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What is fluid balance?  

What Fluid balance is about drinking the right amount every day. Half of your body is made of water and most of what you drink (tea, fruit juice, beer) is water. 

People with normal functioning kidneys can keep the water in their body at about the same level by getting rid of fluid in their urine. A smaller amount is removed by sweat and in your stools. 

Managing your fluid intake is very important for dialysis patients. Normally your kidneys are responsible for removing extra fluid. But when your kidneys fail they can no longer do this. Dialysis can only remove some of the extra fluid from your body so you need to make sure you consume less. 

You also lose water by sweating and on really hot days you need to drink more,

but if you drink too much it will stay inside your body. Some patients on dialysis will pass some urine and this means you can drink a little bit more. 

Fluid overload can result in:

  • breathlessness
  • swelling in your face and/or ankles
  • high blood pressure
  • headaches and low energy
  • and over time, enlargement of the heart.

Excessive weight gain between dialysis sessions means that you need to cut back on your salt and water intake. 

Controlling sodium (salt) intake will help to avoid large fluid gains, cramping and low blood pressure. 

Fluid can come from obvious sources (drinks) but also from food with a high water content such as soups, gravy, nutritional drinks, ice cream, custard and ice cubes. 

Because each half litre of water weighs just over a pound (500g), your weight goes up if you start to retain water. Retaining water can lead to high blood pressure as well. 

However, if you don’t drink enough and you are sticky or sweating a lot, too little water in your body can make your blood pressure drop making you feel weak and dizzy when you stand. 

What you need to do

Be careful how much you drink. You will be told how much fluid you can drink by your renal nurse, doctor, or dietitian. For patients on haemodialysis this could be around two pints per day and for patients on peritoneal dialysis it could be up to three pints per day. On hot days you might need to drink a little more. Over time on dialysis, you will notice a decrease in the production of urine and hence the need for further restriction on your fluid intake. 

Limiting your intake of water is not easy, and is worth exploring the options that work for you. Drink from small cups of fluid, frequent rinsing of your mouth, sucking on sugar-free candy/gum or freeze your favourite drink in small bottles so that you can drink from it as the ice melts. 

Salt drives thirst and increases water retention in the body. It is important that you don’t eat much salt so you must avoid adding extra salt on table, avoid salty snacks such as crisps, cut back on prepacked frozen meals and fast foods. Addition of spices and herbs in your cooking helps mask the lack of salt. 

It is important to know how much you should weigh. This is called your base

weight (dry weight). You need to weigh yourself regularly. If you put on a few

pounds quickly then try drinking less. If you are not sure, you should ask your renal nurse, doctor, or dietitian. 

Comply with medication. If you are producing urine and are on water tablets, make sure that you take them as prescribed. 

Dress and stay cool on warm days; use a fan that produces humidified air to help reduce rapid fluid loss.   

Water tablets (DIURETICS)

Water tablets are used to help your kidneys remove extra fluid. They are best taken in the morning (taking them at night could keep you running to the toilet during the night). Side effects can include dizziness or feeling sick – try taking the tablets with food to reduce any side effects. Always take tablets as directed by your doctor and only stop them on the advice of your doctor. 

You should see your doctor or nurse to talk about changes to your fluid balance if:

  • You start to find it hard to breathe
  • If you feel weak and dizzy when you stand up
  • If you notice that your ankles are swelling up.

Written June 2023
Next review June 2026

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The National Kidney Federation cannot accept responsibility for information provided. The above is for guidance only. Patients are advised to seek further information from their own doctor.