Why is the ratio to creatinine used instead of measuring albumin alone?

Creatinine corrects for urine concentration and hydration state, so the ratio provides a stable index of albumin excretion that estimates 24-hour loss from a single spot specimen, avoiding the need for a timed collection.

Is a first-morning or random urine sample preferred?

A first-morning specimen is preferred because it is more concentrated and reproducible, but a random sample is acceptable for screening. Either should be collected when the patient is well-hydrated and has avoided vigorous exercise in the preceding 24 hours.

Does an elevated ACR always mean kidney disease?

No. A single elevated result can be caused by urinary-tract infection, menstruation, vigorous exercise, fever, or poorly controlled diabetes. Persistent albuminuria should be confirmed with at least one repeat specimen within three months before diagnosing chronic kidney disease.

Can the test be done at home?

Yes. Boston Heart Diagnostics provides an at-home collection kit with a sterile container and prepaid return mailer, allowing patients to collect a first-morning specimen and post it to the laboratory.

How often should ACR be monitored in diabetes?

Annual screening is recommended for all patients with type 2 diabetes from diagnosis and for those with type 1 diabetes after five years' duration. More frequent monitoring is appropriate when albuminuria is present or treatment is being intensified.

How is albuminuria treated?

Treatment targets the underlying cause: optimising glycaemic control in diabetes, blood-pressure control (particularly with ACE inhibitors or angiotensin-receptor blockers), and cardiovascular-risk modification. The ACR is monitored to assess response.

How long do results take?

Results are typically available within 3–5 business days from specimen receipt at Boston Heart Diagnostics, including postal transit time for the at-home kit.

BML-KID-002kidney renalUSA

Albumin/Creatinine Ratio (Urine)

Q: What is the difference between microalbuminuria and macroalbuminuria?

These terms describe the degree of albumin excretion. Microalbuminuria (now 'moderately increased albuminuria') is an ACR of 30–300 mg/g and signals early kidney damage; macroalbuminuria ('severely increased albuminuria') is ≥300 mg/g and indicates more advanced injury, often overt diabetic nephropathy or active glomerular disease.

Q: What does a normal ACR rule out?

A normal ACR is reassuring for glomerular integrity but does not exclude all kidney disease — tubulointerstitial and vascular disease may not produce albuminuria. Serial monitoring remains appropriate in high-risk groups.

The urine albumin-to-creatinine ratio quantifies albumin excretion normalised to creatinine in a random or first-morning specimen, serving as a convenient surrogate for 24-hour albuminuria. It is the preferred test for detecting and monitoring kidney damage in diabetes, hypertension, and chronic kidney disease, and it independently predicts cardiovascular risk.

Biomarkers

Urine (random)

Sample

3–5 business days

Turnaround

Fasting

What is the ACR test?

The Albumin/Creatinine Ratio (Urine) test quantifies the amount of albumin excreted relative to creatinine in a random or first-morning urine specimen, providing a convenient, single-sample surrogate for 24-hour albumin excretion. It is the preferred method for detecting and monitoring albuminuria because it avoids the logistical burden of a timed collection while correcting for urine concentration. Albuminuria is both a marker of kidney damage and an independent cardiovascular risk factor. In people with diabetes it heralds the onset of diabetic nephropathy and is a target for intervention; in hypertension it reflects vascular injury; in chronic kidney disease of any cause it stratifies progression risk. Practitioners order ACR to screen for early renal involvement, to monitor disease progression and the response to renin-angiotensin-system blockade, and to refine cardiovascular-risk estimates beyond traditional lipid and blood-pressure measurements.

What does the ACR test measure?

Alb(Urine Albumin)

Range: <20 mg/L in a random specimen.Optimal: Consensus definitions use <30 mg/g creatinine as normal and ≥30 mg/g as albuminuria, with ≥300 mg/g defining macroalbuminuria.mg/L / mg/dL

Albumin is a plasma protein synthesised exclusively by the liver. The glomerular filtration barrier normally restricts albumin passage on the basis of size and negative charge; the small amount that crosses is largely reabsorbed by proximal tubular cells. When glomerular permeability rises or tubular reabsorption falls, urinary albumin excretion increases, providing a sensitive index of early kidney damage before the glomerular filtration rate declines measurably.

