It protects your kidneys and bladder
Chemotherapy and its breakdown products leave in the urine. Dilute, fast-moving urine cuts the time they spend against the kidney tubules and the bladder lining.
Staying hydrated on chemotherapy
How much water should you drink during chemotherapy?
Most cancer organisations point to eight to ten glasses — about two and a half litres. The honest answer is that your number depends on your drugs, your kidneys and your heart.
- Written for people having chemotherapy in Hyderabad and across Telangana
- Reviewed by a CION consultant medical oncologist
- Every clinical figure on this page is sourced and linked
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Medically reviewed by Dr. Naresh Gundu
Consultant Medical Oncologist · MBBS, DNB, DM (Medical Oncology) · last reviewed September 2026, next review due September 2027
On this page
- The short answer
- Why fluid matters so much on chemotherapy
- The drugs that come with a fluid instruction
- When you need more than usual
- When you may need less — and must ask
- What to drink, in an Indian kitchen
- What to go easy on
- Spotting dehydration early
- Five habits that make it easy
- Frequently asked questions
- Sources
The short answer
The short answer
Aim for eight to ten glasses of fluid a day — roughly two to two and a half litres — unless your oncology team has given you a different number. That range is what Cancer Research UK, the National Cancer Institute and Memorial Sloan Kettering all point to, and Macmillan asks for at least two litres on several chemotherapy drugs.
Two groups should not use that range. On cisplatin you will be asked to drink considerably more, starting the day before. With heart failure, reduced kidney function, low blood sodium or fluid in the abdomen, your team may set a lower limit — and their number replaces this one.
8–10glasses of fluid a day, the range most cancer bodies give
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Start here
Why fluid matters so much on chemotherapy
Fluid is not a wellness add-on during chemotherapy. For some drugs it is part of the treatment, written into the protocol alongside the dose.
It lightens the side effects you feel
Dehydration and chemotherapy cause the same complaints — tiredness, headache, dizziness, constipation, cramps. Some of what feels like the drug is fluid loss, and that part is fixable.
It keeps treatment on schedule
On cisplatin regimens, arriving under-hydrated can mean the cycle is postponed. One cancer centre tells patients exactly that.
Worth being clear about
The drugs that come with a fluid instruction
If your regimen is here, your team has already given you a fluid instruction. Knowing why is what makes it easy to follow on a bad day.
The drug, and what your team will askWhy the fluid is part of the treatment
Cisplatin — drip fluid before and after the dose, plus ten glasses the day before and eight to twelve a day for the week after.Cisplatin is directly toxic to the kidney tubules. Hydration is the established protection, and dose-banded fluid schedules are written into hospital protocols.
High-dose methotrexate — fast drip fluid, urine deliberately made alkaline, urine output measured.Methotrexate crystallises out of acidic urine and blocks the tubules. Published protocols run near three litres per square metre over 24 hours, with output above 100 mL an hour.
High-dose cyclophosphamide, and ifosfamide — at least two litres a day, emptying the bladder often, alongside a protective drug called mesna.These produce acrolein, which irritates the bladder lining and can cause bleeding. Mesna neutralises it; fluid and frequent emptying dilute it.
Most other regimens — the general eight to ten glasses.No special protocol, but the ordinary reasons hold: fewer symptoms and better bowel function.
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The days to drink more
When you need more than usual
- Vomiting or diarrhoea. Replace losses with something containing salt and sugar — oral rehydration salts, thin buttermilk, or water with salt, sugar and a little juice.
- Fever. Fluid needs rise with temperature. Call your team about the fever first, before anything else.
- Hot or humid weather. Hyderabad's pre-monsoon months are a real factor. Even people on a fluid limit may need it relaxed — with their team's say-so, never alone.
- Mouth sores. Mucositis makes drinking hurt, so intake quietly drops just when it should rise. Cool, bland and through a straw is easier than cold and sharp.
- The two days after a cisplatin infusion. One protocol calls these the most important 48 hours of the cycle for fluid.
- Constipation. The National Cancer Institute names fluid as a first step, alongside fibre and movement.
The other direction
When you may need less — and must ask
Meeting any one of these means your fluid target is a clinical decision rather than a general guideline. The rule that matters here is the one the British Heart Foundation states for its own patients: never change your fluid limit on your own.
- Heart failure
Some patients are given a daily limit, often quoted at around 1.5 to 2 litres. It is set individually, and it is not something to copy from a page.
