Kidney Health 10 min read·Updated 22 July 2026 Clinician-reviewed

Potassium and Kidney Disease

A UK Consultant Nephrologist on why potassium control matters in chronic kidney disease — what hyperkalaemia is, how it is managed, and which foods to watch.

  • Clinically Reviewed
  • NHS & NICE Aligned
  • UK Evidence-Based
  • Last Reviewed 22 July 2026

Professor Mohammed Mahdi Althaf

Consultant Nephrologist & Acute Physician

View Credentials

Professor Mohammed Mahdi Althaf

MD, MSc, PgDip (Clin Ed), FRCP, FHEA, FASN

Consultant Nephrologist & Acute Physician · GMC 7216325

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Direct answer

Potassium is an essential mineral, but in CKD it can build up in the blood (hyperkalaemia) and cause dangerous heart rhythm problems. Restriction is usually needed from stage 4 onwards or when blood potassium rises above 5.0 mmol/L. A renal dietitian can personalise your potassium budget.

Key recommendation: Normal blood potassium: 3.5–5.0 mmol/L.

Quick answer

✓ Best choices

  • Apples, pears, berries, grapes, pineapple, watermelon
  • Leached potatoes (peel, dice, soak, double-boil) and lower-potassium veg
  • White rice, pasta, couscous, bread

✓ Foods to limit

  • Bananas, oranges, kiwi, mango, avocado, dried fruit
  • Tomato-based sauces, baked potato skin, large servings of beans
  • Chocolate, nuts and seeds in big portions
  • Potassium-based salt substitutes ('LoSalt') — avoid completely

Key takeaway

Potassium is an essential mineral, but in CKD it can build up in the blood (hyperkalaemia) and cause dangerous heart rhythm problems. Restriction is usually needed from stage 4 onwards or when blood potassium rises above 5.0 mmol/L. A renal dietitian can personalise your potassium budget.

Who should be cautious

People on dialysis, post-transplant, pregnant or breastfeeding, or taking prescription medication — confirm with your renal team before changes.

Potassium and Kidney Disease

How the kidneys handle potassium

Potassium is critical for heart rhythm, muscle function and nerve signalling. Healthy kidneys filter about 90% of excess potassium into urine. In CKD, as nephrons are lost, the remaining kidneys struggle to excrete potassium. The body has backup mechanisms (shifting potassium into cells via insulin and aldosterone), but these become overwhelmed as eGFR falls below 30 ml/min/1.73 m².

Medicines that raise potassium

Several protective CKD medicines reduce potassium loss — this is usually a good trade-off, but requires monitoring. ACE inhibitors (ramipril, lisinopril), ARBs (losartan, valsartan), and potassium-sparing diuretics (spironolactone, eplerenone, amiloride) all raise potassium. NSAIDs (ibuprofen, naproxen) also raise potassium by reducing kidney blood flow. Never stop prescribed medicines without discussing with your clinician — blood tests and diet adjustment are usually enough.

Some standard multivitamins include added potassium salts. Kidney Vitality is formulated without added potassium. See the formulation.

The potassium food league table

Very high (> 500 mg per 100 g): dried fruit, tomato paste, spinach, Swiss chard, beetroot greens, salt substitutes. High (300–500 mg): bananas, oranges, potatoes, sweet potatoes, avocado, beans, lentils, nuts, seeds. Moderate (150–300 mg): tomatoes, broccoli, carrots, peas, yoghurt, milk, fish, chicken. Low (< 150 mg): apples, berries, pears, cauliflower, cabbage, cucumber, peppers, white rice, pasta, bread, eggs, oils. Tip: boiling root vegetables and draining the water can remove 30–50% of potassium.

Cooking techniques that lower potassium

  • Double-boiling (boil, drain, boil again in fresh water): best for potatoes and root vegetables.
  • Steaming: removes less potassium than boiling.
  • Roasting: water evaporates, concentrating potassium per gram.
  • Soaking: cut vegetables into small pieces and soak in warm water for 2+ hours before cooking.
  • Avoid: slow-cooker stews where potassium leaches into the liquid and is then consumed as gravy.

When to seek urgent help

If your blood potassium has been flagged as dangerously high, or you develop palpitations, chest pain, muscle weakness, or fainting, seek urgent medical advice. Severe hyperkalaemia can cause life-threatening arrhythmias and needs hospital treatment with calcium, insulin/glucose, or dialysis.

Foods to Avoid with Kidney Disease
Related reading: Foods to Avoid with Kidney Disease.