Increased urinary albumin excretion is a marker of both kidney disease and cardiovascular risk. In diabetes, microalbuminuria signals early diabetic nephropathy and prompts intensification of glycaemic and blood-pressure control; in hypertension, it reflects target-organ damage. Population studies have linked even moderately elevated albuminuria with incident cardiovascular events independent of traditional risk factors.

Cr(Urine Creatinine)

Range: Typically 4–20 mmol/L in a random specimen; varies with muscle mass and hydration.Optimal: Not applicable; the ratio is the interpretable metric.mmol/L / mg/dL

Creatinine is generated at a relatively constant rate from muscle creatine and filtered freely by the glomerulus with minimal tubular secretion or reabsorption, making urinary creatinine excretion a function of muscle mass and daily turnover. In a random urine sample, creatinine concentration reflects the specimen's dilution, allowing normalisation of other analytes for comparison across samples and individuals.

Urine creatinine is not interpreted in isolation; it serves to index albumin concentration and correct for the variable dilution of a random or first-morning specimen. This ratio improves the clinical utility of a spot collection and removes the need for timed urine in routine albuminuria screening.

ACR(Albumin-to-Creatinine Ratio)

Range: Normal <30 mg/g; moderately increased albuminuria (formerly 'microalbuminuria') 30–300 mg/g; severely increased albuminuria (formerly 'macroalbuminuria') ≥300 mg/g.Optimal: KDIGO and diabetes guidelines define <30 mg/g as normal, 30–300 mg/g as moderately increased, and ≥300 mg/g as severely increased albuminuria.mg/g / mg/mmol

The ACR normalises urinary albumin excretion to creatinine excretion, providing a dimensionless concentration-independent index that estimates 24-hour albumin loss from a spot specimen. Because creatinine excretion is relatively stable in an individual, the ratio reduces the confounding effect of variable urine concentration and hydration state.

ACR is the preferred screening and monitoring test for albuminuria in chronic kidney disease, diabetes, and hypertension. It predicts progression to end-stage renal disease and independently forecasts cardiovascular morbidity and mortality. Guidelines recommend annual screening in diabetes and consider ACR part of cardiovascular-risk assessment in hypertension and metabolic syndrome.

Why is the ACR test ordered?

Annual screening of patients with type 1 diabetes (after five years' duration) and all patients with type 2 diabetes at diagnosis and yearly thereafter
Baseline and serial assessment in patients with hypertension, particularly when target-organ damage or cardiovascular-risk stratification is needed
Monitoring of chronic kidney disease progression and response to angiotensin-converting enzyme inhibitors or angiotensin-receptor blockers
Cardiovascular-risk assessment in metabolic syndrome, where even moderately elevated ACR independently predicts events
Investigation of glomerular disease suspected on clinical grounds or after an incidental finding of proteinuria on dipstick
Evaluation of patients with systemic lupus erythematosus, vasculitis, or other systemic diseases that may affect the kidney
Pre-conception counselling in women with diabetes or chronic kidney disease, where baseline ACR informs risk
Follow-up of previously elevated ACR to confirm persistence, given day-to-day biological variation

Sample collection and turnaround

Sample type

Urine (random)

Fasting required

Collection method

At-home collection kit

Turnaround

3–5 business days

Collection notes

Boston Heart Diagnostics provides an at-home urine collection kit with a sterile container and return mailer. Ideally collect a first-morning specimen for greater concentration and reproducibility, though a random sample is acceptable. Avoid collection during menstruation, within 24 hours of vigorous exercise, or during an acute febrile illness. Midstream technique reduces contamination.

Specimen requirements

Minimum 10 mL random or first-morning urine in a sterile container. Refrigerate the specimen if it cannot be posted immediately; avoid freezing unless the laboratory specifies. The specimen should be free of visible blood and collected when the patient does not have a urinary-tract infection.

