🫘 Men's Health
Kidney Function Tests Explained
What urea, creatinine, eGFR and electrolytes tell you about your kidneys
Kidney function tests (also called renal function tests or U&E — urea and electrolytes) are a group of blood and urine tests that assess how well the kidneys are filtering waste and regulating body chemistry. In Nigeria, chronic kidney disease (CKD) affects an estimated 22.5% of adults — driven by hypertension, diabetes, sickle cell disease, and chronic use of nephrotoxic NSAIDs and herbal remedies. Most people with early CKD have NO symptoms — kidney function tests are the only way to detect it early, when treatment can still preserve kidney function.
Signs and Symptoms
✓ Kidney tests ordered for: hypertension, diabetes, sickle cell disease, recurrent kidney stones, protein in urine, ankle oedema, before starting potentially nephrotoxic drugs (NSAIDs, aminoglycosides, contrast)
✓ Early CKD: usually no symptoms — detected only on blood or urine tests
✓ Advanced CKD (GFR < 30): fatigue, nausea, reduced appetite, ankle oedema, shortness of breath, itching
When to Seek Help
eGFR suddenly drops > 25% from baselineAcute kidney injury (AKI) — stop nephrotoxic drugs, assess fluid status, urgent review
Potassium > 6.5 mmol/L (hyperkalaemia)Life-threatening cardiac arrhythmia risk — emergency. Very common in advanced CKD and on ACE inhibitors
Creatinine > 500 µmol/L or eGFR < 15Stage 5 CKD / near-dialysis — urgent nephrology referral
Protein > 3g/day in urine (nephrotic syndrome)Massive protein loss — ankle oedema, low albumin, high cholesterol. Specialist investigation needed
Blood in urine + raised creatinineNephritic syndrome or vasculitis — urgent nephrology assessment
Tests & Diagnosis
🧪 Serum creatinine
Normal: men 60–110 µmol/L; women 45–90 µmol/L. A waste product of muscle metabolism — rises when kidneys filter poorly. Muscle mass affects creatinine — a muscular person has naturally higher creatinine. Does not rise above normal until approximately 50% of kidney function is lost
🧪 eGFR (estimated Glomerular Filtration Rate)
Calculated from creatinine, age, sex, and ethnicity. Estimates what % of kidney function remains. Normal > 90 mL/min/1.73m². Stages: G1 (≥90 normal), G2 (60–89 mildly reduced), G3 (30–59 moderate CKD), G4 (15–29 severe), G5 (<15 kidney failure requiring dialysis)
🧪 Serum urea
Normal 2.5–7.5 mmol/L. Also rises with kidney failure but also raised by high protein diet, dehydration, GI bleeding. Less specific than creatinine for kidney function
🧪 Urea:creatinine ratio
High ratio (> 100) = pre-renal cause (dehydration, reduced blood flow). Normal ratio with raised both = intrinsic kidney disease
🧪 Sodium
Normal 136–145 mmol/L. Low sodium (hyponatraemia) = heart failure, cirrhosis, SIADH, overhydration. High sodium (hypernatraemia) = dehydration
🧪 Potassium
Normal 3.5–5.0 mmol/L. High potassium (hyperkalaemia) = CKD, ACE inhibitors, low aldosterone, severe acidosis. DANGEROUS if > 6.5. Low potassium (hypokalaemia) = diuretics, diarrhoea, vomiting
🧪 Urine albumin:creatinine ratio (ACR)
The most sensitive early marker of kidney damage. Normal < 3 mg/mmol. Microalbuminuria 3–30 mg/mmol (early CKD in diabetes/hypertension). Macroalbuminuria > 30 mg/mmol (significant proteinuria)
🧪 Uric acid
Elevated in gout, CKD, and conditions with high cell turnover. Sickle cell, leukaemia, diuretic use. High uric acid damages kidney tubules
Frequently Asked Questions
My creatinine is 120 — is that normal?
It depends on your sex and muscle mass. For a muscular man, 120 µmol/L may be normal. For a small woman, it's above normal and suggests reduced kidney function. The eGFR (calculated from creatinine + age + sex) is more useful than creatinine alone. Ask your doctor for your eGFR rather than just the creatinine number.
Does drinking more water improve kidney function?
Staying well-hydrated prevents kidney stones and reduces risk of AKI. However, drinking excessive water does not improve already-damaged kidneys or raise a low eGFR in CKD. The 'flush your kidneys with water' concept is a myth for established CKD.
Can herbal medicine damage the kidneys?
Yes — this is a well-documented and serious problem in Nigeria. Many traditional remedies contain aristolochic acid, nephrotoxic heavy metals, and other substances that cause irreversible kidney scarring (interstitial nephritis). Some patients arrive at dialysis units with severe kidney failure attributable primarily to traditional medicine use. Always mention herbal use to your doctor.
Can I take ibuprofen if I have kidney disease?
No. NSAIDs (ibuprofen, diclofenac, aspirin in high doses) reduce blood flow to the kidneys and can precipitate acute kidney injury even in people with mild CKD. Paracetamol is the safe painkiller of choice in kidney disease — at standard doses, it does not damage the kidneys.