What is Chronic Kidney Disease?
Chronic kidney disease means the kidneys have been damaged or are filtering less effectively for three months or longer. It is assessed with two measures: eGFR, which estimates filtration rate, and urine albumin-to-creatinine ratio, which detects protein leakage. It is usually silent in early stages, and diabetes and high blood pressure are the leading causes.
Key takeaways
- CKD is defined by reduced eGFR or kidney damage markers persisting for at least three months.
- Two tests matter, not one: eGFR and urine albumin-to-creatinine ratio together define stage and risk.
- Diabetes and high blood pressure cause the majority of cases, and controlling both slows progression.
- Most people with CKD will die of cardiovascular disease rather than reach dialysis.
- SGLT2 inhibitors and renin-angiotensin system blockers have substantially changed the outlook in recent years.
Overview
The kidneys filter roughly 180 litres of blood a day, removing waste products, balancing electrolytes and fluid, regulating blood pressure, activating vitamin D, and signalling for red blood cell production. Chronic kidney disease means this capacity has been reduced, or that there is evidence of kidney damage, for three months or more. The critical point for readers is that early and moderate CKD produces almost no symptoms — filtration can fall by more than half before anything is noticeable, so it is found on blood and urine testing rather than by how someone feels.
The leading causes globally are diabetes and high blood pressure, both of which damage the tiny filtering units called glomeruli over years. Progression is not inevitable. Blood pressure control, renin-angiotensin system blockade, SGLT2 inhibitors, and glucose management have all been shown to slow decline, and the last decade has produced genuinely significant advances. Cardiovascular risk rises sharply as kidney function falls, which is why CKD care always addresses the heart as well.
What Chronic Kidney Disease is
CKD is staged by two axes. Estimated glomerular filtration rate (eGFR) gives G stages: G1 is 90 or above with damage markers, G2 is 60-89 with damage markers, G3a is 45-59, G3b is 30-44, G4 is 15-29, and G5 is below 15 mL/min/1.73 m², described as kidney failure. Albuminuria gives A stages: A1 is below 30 mg/g, A2 is 30-300 mg/g, and A3 is above 300 mg/g on a urine albumin-to-creatinine ratio.
Both matter independently. Someone with an eGFR of 55 and no albuminuria has a very different outlook from someone with the same eGFR and heavy protein leakage. Since 2021, US eGFR equations no longer include a race coefficient, which improved equity in how kidney function is estimated and in access to specialist care and transplantation.
Common symptoms
Early CKD is silent; symptoms typically appear only when kidney function is substantially reduced.
- No symptoms in early and moderate stages — the usual situation
- Fatigue and reduced energy
- Swelling of the ankles, feet, or around the eyes
- Foamy or frothy urine — suggesting protein leakage
- Needing to urinate more often, particularly at night
- Poor appetite and a metallic taste
- Difficulty concentrating
Less common symptoms
- Persistent itching without a rash
- Muscle cramps, especially at night
- Nausea and vomiting in advanced disease
- Shortness of breath from fluid overload or anemia
- Restless legs and disturbed sleep
- Pale skin from anemia of kidney disease
Risk factors
- Diabetes — the single leading cause of CKD worldwide
- High blood pressure, cardiovascular disease, and heart failure — both causes and consequences of kidney damage, and closely intertwined with kidney function
- Older age — filtration declines gradually with age
- Family history of kidney disease, including polycystic kidney disease
- Black, Hispanic, and Native American ancestry — higher rates in the US, reflecting genetic factors such as APOL1 variants and social determinants
- Obesity — raises risk independently of diabetes and hypertension
- Recurrent kidney stones, urinary obstruction, or repeated urinary infections
- Long-term NSAID use and repeated episodes of acute kidney injury
- Autoimmune conditions such as lupus, and chronic hepatitis B or C infection
Causes
Diabetes damages the glomeruli through sustained high glucose, which thickens their basement membranes and causes protein to leak into the urine. High blood pressure damages the small vessels feeding the filters, producing scarring. Together these account for most cases. Glomerulonephritis — a group of inflammatory conditions of the filters — polycystic kidney disease, and obstruction from an enlarged prostate or stones are other significant causes.
Once a critical amount of filtering capacity is lost, remaining glomeruli work harder and undergo pressure-related damage themselves, so the disease can progress even after the original insult is controlled. This is why treatments that reduce pressure within the glomerulus — renin-angiotensin blockers and SGLT2 inhibitors — slow progression rather than merely lowering blood pressure.
How it is diagnosed
Diagnosis requires evidence of reduced function or damage persisting for at least three months, using two complementary tests.
| Test or assessment | What it looks at |
|---|---|
| Serum creatinine and eGFR | A blood test used to estimate filtration. eGFR below 60 mL/min/1.73 m² sustained for three months indicates CKD. Cystatin C is used to confirm when creatinine may be misleading. |
| Urine albumin-to-creatinine ratio (uACR) | Detects protein leakage on a spot urine sample. Above 30 mg/g indicates kidney damage even when eGFR is normal, and it is a strong predictor of progression. |
| Urinalysis | Looks for blood, protein, and cells that may point to glomerular inflammation or infection. |
| Kidney ultrasound | Assesses kidney size, obstruction, cysts, and stones. Small scarred kidneys suggest long-standing disease. |
| Blood tests for complications | Hemoglobin, potassium, bicarbonate, calcium, phosphate, and parathyroid hormone to detect anemia, acidosis, and bone-mineral disorder. |
| Kidney biopsy | Used when the cause is unclear or an inflammatory glomerular disease is suspected, since the specific diagnosis changes treatment substantially. |
Treatment overview
Treatment aims to slow progression, reduce cardiovascular risk, and manage complications. The categories below describe available approaches; all prescribing and dosing decisions belong with your clinician, and many medicines need dose adjustment in CKD.
