What do the KDIGO categories A1, A2, and A3 mean?

A1 is normal to mildly increased (under 30 mg/g, or under 3 mg/mmol). A2 is moderately increased (30–300 mg/g, or 3–30 mg/mmol) — this used to be called microalbuminuria. A3 is severely increased (over 300 mg/g, or over 30 mg/mmol), once called macroalbuminuria. Higher categories mean higher risk of kidney disease progressing.

How do you calculate ACR from lab values?

In conventional units, ACR (mg/g) = urine albumin (mg/dL) ÷ urine creatinine (mg/dL) × 1000. In SI units, ACR (mg/mmol) = urine albumin (mg/L) ÷ urine creatinine (mmol/L). This tool does either — just match the unit set your lab used.

What's the difference between mg/g and mg/mmol?

They're the same measurement in different units. US labs report mg/g; the UK and much of Europe use mg/mmol. To convert, multiply mg/mmol by about 8.84 to get mg/g. The A1/A2/A3 cut-offs are 30 and 300 in mg/g, or 3 and 30 in mg/mmol.

Why does albuminuria matter so much?

Because two people with the same eGFR can have very different outlooks depending on their albuminuria. It independently predicts how kidney disease will progress and also flags cardiovascular risk, which is why guidelines stage CKD using both eGFR and ACR together — and why the kidney failure risk equation weights ACR heavily.

Clinical tool · albuminuria

ACR calculator — albumin-to-creatinine ratio.

Find your KDIGO albuminuria category — A1, A2, or A3 — from a urine albumin-to-creatinine ratio. Already have your ACR? Enter it. Only have the raw lab numbers? Switch to calculate mode and we'll work it out.

Maintained by TheHealthTools team. Not medical advice.

Your ACR

The KDIGO albuminuria categories

Category	mg/g	mg/mmol	Meaning
A1	< 30	< 3	Normal to mildly increased
A2	30 – 300	3 – 30	Moderately increased (microalbuminuria)
A3	> 300	> 30	Severely increased (macroalbuminuria)

Your ACR category is most useful next to your eGFR — together they place you on the KDIGO risk grid. Once you know both, the kidney failure risk calculator turns them into a 2- and 5-year risk estimate.

Frequently asked questions

ACR is the urine albumin-to-creatinine ratio — the amount of albumin (a protein) leaking into your urine, standardized against urine creatinine so a single random sample is reliable. It's one of the earliest and most important signs of kidney damage, which is why it sits alongside eGFR in modern CKD staging.

Related kidney tools

Kidney failure risk (KFRE) →eGFR calculator →CKD stages explained →

For general education only — not medical advice or a diagnosis. KDIGO albuminuria categories: A1 <30, A2 30–300, A3 >300 mg/g (÷8.84 for mg/mmol). Reference: KDIGO 2024 Clinical Practice Guideline for CKD.