High Creatinine & Kidney Disease — Causes, Symptoms & Treatment Guide — Symptoms, Causes & Treatment | MyMedicPlus

Creatinine is a waste product generated from the normal breakdown of creatine phosphate in muscle tissue, produced at a relatively constant rate proportional to muscle mass, and excreted exclusively by the kidneys through glomerular filtration. Serum creatinine concentration therefore serves as an indirect marker of glomerular filtration rate (GFR) — the single most important measure of kidney function. Normal serum creatinine: approximately 60-110 micromol/L (0.7-1.3 mg/dL) in men; 45-90 micromol/L (0.5-1.0 mg/dL) in women — values are lower in women due to lower muscle mass. Creatinine must be interpreted with clinical context: muscle wasting (sarcopaenia, cachexia) causes falsely low creatinine despite significantly impaired kidney function; conversely, high muscle mass (bodybuilders, meat-heavy diet) can raise creatinine without kidney impairment. The more clinically useful measure is estimated GFR (eGFR) — calculated from serum creatinine, age, and sex using the CKD-EPI equation — expressed as mL/min/1.73m². Normal eGFR is above 90 mL/min/1.73m². eGFR forms the basis of CKD staging (G1-G5). Critically, by the time serum creatinine is visibly elevated above normal, approximately 50% of nephron function has already been lost — reflecting the remarkable functional reserve of the kidneys. Elevated creatinine can indicate either acute kidney injury (AKI — sudden reduction in kidney function over hours to days) or chronic kidney disease (CKD — gradual and sustained loss of kidney function over months to years).

Causes of elevated creatinine are divided anatomically into pre-renal, renal (intrinsic), and post-renal causes — particularly for acute kidney injury (AKI). Pre-renal (reduced kidney perfusion): hypovolaemia (dehydration, haemorrhage, burns, vomiting, diarrhoea); cardiogenic shock or congestive heart failure; sepsis (vasodilatory shock with relative renal hypoperfusion); hepatorenal syndrome (advanced cirrhosis with renal vasoconstriction); and renal artery stenosis (bilateral). Renal (intrinsic kidney disease): acute tubular necrosis (ATN — the most common cause of hospitalised AKI — from prolonged ischaemia or nephrotoxins — contrast agents, aminoglycoside antibiotics, NSAIDs, vancomycin); glomerulonephritis (IgA nephropathy, lupus nephritis, ANCA vasculitis — haematuria and proteinuria on dipstick); acute interstitial nephritis (AIN — drug hypersensitivity reaction — NSAIDs, penicillins, PPIs, sulfonamides — fever, rash, eosinophilia); thrombotic microangiopathy (HUS, TTP — fragmented red cells on film); myeloma kidney; and rhabdomyolysis (muscle breakdown releasing myoglobin — from crush injuries, statins, severe exercise, hypokalaemia). Post-renal (urinary obstruction): benign prostatic hyperplasia (BPH — bilateral ureteric obstruction from severe bladder outlet obstruction causing hydronephrosis); ureteric stones; pelvic malignancy; and urethral stricture. Chronic elevation of creatinine (CKD causes): diabetic nephropathy (leading cause of CKD globally — 40% of dialysis patients have diabetic kidney disease); hypertensive nephropathy; polycystic kidney disease (ADPKD); glomerulonephritis; and interstitial nephritis.

Mildly elevated creatinine (eGFR 45-89 mL/min — CKD stages G2-G3) is typically asymptomatic and detected only on blood testing. Symptoms of uraemia (toxic accumulation of metabolic waste products from severely impaired kidney function — eGFR below 15-20 mL/min) include: nausea and vomiting (uraemic gastritis); anorexia and weight loss; fatigue and malaise; pruritus (generalised itch — from uraemic toxins and calcium-phosphate deposition in skin); oedema (fluid retention from sodium and water retention — ankle, peripheral, and periorbital); hypertension (fluid overload and activation of renin-angiotensin system); anaemia (reduced erythropoietin production from failing kidneys — normochromic normocytic anaemia — causes fatigue, pallor, breathlessness); breathlessness (pulmonary oedema from fluid overload; also uraemic pleuritis); confusion and encephalopathy (uraemic encephalopathy — asterixis, disorientation, seizures — indicates very advanced kidney failure); metallic taste or uraemic fetor (ammonia smell on breath); and muscle cramps (from electrolyte disturbances — hypocalcaemia, hyponatraemia). Oliguria (urine output below 400 mL/day) or anuria (below 50 mL/day) — particularly in AKI — are urgent signs requiring immediate assessment. Hyperkalaemia (elevated potassium from impaired excretion) is a life-threatening emergency — causes cardiac arrhythmias and cardiac arrest.

