Albumin-Creatinine Ratio (ACR)
Calculate urine albumin-to-creatinine ratio for kidney disease screening and monitoring per KDIGO guidelines.
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Why: Understanding albumin-creatinine ratio (acr) helps you make better, data-driven decisions.
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Normal Kidney Function
Healthy adult with normal albumin excretion
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Microalbuminuria (A2)
Diabetic patient with moderate albuminuria
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Macroalbuminuria (A3)
Patient with severely increased albuminuria
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Diabetic Nephropathy Screening
Type 1 diabetic annual screening
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Hypertensive Nephropathy
Long-standing hypertension with kidney involvement
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Urine Measurements
Patient Information
Clinical Context
For informational purposes only — not medical advice. Consult a healthcare professional before acting on results.
What is Albumin-Creatinine Ratio (ACR)?
The Albumin-Creatinine Ratio (ACR) is a urine test that measures the amount of albumin (a type of protein) relative to creatinine in a spot urine sample. It is the gold standard screening method recommended by KDIGO (Kidney Disease: Improving Global Outcomes) for detecting albuminuria, an early marker of kidney damage. This test is particularly valuable for patients with diabetes, hypertension, cardiovascular disease, and those at risk for chronic kidney disease.
KDIGO Gold Standard
Recommended by international guidelines as the preferred method for albuminuria screening and CKD staging.
Guideline Support:
- KDIGO 2024 CKD guidelines
- ADA diabetes standards
- ACC/AHA hypertension guidelines
Convenient Spot Sample
Uses a single spot urine sample rather than cumbersome 24-hour collection, improving patient compliance and workflow.
Practical Benefits:
- No 24-hour collection needed
- First morning void preferred
- Results same day
Early Detection Power
Detects kidney damage years before GFR decline, enabling early intervention to slow disease progression.
Clinical Significance:
- Precedes GFR decline
- Reversible in early stages
- Predicts CV risk independently
How ACR Assessment Works
Sample Collection
Ideally first morning void (most concentrated); random sample acceptable for screening.
Laboratory Analysis
Both albumin and creatinine measured in the same sample.
Ratio Calculation
ACR corrects for urine concentration, providing standardized measurement.
Clinical Interpretation
Results classified per KDIGO guidelines into A1, A2, or A3 categories.
When to Test ACR
Diabetes Screening
Annual screening for all diabetics; at diagnosis for Type 2, after 5 years for Type 1
Hypertension
Assess target organ damage; guide treatment selection
CKD Monitoring
Track disease progression and treatment response
Cardiovascular Risk
Albuminuria is an independent cardiovascular risk factor
Pregnancy
Screening for preeclampsia; monitoring renal function
Treatment Monitoring
Assess response to ACEI/ARB or SGLT2 inhibitor therapy
ACR Calculation & Classification
ACR Formula
ACR (mg/g) = [Urine Albumin (mg/L) / Urine Creatinine (mmol/L)] × 8.84Or directly: ACR = Urine Albumin (mg) / Urine Creatinine (g)
KDIGO Classification
| Category | ACR (mg/g) | Description |
|---|---|---|
| A1 | <30 | Normal to mildly increased |
| A2 | 30-300 | Moderately increased (microalbuminuria) |
| A3 | >300 | Severely increased (macroalbuminuria) |
Frequently Asked Questions
Why use ACR instead of 24-hour urine collection?
ACR from a spot urine sample correlates well with 24-hour protein excretion (r = 0.93), is more convenient, has better patient compliance, and provides faster results without collection errors. Studies show ACR is equally accurate for CKD staging.
What can cause false elevations in ACR?
UTI, menstruation, recent vigorous exercise, fever, heart failure exacerbation, uncontrolled hypertension, hematuria, and very dilute or concentrated urine can affect ACR. Confirm abnormal results with repeat testing after addressing transient causes.
How often should diabetics have ACR tested?
Annual screening is recommended for all diabetics. For Type 2 diabetes, screening begins at diagnosis. For Type 1, it starts 5 years after diagnosis. If ACR is elevated, more frequent monitoring (every 3-6 months) helps track progression and treatment response.
What is the difference between microalbuminuria and macroalbuminuria?
Microalbuminuria (ACR 30-300 mg/g) represents early, potentially reversible kidney damage and is a strong cardiovascular risk marker. Macroalbuminuria (ACR >300 mg/g) indicates more advanced nephropathy with higher risk of progression to kidney failure.
Can ACR be used for cardiovascular risk assessment?
Yes, elevated ACR is an independent cardiovascular risk factor. Even mildly elevated ACR (A2 category) significantly increases risk of MI, stroke, and heart failure. It should be part of comprehensive CV risk assessment in high-risk patients.
What treatments can reduce albuminuria?
ACE inhibitors and ARBs are first-line for reducing albuminuria. SGLT2 inhibitors and finerenone provide additional nephroprotection. Blood pressure control (<130/80), glycemic control, and lifestyle modifications (weight loss, smoking cessation) also help reduce ACR.
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