It would be sensible to follow a healthy diet, which will help to reduce the risk of the kidney disease becoming worse.
If your kidney function is becoming worse (stage 4 to 5), you will probably be referred to a specialist in renal (kidney) medicine. If they think that you need to follow a special diet, they will refer you to a dietician who can give you advice about what you should eat.
Some of the chemicals or salts that healthy kidneys balance are sodium, potassium and phosphate. If they are not removed by the kidneys, their levels can build up in the body.
Sodium in the diet primarily comes from eating salt. People who have CKD should aim to eat no more than 2-3 g of sodium daily. You should not add salt to your food when cooking or at the table. Also, try to avoid buying foods which are high in salt, such as:
- Bacon and other cured meats.
- Hard cheese.
- Yeast extract.
- Stock cubes.
- Salted nuts and crisps.
However, there is also quite a bit of salt in bread, breakfast cereals, biscuits and sauces. Checking the labelling on the packet will help you to look for brands which are lower in sodium.
Normal blood levels of potassium help keep your heart beating steadily. However, too much potassium can build up when the kidneys no longer function well. Dangerous heart rhythms may result, which can lead to death. Potassium restriction is usually only advised if your potassium levels have been found to be high.
Potassium is found in many food groups, including fruits and vegetables. Choosing items from the lower potassium groups can help to control your potassium levels.
When eating fruits
Choose peaches, grapes, pears, cherries, apples, berries, pineapple, plums, tangerines, watermelon, cranberries and strawberries.
Limit or avoid oranges and orange juice, nectarines, kiwis, raisins (or other dried fruit), bananas, cantaloupe melon, honeydew melon, prunes and nectarines.
When eating vegetables
Choose broccoli, cabbage, carrots, cauliflower, celery, cucumber, aubergine, green and wax beans, lettuce, onion, peppers, watercress, courgette, bean sprouts, sweetcorn and mushrooms.
Limit or avoid asparagus, avocado, potatoes, tomatoes or tomato sauce, butternut squash, pumpkin, artichoke, sweet potato, beetroot, Brussels sprouts and cooked spinach.
When eating other foods
Choose pitta, tortillas and white breads, white rice, beef and chicken.
Limit or avoid higher-fibre whole grains (such as brown rice or bran) and beans (for example, baked beans).
Phosphate and calcium are important for bone strength. If the phosphate level becomes too high it will reduce the calcium level and that can weaken the bones. High phosphate can also cause itching. You probably don't need to worry about phosphate levels if you have early CKD (stage 1 or 2).
Foods lower in phosphorus
- White bread, pasta and rice.
- Most fruits and vegetables.
- Corn or rice cereals, popcorn.
- Some light-colored sodas and lemonade.
Foods higher in phosphorus
- Meat (including poultry) and fish.
- Wholegrain bread.
- Dairy products.
- Bran cereals and oatmeal.
- Nuts and sunflower seeds.
- Dark-colored colas.
- Vegetables such as sweet potatoes, peas and mushrooms.
- Pulses such as lentils.
The kidneys remove waste products of protein from the body as a chemical called urea. In the past, diet advice for people with kidney disease has included advice about restricting protein. However, current advice looks at getting a good balance: not too much and not too little.
Foods which contain protein include meat, fish, eggs, cheese, pulses and nuts.
A diet which is too low in protein can lead to muscle wasting and fatigue. Such a diet can also lead to problems with insulin and blood sugar levels.
The kidneys balance the overall water level in the body (hydration). There is no need to restrict fluid intake in the early stages of kidney disease. However, if you have more advanced kidney disease, your kidneys are no longer producing much urine. In this situation, you need to reduce the amount of fluid you take in as drinks or in food. Your renal doctor or your dietician will be able to advise you about this.
There are no special guidelines about alcohol intake for people with kidney disease. However, it is sensible to stick to the usual guidelines of no more than two units of alcohol per day.