Serum creatinine and calculated eGFR (CKD-EPI equation preferred) — the primary measure of kidney function; serial measurements distinguish AKI (acute rise) from CKD (chronically reduced). KDIGO 2012 defines AKI as: creatinine rise of 26.5 micromol/L or more within 48 hours; or creatinine rise of 1.5x baseline within 7 days; or urine output below 0.5 mL/kg/hour for 6+ hours. CKD is defined as eGFR below 60 mL/min/1.73m² for more than 3 months, or markers of kidney damage (proteinuria, haematuria, structural abnormality) for more than 3 months regardless of eGFR. Urine dipstick: proteinuria and haematuria are key markers of glomerular or tubular injury. Urine albumin:creatinine ratio (ACR): quantifies proteinuria — above 3 mg/mmol is abnormal; above 30 mg/mmol (macroalbuminuria/nephrotic range) indicates significant glomerular disease. Spot urine protein:creatinine ratio (UPCR). Electrolytes: hyperkalaemia (K+ above 5.5 mmol/L) is the most immediately life-threatening complication; hyperphosphataemia; hypocalcaemia; metabolic acidosis (low bicarbonate). FBC: normochromic normocytic anaemia (from reduced EPO); thrombocytopaenia in TTP/HUS. Ultrasound kidneys: first-line imaging — assesses kidney size (small kidneys suggest CKD — end-stage atrophied kidneys; large kidneys suggest ADPKD, infiltrative disease, or acute obstruction); cortical echogenicity (increased in CKD); hydronephrosis (obstructive uropathy); cysts; masses; and calculi. CT KUB: for nephrolithiasis. Renal biopsy: indicated in suspected glomerulonephritis, unexplained AKI, or CKD with active urinary sediment — histology directs specific immunosuppressive treatment. Additional blood tests: LDH, haptoglobin, blood film (TMA); complement (C3, C4 — lupus, MPGN); ANCA, ANA, anti-GBM antibodies; serum protein electrophoresis; hepatitis B and C serology.

Treatment depends on whether the cause is AKI or CKD, and the specific underlying aetiology. AKI management: identify and treat the cause (rehydration for pre-renal AKI — IV crystalloid fluid; remove nephrotoxins — stop NSAIDs, contrast agents, aminoglycosides; relieve obstruction — catheterisation for BPH, ureteric stenting for obstructive uropathy); hourly fluid balance and urine output monitoring; strict fluid management (avoid over-hydration); manage hyperkalaemia emergently (ECG monitoring; calcium gluconate IV to stabilise the myocardium if ECG changes; insulin-dextrose to shift potassium intracellularly; consider renal replacement therapy for severe or refractory hyperkalaemia); manage metabolic acidosis; and renal replacement therapy (haemodialysis or haemofiltration/CRRT in ICU) for AKI refractory to medical management (persistent hyperkalaemia, severe acidosis, fluid overload causing pulmonary oedema, uraemic encephalopathy or pericarditis). CKD management (slowing progression): ACE inhibitors (ramipril, lisinopril) or ARBs (losartan, candesartan) reduce intraglomerular pressure, reduce proteinuria by 30-40%, and slow CKD progression — first-line for diabetic nephropathy and hypertensive CKD with proteinuria; target ACR reduction; SGLT-2 inhibitors (dapagliflozin, canagliflozin) — demonstrated 35-45% reduction in CKD progression and renal death in the DAPA-CKD and CREDENCE trials — now recommended in CKD with albuminuria regardless of diabetes status; blood pressure target below 130/80 mmHg in CKD; dietary sodium restriction (below 2g/day); finerenone (non-steroidal mineralocorticoid receptor antagonist) reduces CKD progression and cardiovascular events in diabetic CKD; dietary protein restriction (0.6-0.8 g/kg/day) in advanced CKD slows progression; anaemia management (erythropoiesis-stimulating agents — darbepoetin, epoetin alfa; iron supplementation — target Hb 100-120 g/L); phosphate binders (sevelamer, calcium carbonate) for hyperphosphataemia; vitamin D supplementation. Renal replacement therapy: haemodialysis (hospital or home-based — 3x/week for 4 hours); peritoneal dialysis (home-based daily); renal transplantation (the optimal treatment for end-stage renal disease — restores near-normal kidney function; 10-year graft survival 60-70% with deceased donors, 70-80% with living donors).

