The renal diet: your kidneys, your dietitian's numbers. Not the internet's.
A renal diet limits sodium, and sometimes protein, potassium, phosphate and fluid, when your kidneys can't keep up. The right limits depend on your blood tests and your stage of kidney disease. Here's how it works, what the guidelines say, and why a generic list can do more harm than good.
The short version
- What it is
- A diet for chronic kidney disease (CKD), set by your kidney team: less sodium, the right amount of protein, and potassium, phosphate and fluid limits only if your results need them.
- Good for
- Lowering the load on damaged kidneys and keeping blood levels of potassium and phosphate in a safe range.
- Bad at
- Being one-size-fits-all. Early CKD, late CKD and dialysis need very different diets.
- Evidence
- Strong guidelines, mostly moderate-to-low certainty trials behind each number.
- Our take
- Pure doctor territory. Our high-protein, fasting plan is exactly what kidney patients shouldn't follow on their own.
What the renal diet actually is
"Renal" just means kidney. A renal diet is an eating plan for people whose kidneys don't filter as well as they should. It's not one fixed list. The international kidney guideline (KDIGO) asks doctors to send people with CKD to a renal dietitian, who adapts sodium, phosphorus, potassium and protein to the person, the stage of their disease and their other conditions.1
The same guideline's general advice for everyone with CKD is refreshingly normal: a varied diet with more plant foods than animal foods, and less ultra-processed food.1 Everything beyond that depends on your blood tests.
That's why you'll find contradictory renal diet lists online. One says avoid bananas, another says eat more plants. Both can be right, for different people.
How it works in your body
Healthy kidneys filter waste out of your blood, balance salt and water, and get rid of extra potassium and phosphate. When kidney function drops, those jobs fall behind.
- Sodium: damaged kidneys struggle to get rid of salt and water, which raises blood pressure and causes swelling. Lower sodium takes pressure off.
- Protein: breaking down protein makes waste products your kidneys have to clear. Very high protein adds to the workload.
- Potassium: if it builds up in the blood (hyperkalaemia), it can become dangerous.
- Phosphate: it comes naturally from protein foods, and as additives in processed food. Your body absorbs more of it from animal foods than from plants.3
- Fluid: damaged kidneys can't remove extra fluid well, so some people need to limit how much they drink.3
Which of these apply to you depends on your stage of CKD, your other conditions and your blood tests.1
What you eat, what you don't
This is a general picture. Your kidney team's list wins every time.
Eat (in the amounts your team sets)
- Fresh vegetables and fruit, portions sized to your potassium limit
- Fresh fish, eggs, chicken, in measured portions
- Plant protein: tofu, lentils, beans (rinsed if tinned)
- Rice, noodles, bread, oats, as your team advises
- Olive oil, rapeseed oil
- Herbs, spices, garlic, lemon instead of salt
- Water, within any fluid limit
Forget it
- Salt substitutes made with potassium chloride
- Processed and deli meats, Wurst, ham, luncheon meat
- Instant noodles, stock cubes, ready meals, soy and oyster sauce by the splash
- Cola and flavoured drinks with added phosphate
- Herbal remedies and supplements your doctor hasn't okayed
- High-protein shakes and "protein everything" snacks
- Long fasts and extreme diets
Alcohol on a renal diet
Only if your kidney team says yes
- A small glass of wine, with food, counted in your fluid limit
- A spirit with water or soda water, counted in your fluid limit
Out
- Cola mixers (added phosphate)
- Big glasses and pints if you're on a fluid limit
- Salty bar snacks
- Drinking on top of medicines without asking
50 Club: not on a prescribed diet. Ask your doctor or dietitian what's safe for you.
The practical points: every drink counts towards a fluid limit if you have one,3 and colas often contain phosphoric acid, one of the "PHOS" additives renal patients are told to avoid.3 Whether alcohol is OK at all depends on your medicines and your other conditions. All the details are in our alcohol guide.
What it's good for, with proof
Lower sodium, lower blood pressure
KDIGO suggests people with CKD eat less than 2 g of sodium a day, which is under 5 g of salt.1 High blood pressure and kidney damage tend to feed each other, so salt is usually the first lever. More on that in our low sodium article.
The right amount of protein
KDIGO suggests about 0.8 g of protein per kg of body weight a day for adults with moderate to severe CKD (stages 3 to 5), and says to avoid high intakes above 1.3 g/kg in people at risk of their CKD getting worse.1 For a 70 kg adult that's roughly 56 g a day. That's a normal, sensible amount, not a starvation diet.
