How Does Hydration Support Cancer Recovery?
When you're going through cancer treatment, hydration might seem like a fairly mundane concern. After all, you have chemotherapy, radiotherapy, surgery, medications and a whole range of other things to think about. Does drinking enough water really make that much difference?
It does.
Water plays a fundamental role in almost every process in your body. Every cell depends on an adequate supply of fluid to function properly, and your body needs water to transport nutrients, remove waste products, regulate temperature and support the normal functioning of your organs.
During cancer treatment, these functions become particularly important. Cancer and its treatments can increase the risk of dehydration, particularly when nausea, vomiting, diarrhoea, poor appetite or difficulty drinking accompany treatment (1, 2)
But there's an important qualification: more water isn't always better. Some people with cancer need to restrict their fluid intake because of kidney, heart or liver problems, or because of the effects of particular cancers or medications. Your oncology team can advise you about the amount that's appropriate for you (3).
Why Do We Need Water?
Think of water as one of the body's essential transport systems.
Every cell in your body exists in a fluid environment. Water helps transport nutrients and other substances around the body and helps remove waste products. Your body also relies on water to regulate temperature, support circulation and maintain normal physiological functions.
Your kidneys depend on adequate fluid to filter your blood and eliminate waste products. Some cancer treatments can place additional demands on the kidneys, too. Cisplatin, for example, can cause kidney toxicity, and clinicians use carefully designed hydration protocols to reduce this risk. A 2024 systematic review found evidence supporting specific hydration strategies, including attention to fluid volume and magnesium supplementation, for people receiving cisplatin chemotherapy (4).
So, when you're undergoing treatment, maintaining adequate hydration forms one part of good supportive care.
What Are the Signs of Dehydration?
It's worth learning to recognise dehydration early, particularly because some of its symptoms overlap with common cancer treatment side effects.
Signs can include:
Fatigue that feels worse or different from your usual treatment-related tiredness
Dizziness, particularly when you stand up
Dark yellow or amber-coloured urine
A dry mouth
Dry skin
Urinating less frequently than usual
Headaches
A rapid heartbeat
Confusion or difficulty thinking clearly.
This overlap can make dehydration difficult to recognise. Chemotherapy, for example, can cause fatigue and nausea, while radiotherapy can cause dry mouth and digestive problems.
So, pay attention to patterns. If you notice that a headache, dizziness or a general feeling of being unwell improves after you drink some fluid, dehydration may have contributed to the problem.
When should you seek medical help?
Severe dehydration can become a medical emergency.
Seek medical advice promptly if you experience severe dizziness, confusion or disorientation, very dark urine, or a significant reduction in urination. If you cannot keep fluids down for an extended period, you may also need medical attention.
Your oncology team can advise you about which symptoms warrant urgent assessment during your particular treatment.
What Can You Drink Besides Plain Water?
Plain water provides an excellent source of hydration, but you don't have to rely on it exclusively.
In fact, cancer treatment can alter your sense of taste, so having several options available can make it easier to drink enough.
Herbal teas
Herbal teas can provide fluid while offering additional properties that some people find helpful.
Ginger tea may help with nausea. Research into ginger and chemotherapy-induced nausea and vomiting has produced mixed results, although some systematic reviews suggest that ginger may reduce acute vomiting (5, 6). Exercise caution during treatment itself, though, as it can interfere with some treatments.
Chamomile tea and lemon balm are relaxing drinks that some people find helpful before bedtime.
Peppermint tea may provide a refreshing alternative when treatment leaves you with an unpleasant or metallic taste.
However, don't assume that every herb will suit every cancer treatment. Some herbs and concentrated herbal products can interact with medications. Always check with your oncology pharmacist or doctor
Hydrating foods
Food can contribute quite a lot to your daily fluid intake, particularly if you struggle to drink large quantities.
Good choices include:
Cucumber
Watermelon
Strawberries
Cantaloupe/Rockmelon
Celery
Lettuce
Zucchini/Courgettes
Tomatoes
Broth-based soups.
