Urine protein
Also known as: albumin:creatinine ratio, protein:creatinine ratio, microalbumin, proteinuria test
Healthy kidney filters hold back almost all protein. Measuring albumin leaking into urine, corrected for how dilute the sample is, detects kidney damage years before blood tests change, particularly in diabetes and high blood pressure.
- Abbreviations
- ACR, PCR
- Kind
- Laboratory test
- Categories
- Kidney & urinary
- Specimen
- Urine (spot sample)
- Method
- Chemistry analyser, Immunoassay
- Terminology
- LOINC 9318-7
What it measures
| Measure | What it tells you |
|---|---|
| Albumin:creatinine ratio (ACR) | Below 3 mg/mmol normal; 3-30 moderately raised (formerly microalbuminuria); above 30 severe. Combined with eGFR to stage kidney disease. |
| Protein:creatinine ratio | All proteins, used when large amounts leak (nephrotic range above 300 mg/mmol). |
| 24-hour collection | The old gold standard, now rarely needed. |
Why it is ordered
- Yearly in diabetes
- High blood pressure, kidney disease, lupus
- Frothy urine or unexplained swelling
- Pregnancy with high blood pressure (pre-eclampsia)
- Staging chronic kidney disease and deciding on ACE inhibitors and SGLT2 inhibitors
How it is done
An early-morning spot urine sample.
Preparation. Avoid hard exercise the day before; repeat if there is infection or fever.
Reading the result
| Finding | Usual meaning |
|---|---|
| ACR persistently 3 or more | Kidney damage: start or intensify an ACE inhibitor/ARB, control blood pressure and glucose |
| Nephrotic-range protein with low albumin and swelling | Nephrotic syndrome, needs a kidney biopsy in adults |
| Protein with blood | Glomerulonephritis; urgent specialist referral |
Reference ranges vary by laboratory, method, age, sex and clinical context; a result is read against the person, not a table.
Limitations
Exercise, fever, infection and standing for long periods raise protein transiently; two out of three samples must be positive to confirm.
Medicines monitored with this test
Each medicine page cites the official document that names this test in its monitoring plan.
Catalogued concepts this page covers
Concepts of the master test taxonomy that resolve to this page; each links to its category.