General CKD reference guide. Always follow advice from your renal dietitian.
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Remember: soup, jelly, ice cream and ice lollies all count toward your fluid limit
Understanding Your Kidneys
Plain-English explanations of what your kidneys do and what CKD means for you.
Your kidneys sit just below your ribcage, one on each side of your spine. The right kidney sits slightly lower than the left because the liver is above it.
Your kidneys are two small organs — each about the size of your fist — but they do an enormous amount of work. Every single day, they filter around 200 litres of blood, removing waste products and excess fluid that would otherwise build up and become toxic.
Think of them as your body's filtration and control centre. They do six main jobs:
They remove urea, creatinine, and other waste products from your blood, passing them out in urine.
They regulate how much water stays in your body. Too much, and you swell. Too little, and your blood pressure drops.
They keep sodium, potassium, phosphate and calcium at safe levels — minerals that affect your heart, muscles and bones.
A hormone that tells your bone marrow to make red blood cells. When kidneys fail, less EPO is made — causing anaemia and fatigue.
They convert vitamin D into its active form, which keeps your bones strong. CKD can cause bone disease if vitamin D isn't supplemented.
They release a hormone called renin that helps regulate blood pressure. Damaged kidneys often cause high blood pressure — and high blood pressure damages kidneys further.
Chronic Kidney Disease (CKD) means your kidneys have been damaged and can't filter blood as well as they should. The word chronic just means it develops slowly over time and doesn't go away.
Healthy kidneys contain around one million tiny filtering units called nephrons. In CKD, nephrons get damaged and stop working. The remaining healthy nephrons work harder to compensate — but over time, they too can become overworked and damaged.
Because the kidneys adapt so well, you often don't notice any symptoms until 50–60% of kidney function is already lost. This is why CKD is sometimes called a "silent" disease — and why blood tests are so important.
eGFR stands for Estimated Glomerular Filtration Rate — and it's the key number used to measure how well your kidneys are working.
It estimates how many millilitres of blood your kidneys can clean per minute, adjusted for your body size. A healthy young adult has an eGFR of around 90–120 mL/min/1.73m².
eGFR is calculated from a blood test measuring creatinine — a waste product your muscles naturally produce. If creatinine is high, it means the kidneys aren't clearing it efficiently, so eGFR is low.
- A single result is less important than the trend over time — small fluctuations are normal
- eGFR naturally declines with age (about 1 mL/min per year after 40)
- Dehydration, illness, or certain medications can temporarily lower eGFR
- An eGFR under 60 for more than 3 months is needed to diagnose CKD
- Your creatinine level tells a similar story but in reverse — higher creatinine = lower kidney function
What you eat directly affects how hard your kidneys have to work. With CKD, kidneys struggle to process and excrete certain minerals — so managing your diet can genuinely slow the progression of the disease.
Potassium is essential for your heart and muscles — but damaged kidneys can't remove excess potassium, causing it to build up in the blood. High potassium (hyperkalaemia) can cause dangerous heart rhythms. Foods high in potassium include bananas, potatoes, tomatoes, oranges and nuts.
Your kidneys normally remove excess phosphate. In CKD, it accumulates and pulls calcium out of your bones — weakening them and causing itchy skin. Phosphate is high in dairy, processed foods, cola drinks and nuts. Phosphate binders (medication taken with meals) can help.
In early CKD you usually don't need to restrict fluids. But in later stages (or if on dialysis), the kidneys can't remove enough fluid — causing swelling, breathlessness and high blood pressure. Your renal team will tell you if you need a fluid limit.
Protein produces waste products that kidneys must filter. Eating less protein can reduce the workload on damaged kidneys — but too little protein causes muscle loss. A renal dietitian can help you find the right balance. If you're on dialysis, you actually need more protein.
CKD is often symptom-free until the later stages. When symptoms do appear, they're caused by the build-up of waste products and fluid, and the knock-on effects on other body systems.
One of the most common symptoms. Caused by anaemia (low red blood cells) due to reduced EPO production.
Fluid retention causes swelling in the ankles, legs, and around the eyes — especially in the morning.
Fluid can build up around the lungs. Breathlessness at rest is a sign to contact your renal team promptly.
Waste products building up in the blood (uraemia) can cause nausea, vomiting and loss of appetite.
High phosphate and the build-up of waste products causes skin itching (pruritus), often worse at night.
Difficulty concentrating, memory problems and feeling mentally slow — caused by uraemia and anaemia.
Imbalances in calcium, potassium and sodium cause muscle cramps, often in the legs at night.
Damaged kidneys release too much renin, raising blood pressure — which in turn causes further kidney damage.
There is no cure for CKD, but the right management can significantly slow its progression and keep you feeling better for longer.
- Control blood pressure — aim for below 130/80 mmHg. ACE inhibitors and ARBs both treat blood pressure and protect kidneys.
- Manage blood sugar — if you have diabetes, tight glucose control is one of the most powerful ways to protect your kidneys.
- Follow a kidney-friendly diet — work with a renal dietitian to find the right balance of protein, potassium, phosphate and fluid.
- Stay active — regular gentle exercise (walking, cycling, swimming) supports cardiovascular health and helps with fatigue.
- Avoid NSAIDs — ibuprofen, naproxen and similar anti-inflammatories are harmful to kidneys. Use paracetamol instead.
- Stay hydrated — unless you have a fluid restriction, drinking enough water helps kidneys flush waste products.
- Don't smoke — smoking accelerates kidney disease progression and greatly increases cardiovascular risk.
- Take your medications — phosphate binders, EPO injections, vitamin D supplements and blood pressure medications all play important roles.
- Attend all appointments — regular blood tests allow your team to spot changes early and adjust treatment.