These foods provide water along with valuable nutrients. Broths can also provide electrolytes, which become important if vomiting or diarrhoea causes you to lose significant amounts of fluid.
Your total water intake comes from both beverages and food, so you don't need to obtain all your fluid from drinks. The National Academies also emphasise that water requirements vary between individuals and increase with factors such as physical activity and exposure to hot environments (7).
Electrolyte drinks
Vomiting and diarrhoea can cause you to lose substantial amounts of sodium, potassium and other electrolytes. In these circumstances, replacing both fluid and electrolytes may work better than drinking plain water alone.
Pharmacy oral rehydration solutions provide a carefully balanced combination of water, glucose and electrolytes and can prove useful when significant fluid loss occurs.
Coconut water also provides electrolytes, although its composition differs from a medical oral rehydration solution.
You can also make a simple oral rehydration solution at home using:
1 litre of water
6 level teaspoons of sugar
½ teaspoon of salt
Add flavourings, such as food essences (NOT essential oils), to make it more palatable (optional)
If you have significant vomiting or diarrhoea, however, speak with your healthcare team rather than relying solely on homemade solutions.
What about coffee and tea?
You don't need to eliminate caffeinated drinks.
Although caffeine has a mild diuretic effect, moderate caffeine consumption rarely causes dehydration in people who consume it regularly. However, coffee and strong tea may aggravate nausea, reflux, or digestive discomfort in some people.
Alcohol presents a different issue. It can contribute to dehydration and may interact with some medications, so discuss alcohol consumption with your oncology team.
And what about grapefruit juice?
This one deserves particular caution.
Grapefruit and grapefruit juice can interfere with enzymes and transport proteins involved in the metabolism and absorption of some medicines. These interactions can alter the amount of medication that reaches your bloodstream and, in some circumstances, increase the risk of adverse effects (8, 9).
If you take any medication, ask your doctor or pharmacist whether you should avoid grapefruit and grapefruit juice.
How Can Hydration Help With Common Treatment Side Effects?
Nausea and digestive problems
When nausea strikes, drinking may be the last thing you feel like doing. Unfortunately, dehydration can make you feel even worse, creating an ongoing problem.
Rather than trying to drink a large glass of water, try taking tiny amounts frequently.
For example, you could:
Take a teaspoon or tablespoon of fluid every few minutes.
Suck on ice chips.
Try chilled or room-temperature drinks to see which you tolerate best.
Try ginger tea if you find ginger helpful for nausea.
The aim isn't to force yourself to drink a large amount at once. Small, frequent sips may prove much easier to tolerate.
If vomiting prevents you from keeping fluids down, contact your healthcare providers rather than trying to manage the problem simply by drinking more.
This article may give you other ideas for combating nausea and vomiting.
Dry mouth and mucositis
Radiotherapy to the head and neck can damage the salivary glands and cause persistent dry mouth. Cancer treatments can also cause inflammation and damage to the mucous membranes lining the mouth and throat (10).
Keeping your mouth moist can provide some relief.
Rather than drinking a large amount occasionally, try taking frequent small sips throughout the day.
You may also find that the temperature of your drinks makes a difference. Some people prefer cool drinks, while others find room-temperature fluids more comfortable when their mouth feels sore.
Avoid acidic drinks such as orange juice and lemonade if they sting or irritate damaged tissues.
Some people find that a little honey in warm or room-temperature water soothes an irritated throat. However, honey contains sugar, so people with particular dietary requirements should take this into account.
If dry mouth persists after radiotherapy, don't assume that drinking more water represents the only option. Treatments such as saliva substitutes and medications that stimulate saliva production may help some people. A systematic review found evidence supporting pilocarpine and cevimeline for radiotherapy-induced xerostomia (dry mouth), although treatment needs to suit the individual (11).
Practical Ways to Drink More During Treatment
Knowing that you need to drink more doesn't always make it easy to do so.
Treatment fatigue, nausea, altered taste and simply having too many other things to think about can all make hydration difficult.
A few simple strategies can help.
Set reminders
Use your phone to remind you to drink every hour or two. You don't need to drink a huge amount each time — several sips can keep you moving in the right direction.
