What is microalbuminuria?

Microalbuminuria is defined as ACR 30-300 mg/g (KDIGO A2). It indicates early kidney damage and is a marker of generalized endothelial dysfunction and cardiovascular risk.

Why use ACR instead of 24-hour urine collection?

Spot urine ACR correlates well with 24-hour albumin excretion and is far more practical. A first morning void is preferred to minimize postural and exercise effects.

How often should ACR be checked in diabetic patients?

ADA and KDIGO recommend annual ACR screening in all type 2 diabetes patients from diagnosis and in type 1 patients starting 5 years after diagnosis.

Can ACR be falsely elevated?

Yes — exercise, UTI, fever, heart failure, menstruation, and very dilute urine can transiently increase albumin. Confirm abnormal results with repeat testing on 2 of 3 samples over 3 months.

What is the difference between albuminuria and proteinuria?

Albumin is a specific protein; proteinuria includes all proteins. ACR specifically measures albumin, which is the most sensitive marker for glomerular damage. Total protein/creatinine ratio (PCR) captures other proteins too.

Why are sex-specific thresholds used?

Men typically excrete more creatinine due to higher muscle mass, which dilutes the ratio. Sex-specific thresholds improve sensitivity — <17 mg/g for males and <25 mg/g for females are considered truly normal.

Albumin-to-Creatinine Ratio Calculator

Calculate urine albumin-to-creatinine ratio (ACR) with KDIGO staging. Classifies microalbuminuria, macroalbuminuria, and CKD prognosis by GFR and albuminuria.

⚠️ Medical Disclaimer: ACR must be confirmed with repeat testing. Single spot urine results can be affected by exercise, infection, and hydration. Consult a physician.

Urine Albumin

mg/L

Albumin Units

Urine Creatinine

g/L

Creatinine Units

Sex

eGFR (optional)

mL/min/1.73m²

Albumin-to-Creatinine Ratio

37.5 mg/g

Moderately Increased (Microalbuminuria)

A2 (Moderately increased)

ACR

37.5 mg/g

Moderately Increased (Microalbuminuria)

KDIGO Albuminuria

Moderately increased

eGFR Category

eGFR 75 mL/min/1.73m²

Microalbuminuria?

Yes

ACR 30-300 mg/g = moderately increased albumin excretion

Macroalbuminuria?

ACR ≥300 mg/g = severely increased (overt proteinuria)

Nephrotic Range?

ACR ≥ 2000 mg/g suggests nephrotic-range proteinuria

ACR Classification

Category	ACR (mg/g)	Terms
A1	< 30	Normal to mildly increased
A2	30-300	Moderately increased (microalbuminuria)
A3	> 300	Severely increased (macroalbuminuria)

KDIGO CKD Prognosis by GFR & Albuminuria

Albuminuria	G1 (≥90)	G2 (60-89)	G3a (45-59)	G3b (30-44)	G4 (15-29)	G5 (<15)
A1 (<30)	Low	Low	Moderate	High	Very High	Very High
A2 (30-300)	Moderate	Moderate	High	Very High	Very High	Very High
A3 (>300)	High	High	Very High	Very High	Very High	Very High

Your ACR on the Scale

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03030020003000+

Planning notes, formulas, and examples

About the Albumin-to-Creatinine Ratio Calculator

The Albumin-to-Creatinine Ratio (ACR) Calculator converts spot urine albumin and creatinine measurements into the standardized ACR used for kidney screening and staging. It classifies results per KDIGO guidelines (A1, A2, A3), identifies moderately and severely increased albuminuria, and can be viewed alongside eGFR for broader CKD context.

The urine ACR is widely used for detecting early kidney damage because it corrects for urine concentration by normalizing albumin to creatinine. A spot urine ACR correlates reasonably well with 24-hour albumin excretion and is far more practical for routine screening. Abnormal ACR can appear early in diabetic kidney disease and hypertensive kidney disease, often before eGFR falls.