Uncontrolled elevated creatinine from progressive CKD or untreated AKI leads to multiple systemic complications. Hyperkalaemia (serum potassium above 5.5 mmol/L) from impaired renal excretion causes life-threatening cardiac arrhythmias — including ventricular fibrillation — and is the most immediately dangerous complication requiring emergency management. Metabolic acidosis (reduced serum bicarbonate from impaired acid excretion) accelerates bone demineralisation, muscle wasting, and CKD progression. Anaemia of chronic kidney disease from reduced erythropoietin (EPO) production causes chronic fatigue, impaired cognitive function, reduced exercise capacity, and worsens cardiovascular outcomes. Hyperphosphataemia and secondary hyperparathyroidism (from impaired renal phosphate excretion and reduced vitamin D activation) lead to vascular calcification, renal osteodystrophy, bone pain, and fractures. Chronic volume overload causes resistant hypertension, left ventricular hypertrophy, and heart failure. Uraemic encephalopathy, pericarditis, and peripheral neuropathy are indicators of very advanced kidney failure requiring urgent dialysis. Cardiovascular disease accounts for 50% of all deaths in CKD — patients with eGFR below 30 have a 10-20x higher major cardiovascular event rate than the general population, even after controlling for traditional risk factors.

Prevent AKI: stay adequately hydrated, particularly during illness, hot weather, or physical exercise; avoid nephrotoxic medications where possible (NSAIDs, especially in elderly, dehydrated, or CKD patients); ensure appropriate contrast pre-hydration (IV saline for CKD patients before contrast CT or angiography); avoid aminoglycoside antibiotics unless essential (monitor levels); and prevent rhabdomyolysis (maintain hydration during intense exercise; monitor CK if statin-related muscle symptoms develop). Prevent and slow CKD progression: optimise diabetes management (HbA1c below 53 mmol/mol); maintain blood pressure below 130/80 mmHg; avoid smoking (accelerates CKD progression); maintain healthy weight; use ACE inhibitors/ARBs for diabetic kidney disease; annual eGFR and ACR monitoring in all patients with diabetes or hypertension enables early CKD detection when nephroprotective treatments are most effective. Avoid prolonged use of NSAIDs (analgesic nephropathy); stay well hydrated; prevent UTIs (recurrent UTIs can cause reflux nephropathy leading to CKD). Kidney donation awareness: living kidney donation from healthy individuals is safe — donors live normal lifespans with a single healthy kidney.

Call emergency services immediately for: sudden onset oliguria or anuria (inability to pass urine) especially after a medical event (surgery, severe vomiting, haemorrhage, contrast procedure); muscle weakness or cardiac symptoms in a patient with known renal impairment (possible hyperkalaemia causing cardiac arrhythmia); severe breathlessness with frothy pink sputum and ankle swelling (pulmonary oedema from fluid overload in acute kidney injury); confusion or seizures with known kidney disease (uraemic encephalopathy); and suspected rhabdomyolysis (dark cola-coloured urine after crush injury, severe exercise, or statin therapy). See your GP or nephrologist urgently for: eGFR reduction of more than 25% or creatinine rise of 30%+ from a recent result (possible AKI); new or worsening proteinuria on dipstick or ACR; blood in the urine (haematuria — alongside proteinuria); and blood pressure above 180/110 mmHg in a patient with known CKD. Annual blood and urine monitoring (eGFR, ACR, blood pressure) is essential for all patients with diabetes, hypertension, or established CKD to detect deterioration early when treatment can be most effective.