Blood Tests for Kidney Disease
eGFR, creatinine, urine ACR, and CKD staging explained in plain English — with Australian reference ranges and the GP-to-specialist pathway.
The Quick Answer
Chronic kidney disease (CKD) affects over 1.7 million Australians and is largely silent in its early stages. The two most important tests are eGFR(a blood test estimating how well the kidneys filter) and urine ACR(albumin-creatinine ratio in urine — detecting protein leakage). CKD is diagnosed when either or both are abnormal for at least 3 months.
The urine ACR is critically important and often missed. eGFR can be normal even when the kidneys are already being damaged — the ACR catches this early protein leakage before eGFR starts to fall. Both tests together are required for a complete kidney health picture.
Who Should Be Tested — The Kidney Health Check
Kidney Health Australia recommends a Kidney Health Check (eGFR + urine ACR + blood pressure) for all Australians in higher-risk groups. Most people with CKD have NO symptoms until it is quite advanced — only testing detects it early.
Type 2 diabetes
Annual urine ACR and eGFR from diagnosisHighest risk — diabetic nephropathy is the leading cause of CKD in Australia
High blood pressure (hypertension)
Annual eGFR and urine ACRSecond most common cause of CKD — sustained BP elevation damages glomeruli
Obesity (BMI > 30)
Every 2 years or annually if other risk factorsInsulin resistance and inflammation damage renal vasculature
Family history of kidney disease
Discuss screening frequency with GPMultiple inherited kidney conditions (ADPKD, IgA nephropathy, Alport syndrome)
Aboriginal and Torres Strait Islander peoples
Annual Kidney Health Check from age 18CKD is 3-4× more prevalent; often detected at a younger age and progresses faster
Age > 60
Every 2 years if no other risk factorseGFR naturally declines with age; important to distinguish aging from pathological CKD
The Tests — What Each One Measures
A complete CKD assessment includes kidney filtration markers, damage markers (urine ACR), electrolytes, bone-mineral markers, and a blood count. Here is what each test shows and why it matters.
eGFR (Estimated Glomerular Filtration Rate)
Calculated from serum creatinine, age, and sex (CKD-EPI equation). Declines naturally with age (~1 mL/min/year after 40). A single low eGFR may reflect dehydration — always confirm over at least 3 months.
Serum Creatinine
A byproduct of muscle metabolism, cleared by the kidneys. Higher muscle mass = higher creatinine (misleading in bodybuilders). Lower muscle mass = lower creatinine (misleading in frail elderly — may hide moderate CKD). eGFR is a better measure than creatinine alone.
Urine ACR (Albumin-Creatinine Ratio)
THE MOST IMPORTANT test for early kidney damage — often abnormal before eGFR falls. A first morning urine sample is preferred. A single elevated result should be confirmed on two further samples over 3 months (transient elevation possible with heavy exercise, infection, fever).
Electrolytes (Sodium, Potassium, Bicarbonate)
Hyperkalaemia (high potassium) is the most dangerous CKD electrolyte complication — it can cause cardiac arrhythmias. Metabolic acidosis accelerates CKD progression and bone loss. Both become more common as eGFR drops below 30.
Phosphate
Failing kidneys cannot excrete phosphate efficiently. High phosphate binds calcium, lowering serum calcium and stimulating PTH (secondary hyperparathyroidism), causing bone disease and vascular calcification. Dietary phosphate restriction and phosphate binders are used in advanced CKD.
Calcium
CKD reduces vitamin D activation (1,25-dihydroxyvitamin D), lowering calcium absorption. Always correct for albumin — low albumin (common in CKD) artificially lowers measured total calcium.
PTH (Parathyroid Hormone)
The kidney-bone axis response to low calcium and high phosphate. Chronically elevated PTH causes renal osteodystrophy (weakened bones) and cardiovascular calcification. Treated with vitamin D analogues, phosphate binders, and cinacalcet.
FBC (Haemoglobin)
The kidneys produce erythropoietin (EPO), which stimulates red cell production. CKD reduces EPO production, causing normocytic anaemia. Treated with iron supplementation and erythropoiesis-stimulating agents (ESAs) when Hb falls below 100-110 g/L in CKD.
CKD Staging — What the KDIGO G-Categories Mean
The KDIGO (Kidney Disease: Improving Global Outcomes) staging system classifies CKD into G1-G5 based on eGFR, and A1-A3 based on urine ACR (albumin category). Together, these determine prognosis and guide monitoring frequency. Australian guidelines align with KDIGO.
Normal or high filtration (with kidney damage markers)
Treat underlying cause, control BP and glucose, annual monitoring
Mildly reduced filtration (with kidney damage markers)
As above; identify and manage risk factors
Mildly to moderately reduced filtration
GP monitoring every 6 months; consider endocrinology/nephrology input
Moderately to severely reduced filtration
More frequent monitoring; assess for CKD complications; consider nephrology referral
Severely reduced filtration
Nephrology referral; prepare for kidney replacement therapy; intensive monitoring
Kidney failure
Specialist care; dialysis or transplant planning; palliative pathway if applicable
Red Flags — When to Act Urgently
eGFR < 30 (CKD G4)
Nephrology referral is recommended. Preparation for kidney replacement therapy should begin even if dialysis is not yet needed. Complications (anaemia, bone disease, acidosis) become more frequent.