Make drinking part of your routine
Link drinking to things you already do.
For example:
Have a drink when you take your medication.
Keep a water bottle beside you while watching television.
Drink a glass when you sit down for a meal.
Keep water beside your bed.
Take a water bottle with you whenever you leave the house.
The less you have to think about drinking, the easier it becomes to maintain the habit.
Make water more appealing
Treatment can change your sense of taste, sometimes making plain water surprisingly unpleasant.
If that happens, experiment.
You could add:
Cucumber slices
Fresh berries
A little lemon or lime, provided citrus doesn't irritate your mouth
Fresh mint.
You can also alternate between water, herbal tea and broth rather than forcing yourself to drink the same thing all day.
If everything tastes metallic, try sucking on ice chips or frozen pieces of fruit.
Use a water bottle you enjoy
This might sound trivial, but having a bottle that keeps your drink at the temperature you prefer can make drinking much easier.
Some people prefer cold water. Others find room-temperature or warm drinks more comfortable, particularly if treatment causes chills or mouth sensitivity.
A straw can also help if fatigue makes lifting a bottle or glass difficult.
Keep track of your intake
If you regularly forget to drink, use a simple tally on paper or a smartphone app.
Seeing how much you've actually consumed can help you identify patterns and remind you to drink before dehydration becomes a problem.
If you're caring for someone undergoing cancer treatment, you can make hydration easier without turning it into another source of stress.
Try:
Keeping a filled water bottle within easy reach.
Offering drinks regularly rather than waiting for the person to ask.
Providing hydrating foods such as watermelon, cucumber or broth-based soups.
Offering favourite drinks when appetite and motivation are low.
Keeping track of fluid intake when necessary.
Watching for changes such as reduced urination, increasing dizziness or confusion.
The goal isn't to remind someone constantly to drink. Instead, make fluids an easy and natural part of the daily routine.
Can You Drink Too Much Water?
Yes.
While dehydration presents the more common concern, drinking excessive amounts of water can also cause problems.
When you drink far more fluid than your kidneys can eliminate, you can dilute the sodium in your blood. This condition, called hyponatraemia, can become serious.
Sodium helps regulate the movement of water between your bloodstream and cells. When sodium levels fall too low, water moves into cells and causes them to swell. In severe cases, swelling in the brain can cause confusion, seizures and potentially life-threatening complications (12).
It is easy to dismiss these symptoms, but I found out how dangerous this was when I was going through chemotherapy. I had severe diarrhoea and was drinking a lot of water and commercial electrolyte drinks to compensate for the fluid I was losing. When I felt really unwell, I went to ER, where they put me on a saline drip immediately. The doctor attending me told me I was almost at the point where my heart would have stopped without their intervention.
Some people with cancer face a greater risk of fluid and electrolyte disturbances. Kidney problems (which can happen because of treatment), heart failure, liver disease, certain cancers and some medications can all affect the body's ability to regulate fluid.
Some cancers can also cause the body to produce hormones that encourage the kidneys to retain water. Cancer treatments, nausea, and pain can contribute to a condition called the syndrome of inappropriate antidiuresis (SIAD), which can cause hyponatraemia (12).
Symptoms of significant hyponatraemia or fluid imbalance can include:
Headache
Nausea or vomiting
Confusion
Muscle weakness or cramps
Seizures in severe cases.
If you have kidney disease, heart failure or liver cirrhosis, your healthcare team may recommend fluid restriction rather than encouraging you to drink more.
Always follow the fluid recommendations your oncology team gives you.
The goal is balance
You don't need to force down enormous quantities of water to support your recovery.
For most people, regular fluid intake throughout the day makes more sense than drinking large amounts at once. If you drink constantly or consume unusually large amounts of fluid, mention it to your healthcare professional. They may want to investigate the cause and check your electrolyte levels.
How Does Hydration Support Recovery After Treatment?
Your need for adequate hydration doesn't end when active treatment finishes.
Your body continues to recover after chemotherapy, radiotherapy and surgery, and adequate fluid intake supports normal physiological processes during this period.
