Step 1: Get your serum creatinine
Serum creatinine is measured with a simple blood test. Make sure your clinician knows you take creatine, because supplementation can raise this value slightly.
Step 2: Choose a formula
Use Cockcroft-Gault if you need a drug-dosing estimate: ((140 − age) × weight in kg) ÷ (72 × serum creatinine), with a 0.85 multiplier for women. Use CKD-EPI eGFR for general kidney screening.
Step 3: Interpret the result
A clearance above 90 ml/min is typically normal. Between 60–89 may be slightly reduced depending on age and health. Below 60 for three months or more suggests chronic kidney disease and warrants medical review.
Example for a 40-year-old woman
If she weighs 65 kg and has a serum creatinine of 0.9 mg/dL: ((140 − 40) × 65) ÷ (72 × 0.9) × 0.85 = 85 ml/min. This is generally considered normal.
Creatine and test interpretation
Because creatine raises serum creatinine, your calculated clearance or eGFR might look slightly lower than it would without supplementation. This does not necessarily mean your kidneys are damaged.
When to seek medical advice
Always discuss abnormal results with a clinician, especially if you have diabetes, high blood pressure, or a family history of kidney disease.
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Open the free creatine calculatorFrequently asked questions.
What units are used for creatinine clearance?
It is usually reported in milliliters per minute (ml/min).
Does weight affect clearance calculation?
Yes. Cockcroft-Gault uses actual body weight, while eGFR is normalized to body surface area.
Should creatine users calculate clearance differently?
No. The formula is the same, but creatine users should interpret slightly elevated creatinine with their clinician.
Can I use an online calculator?
Yes, many medical calculators exist, but they should not replace professional medical advice.
How often should I check kidney function?
Healthy adults usually check annually. People with risk factors may need more frequent testing.
What is the difference between creatinine and creatine?
Creatine is a supplement and natural compound. Creatinine is its breakdown product, used as a marker of kidney function.