Rapid eGFR decline (> 5 mL/min/year)
Faster than expected decline suggests an acute or reversible process on top of CKD. Causes include dehydration, NSAIDs, contrast dye, ACE inhibitor/ARB in the setting of renal artery stenosis, or urinary obstruction. Urgent review.
Urine ACR > 70 mg/mmol
High-grade albuminuria significantly accelerates CKD progression and cardiovascular risk. Specialist referral is recommended regardless of eGFR stage.
Serum potassium > 6.0 mmol/L
Severe hyperkalaemia can cause fatal cardiac arrhythmias. This requires urgent management — often same-day or emergency presentation. Common in CKD patients on ACE inhibitors, ARBs, potassium-sparing diuretics, or NSAIDs.
Haematuria (blood in urine) plus proteinuria
This combination (the "nephritic-nephrotic" picture) suggests a glomerulonephritis that needs urgent renal biopsy and immunosuppressive treatment. Refer to nephrology promptly.
Sudden drop in eGFR in a hospitalised patient
Acute kidney injury (AKI) superimposed on CKD is common and often preventable. Identify and remove triggers: nephrotoxic drugs (NSAIDs, aminoglycosides, contrast), dehydration, hypotension, urinary obstruction.
What Happens After Abnormal Results — The GP Pathway
Confirm the results
A single abnormal eGFR or urine ACR should be repeated over 3 months. Transient causes (dehydration, heavy exercise, urinary infection, fever) can temporarily worsen both results. Only when abnormal on at least two of three tests over 3 months is CKD confirmed.
Identify the underlying cause
Common causes: diabetic kidney disease (most common), hypertensive nephrosclerosis, IgA nephropathy, polycystic kidney disease. Your GP will order additional tests: hepatitis serology, ANA, complement (C3, C4), urine protein electrophoresis, renal ultrasound.
Optimise blood pressure
Target blood pressure in CKD is below 130/80 mmHg. ACE inhibitors (ramipril, perindopril) or ARBs (irbesartan, losartan) are first-line — they reduce proteinuria and slow CKD progression beyond their BP-lowering effect. Monitor potassium and creatinine 1-2 weeks after starting or up-titrating.
Treat diabetes aggressively
Target HbA1c below 53 mmol/mol (7%) in most patients with CKD and diabetes. SGLT2 inhibitors (empagliflozin, dapagliflozin, canagliflozin) have strong evidence for reducing CKD progression and cardiovascular events — now first-line in diabetic kidney disease regardless of baseline HbA1c.
Monitor for CKD complications
As eGFR falls, check for: anaemia (FBC), secondary hyperparathyroidism (calcium, phosphate, PTH, vitamin D), metabolic acidosis (bicarbonate), hyperkalaemia (potassium), and dyslipidaemia. Each complication has specific management.
Nephrology referral
Recommended at eGFR < 30, rapid decline, high ACR, or uncertain diagnosis. A nephrologist will perform a detailed assessment, optimise management, and plan for kidney replacement therapy if needed. Early referral (before kidney failure) leads to better outcomes.
Slowing CKD Progression — What Works
Blood pressure control
The single most important modifiable factor. Target below 130/80 mmHg. ACE inhibitors or ARBs are preferred in proteinuric CKD (urine ACR > 3 mg/mmol) — they reduce intraglomerular pressure independently of systemic BP reduction. Avoid both an ACE inhibitor AND an ARB simultaneously (dual blockade increases hyperkalaemia and AKI risk).
SGLT2 inhibitors (game-changing new evidence)
Empagliflozin, dapagliflozin, and canagliflozin reduce CKD progression and cardiovascular events in patients with CKD and type 2 diabetes, and increasingly in non-diabetic CKD. PBS-listed in Australia for eligible patients. They reduce urine ACR, slow eGFR decline, and may even cause a modest initial eGFR dip (expected and not a reason to stop).
Lifestyle modification
Aim for a healthy weight, limit sodium intake (less than 2 g/day, roughly 5 g of salt) to reduce blood pressure and proteinuria, moderate protein intake (0.8 g/kg/day — very low protein diets are no longer recommended), avoid NSAIDs (ibuprofen, naproxen, diclofenac — all worsen CKD), quit smoking, and limit alcohol.
Costs and Medicare — Kidney Tests in Australia
eGFR / creatinine / electrolytes
Fully Medicare-rebatable with GP referralBulk-billed at most collection centres
Urine ACR (albumin-creatinine ratio)
Fully Medicare-rebatable with GP referralFirst morning urine sample — can be self-collected at home
Calcium, phosphate, PTH, vitamin D
Medicare-rebatable with clinical indicationRequired from CKD G3b onwards
Renal ultrasound
Medicare-rebatable with GP referralChecks kidney size, structure, obstruction, and cysts
SGLT2 inhibitor (empagliflozin, dapagliflozin)
PBS-subsidised for eligible CKD patientsCriteria include eGFR threshold and urine ACR — ask your GP
Nephrology consultation
Specialist rebate via MedicareGP referral required; gap fees may apply privately
Related Reading
See What Your Kidney Results Mean
Upload your blood test and SmarterBlood will explain your eGFR, creatinine, electrolytes, and other kidney markers in plain English — with Australian reference ranges.
This page provides general educational information about chronic kidney disease (CKD) and the blood tests used to detect and monitor it. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your GP or nephrologist about kidney function results. SmarterBlood does not provide medical care.