What can affect ACR results?

elevatesUrinary tract infection and haematuria

Infection and blood in the urine spuriously raise albumin excretion; testing should be deferred until the urine is sterile and blood-free, and any unexplained elevation should prompt dipstick or microscopy.

elevatesVigorous exercise within 24 hours of collection

Strenuous physical activity transiently increases glomerular permeability, causing a reversible rise in albuminuria; patients should avoid heavy exertion the day before the sample.

elevatesAcute febrile illness and severe hyperglycaemia

Fever and poorly controlled diabetes can cause transient increases in albumin excretion; ideally, test when the patient is metabolically stable and afebrile.

variableDehydration and very concentrated urine

Although the ratio corrects for concentration, extremes of dilution or concentration can affect the albumin assay; a first-morning specimen is preferred because it is more concentrated and reproducible than a random sample.

elevatesMenstrual blood contamination

Blood from menstruation can spuriously elevate both albumin and haemoglobin; women should avoid collection during menses or ensure the specimen is midstream and uncontaminated.

variableDiurnal and day-to-day biological variation

ACR shows considerable within-person variability; a single elevated value should be confirmed with a repeat specimen within three months before diagnosing persistent albuminuria.

What do ACR results mean?

Elevated

ACR 30–300 mg/g — moderately increased albuminuria (formerly microalbuminuria) — suggests early glomerular injury, most commonly diabetic nephropathy, hypertensive nephrosclerosis, or early glomerular disease; it is an indication for renin-angiotensin-system blockade and cardiovascular-risk modification. ACR ≥300 mg/g — severely increased albuminuria (macroalbuminuria) — indicates more advanced kidney damage, overt diabetic nephropathy, or active glomerulonephritis, and warrants nephrological input if the cause is uncertain or the patient is not responding to therapy. Transient elevations can occur with exercise, fever, or poor metabolic control and should be confirmed on a repeat specimen.

Normal

A normal ACR is reassuring but does not exclude kidney disease — tubulointerstitial and vascular disease may not produce albuminuria, and some glomerular diseases are episodic. Serial monitoring is appropriate in high-risk groups even when the baseline is normal.

Reduced

ACR <30 mg/g is normal. Very low values are not clinically meaningful but reflect well-preserved glomerular barrier function.

Note: A single elevated ACR should be confirmed with at least one repeat specimen within three months, because day-to-day variation is high and transient elevations are common. Exclude urinary-tract infection, menstruation, vigorous exercise, and fever before interpreting. ACR does not replace a formal urinalysis and microscopy when glomerular disease is suspected; the pattern of proteinuria and the urine sediment add diagnostic information. First-morning specimens are preferred for reproducibility, though random samples are acceptable for screening.

Frequently asked questions

These terms describe the degree of albumin excretion. Microalbuminuria (now 'moderately increased albuminuria') is an ACR of 30–300 mg/g and signals early kidney damage; macroalbuminuria ('severely increased albuminuria') is ≥300 mg/g and indicates more advanced injury, often overt diabetic nephropathy or active glomerular disease.

How to access the ACR test

The ACR reference page is free and open to all practitioners. Create a free practitioner account to see pricing, save tests to your list, and generate requisition forms. Verification takes 1–2 business days.

Create Free Account

About this page

Published: October 7, 2026

Last reviewed: October 7, 2026

References:

KDIGO clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney Int Suppl. (2024)
American Diabetes Association Standards of Care in Diabetes — microvascular complications and foot care. Diabetes Care. (2025)
Gerstein HC, et al. Albuminuria and risk of cardiovascular events, death, and heart failure in diabetic and nondiabetic individuals. JAMA. (2001)
National Institute for Health and Care Excellence. Chronic kidney disease in adults: assessment and management (NICE guideline NG203). (2021)
Lambers Heerspink HJ, et al. Albuminuria assessed from first-morning-void urine samples versus 24-hour urine collections as a predictor of cardiovascular morbidity and mortality. Am J Epidemiol. (2008)

This content is for licensed healthcare practitioners only and does not constitute medical advice. Clinical decisions should be based on the full clinical picture and not on any single test result.

Related tests

metabolic diabetes

HbA1c

The haemoglobin A1c (HbA1c) test measures glycated haemoglobin in whole blood, reflecting average blood glucose over the preceding two to three months. It is the standard test for diagnosing type 2 diabetes and prediabetes and for monitoring long-term glycaemic control, and it does not require fasting.

BML-MET-008View reference →