Going lower, under close supervision, may help some people. A Cochrane review of adults without diabetes found that very low-protein diets probably reduced the number of people reaching kidney failure compared with low-protein diets (10 studies, 1,010 people).2 But simply going from normal to low protein made little or no clear difference. Very low-protein diets are a specialist tool, with added amino acids, and KDIGO says they shouldn't be used in people who are unwell or unstable.1
Keeping potassium and phosphate safe
If your potassium runs high, KDIGO advises limiting foods rich in easily absorbed potassium, such as processed foods, with a renal dietitian guiding the details.1 The US kidney institute (NIDDK) adds simple tricks: watch portion size, drain tinned fruit and vegetables, and boil or soak some vegetables to remove potassium. For phosphate, it suggests checking ingredient lists for anything with "PHOS" in it, like phosphoric acid or disodium phosphate.3
The uncomfortable truth
"Kidney patients should avoid fruit and vegetables." Not as a rule. KDIGO actually asks for more plant foods than animal foods in CKD.1 Only people with high potassium need to limit certain ones, and processed food is often the bigger problem. Banning all bananas from everyone with CKD is the internet's idea, not the guideline's.
"Drink lots of water to flush your kidneys." Fine for healthy people. For some people with advanced kidney disease, extra fluid is exactly what their kidneys can't remove, and they're told to limit it.3 Ask your team for your number before you buy the two-litre bottle.
The risks
- Malnutrition. Cut protein and food too hard and you lose muscle and strength. Too little protein can lead to malnutrition, which is why the goal is balance.3
- High-protein diets. Fashionable for weight loss and muscle, but KDIGO advises avoiding intakes above 1.3 g/kg a day if your CKD may progress.1 Our own high-protein rule is not for you without your doctor.
- Fasting on SGLT2 drugs. Many people with CKD now take SGLT2 drugs such as dapagliflozin or empagliflozin. KDIGO says it's reasonable to pause them during prolonged fasting, because of the risk of ketosis.1 Never start a long fast or a keto diet on these drugs without your doctor.
- Salt substitutes. Many are high in potassium chloride. NIDDK tells people with kidney disease to avoid them.3
- Herbal remedies and supplements. Some can harm the kidneys. KDIGO asks doctors to review and limit over-the-counter and herbal products in CKD.1 "Natural" is not a safety rating.
- Dialysis changes the rules. People on dialysis often need more protein, because dialysis removes some of it.3 An old pre-dialysis diet sheet can be wrong after you start.
Allergies: watch the staples
Renal meal plans commonly use eggs, fish, rice, noodles and plant protein. Several of those are major allergens, and allergy plus kidney limits makes planning harder. Your dietitian needs to know both.
| Staple | Allergen (EU list of 14)4 | Swap (check with your dietitian) |
|---|---|---|
| Eggs, egg whites | Eggs | Fresh fish, chicken |
| Fresh fish | Fish | Eggs, chicken |
| Tofu, soy milk | Soybeans | Eggs, lentils within your potassium limit |
| White bread, pasta, noodles | Cereals containing gluten | Rice, rice noodles |
| Milk, yoghurt (often limited anyway) | Milk | Unfortified rice drink, if your dietitian agrees |
| Prawns, shellfish | Crustaceans, molluscs | Fresh fish, chicken |
Don't follow a renal diet off the internet if you…
- haven't had your kidney function and blood potassium checked
- are on dialysis or have had a kidney transplant
- also have diabetes, heart failure or liver disease
- take SGLT2 drugs, diuretics, or blood pressure drugs that affect potassium
- are pregnant, under 18, or underweight
Healthen me asks about all of these and gives you a different plan if any apply.
How we use the renal diet in your plan
We don't plan renal diets. Kidney disease needs blood tests, a kidney doctor and a renal dietitian, and we are none of those.
Healthen me asks about kidney disease. If you have it, you don't get our fasting or high-protein rules. You get a gentle, non-fasting plan and a clear message to take it to your doctor or dietitian first.
What that plan keeps: real food cooked from scratch, few packets, less salt, no soft drinks, more vegetables than meat. Your dietitian can then adjust protein, potassium, phosphate and fluid to your numbers. We don't do that part, and we won't pretend to.
This article is general information, not medical advice. If you have a medical condition or take medication, talk to your doctor before changing how you eat.
Sources
- Kidney Disease: Improving Global Outcomes (KDIGO) CKD Work Group. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney International 2024;105(4S):S117–S314. doi.org/10.1016/j.kint.2023.10.018
- Hahn D, Hodson EM, Fouque D. Low protein diets for non-diabetic adults with chronic kidney disease. Cochrane Database of Systematic Reviews 2020;10:CD001892. doi.org/10.1002/14651858.CD001892.pub5
- National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK). Healthy eating for adults with chronic kidney disease. niddk.nih.gov
- Regulation (EU) No 1169/2011 on food information to consumers, Annex II (the 14 allergens). eur-lex.europa.eu/eli/reg/2011/1169/oj