Key practical tips

Designed for quick scanning — what to order, what to avoid, sensible portions, common mistakes.

  • The leaching method removes ~50% of potassium from root veg
  • Smaller, more frequent portions of fruit are safer than one large serving
  • Always check your latest blood result before tightening or loosening

Clinical guidance

TL;DR summary

Potassium is an essential mineral, but in CKD it can build up in the blood (hyperkalaemia) and cause dangerous heart rhythm problems. Restriction is usually needed from stage 4 onwards or when blood potassium rises above 5.0 mmol/L. A renal dietitian can personalise your potassium budget.

Key takeaways
  • Normal blood potassium: 3.5–5.0 mmol/L.
  • Hyperkalaemia > 5.5 mmol/L needs action; > 6.5 is an emergency.
  • ACE inhibitors, ARBs and spironolactone can raise potassium.
  • Dried fruit, bananas, potatoes, tomatoes and beans are highest in potassium.
  • Leaching (boiling and draining) reduces potassium in vegetables.
Kidney Diet & Nutrition Considerations

Potassium needs are personal — only your blood result tells you whether you need to restrict. If your renal team has asked you to lower dietary potassium, the focus is on portion size, swaps and the cooking method, not removing fruit and vegetables entirely.

Foods to prioritise

  • Apples, pears, berries, grapes, pineapple, watermelon
  • Leached potatoes (peel, dice, soak, double-boil) and lower-potassium veg
  • White rice, pasta, couscous, bread

Foods to limit

  • Bananas, oranges, kiwi, mango, avocado, dried fruit
  • Tomato-based sauces, baked potato skin, large servings of beans
  • Chocolate, nuts and seeds in big portions
  • Potassium-based salt substitutes ('LoSalt') — avoid completely

Potassium, phosphate and protein needs vary between individuals — please confirm personal targets with your renal team or dietitian. Browse the Kidney Diet Hub for more guides in this cluster.

Frequently asked questions

Why does kidney disease raise potassium levels?

Healthy kidneys remove excess potassium through the urine. As CKD progresses, the kidneys filter less efficiently and potassium builds up in the blood. Medications that protect the kidneys — ACE inhibitors, ARBs and spironolactone — can also raise potassium by reducing its loss in urine. The result is hyperkalaemia (high blood potassium).

What is a dangerous potassium level?

Normal blood potassium is 3.5–5.0 mmol/L. Between 5.1 and 5.5 is mildly high. Above 5.5 needs action. Above 6.0 is dangerous and can cause abnormal heart rhythms. Above 6.5 is a medical emergency. If you have CKD, your GP or renal team will tell you your personal target.

What are the symptoms of high potassium?

Mild hyperkalaemia often causes no symptoms — it is usually found on a blood test. Moderate-to-severe levels can cause muscle weakness, tingling, palpitations, chest discomfort, or an irregular heartbeat. Because symptoms are unreliable, regular blood tests are essential in CKD.

Which foods are highest in potassium?

The highest-potassium foods include: dried fruit (raisins, apricots, dates), bananas, oranges and orange juice, tomatoes and tomato paste, potatoes and sweet potatoes, spinach and other dark leafy greens, beans and lentils, nuts and seeds, avocado, and salt substitutes made with potassium chloride.

Can I still eat fruit with high potassium?

Yes — choose lower-potassium fruits. Safe options include apples, berries, pears, peaches, plums, and tinned fruit in juice (drained). Avoid fruit juices, smoothies, dried fruit, and large portions of banana, orange, melon or kiwi.

Do I need a low-potassium diet at every CKD stage?

Not necessarily. Potassium restriction is usually introduced when blood potassium rises above 5.0 mmol/L, or in stage 4–5 CKD and on dialysis. Many people with stage 1–3 CKD have normal potassium and do not need restriction. Your renal dietitian will tailor advice to your blood results.

What are the worst foods for high potassium?

The highest-potassium everyday foods are potatoes (especially baked with skin), tomatoes and tomato purée, bananas, oranges and orange juice, dried fruit, avocado, beans in large portions, chocolate, and potassium-based salt substitutes such as 'LoSalt'.

Nutritional challenges in kidney disease

Many people living with kidney disease have to limit foods because of potassium, phosphate, diabetes, dialysis, appetite changes or simply the time it takes to cook from scratch every day. That can make it harder to keep daily nutrition balanced — particularly for vitamins and minerals that food alone may not fully cover.

