When you are on dialysis, your diet and fluid intake must be carefully managed because your kidneys can no longer effectively remove waste products and excess water from your blood. The primary focus is usually on limiting potassium, phosphate, salt, and total fluid intake to prevent them from building up to dangerous levels between treatments. While these restrictions can be challenging, following them is vital for protecting your heart and ensuring your dialysis sessions are as comfortable as possible.
Dietary management is a cornerstone of renal care in the UK. Because every patient is different, you will be supported by a specialist renal dietitian who will create a personalised plan based on your blood results and the type of dialysis you use. For instance, patients on peritoneal dialysis often have slightly more flexibility with their diet than those on hospital-based haemodialysis because their treatment is performed daily.
What We Will cover in This Article
- Why fluid restriction is necessary and how to manage daily limits
- The importance of controlling potassium levels to protect the heart
- Managing phosphate intake to keep bones strong and skin healthy
- The role of salt (sodium) in controlling thirst and blood pressure
- Protein requirements and why they often increase on dialysis
- How dietary needs differ between haemodialysis and peritoneal dialysis
Managing fluid intake and ‘fluid weight’
Fluid restriction is often the most difficult part of the dialysis diet. When kidneys fail, they stop producing urine, meaning any liquid you drink stays in your body. This ‘fluid weight’ builds up between sessions, putting a strain on your heart and lungs. Most patients on haemodialysis are advised to limit their fluid intake to about 500ml to 750ml plus the amount of urine they still produce each day.
It is important to remember that ‘fluid’ includes anything that is liquid at room temperature, such as soup, jelly, ice cream, and yogurt. If you gain too much fluid weight between sessions, you may experience shortness of breath or swelling in your ankles. During dialysis, the machine must remove this extra fluid quickly, which can cause painful muscle cramps and dizziness.
Controlling potassium and phosphate levels
Potassium is a mineral found in many healthy foods like bananas, potatoes, and tomatoes. While essential for muscle function, high levels of potassium (hyperkalaemia) can cause the heart to beat irregularly or even stop. Most dialysis patients need to choose ‘low-potassium’ alternatives or use specific cooking methods, like boiling vegetables in large amounts of water, to leach out the potassium before eating.
Phosphate is another mineral that can build up, leading to itchy skin and brittle bones over time. It is found in high amounts in dairy products, nuts, and many processed foods. Because dialysis is not very efficient at removing phosphate, most patients must take ‘phosphate binders’ tablets taken with meals that prevent the phosphate in food from being absorbed into the bloodstream.
Comparing Dietary Needs: Haemodialysis vs. Peritoneal Dialysis
The following table differentiates between the typical dietary focuses for the two main types of dialysis:
| Nutritional Factor | Haemodialysis (3x per week) | Peritoneal Dialysis (Daily) |
| Fluid Restriction | Usually strict (500ml to 750ml) | Often more relaxed |
| Potassium | Strict limit required | Often less restricted |
| Phosphate | Strict limit + binders | Limit required + binders |
| Protein | Increased (lost during treatment) | Very high (significant loss) |
| Salt (Sodium) | Very low to control thirst | Low to moderate |
| Calories | Focus on healthy weight | Watch for sugar in dialysis fluid |
Causes for increased protein requirements
Interestingly, while people with early-stage kidney disease are often told to limit protein, those on dialysis usually need to increase it. This is because the dialysis process itself removes protein from your blood. If you do not eat enough high-quality protein (like meat, fish, eggs, or tofu), your body may begin to break down its own muscle, leading to weakness and a higher risk of infection.
Peritoneal dialysis patients lose even more protein through their abdominal lining than haemodialysis patients do. This is the primary cause for the ‘high-protein’ recommendation often given by renal dietitians. Ensuring you have a portion of protein with every meal helps keep your energy levels up and supports the healing of your access site or catheter.
Triggers for dietary adjustments
Your diet is not set in stone; it is adjusted based on ‘triggers’ found in your monthly blood tests. If your blood results show a sudden rise in potassium, this will trigger a review with your dietitian to identify hidden sources in your diet. Common triggers include seasonal fruits (like stone fruits in summer) or ‘hidden salt’ in processed holiday foods.
Another major trigger for dietary change is a change in your ‘dry weight’. This is your weight when you have no extra fluid in your body. If your dry weight increases because you are eating better and gaining muscle, your dietitian will celebrate this. However, if your weight increases due to fluid, it will trigger a stricter fluid limit to protect your cardiovascular health.
Differentiation: Salt, Thirst, and Blood Pressure
A vital differentiation to understand is the link between salt and fluid. Salt (sodium) acts as a trigger for thirst. If you eat a salty meal, your body will naturally crave more water. For a dialysis patient, this creates a dangerous cycle where the salt makes you thirsty, you drink more fluid, and your blood pressure rises.
Clinical teams differentiate between ‘added salt’ and ‘hidden salt’. While you can control the salt you add at the table, most salt in the UK diet comes from processed foods like bread, tinned soups, and ready meals. By choosing fresh ingredients and using herbs and spices for flavour instead of salt or salt substitutes (which are often high in potassium), you can better manage your thirst and make following your fluid limit much easier.
My final conclusion
Diet and fluid management are essential for staying healthy on dialysis. By limiting salt, potassium, and phosphate while increasing your protein intake, you can prevent dangerous complications and feel much better between treatments. Your renal dietitian is your best resource for finding a balance that works for your health and your lifestyle.
If you experience severe, sudden, or worsening symptoms, such as extreme breathlessness, sudden chest pain, or severe confusion, call 999 immediately.
Can I use salt substitutes like Lo-Salt?
No, most salt substitutes replace sodium with potassium, which can be life-threatening for someone on dialysis.
What is the best way to manage thirst?
Try sucking on ice cubes, using a mouth spray, or chewing sugar-free gum to keep your mouth moist without drinking.
Why are potatoes a problem?
Potatoes are very high in potassium. Boiling them in a large pot of water (and throwing the water away) helps reduce the potassium content.
Can I drink alcohol on dialysis?
Small amounts may be okay, but alcohol counts toward your daily fluid limit and can affect your blood pressure.
Are all fruits off-limits?
No, but you should choose ‘low-potassium’ fruits like apples, pears, and berries instead of high-potassium ones like bananas or oranges.
Why do I need to take binders with every meal?
Binders only work if they are in your stomach at the same time as your food to ‘mop up’ the phosphate before it enters your blood.
Can I still eat out at restaurants?
Yes, but you should look for fresh dishes and ask the chef not to add salt to your meal.
Authority Snapshot
This article was written by Dr. Rebecca Fernandez, a UK-trained physician with an MBBS and experience in cardiology, internal medicine, and emergency care. Dr. Fernandez has provided comprehensive care for patients across various medical specialities, ensuring this guide on renal diet and fluid management is grounded in clinical accuracy and safety. The information provided aligns with current NHS and clinical standards for renal replacement therapy.
