Chronic kidney disease explained

What the kidneys do and what goes wrong

Your kidneys are two bean-shaped organs that filter waste and excess fluid from the blood, making urine. They also balance salts and minerals, help control blood pressure, activate vitamin D for healthy bones, and signal the body to make red blood cells. In chronic kidney disease, tiny filtering units are gradually damaged, so waste products and fluid can build up and these other jobs are affected too. The most common causes in the UK are diabetes and high blood pressure, which damage the delicate blood vessels in the kidneys over time. Other causes include long-term inflammation, inherited conditions such as polycystic kidney disease, recurrent infections and certain medicines.

How CKD is found and staged

CKD is usually silent early on, which is why it is often discovered during tests for something else. Two measurements matter. The first is the estimated glomerular filtration rate, or eGFR, a blood test that estimates how well the kidneys filter. The second is the urine albumin-to-creatinine ratio, or ACR, which detects protein leaking into the urine — an early and important warning sign. Together these classify CKD by stage and by how much protein is present, which predicts risk far better than eGFR alone. Because a single reading can be misleading, results are confirmed over time before a diagnosis is made, and mild changes are common as people age.

Why CKD matters beyond the kidneys

CKD is not only about the risk of kidney failure — which for most people is low. Its biggest impact is on the heart and blood vessels, because reduced kidney function and protein in the urine both raise the risk of heart attacks and strokes. As CKD advances, other problems can appear: anaemia causing tiredness, weakened bones from mineral imbalance, high blood pressure, fluid retention and raised potassium. This is why care focuses on the whole person, not just a number. Regular monitoring aims to catch changes early, and most people with mild to moderate CKD live full lives with their condition kept stable through good management.

Treatment and self-care

There is no pill that reverses CKD, but a great deal can be done to slow it and protect the heart. Controlling blood pressure and, where relevant, blood sugar is central. Certain medicines that lower blood pressure and reduce protein in the urine specifically protect the kidneys, and newer diabetes medicines have been shown to slow CKD progression. Not smoking, staying active, keeping to a healthy weight and a balanced, lower-salt diet all help. Because damaged kidneys clear medicines more slowly, some drugs need adjusting or avoiding — always check with a pharmacist before taking anti-inflammatory painkillers, which can harm the kidneys.

Living with CKD and when to seek help

Most people with CKD are looked after by their GP with regular blood and urine checks, and only a minority are referred to a kidney specialist — usually those with faster decline, heavy protein loss or complications. Vaccinations, heart-health checks and reviewing medicines are all part of routine care. It helps to know your numbers, attend reviews and ask questions. During short illnesses such as vomiting, diarrhoea or fever, some kidney medicines may need pausing temporarily — so-called sick day guidance — which your clinician can explain. Seek prompt advice for a big drop in urine, swelling, breathlessness, or feeling suddenly much worse.