This calculator handles multiple input units (mg/L, mg/dL for albumin; g/L, mg/dL, mmol/L for creatinine), provides the KDIGO prognosis heat map combining GFR and albuminuria categories, and includes optional sex-specific reference context for very low-range results. Use it for screening, CKD staging, and monitoring change over time.

When This Page Helps

ACR is a practical screening test because it normalizes albumin to creatinine and can be repeated over time to monitor change. It is useful for comparing one urine result with another and for placing the result into KDIGO context.

How to Use the Inputs

Enter the urine albumin concentration and select the measurement units.
Enter the urine creatinine concentration and select the units.
Select patient sex (affects normal threshold — lower for males).
Optionally enter eGFR for combined KDIGO risk staging.
Review the ACR value, KDIGO albuminuria category, and risk classification.
Use the KDIGO prognosis table to assess combined GFR-albuminuria risk.

Formula used

ACR (mg/g) = (Urine Albumin [mg/L]) / (Urine Creatinine [g/L])
A1: <30 mg/g | A2: 30-300 mg/g | A3: >300 mg/g
Sex-specific normals: Male <17 mg/g, Female <25 mg/g

Example Calculation

Result: ACR = 80 mg/g, A2 (Moderately increased / Microalbuminuria)

An ACR of 80 mg/g falls in the A2 category (30-300), indicating microalbuminuria. Combined with the eGFR, this determines the CKD risk level per KDIGO guidelines.

Tips & Best Practices

Use first morning void for the most accurate and reproducible ACR measurement.
Always confirm an abnormal result with at least one repeat test.
An ACR reduction of ≥30% with treatment is associated with improved renal outcomes.
SGLT2 inhibitors reduce ACR by 30-40% independent of glucose control.
Very high ACR (>2000 mg/g) may indicate nephrotic syndrome requiring specialist referral.

ACR in Diabetic Kidney Disease

Diabetic nephropathy progresses through predictable stages: normoalbuminuria → microalbuminuria → macroalbuminuria → declining GFR → ESRD. The ACR is the most sensitive tool for detecting the transition from normal to microalbuminuria. Intervention at this stage (intensive glucose control, RAS blockade, SGLT2 inhibitors) can halt or reverse progression.

KDIGO CKD Classification System

The KDIGO guidelines classify CKD risk using a 2-dimensional matrix: GFR categories (G1-G5) on one axis and albuminuria categories (A1-A3) on the other. The resulting "heat map" ranges from green (low risk) to red (very high risk) and determines monitoring frequency, treatment thresholds, and referral indications.

ACR as a Cardiovascular Risk Marker

Beyond kidney disease, an elevated ACR independently predicts cardiovascular events, stroke, and all-cause mortality. Even microalbuminuria (A2) is associated with 2-3× increased cardiovascular risk, regardless of eGFR. This makes ACR a valuable addition to standard cardiovascular risk assessment frameworks.

Sources & Methodology

Last updated: March 27, 2026

Methodology

This page converts the entered urine albumin and urine creatinine values into a spot urine albumin-to-creatinine ratio in mg/g, then maps the result to the KDIGO A1, A2, and A3 albuminuria categories. When eGFR is provided, it combines the albuminuria stage with GFR stage to place the result on the standard CKD prognosis grid.

The output is intended for screening and longitudinal kidney-risk review rather than as proof of chronic kidney disease from a single sample. Temporary albuminuria can occur with exercise, infection, fever, menstruation, heart failure, and other transient conditions, so abnormal results should be confirmed the way the underlying guideline recommends.

Sources

KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease (Kidney Disease: Improving Global Outcomes)
Standards of Care in Diabetes (American Diabetes Association) — Routine ACR screening context for diabetes care.

Frequently Asked Questions

Microalbuminuria is defined as ACR 30-300 mg/g (KDIGO A2). It indicates early kidney damage and is a marker of generalized endothelial dysfunction and cardiovascular risk.