Our bodies are mainly water. Maintaining a good water balance is crucial for proper bodily function and for survival. If you are not taking in enough water, or if you are expending too much, you will become dehydrated. You need to ensure that you are drinking at least as much water as you are expending. 

During breast cancer treatments, some people eat and drink less or experience vomiting and diarrhea, which increase the risk of dehydration. Good hydration is especially important during this time, particularly to flush excess medication from your body. What’s more, even slight dehydration can exacerbate some side effects of cancer and treatments such as:  

•  – Fatigue,  
•  – Dry mouth, 

•  – Taste disorders, 
•  – Mouth pain, 
•  – Constipation, and 
•  – Nausea. 

Dehydration can also affect attention, memory, and even mood. 

Here are a few tips for preventing and combatting dehydration after a breast cancer diagnosis. 

Consuming an average of 2 to 3 litres of water a day is generally enough to prevent dehydration.  

Water needs vary based on age, weight, health status, the ambient temperature, and activity levels. Your dietician can tell you the amount of water you need.  

To meet your water needs, drink liquids (1.5 to 2 litres a day) and eat hydrating foods (½ to 1 litre a day).  

Which liquids are good for staying hydrated?  

Water remains the drink of choice, but other liquids contain significant amounts of water to keep you hydrated: vegetable broth, herbal tea, tea, coffee, milk, vegetable cocktail, fruit and vegetable juice, smoothies, soups, etc.  

Choose hydrating foods 

Some foods are also high in water and can help to keep you hydrated. These are especially fruits and vegetables (cucumber, citrus, watermelon, grapes, etc.), or dairy products (yogurt, etc.), popsicles, or even gelatin desserts. 

Tips for staying hydrated:  

• Try to drink small amounts of liquid on a regular basis throughout the day. Don’t wait until you feel thirsty. 

• If you are fatigued or have a bad taste in your mouth, drinking with a straw may be easier. 
• If your mouth hurts, sucking on a popsicle or frozen grapes can be soothing as well as hydrating. 
• Always keep a bottle or flask full of your favourite liquid with you. 
• If you are sweating or are experiencing diarrhea or vomiting, try to drink more. 

What are the signs of dehydration? 

Depending on the cause, mild dehydration is generally easy to treat. However, severe dehydration can be serious, even developing into a medical emergency that may require hospitalization. It is therefore important to monitor the signs of dehydration in people with breast cancer.  

Thirst, dark urine, and less frequent urination are the first signs of dehydration. If dehydration worsens, other symptoms may appear, such as headaches; dry skin, lips or tongue; dizziness; weakness; or confusion.  

What do I do if I get dehydrated? 

If you are concerned about your level of hydration, if you show signs of dehydration, or if you are experiencing diarrhea or vomiting, contact a member of your care team for appropriate medical advice. 

Tips for handling dehydration: 

• Try to drink more liquid, regularly and in small quantities, throughout the day. If water is not sufficient to rehydrate you, you may be advised to instead drink an oral rehydration solution (ORS). ORSs contain specific concentrations of electrolytes and glucose, which help to re-establish water balance more quickly than water. These solutions are available at pharmacies in different formats and flavours. 
• Limit your consumption of diuretic beverages such as coffee, tea, and alcoholic beverages. 

• Try not to sweat out water and electrolytes by avoiding hot settings and intense physical activities, especially when it is very hot. 
• Follow your care team’s recommendations for diarrhea and vomiting.  

See our other My Active Health Nutrition topics for more advice on nutrition following a breast cancer diagnosis.