Water also forms an important part of lymph and blood, which transport nutrients, waste products and immune cells around the body. Maintaining adequate hydration therefore supports the normal functioning of these systems.
Adequate fluid intake can also support some of the everyday aspects of recovery, including:
Normal bowel function and prevention of constipation
Cardiovascular health
Cognitive function
Healthy skin
Normal digestion.
As your recovery progresses, your fluid needs may change. Your activity level, body size, climate and diet all influence how much you need.
Rather than becoming fixated on a particular number of glasses, pay attention to your body's signals and follow any advice your healthcare team has given you. The National Academies specifically caution against interpreting their adequate intake figures as a precise requirement for every individual (7).
Urine colour can provide a useful, though imperfect, indication of hydration. A systematic review found that urine colour usually correlated with more objective measures of hydration, although the research remains limited and the method works less reliably in some older adults (13).
Frequently Asked Questions
Can particular beverages interfere with cancer medications?
Yes.
Grapefruit and grapefruit juice can interfere with the metabolism or absorption of some medicines, potentially changing the amount of medication that reaches your bloodstream (8, 9).
Alcohol can also interact with some medications and may worsen dehydration.
Some concentrated herbal products can interact with cancer treatments too. Don't assume that a drink is automatically safe simply because it comes from a plant.
If you regularly drink herbal teas or other specialty beverages, tell your healthcare practitioners. They can check for potential interactions with your particular medications.
How can caregivers help cancer patients stay hydrated?
Keep drinks within easy reach and offer them regularly. You can also provide hydrating foods such as watermelon, cucumber and broth-based soups.
Most importantly, learn the warning signs of dehydration and report concerning symptoms to the healthcare team.
Should you drink water before or after meals?
There's no need to avoid drinking with meals.
Small amounts of fluid can help with swallowing, particularly if you have a dry mouth. However, drinking a large volume immediately before eating may make you feel full, which can create a problem if you're already struggling to consume enough food. It can also dilute your stomach acid, which may affect your digestion.
If nausea affects you, you may find it easier to drink most of your fluids between meals.
Ultimately, getting enough fluid throughout the whole day matters more than exactly when you drink it.
What role do electrolytes play?
Electrolytes such as sodium, potassium and magnesium help regulate fluid balance, nerve function, muscle function and heart rhythm.
Vomiting and diarrhoea can cause significant electrolyte losses. In these situations, replacing electrolytes alongside fluids may prove more effective than drinking plain water alone.
Your healthcare team may check your electrolyte levels with a blood test and recommend a suitable oral rehydration solution or electrolyte replacement if necessary.
Can I add anything to water to make it more beneficial?
You don't need to add anything to water to make it "work" as a hydration source.
However, adding natural flavours can make drinking easier when treatment changes your sense of taste.
Try:
Fresh mint
Cucumber
Berries
Lemon or lime, if citrus doesn't irritate your mouth
A small amount of honey may soothe an irritated throat, although it adds sugar, which may be a problem if you have diabetes.
Take care with concentrated herbal extracts, powders, and supplements. They can have pharmacological effects and may interact with cancer medications. Always check with your healthcare team.
Conclusion
Hydration might seem like a small part of cancer care, but it supports many of the normal physiological processes your body relies on during treatment and recovery.
Rather than waiting until you're thirsty, try to drink regularly throughout the day. Keep fluids within easy reach, experiment with different temperatures and flavours, and use hydrating foods when drinking becomes difficult.
Most importantly, remember that your ideal fluid intake depends on your individual circumstances. If your cancer treatment, medications, or another health condition affects your kidneys, heart, liver or electrolyte balance, ask your healthcare team how much fluid you should consume.
And if nausea, vomiting, diarrhoea or other treatment side effects make it difficult to drink enough, don't struggle on your own. Your healthcare team can help you prevent dehydration and manage the underlying problem.
Small, consistent habits can make a surprisingly valuable contribution to your wellbeing while your body does the much bigger job of healing and recovering.
If you found this article useful, sign up for the monthly newsletter on Cancer Prevention. As a thank you for signing up for that, you will receive a short recipe book, 30 Delicious Recipes for Cancer Patients.
