What is a urine albumin-creatinine ratio (ACR) test?

ACR measures the amount of albumin (a protein) leaking into your urine, compared to creatinine, in a single urine sample. It is one of the most sensitive early markers of kidney damage — albumin starts leaking through damaged kidney filters often before the eGFR (filtering rate) falls. It is reported in mg/mmol (UK, Australia, Singapore) or mg/g (US). A low ACR is normal; a raised ACR, called albuminuria, flags early kidney damage and is especially important in people with diabetes or high blood pressure.

What is a normal ACR level?

Generally, an ACR below 3 mg/mmol (below 30 mg/g) is considered normal to only mildly increased (category A1). A result of 3–30 mg/mmol (30–300 mg/g) is moderately increased, previously called microalbuminuria (A2), and above 30 mg/mmol (above 300 mg/g) is severely increased, or macroalbuminuria (A3). Ranges vary by lab and country, so always check your own report. A first abnormal result is usually confirmed with a repeat early-morning sample before any conclusion is drawn.

Can ACR be high without kidney disease?

Yes, temporarily. Vigorous exercise in the previous 24 hours, a urinary tract infection, fever or acute illness, menstruation or blood in the urine, dehydration, and very high blood pressure on the day can all transiently raise urine albumin. This is exactly why a single raised ACR is not a diagnosis — your doctor will usually repeat it on a first-morning urine sample, when the result is most reliable, before deciding what it means.

What is the difference between ACR and eGFR?

They measure different things and are best used together. eGFR estimates how well your kidneys are filtering blood (the 'G' stage of kidney health), based mainly on creatinine. ACR measures whether the kidneys are leaking protein into the urine (the 'A' stage). Albuminuria often appears before eGFR falls, so ACR is an early-warning test, while eGFR tracks filtering capacity. A low eGFR combined with a high ACR carries a higher risk than either alone, which is why doctors order both to stage kidney health accurately.

How can I lower a raised ACR?

Lowering albuminuria is a recognised treatment goal because it slows kidney disease and reduces cardiovascular risk. The main levers are tight blood pressure control, good blood glucose control if you have diabetes, and specific medications — ACE inhibitors or ARBs, and increasingly SGLT2 inhibitors — that reduce protein leakage and protect the kidneys. Stopping smoking, reducing excess salt, and managing weight also help. Your doctor will tailor this to the cause of your albuminuria, so discussing your specific result and targets is the key step.

Understanding Your ACR (Albumin-Creatinine Ratio) Results

Quick answer: The urine albumin-creatinine ratio (ACR) measures how much albumin (a protein) is leaking into your urine — an early and sensitive sign of kidney damage, often appearing before your eGFR falls. It is reported in mg/mmol (or mg/g). A normal ACR is low; a raised ACR (albuminuria) flags the kidney’s filters leaking protein and is a key marker for diabetes and high-blood-pressure kidney disease. A single raised result is usually repeated, because exercise, infection, and menstruation can temporarily raise it.

ACR is one of the two pillars of kidney assessment — the other being eGFR. While eGFR tells you how well the kidneys are filtering, ACR tells you whether they are leaking. Together they classify kidney health far more accurately than either alone, which is why doctors increasingly order them as a pair.

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What ACR Measures

Healthy kidneys keep protein in the blood and out of the urine. When the kidney’s filters (glomeruli) are damaged, albumin — the most abundant blood protein — starts to leak through. ACR compares the amount of albumin to creatinine in a urine sample, which corrects for how dilute or concentrated the urine is, giving a reliable single-sample measure.

ACR Reference Ranges

ACR (mg/mmol)	ACR (mg/g)	Category
Below 3	Below 30	Normal to mildly increased (A1)
3 – 30	30 – 300	Moderately increased — ‘microalbuminuria’ (A2)
Above 30	Above 300	Severely increased — ‘macroalbuminuria’ (A3)

Units differ by country (mg/mmol is common in the UK, Australia, and Singapore; mg/g in the US). Always read your result against your lab’s reference range. A first abnormal ACR is typically confirmed with a repeat early-morning sample.

Why ACR Matters — Even With a Normal eGFR

This is the key point: albuminuria often appears before eGFR drops. A person can have a normal eGFR but a raised ACR — meaning early kidney damage is already underway. ACR is therefore an early-warning test, especially important if you have diabetes or high blood pressure, the two leading causes of chronic kidney disease.

A raised ACR is an independent risk marker for kidney disease progression and cardiovascular disease.
In diabetes, annual ACR screening is recommended to catch early diabetic kidney disease.
Reducing albuminuria (with blood pressure control and certain medications) is itself a treatment goal.

What Can Temporarily Raise ACR

A single raised result is not a diagnosis. These can transiently increase albumin in urine:

Vigorous exercise in the previous 24 hours
Urinary tract infection
Fever or acute illness
Menstruation or visible blood in the urine
Very high blood pressure on the day
Dehydration

This is why an abnormal ACR is repeated, ideally on a first-morning urine sample, before conclusions are drawn.

How the eGFR + ACR Grid Works

Kidney health is staged using both numbers together (the “G” stage from creatinine-based eGFR, and the “A” stage from ACR). A low eGFR and a high ACR together carry a higher risk than either alone — which is exactly why your doctor wants both.

How to Prepare for the Test

First-morning sample is often preferred — it is the most reliable.
Avoid vigorous exercise the day before if possible.
Mention any UTI symptoms, fever, or if you are menstruating — the test may be deferred.
Track results over time: ACR is most useful as a trend. Keeping your kidney results together in a Doctor Appointment Journal helps you and your doctor see the direction of travel.

Questions to Ask Your Doctor

Is my ACR normal, moderately, or severely increased — and does it need repeating?
Combined with my eGFR, what kidney stage am I in?
If my ACR is raised, what is driving it — diabetes, blood pressure, or something else?
What can I do to lower it, and are there medications (like ACE inhibitors or SGLT2 inhibitors) that would help?
How often should my ACR be monitored from now on?

Because blood pressure is central to both causing and treating albuminuria, your doctor may ask you to track readings at home — a home blood pressure monitor lets you bring a week of readings to the appointment rather than relying on a single clinic measurement.

Regional Notes

Singapore: ACR is standard in diabetes and hypertension reviews at polyclinics and restructured hospitals, usually annually. Singapore has one of the world’s highest rates of kidney failure, largely diabetes-driven, so ACR screening is emphasised.

Australia: ACR is part of the Kidney Health Check (eGFR + ACR + blood pressure) recommended for at-risk adults. Bulk-billed or low-cost through pathology providers; Kidney Health Australia has patient resources.

United States: Reported in mg/g; annual urine albumin testing is recommended for people with diabetes and many with hypertension. Covered by most insurers as part of routine chronic-disease monitoring.

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Medical Disclaimer: This guide is for informational and preparation purposes only. It does not constitute medical advice, diagnosis, or treatment. Always consult a qualified medical professional for guidance specific to your situation.