Urine ACR
A urine test for protein leak, which predicts kidney outcomes better than the blood eGFR does.
What it means
A test measuring how much albumin — a protein — is leaking from your kidneys into your urine, expressed as a ratio against creatinine to correct for how dilute the sample is.
Healthy kidneys keep protein in the blood. Protein appearing in urine means the filters are damaged, and it appears earlier than a falling eGFR does.
This is the more important of the two kidney tests, and the one more often omitted. A stable eGFR with a normal ACR is a genuinely reassuring combination; a normal eGFR with a raised ACR is not.
In practice
On diabetes and hypertension annual reviews, and in any chronic kidney disease assessment.
Usually needs a first-morning urine sample, which is why it is sometimes given to you to bring back rather than done on the spot.
Why it matters
If you have diabetes or high blood pressure and cannot remember ever giving a urine sample, ask for one. It should be annual and it is frequently skipped.
A raised result usually changes treatment — typically starting or increasing an ACE inhibitor or similar, which protects the kidneys directly.
One raised result needs confirming, since exercise, fever, infection and menstruation can all raise it temporarily.
Clinically reviewed by Dr Mohammad Zubair Khan, GMC 7563469
Last reviewed
August 30, 2026