Kidney Vitality is a UK-formulated daily nutritional support product designed by Consultant Nephrologist Professor Mohammed Mahdi Althaf with renal nutrition in mind from the start. It keeps doses moderate, leaves out added potassium, phosphate and magnesium, and avoids megadose vitamin A — sitting alongside a kidney-friendly diet, not replacing it.

Why Kidney Vitality fits this need

Built around UK renal guidance

Aligned with NICE NG203, the BDA renal nutrition fact sheet on potassium, and KDIGO 2024.

Designed by a UK Consultant Nephrologist

Formulated and reviewed by Professor Mohammed Mahdi Althaf (GMC 7216325).

Evidence-based by design

Practical food tables and cooking tips you can use at home, with safety-netting for dangerous potassium levels.

Designed by a UK Consultant Nephrologist

Ready to support your kidney health?

If you have been researching kidney health, supplements, CKD nutrition or kidney-friendly living, Kidney Vitality was developed specifically around those principles by Professor Mohammed Mahdi Althaf (GMC 7216325). A daily multivitamin formulated without added potassium.

  • No Added Potassium
  • No Added Magnesium
  • No Added Phosphorus
  • Developed by a Consultant Nephrologist
  • One capsule daily
  • UK GMP — BRCGS, NSF GMP, Halal
Subscribe & Save — £20.39/monthCheck your current multivitamin

✓ Free UK tracked delivery  ·  ✓ Delivered every 30 days  ·  ✓ Pause or cancel anytime  ·  ✓ Never run out

ComparisonKidney VitalityTypical high-street multivitamin
Added potassiumNoneOften included
Added phosphateNoneOften included (E338–E452)
Vitamin A (retinol)No megadoseOften high-dose retinol
Kidney-focused formulationYesNo — general population
Consultant Nephrologist involvementYes (GMC 7216325)No
UK GMP manufacturedYes (BRCGS, NSF GMP)Varies

Food supplement. Not a medicine and not a treatment for kidney disease. Speak with your GP, pharmacist or renal team before starting any new supplement, especially in advanced CKD, on dialysis, post-transplant, pregnant or breastfeeding.

Clinical reviewer

Professor Mohammed Mahdi Althaf

Consultant Nephrologist

Acute Physician

GMC 7216325

View Full Biography

Professor Mohammed Mahdi Althaf is a UK Consultant Nephrologist and Acute Physician with a special interest in chronic kidney disease, AKI prevention and renal nutrition. He combines hospital practice with patient education and clinical guidance review.

View professional profile →
View Credentials
  • MD
  • MSc
  • PgDip (Clin Ed)
  • FRCP
  • FHEA
  • FASN

About this article

Written for UK patients and based on:

  • NICE guidance
  • NHS resources
  • British Dietetic Association guidance
  • Kidney Care UK resources
View methodology

Each article is researched against current UK clinical guidance (NICE NG203, NG118, NG136), NHS patient resources, KDIGO and KDOQI international guidelines, and the British Dietetic Association Renal Nutrition Group. Drafts are written by the Kidney Vitality editorial team and reviewed by a UK Consultant Nephrologist before publication. Content is reviewed on a rolling basis and updated when guidance changes.

Editorial standards

  • Clinically reviewed
  • NHS-aligned
  • NICE-aligned
  • Evidence-based
  • Reviewed before publication
View full editorial process

Every article is researched and written by the Kidney Vitality editorial team using current UK clinical guidance (NICE NG203, NG118, NG136), NHS patient resources, KDIGO/KDOQI international guidelines, and British Dietetic Association renal nutrition guidance. Drafts are reviewed for clinical accuracy by Professor Mohammed Mahdi Althaf, MD, MSc, PgDip (Clin Ed), FRCP, FHEA, FASN (Consultant Nephrologist & Acute Physician, GMC 7216325) before publication. Content is updated when UK guidance changes.

References (4)View Sources
  1. NICE NG203: Chronic kidney disease — assessment and management
  2. KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of CKD
  3. KDOQI Clinical Practice Guideline for Nutrition in CKD: 2020 Update
  4. British Dietetic Association — Renal Nutrition Group

Medical disclaimer

This content is educational only and does not replace personalised medical advice.

Read full disclaimer

This page is general information, not personal medical advice. If you have chronic kidney disease, are on dialysis, have had a kidney transplant, are pregnant or breastfeeding, or take prescription medication, please confirm any supplement with your GP, pharmacist or renal team before starting.

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