Understand your kidneys. Protect your health.
Clear, evidence-based information about kidney function, disease stages, and prevention — written for patients, families, and community advocates.
Kidneys filter 150 litres of blood daily
Kidney Anatomy & How They Work
A closer look at the body's filtration system
The Nephron: Functional Unit
Each kidney contains about 1 million nephrons. A nephron consists of a glomerulus (a tiny blood vessel cluster) and a tubule. Blood is filtered in the glomerulus, and the tubule reabsorbs needed substances while secreting wastes.
Filtration process: Blood enters via afferent arteriole → glomerulus filters fluid and solutes → filtrate passes through tubule where glucose, amino acids, and water are reabsorbed → remaining waste becomes urine.
Key Functions
- Waste excretion: urea, creatinine, uric acid
- Fluid balance: adjust urine concentration
- Electrolyte regulation: sodium, potassium, calcium, phosphate
- Acid-base balance: excrete H⁺, reabsorb bicarbonate
- Hormone production: renin (BP), erythropoietin (RBC), calcitriol (calcium)
Key Tests & What They Mean
How kidney function is measured
| Test | What It Measures | Normal Range / Target |
|---|---|---|
| Serum Creatinine | Waste product from muscle breakdown; higher levels indicate reduced filtration | 0.6–1.2 mg/dL (varies with muscle mass) |
| eGFR | Estimated Glomerular Filtration Rate – calculated from creatinine, age, sex, race | >90 mL/min/1.73m² (normal); >60 generally OK |
| Urine ACR | Albumin-to-creatinine ratio – detects protein leakage, an early sign of kidney damage | <30 mg/g normal; 30–300 microalbuminuria; >300 macroalbuminuria |
| Blood Urea Nitrogen (BUN) | Urea level; can be affected by dehydration, protein intake | 7–20 mg/dL |
eGFR formula: (140 - age) × weight / (72 × creatinine) × 0.85 if female. Online calculators available.
Chronic Kidney Disease (CKD) Stages
Based on eGFR and albuminuria. The lower the eGFR, the more advanced the disease.
eGFR is calculated from a blood creatinine test, age, and gender. Ask your doctor for your number.
Causes & Risk Factors
What leads to chronic kidney disease?
Diabetes (48% of cases)
High blood glucose damages glomeruli over time (diabetic nephropathy). Tight glycemic control reduces risk.
High Blood Pressure (27%)
Uncontrolled hypertension damages kidney vessels. Target BP <130/80 mmHg.
Genetic / Autoimmune
Polycystic kidney disease, lupus nephritis, IgA nephropathy, Alport syndrome.
Infections & Obstructions
Recurrent pyelonephritis, kidney stones, enlarged prostate, vesicoureteral reflux.
Toxins & Medications
Long-term NSAIDs (ibuprofen), certain antibiotics, herbal remedies containing aristolochic acid.
Other Factors
Smoking, obesity, recurrent dehydration, family history, age >60.
Symptoms: Early vs Advanced
CKD is often silent until later stages. Know these signs.
When to See a Doctor
- Foamy or bubbly urine (protein)
- Blood in urine (pink, cola colour)
- Swelling in ankles, feet, or hands
- Fatigue, trouble concentrating
- Frequent urination, especially at night
- Persistent puffiness around eyes
- Muscle cramps, itchy skin
- Poor appetite, metallic taste
- Shortness of breath (fluid overload)
- Nausea, vomiting (advanced)
Important Note: Early CKD often has no symptoms. Screening is key if you have diabetes, hypertension, or family history.
Prevention & Slowing Progression
Lifestyle and medical strategies to protect kidneys
Regular Exercise
150 min/week moderate activity helps control BP, glucose, weight.
Heart-Healthy Diet
Low sodium (<2g/day), limit processed foods, emphasize fruits/veg, whole grains.
Hydration
2-3 litres daily unless fluid restricted. Water is best; avoid sugary drinks.
Monitor BP & Sugar
Keep BP <130/80, HbA1c <7% (if diabetic). Take medications as prescribed.
Avoid Nephrotoxins
Limit NSAIDs; avoid herbal supplements with unknown content. Check with doctor.
Don't Smoke
Smoking reduces blood flow to kidneys and accelerates decline.
Annual Screening
Urine ACR, serum creatinine, eGFR. High-risk groups: every 6 months.
Healthy Weight
BMI <25 reduces inflammation and metabolic stress.
Treatment for CKD
Management depends on stage and underlying cause
Medications
- ACE inhibitors / ARBs: Lower BP and reduce proteinuria
- SGLT2 inhibitors: Slow CKD progression in diabetic and non-diabetic patients
- Diuretics: Manage fluid overload
- Erythropoiesis-stimulating agents: For anaemia
- Phosphate binders: Control high phosphorus
Renal Replacement Therapy
- Hemodialysis: Blood filtered by machine, usually 3x/week at centre or home
- Peritoneal dialysis: Uses abdominal lining; done daily at home
- Kidney transplant: Living or deceased donor; offers best quality of life
Palliative care and conservative management are options for those who choose not to pursue dialysis.
Diet & Nutrition by Stage
Dietary adjustments can slow progression and manage symptoms
Sodium
All stages: limit to <2g/day (5g salt). Avoid processed foods, canned soups, fast food. Use herbs/spices instead of salt.
Protein
Early stages: moderate protein (0.8g/kg). Advanced CKD (stage 4-5): may need restriction (0.6g/kg) to reduce urea load.
Potassium
If blood potassium high (hyperkalemia), limit bananas, oranges, potatoes, tomatoes, salt substitutes.
Phosphorus
When eGFR <30, limit dairy, nuts, beans, cola. May need phosphate binders.
Fluids
Early stages: drink to thirst. Later stages (especially if on dialysis): may need restriction (usually 1-1.5L/day).
Other Considerations
Limit alcohol, avoid grapefruit if on certain meds. Consider dietitian referral.
Kidney Health: Myths & Facts
Separating fact from fiction
Fact: Kidney disease is silent until very advanced.
Fact: Only restrict protein if you have advanced CKD; otherwise normal intake is fine.
Glossary of Terms
Essential kidney health vocabulary
Knowledge is the First Step
Have questions? Our health educators are available to help.