and diarrhea can often be a side effect of chemotherapy, and dehydration may be a result.

Young man in a wheelchair and adult woman
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Dehydration is the loss of body fluids that can occur because of diarrhea, vomiting, heavy sweating, fever, and overexposure to the sun. Our bodies cannot function properly without these essential fluids. The body struggles to maintain the right balance of fluid and electrolytes such as sodium and potassium. When dehydration sets in, the imbalance often leads to confusion and can be life-threatening for the cancer patient.

Signs and Symptoms

  • dizziness, lightheaded feeling
  • general feeling of weakness
  • less urine output
  • dry mouth
  • thirst
  • difficulty in swallowing dry foods
  • dry skin
  • dry lips

When to Call a Healthcare Provider

Your urine can be an easy-to-observe indicator that you may be dehydrated. During chemotherapy, you may want to pay closer attention to your urination habits, volume, frequency and the color of your urine. You will produce less urine and more concentrated and darker yellow urine when you are dehydrated.

You should call your healthcare provider if you experience little or no urine output for 12 hours or more or urine that is dark in color. Also call your healthcare provider if you experience dizziness while standing up, have feelings of confusion, or faint.


The best way to prevent dehydration is to drink fluids. Don't wait until you are thirsty, drink small amounts frequently. It may be difficult to drink and eat during bouts of nausea and diarrhea, but even small amounts help. You can try drinking a few ounces at a time of clear liquids every 15-30 minutes until you can keep larger amounts down. Ice chips can work wonders for dry mouth to intake small amounts of fluid.

Try to include foods in your diet that are high in fluid such as yogurt, soup, gelatin, broth, fruit, and vegetables. Popsicles and other frozen treats may be tolerated well. 

If you have diarrhea you should try to drink beverages such as sports drinks and oral rehydration solutions or bouillon to replace the lost electrolytes. Ask your healthcare provider which may be right for you.

You should also try to avoid drinking large amounts of caffeinated beverages like sodas and coffee. Caffeine in large amounts can increase your urine output and possibly lead to dehydration. Alcohol is a known diuretic (increasing urine production and loss of water) and can also lead to dehydration. 


Remember, if you think you are dehydrated or at risk of becoming dehydrated, call your healthcare provider. He or she can prescribe medications to relieve vomiting and diarrhea, thus reducing the risk of dehydration. Your healthcare provider may recommend certain fluids or oral rehydrating solutions for your specific situation. Fluids can be delivered intravenously if needed. Always talk to your healthcare provider before making your own oral hydrating solution or taking salt tablets to relieve dehydration.

A Word From Verywell

You may be at greater risk of dehydration if you are alone at home while undergoing chemotherapy. The confusion that sets in with dehydration can sneak up on you, leading to drinking even less, risking falls, etc. This is a good time to arrange for a friend to be present to encourage you to keep drinking and watch for danger signs. This is especially important if you are having any vomiting or diarrhea.

2 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. American Society of Clinical Oncology (ASCO). Dehydration.

  2. American Cancer Society. Dehydration and Lack of Fluids.

By Lisa Fayed
Lisa Fayed is a freelance medical writer, cancer educator and patient advocate.