Blood pressure control
Usually the single most important intervention, with targets individualized and often lower when albuminuria is present.
Renin-angiotensin system blockade
ACE inhibitors or angiotensin receptor blockers reduce pressure within the glomerulus and lower albuminuria, slowing progression particularly in diabetic kidney disease.
SGLT2 inhibitors
Now a foundation of CKD care, with trial evidence for slowing progression and reducing cardiovascular events in people with and without diabetes.
Glucose management
Tight but individualized glucose control in diabetes, with medication choices adjusted for kidney function.
Additional protective therapies
Non-steroidal mineralocorticoid receptor antagonists and GLP-1 receptor agonists have shown kidney and cardiovascular benefit in selected groups.
Managing complications
Treating anemia, metabolic acidosis, high potassium, and bone-mineral disorder, alongside dietary sodium, potassium, and protein guidance from a renal dietitian.
Planning for kidney failure
Timely discussion of hemodialysis, peritoneal dialysis, pre-emptive transplantation, or conservative management, ideally well before it is needed.
Lifestyle considerations
- Keep blood pressure at your agreed target and measure it at home.
- Reduce dietary sodium, which improves blood pressure and reduces protein leakage.
- Avoid NSAIDs such as ibuprofen and naproxen unless your clinician has specifically approved them.
- Stay well hydrated in ordinary circumstances, but follow individual fluid advice in advanced CKD.
- Ask a renal dietitian about protein, potassium, and phosphate rather than restricting on your own.
- Stop smoking, which accelerates kidney decline as well as cardiovascular disease.
- Check with a pharmacist before taking any new supplement, since many are not eliminated normally in CKD.
- Know your sick-day rules — some medicines need to be paused during vomiting, diarrhea, or fever.
Prevention
- Manage diabetes and blood pressure well — together these prevent the majority of CKD.
- Have annual eGFR and urine albumin testing if you have diabetes, hypertension, or cardiovascular disease.
- Avoid regular NSAID use.
- Maintain a healthy weight and stay physically active.
- Stop smoking.
- Stay hydrated and seek care promptly for urinary obstruction or repeated infections.
- Discuss family history of kidney disease with your clinician, particularly with polycystic kidney disease.
Warning signs and when to get help
Signs that need emergency care
If you believe you are experiencing a medical emergency, call emergency services immediately (911 in the United States).
- Chest pain, palpitations, or severe muscle weakness — possible dangerously high potassium, seek emergency care
- Severe breathlessness or inability to lie flat — possible fluid overload
- Passing very little or no urine over many hours
- Confusion, seizure, or marked drowsiness
- Sudden severe flank pain with fever and vomiting
Signs that warrant a prompt appointment
These are not emergencies, but they are worth a call to your clinician rather than a wait-and-see.
- New or worsening swelling of the legs, ankles, or face
- Foamy urine, or visible blood in the urine
- A rising creatinine or falling eGFR on repeat testing
- Persistent nausea, loss of appetite, or unexplained weight loss
- Persistent itching, cramps, or restless legs
- Any illness with vomiting or diarrhea while on medicines that need sick-day adjustment
Questions to ask a healthcare professional
Take these to your next appointment — or build an agenda with the Appointment Prep tool.
- What are my eGFR and urine albumin-to-creatinine ratio, and what stage does that put me at?
- What is causing my kidney disease?
- How quickly has my kidney function been changing over the past few years?
- What is my blood pressure target?
- Am I on an SGLT2 inhibitor or ACE inhibitor or ARB, and if not, why not?
- Which of my medicines need dose adjustment or should be avoided?
- Should I see a renal dietitian?
- At what point would we start discussing dialysis or transplant options?
Frequently asked questions
What does my eGFR number mean?
It estimates how many millilitres of blood your kidneys filter per minute, adjusted for body size. Above 90 is normal, 60-89 is mildly reduced, 30-59 is moderately reduced, 15-29 is severely reduced, and below 15 is kidney failure. A single low value needs repeating — CKD requires the change to persist for three months.
Does chronic kidney disease always lead to dialysis?
No. Most people with CKD never reach kidney failure, and many remain stable for years or decades, particularly with good blood pressure and glucose control. Statistically, people with CKD are more likely to have a cardiovascular event than to need dialysis.
Should I avoid protein if I have kidney disease?
Very high protein intake is generally discouraged, and moderate restriction is sometimes advised in more advanced CKD — but under dietitian supervision, since inadequate protein causes muscle loss and malnutrition. Do not restrict protein on your own based on general advice.
Are painkillers safe with kidney disease?
NSAIDs such as ibuprofen and naproxen reduce blood flow to the kidneys and should generally be avoided unless specifically approved. Acetaminophen is usually considered a safer option for pain in CKD, though your clinician should confirm what is appropriate for you.
Why did my eGFR change when the equation was updated?
US laboratories removed the race coefficient from eGFR equations in 2021, which changed reported values for many Black patients. The aim was more equitable estimation and earlier access to specialist care and transplant evaluation, rather than any change in your actual kidney function.
Sources
- NIDDK — Kidney Disease — NIH overview of stages, testing, and treatment
- CDC — Chronic Kidney Disease — US prevalence, risk factors, and prevention
- National Kidney Foundation — Patient education on eGFR, diet, and dialysis options
- MedlinePlus — Chronic Kidney Disease — Consumer summary and related tests
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