Urine albumin-to-creatinine ratio
Ratio of albumin to creatinine in urine, an early sign of kidney damage
Also known as
Definition
The urine albumin-to-creatinine ratio (ACR, also UACR) relates the amount of the protein albumin in urine to creatinine. Healthy kidneys let through only traces of albumin at most; if more reaches the urine, this can be an early sign of kidney damage. Creatinine is usually excreted at a steady rate; relating albumin to it makes the result more accurate and allows a single urine sample to be evaluated.
| Parameter | Value |
|---|---|
| Unit | mg/g creatinine or mg/mmol creatinine |
| Reference Range | Below 30 mg/g creatinine (about 3.4 mg/mmol) is considered normal. 30–300 mg/g is called microalbuminuria, 300 mg/g or more macroalbuminuria. Labs differ; the range printed on your report is what counts, and your doctor interprets the result. |
Agree on your personal target range with your doctor.
Conversion: 1 g of creatinine equals 8.84 mmol, so 1 mg/g ≈ 0.113 mg/mmol (30 mg/g ≈ 3.4 mg/mmol; 300 mg/g ≈ 34 mg/mmol). Depending on the lab, cut-offs in mg/mmol may be given in rounded form.
↓ What a low value means
A value in the normal range means that only traces of albumin pass into the urine, as expected with healthy kidneys. MedlinePlus does not describe a separate meaning for a particularly low ratio. A normal value does not reliably rule out other kidney diseases, which is why it is often viewed together with blood values such as creatinine and eGFR.
↑ What a high value means
An elevated ratio can be an early sign of kidney damage, often related to diabetes or high blood pressure. However, albumin in urine can also rise temporarily after intense exercise, with fever, inflammation, urinary tract infections, gum infections or dehydration. That is why an abnormal value is usually repeated: if two out of three tests within three to six months are elevated, this may indicate early kidney disease. Higher or rising values go along with a higher risk of cardiovascular disease. Discuss any deviation with your doctor.
When to test
The test is mainly used for early detection in people at higher risk of kidney disease, such as those with diabetes, high blood pressure, heart disease, a family history, smoking, obesity or age over 50; with diabetes, a yearly check is common. A random urine sample is usually enough. Intense exercise before the sample and eating meat the day before can affect the result. If you are menstruating or have bleeding hemorrhoids, tell the practice beforehand.
Frequently asked questions
How does this differ from albumin in the blood? +
In the blood, albumin is a common protein measured as a serum value. The albumin-to-creatinine ratio instead measures how much albumin passes through the kidneys into the urine. The two values answer different questions and are not interchangeable.
Why is an elevated value repeated? +
Exercise, fever, inflammation or certain medicines can briefly raise albumin in urine. That is why two more tests usually follow within three to six months; only when two out of three results are elevated is the finding considered confirmed.
Is the ratio the same as prealbumin? +
No. Prealbumin is a different protein and plays no role in assessing the kidneys. The similar names are easy to mix up.
Which urine sample is most accurate? +
According to MedlinePlus, a 24-hour urine collection is the most accurate. For routine checks, a random or first-morning sample is usually enough; the 24-hour collection is mainly used to follow up on abnormal single results.
Urine albumin-to-creatinine ratio
Sources
Last updated: October 05, 2026
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.