- Reduced kidney function or dialysis
How much you can safely drink depends on how much urine you still pass and what happens to your weight between sessions. Your nephrology team sets this, not your oncologist alone.
- Low blood sodium
Some cancers and some cancer drugs make the body hold on to water and lose sodium. When blood sodium falls below the normal 135 to 145 range, more water can make things worse rather than better.
- Fluid in the abdomen, or swollen legs
Ascites and oedema are managed with diuretics, drainage and usually less salt. Whether fluid is also restricted is a judgement call on your individual case.
Practical, and local
What to drink, in an Indian kitchen
Everything wet counts, and variety is what gets the total up on a bad day. Two things change during chemotherapy: how the water is treated, and how fresh it has to be.
Safest default
Boiled, filtered or sealed bottled water
While your white cell count is low: filtered, distilled, boiled for a minute, or from a sealed bottle. Avoid loose ice from outside the home.
Evidence-backed
Oral rehydration salts
The right choice when losing fluid to vomiting or loose motions, because it replaces salts too. A home mix of water, salt, sugar and juice is endorsed in cancer-centre guidance.
Usually fine
Tender coconut water
A reasonable natural source of fluid and electrolytes. It does not treat or slow cancer. Ask first if your kidney function is reduced, because of the potassium.
Traditional
Buttermilk, barley water, thin dals and soups
Soups and milk drinks are recognised fluid sources. Buttermilk and barley water have not been studied in oncology — sensible tradition, not tested medicine. Pasteurised dairy, boiled water.
Go easy
What to go easy on
- Alcohol and caffeine
Both increase fluid loss. One cancer centre allows cisplatin patients one cup of caffeinated tea or coffee a day, and no alcohol.
- Full-strength sweet drinks
Concentrated sugar loosens the bowels, costing more fluid than the drink provides. Dilute them.
- Unpasteurised juices and cold-brewed drinks
While counts are low, skip roadside juices, sugarcane juice, fountain drinks, kombucha and shop-bought cold brew. Pasteurised or freshly boiled is the line.
- Grapefruit and related citrus
Grapefruit, pomelo and Seville orange block an intestinal enzyme many drugs depend on, pushing levels up. Ask your oncology pharmacist about your regimen.
Catch it early
Spotting dehydration early
Most of these are things you can see for yourself at home, and most of them appear before you feel properly unwell.
What you might noticeWhat it usually means
Passing less urine than usual; dark or strong-smelling urineThe commonest early sign, and the easiest to check. Pale and plentiful is the target.
Dry mouth, dry lips, dry eyesOften the first thing noticed, and easily mistaken for a drug side effect on its own.
Headache, dizziness, unusual tiredness, cramps or weaknessDehydration symptoms that overlap almost exactly with chemotherapy fatigue — which is why fluid is worth ruling out first.
Urine that is pink, red, orange, blue or greenSome drugs colour urine on their own — doxorubicin pink or red up to 48 hours, mitoxantrone blue-green for a day. Report it anyway, so blood is never mistaken for dye.
Skin that stays pinched when lifted; sunken eyes; weight down a kilo in a day or twoLater signs. This needs a phone call, not another glass of water.
Two things that cannot wait
A fever. If your temperature reaches 38°C (100.4°F) at any point during chemotherapy — or stays above 37.5°C, or drops below 36°C — call your team straight away, day or night. Do not take paracetamol first. It lowers the temperature and hides the one signal your team needs in order to judge how serious the situation is.
Not passing urine, or not keeping fluid down. Eight hours or more without passing urine, or 24 hours unable to keep liquids down, needs a call the same day. Dizziness on standing, confusion, drowsiness, breathlessness or a racing heart needs help immediately.
CION's helpline is 1800 202 8726 and it is answered 24 hours a day. One helpline covers every branch.
The easy part
Five habits that make it easy
None of this needs discipline so much as a system. Four habits cover most of it.
Load up the day before treatment
Start in the morning, not the evening. On cisplatin this is not optional.
Fill one marked bottle and finish it
A bottle of known volume turns a vague instruction into a visible target. Cisplatin patients are asked to log the amount.
Sip steadily, do not gulp
Small amounts often sit more comfortably when you are nauseated, and gulping swallows air.
Make it worth drinking
Lemon, cucumber or mint in water; ice chips to suck; soups, buttermilk, jelly and water-rich fruit all count.
