Protecting your kidneys during chemotherapy

The most important protection is staying well hydrated, especially around treatments that are known to affect the kidneys, such as cisplatin, ifosfamide and high-dose methotrexate. Plenty of fluid keeps blood flowing through the kidneys and helps flush medicines and waste products out in the urine, so they spend less time in contact with the delicate kidney filters. That is why these treatments often start with fluids through a drip before the chemotherapy, called pre-hydration, and continue with fluids during and after.

The other key steps are avoiding things that add strain to the kidneys, such as certain painkillers, some herbal remedies and dehydration from untreated vomiting or diarrhoea, and keeping blood pressure and diabetes well controlled. How much you should drink is not the same for everyone. People with heart failure or existing kidney disease may need less fluid, and too much can cause harm. Your team will tell you the amount that is right for you, and will check kidney function with blood tests before each cycle. This page explains the principles; it does not replace the instructions your own team gives you.

Pre-hydration has a purpose

The hours of fluids before some treatments are not a delay. They prepare the kidneys to clear the medicine safely.

Vomiting and diarrhoea are kidney risks

Losing fluid quickly can strain the kidneys within a day, so report them early.

Your team adjusts to your health

Advice differs for people with heart or kidney conditions, so follow your personal plan.

It cannot tell you exactly how much fluid you should drink. That depends on your medicines, your weight, the weather, your heart and kidney health, and whether you are losing fluid through vomiting or diarrhoea. Your team gives personal instructions, and those always come first.

It also cannot interpret your kidney test results or tell you whether your treatment should change. Your oncologist uses your creatinine and other tests to decide doses and timing.

Heart failure needs a careful balance

If you have heart failure, extra fluid can cause breathlessness and swelling. Follow your team's plan precisely and weigh yourself if advised.

Hot weather increases fluid needs

In summer, and when travelling long distances to treatment, you lose more fluid. Carry water and drink regularly.

Fasting needs discussion

Religious fasts that restrict fluids can strain the kidneys around chemotherapy. Discuss timing with your team before fasting.

Night-time toilet trips

Extra fluids mean waking to pass urine. Use a night light and keep a clear path to avoid falls.

Children and older adults

Both can become dehydrated quickly and may not feel thirsty. Carers should offer drinks regularly and watch urine output.

Salt and mineral replacement

Some medicines cause loss of magnesium and potassium. Supplements may be prescribed; take them only as advised.

Alcohol and very sugary drinks

Alcohol dehydrates, and very sugary drinks can upset blood sugar on steroids. Water and simple fluids are better choices.

Scans with contrast dye

Tell scan staff about your chemotherapy. Extra fluids may be given around a contrast scan to protect the kidneys.

Ask what to avoid

Before taking any new medicine, even for a cold or pain, ask whether it is safe for your kidneys during treatment.

Plan fluids for the journey home

Long journeys after treatment can mean hours without drinking or passing urine. Carry water, plan toilet stops, and avoid cutting back on fluids to reduce stops on the way.

What to do next

Ask your team how much to drink and for how long, drink little and often, watch your urine colour, avoid kidney-harming painkillers and remedies, treat sickness early, and call promptly if you pass very little urine or cannot keep fluids down.