What is the Creatinine Clearance test?

The Creatinine Clearance test is a laboratory assessment used to estimate the kidneys’ ability to filter creatinine from the blood. It reflects the glomerular filtration rate (GFR) by comparing creatinine levels in blood and urine over a defined time period.

Unlike a single blood creatinine result, creatinine clearance incorporates urine excretion, making it a more direct measure of renal filtration. The test typically requires a blood sample and a timed urine collection, most commonly a 24-hour urine sample.

This test is widely used in clinical practice to evaluate kidney function, particularly when more precise assessment is required.

Why do I need a creatinine clearance test?

Creatinine clearance provides a more accurate picture of kidney filtration than blood creatinine alone, especially in individuals where blood values may be misleading.

You may need a creatinine clearance test if:

• Kidney function needs detailed assessment
• Blood creatinine results are borderline or unclear
• Drug dosing depends on renal filtration capacity
• Chronic kidney disease is suspected or monitored
• There is unexplained fatigue, swelling, or fluid retention
• You have diabetes or hypertension affecting kidneys
• Renal function must be assessed before procedures
• Long-term medication use may impact kidneys

Common symptoms linked to impaired kidney function may include:

• Swelling of ankles, feet, or face
• Reduced or excessive urination
• Fatigue or weakness
• Nausea or poor appetite
• Difficulty concentrating

Benefits of the Creatinine Clearance test

• Direct assessment of kidney filtration
  Reflects actual renal clearance capacity.
• More precise than blood creatinine alone
  Accounts for urine excretion.
• Useful for early kidney dysfunction
  Detects changes before severe impairment.
• Supports medication dosing decisions
  Important for renally cleared drugs.
• Helpful in chronic kidney disease monitoring
  Tracks progression over time.
• Standard clinical renal assessment tool
  Widely used in UK practice.
• Improves diagnostic confidence
  Reduces ambiguity from isolated markers.
• Relevant across multiple medical specialties
  Nephrology, endocrinology, cardiology, and general medicine.

Step by step – how the test works

You can complete creatinine clearance testing UK-wide using two options:

1. Clinic testing
   Attend your nearest UK clinic for blood collection and receive instructions for urine collection.
2. Home collection (£60 extra)
   A phlebotomist attends your home or hotel for the blood draw, and you complete the urine collection without leaving your location.

Both services are available nationwide. Clear instructions are provided for accurate urine collection.

Your results explained

Low creatinine clearance

Indicates reduced kidney filtration. This may be associated with acute or chronic kidney impairment and requires clinical correlation.

Typical UK reference range:

• < 60 mL/min (reduced filtration)

Normal creatinine clearance

Suggests healthy kidney filtration and normal renal function.

Typical UK reference range:

• 90–120 mL/min (varies by age, sex, and body size)

High creatinine clearance

May occur in pregnancy, early diabetes, or states of increased kidney filtration. Interpretation depends on clinical context.

Typical UK reference range:

• > 120 mL/min

Reference ranges may vary depending on laboratory methodology and patient characteristics.