Healthy kidneys make vitamin D, so even people with early CKD should be taking vitamin D supplements. Vitamin D is important for bone strength. You may need to take additional calcium with the vitamin D.
Other vitamin supplements may be helpful if you have had a poor diet for a while. CKD can cause a reduction in appetite and feelings of nausea. Therefore, if you are not managing to eat a balanced diet, ask your doctor if they would recommend a multivitamin.
The kidneys have a role in making red blood cells, so CKD can lead to anaemia. Iron levels can also be low if your diet is not very good. Your doctor may prescribe you some iron tablets to take if your iron levels are low.
Maintaining a healthy weight
It is important to maintain a healthy weight if possible, to reduce the risk of other conditions developing.
CKD can cause a reduction in appetite as the condition progresses. A dietician can advise you which foods will help you to avoid losing weight. If you find it difficult to eat enough in regular meals, your doctor may recommend some food supplements to help you maintain your food intake.
Obesity can cause problems if your CKD has progressed far enough to require dialysis or a kidney transplant. If you are trying to lose weight, ask your doctor's advice. A steady weight loss with a low-fat plan including lots of fruits and vegetables will be a better option for your kidneys than a diet of low carbohydrates and high protein.
As your kidney function worsens, your specialist may decide that you need to start dialysis. Haemodialysis is a procedure where your blood is passed through a machine to remove the waste products (as your kidneys would do if they were working). In peritoneal dialysis, fluid is pumped into your abdominal cavity to remove the waste products.
The advice about eating and drinking is slightly different for people who are on dialysis.
Phosphate is not removed very well by dialysis. Therefore, you may need to take medication called phosphate binders to reduce the level of phosphate in the blood.
If your kidney function is worsening so much that you will need to start dialysis, your doctor will probably ask you to reduce your protein intake. This aims to reduce the build-up of urea in the blood (uraemia). Uraemia can make you feel quite unwell.
Once you start on dialysis you may need to increase your protein intake a bit, as some protein is lost in the dialysis fluid. This happens more if you have peritoneal dialysis rather than haemodialysis.
If you are on haemodialysis, your daily fluid intake should be what you pass in urine (generally very little) plus 500 ml.
Peritoneal dialysis is a bit more flexible. However, you should usually have about 750 ml per day on top of the volume of urine you produce.
Soluble vitamins (B and C) are lost in dialysis fluid, so should be replaced with vitamin tablets.
Maintaining a healthy weight
You may need to increase your food intake when you are on dialysis, as it causes an increase in your body's energy needs. If you are having peritoneal dialysis, some sugar (glucose) is lost in the dialysis fluid.
Further reading and references
Chronic kidney disease: early identification and management of chronic kidney disease in adults in primary and secondary care; NICE Clinical Guidelines (July 2014, updated Jan 2015)
Hyperphosphataemia in chronic kidney disease; NICE Clinical Guideline (Mar 2013)
Chronic kidney disease: managing anaemia; NICE Clinical Guideline (June 2015).
Sommerer C, Zeier M; Clinical Manifestation and Management of ADPKD in Western Countries. Kidney Dis (Basel). 2016 Oct2(3):120-127. Epub 2016 Oct 6.
Diet in Renal Disease; Edinburgh Renal Unit
Blann A; Routine blood tests 1: why do we test for urea and electrolytes? Nursing Times 110: 5, 19-21, 2014.
Fraser SD, Blakeman T; Chronic kidney disease: identification and management in primary care. Pragmat Obs Res. 2016 Aug 177:21-32. eCollection 2016.
Alaini A, Malhotra D, Rondon-Berrios H, et al; Establishing the presence or absence of chronic kidney disease: Uses and limitations of formulas estimating the glomerular filtration rate. World J Methodol. 2017 Sep 267(3):73-92. doi: 10.5662/wjm.v7.i3.73. eCollection 2017 Sep 26.