Fluid is the one part of chemotherapy that is almost entirely in the patient’s hands. It is also the part most often quietly abandoned on the days it matters most.Dr. Naresh Gundu, Consultant Medical Oncologist, CION Cancer Clinics
Who reviews this page
The oncologist behind this advice
Dr. Naresh Gundu
Consultant Medical Oncologist, CION Cancer Clinics
MBBS, DNB, DM (Medical Oncology)
Dr. Gundu treats solid tumours with chemotherapy, targeted therapy and immunotherapy, and reviews CION's patient information on systemic treatment.
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The questions patients actually ask
Frequently asked questions
How much water should I drink during chemotherapy?
There is no single number that is right for everyone. The usual range is eight to ten glasses — roughly two to two and a half litres — spread through the day. Cancer Research UK says eight to ten glasses; the National Cancer Institute says eight cups or more; Macmillan's drug pages ask for at least two litres.
Ask your own team for your number. It is higher on cisplatin, and it may be lower if you have heart failure, reduced kidney function or fluid on the abdomen.
Why does cisplatin need so much more fluid than other chemotherapy drugs?
Cisplatin is directly toxic to the kidney tubules, and dilution is the protection. Keeping urine fast and dilute shortens the drug's contact time, which is why intravenous fluid is given before and after the dose.
One cancer centre asks for at least ten eight-ounce glasses the day before, and says plainly that too little can mean the chemotherapy is postponed.
Can I drink coconut water during chemotherapy?
For most people, yes. One cancer centre lists it alongside broths and sports drinks for patients losing fluid to vomiting or diarrhoea.
Two cautions: it does not treat or slow cancer, whatever you may be told; and anyone with reduced kidney function should ask first, because coconut-water-induced high potassium is documented in the medical literature.
Is it normal for my urine to change colour during chemotherapy?
With some drugs, yes. Doxorubicin can turn urine pink or red for up to 48 hours — that is the colour of the drug. Mitoxantrone can turn it blue-green for about a day.
Report any colour change anyway. Pink or red urine after ifosfamide or cyclophosphamide can be blood rather than dye, and that needs checking the same day.
When should dehydration make me call the hospital?
Call the same day if you have passed no urine for eight hours or more, if vomiting, diarrhoea or fever has lasted more than 24 hours, or if you cannot keep liquids down. Call immediately if you are dizzy on standing, confused, drowsy, breathless or your heart is racing.
CION's helpline is answered 24 hours a day, and this is what it is for.
Should I drink less water if my ankles or abdomen are swelling?
Possibly — but that is your team's decision, not yours. Swelling, fluid in the abdomen, heart failure, reduced kidney function and low blood sodium can all mean a personal limit lower than any general advice.
The same applies in reverse: do not relax a limit your team has set because the weather is hot. Ask them first.
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Sources
- Dehydration when you have cancer — Cancer Research UK
- Nutrition in cancer care — fluid intake — National Cancer Institute
- Staying hydrated before and after moderate to high-dose cisplatin — Memorial Sloan Kettering Cancer Center
- Mesna, and doxorubicin with ifosfamide — Macmillan Cancer Support
- Cancer treatment side effect: dehydration — MD Anderson Cancer Center
- Fluids and dehydration — American Cancer Society
- Cisplatin drug monograph — hydration schedules — BC Cancer
- Cisplatin hydration in treatment protocols — eviQ, Cancer Institute NSW
- Mesna and acrolein-induced haemorrhagic cystitis — StatPearls, NIH National Library of Medicine
- Neutropenic diets: what cancer patients should know — MD Anderson Cancer Center
- Neutropenic diet — safe and unsafe drinks — Memorial Sloan Kettering Cancer Center
- Grapefruit juice and some drugs don't mix — US Food and Drug Administration
- Mitoxantrone — blue-green discolouration of urine — MedlinePlus, NIH
- Hyponatraemia and SIADH — National Kidney Foundation
- Fluid restriction in heart failure, and hot weather — British Heart Foundation
- Treating fever and infection — call before taking anything — Cancer Research UK
General information, not a prescription. This page explains what is generally true for people having chemotherapy. It is not advice about your own treatment, and nothing on it should be used to start, stop or change a medicine. Your own oncology team knows your diagnosis, your drugs, your blood results and your other conditions — we do not. If anything here worries you, or anything about your treatment feels wrong, call your team on 1800 202 8726. The helpline is answered 24 hours a day.