If you would also like information on support during cancer treatment, you can sign up for my Cancer Treatment Support newsletter. You will receive a free booklet, Soothing Side Effects: A Natural Support Guide for Cancer Patients, as a thank you gift.
For a more comprehensive collection of evidence-based natural strategies that can support you during cancer treatment and recovery, you need my book, Naturally Supporting Cancer Treatment. It brings together practical information about diet and lifestyle approaches, supplements, and herbs, including their potential benefits, risks and interactions with conventional cancer treatment.
References
Price KA. Hydration in cancer patients. Current Opinion in Supportive and Palliative Care. 2010;4(4):276–280. doi:10.1097/SPC.0b013e32833e48d1.
Hwa YL, Kull MR. The why and how of maintaining hydration during cancer therapy. Current Opinion in Supportive and Palliative Care. 2020;14(4):324–332. doi:10.1097/SPC.0000000000000526.
Hayes J, Bruera E, Crawford G, et al. Multinational Association of Supportive Care in Cancer (MASCC) expert opinion/guidance on the use of clinically assisted hydration in patients with advanced cancer. Supportive Care in Cancer. 2024;32(4). doi:10.1007/s00520-024-08421-6
Sikking C, Niggebrugge-Mentink KL, van der Sman AS, et al. Hydration methods for Cisplatin containing chemotherapy: A systematic review. The Oncologist. 2023;29(2):e173-e186. doi:10.1093/oncolo/oyad297
Marx W, Teleni L, McCarthy AL, et al. Ginger (Zingiber officinale) and chemotherapy-induced nausea and vomiting: a systematic literature review. Nutrition Reviews. 2013;71(4):245–254. doi:10.1111/nure.12016.
Crichton M, Marshall S, Marx W, McCarthy AL, Isenring E. Efficacy of ginger (Zingiber officinale) in ameliorating chemotherapy-induced nausea and vomiting and chemotherapy-related outcomes: a systematic review update and meta-analysis. Journal of the Academy of Nutrition and Dietetics. 2019;119(12):2055–2068. doi:10.1016/j.jand.2019.06.009.
Institute of Medicine. Dietary Reference Intakes for Water, Potassium, Sodium, Chloride, and Sulfate. Washington, DC: National Academies Press; 2005. doi:10.17226/10925.
Hanley MJ, Cancalon P, Widmer WW, Greenblatt DJ. The effect of grapefruit juice on drug disposition. Expert Opinion on Drug Metabolism & Toxicology. 2011;7(3):267–286. doi:10.1517/17425255.2011.553189.
Chan W-JJ, Adiwidjaja J, McLachlan AJ, Boddy AV, Harnett JE. Interactions between natural products and cancer treatments: Underlying mechanisms and clinical importance. Cancer Chemotherapy and Pharmacology. 2023;91(2):103-119. doi:10.1007/s00280-023-04504-z
Jensen SB, Pedersen AM, Vissink A, et al. A systematic review of salivary gland hypofunction and xerostomia induced by cancer therapies: prevalence, severity and impact on quality of life. Supportive Care in Cancer. 2010;18(8):1039–1060. doi:10.1007/s00520-010-0827-8.
Mercadante V, Al Hamad A, Lodi G, Porter S, Fedele S. Interventions for the management of radiotherapy-induced xerostomia and hyposalivation: a systematic review and meta-analysis. Oral Oncology. 2017;66:64–74. doi:10.1016/j.oraloncology.2016.12.031.
McDonald D, Sherlock M, Thompson CJ. Hyponatraemia and the syndrome of inappropriate antidiuresis (SIAD) in cancer. Endocrine Oncology. 2022;2(1):R78–R89. doi:10.1530/EO-22-0056.
Kostelnik SB, Davy KP, Hedrick VE, Thomas DT, Davy BM. The validity of urine color as a hydration biomarker within the general adult population and athletes: a systematic review. Journal of the American College of Nutrition. 2020;40(2):172–179. doi:10.1080/07315724.2020.1750073.
