Urine Albumin-Creatinine Ratio (UACR) Calculator
Urine Albumin-Creatinine Ratio (UACR) Calculator
Grade albuminuria from a spot urine sample using the KDIGO A1–A3 categories, without needing a 24-hour collection.
Urine Albumin-Creatinine Ratio (UACR)
Albumin ÷ creatinine × 100Urine albumin 45 mg/L, urine creatinine 90 mg/dL
Formula
- albumin
- mg/L, spot urine
- creatinine
- mg/dL, spot urine
- ×100
- converts the raw ratio into mg albumin per g creatinine
Worked example
Urine albumin 45 mg/L, urine creatinine 90 mg/dL
45 ÷ 90 × 100 = 50.0 mg/g
Between 30 and 300 → A2, moderately increased
KDIGO albuminuria categories
| Category | mg/g | mg/mmol | Former term |
|---|---|---|---|
| A1 | < 30 | < 3 | Normal |
| A2 | 30 – 300 | 3 – 30 | Microalbuminuria (retired) |
| A3 | > 300 | > 30 | Macroalbuminuria (retired) |
Why the old terms were retired
The urine albumin-creatinine ratio normalises a spot albumin measurement against creatinine excretion, avoiding the impracticality of a timed 24-hour collection while correcting for how concentrated or dilute the sample happens to be. KDIGO uses it, alongside eGFR, to stage chronic kidney disease and grade cardiovascular risk.
The categories A1, A2 and A3 replaced the older terms normoalbuminuria, microalbuminuria and macroalbuminuria. The change was deliberate: “micro” and “macro” implied that risk was negligible below a threshold and only began above it, and large cohort studies showed that is not true — cardiovascular and renal risk rise continuously from the lowest UACR values, with no safe cut-off. The A-category labels avoid that false reassurance.
Results are reported in mg/g in North America and mg/mmol elsewhere; dividing mg/g by 8.84 converts between them, so a UACR of 50 mg/g is roughly 5.7 mg/mmol.
A single result is easily distorted. Exercise in the preceding 24 hours, fever, decompensated heart failure, marked hyperglycaemia, a urinary tract infection and menstruation can all raise albumin excretion transiently without reflecting chronic kidney damage. A first-morning void minimises postural and exercise effects, and KDIGO recommends that two of three specimens collected over three to six months be abnormal before diagnosing persistent albuminuria.
Frequently asked questions
What is a normal UACR?
Below 30 mg/g (roughly 3.4 mg/mmol) is category A1, the KDIGO reference range. Values continue to carry gradually increasing risk even within this band.
Why did microalbuminuria become A2?
KDIGO retired ‘microalbuminuria’ and ‘macroalbuminuria’ because both implied a safe threshold below which risk was negligible. Risk in fact rises continuously, so the neutral labels A1 to A3 replaced them.
How do I convert UACR between mg/g and mg/mmol?
Divide an mg/g value by 8.84 to get mg/mmol, or multiply an mg/mmol value by 8.84 to get mg/g.
Does one abnormal UACR mean chronic kidney disease?
Not on its own. Exercise, fever, heart failure, hyperglycaemia, urinary infection and menstruation can all raise it transiently. Guidelines recommend confirming with two of three specimens abnormal over three to six months.
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References
- KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease. Kidney Int. 2024;105(4S):S117–S314.
- Miller WG et al. Current issues in measurement and reporting of urinary albumin excretion. Clin Chem. 2009;55(1):24–38.