Creatinine Clearance Calculator NHS
This independent UK calculator estimates adult creatinine clearance (CrCl) using the Cockcroft-Gault equation. CrCl is not the same as laboratory eGFR and is still used for dosing some medicines. A clinician or pharmacist should decide which renal-function estimate and body weight are appropriate for a specific medicine.
Cockcroft-Gault creatinine clearance calculator
Weight warning: the correct weight is medicine- and patient-specific. At extremes of body weight, actual weight can misestimate renal function; UK guidance may use actual, ideal or adjusted weight depending on the medicine and local protocol.
Formula
For serum creatinine in µmol/L, the UK form of Cockcroft-Gault is: CrCl = (140 − age) × weight × constant ÷ serum creatinine, where the constant is 1.23 for men and 1.04 for women.
CrCl versus eGFR
CrCl and eGFR are different estimates and are not interchangeable. NHS Specialist Pharmacy Service notes that Cockcroft-Gault CrCl is preferred for some medicine-dosing decisions, including direct-acting oral anticoagulants, because eGFR may overestimate renal function in some people.
Which body weight should be used?
There is no single weight rule that is correct for every medicine and patient. SPS highlights controversy at extremes of body weight. Some NHS protocols use actual weight for particular medicines, while obese or oedematous patients may require ideal or adjusted weight. If a result is near a dosing threshold, use the relevant medicine guidance and local clinical protocol.
Worked example
For an 80-year-old man weighing 60 kg with serum creatinine 120 µmol/L: (140 − 80) × 60 × 1.23 ÷ 120 = 36.9 mL/min, approximately 37 mL/min. This matches the example given by NHS SPS.
Important limitations
Cockcroft-Gault is an estimate. Serum creatinine should be reasonably stable; acute kidney injury can make the estimate unreliable. Muscle mass, diet, hydration, frailty and unusual body composition can also affect creatinine-based estimates. Do not use this page alone to select or change a medicine dose.
Authoritative Sources
- NHS Specialist Pharmacy Service: Calculating kidney function
- NHS England: Creatinine clearance for DOAC dosing
Related Calculators
NHS Calculator · eGFR Calculator NHS · NEWS2 Calculator NHS · Anticholinergic Burden Calculator NHS · NHS Diabetes Risk Calculator
FAQs
What formula does this calculator use?
It uses the Cockcroft-Gault equation with serum creatinine in µmol/L and the UK constants 1.23 for men and 1.04 for women.
Is creatinine clearance the same as eGFR?
No. They are different estimates. For some medicines, Cockcroft-Gault CrCl is specifically used for dosing.
Should I use actual body weight?
Not automatically in every situation. The appropriate weight can depend on body composition, the medicine and local guidance.
Can I use this result to change my medicine dose?
No. Medicine dosing requires the relevant product guidance and clinical assessment.
Disclaimer: Educational renal-function estimate only. It is not a diagnosis, prescription or medicine-dosing instruction.