Albumin-to-Creatinine Ratio (uACR)
The uACR is a urine test, not a blood test, and it answers a question eGFR can't: whether your kidney filters are leaking. A trace of protein in urine can show up years before filtration ever slips.
Part of the Kidney Function Panel — see all 7 values together, including Beta-2 Microglobulin, Microalbumin, Uric Acid.
Two tests share the word albumin and almost nothing else. One is drawn from a vein and measures the protein floating in your blood. This one is run on urine, and what it cares about is whether any albumin is escaping into your pee at all. A healthy kidney keeps albumin in the bloodstream where it belongs. When it starts showing up in urine, the filter has sprung a leak.
The urine albumin-to-creatinine ratio, or uACR, is the test that finds that leak early. MedlinePlus describes albumin as a common blood protein that is not a waste product, so very little of it should ever cross into urine. When the kidney's filtering membrane is damaged, albumin slips through. Picture an earthen dam holding back a reservoir. Long before the wall sags or gives way, you see it first as a thin seep weeping through a hairline crack in the face. The seep is albumin in the urine. The dam still stands and the water is still held, but the wall has begun to fail and the wet patch is the only thing telling you so.
That is the split worth understanding before you read a kidney report. eGFR measures how fast the kidneys filter, which is how well the dam is doing its job overall. The uACR measures whether the wall is leaking. Damage can show in the seep years before it shows in the flow, which is why the National Kidney Foundation calls the uACR an important test for identifying kidney damage in addition to eGFR, and why the two are read as a pair.
The reason this test pairs albumin with creatinine at all is dilution. A spot urine sample is whatever concentration your bladder happened to hold: dilute after a liter of water, concentrated when you show up dry. Urine creatinine is produced at a fairly steady rate, so dividing albumin by it cancels the dilution out. That is why the result is a ratio in milligrams per gram, and why a quick spot sample can stand in for the old timed 24-hour urine collection.
What a uACR value usually means
mg/gThe National Kidney Foundation labels under 30 mg/g as normal or at goal. Healthy kidneys hold albumin back, so a trace this low is the expected reading. This is the same cutoff for men and women.
Once called microalbuminuria. More albumin than a healthy filter should let through, but below the level older protein dipsticks could even detect. A single value here is often repeated before it counts, because exercise, fever, or infection can lift a one-off sample into this band.
Once called macroalbuminuria. A clearer signal of established kidney damage that belongs with a doctor, especially alongside diabetes or high blood pressure. The higher the number, the higher the risk that kidney disease progresses over time.
Those A1, A2, and A3 albuminuria categories are not just descriptions. They form one axis of the grid kidney guidelines use to stage chronic kidney disease, with eGFR as the other. A person can have a normal eGFR and still land in A2 or A3, and that combination means something different from two normal numbers, which is why both are charted together.
What a high uACR means
A raised uACR means albumin is getting into urine that should not be there. The leading reason for a persistently high result is the slow, silent damage that diabetes and high blood pressure do to the kidney's filters. The NIDDK names diabetes as the leading cause of kidney disease, and most people with diabetic kidney disease have no symptoms at all, which is the whole argument for testing rather than waiting to feel something.
But not every high reading is kidney damage. A single elevated sample is common and often temporary, which is why one number is rarely acted on alone.
What can push a single uACR high
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Hard exercise
MedlinePlus lists strenuous activity as a temporary cause; a workout near the time of the sample can lift albumin on its own.
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Fever or infection
Acute illness and inflammation in the body raise albumin in urine for a short stretch, separate from any kidney problem.
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A urinary tract infection
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Menstrual blood or bleeding hemorrhoids
Blood contaminating the sample skews the result; MedlinePlus advises telling your provider before the test.
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Dehydration or very concentrated urine
This is why the result almost always gets a second look. The National Kidney Foundation states that decisions are rarely made on a single sample, and MedlinePlus describes the standard path: two more tests over the three to six months after the first, with early-stage kidney disease considered when two of three come back abnormal. A lone high uACR is a reason to repeat, not a diagnosis.
When albumin loss becomes heavy and sustained, it can pull down the protein level in the blood itself. A falling serum albumin alongside a high urine albumin points to protein genuinely leaving the body through the kidneys rather than a problem with how it is made.
When the uACR reads normal
A result under 30 mg/g is reassuring, and for most people it is the end of the story. The one honest caveat is that a normal uACR does not by itself rule out every kidney problem. Some kidney disease shows up as a falling filtration rate without much albumin leak, so the uACR is read next to eGFR rather than instead of it. A normal seep with a dropping flow is a real pattern, and the reason guidelines pair the two tests.
If your uACR came back above 30
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1
Talk to your doctor before reading too much into one number
A single value in the 30 to 300 range is the most over-read result on a kidney report. Your clinician is the one to decide whether it needs repeating and what else to check.
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2
Mention anything that could have skewed the sample
A hard workout that morning, a current fever or urinary infection, or collecting during a menstrual period can each lift a single uACR. These are worth flagging, because they change how the result should be read.
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3
Expect a repeat, not a verdict
The usual approach is two further samples over three to six months. The National Kidney Foundation notes decisions are rarely made on one result, and a finding is confirmed when two of three are abnormal.
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4
Ask how it sits with your eGFR, blood pressure, and blood sugar
A uACR means the most read against the rest of the picture. If diabetes or high blood pressure is driving it, clinicians work on those drivers, since controlling blood pressure and blood sugar is where the kidney protection happens.
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5
Treat it as a yearly number if you are at risk
The NIDDK advises people with type 2 diabetes, and those who have had type 1 diabetes for more than five years, to be checked for kidney disease every year. This is the test many people who should have it never get.
A number worth tracking, and the test people skip
The uACR rarely travels alone. It anchors the kidney panel beside eGFR and creatinine, and it appears on the diabetes panel because diabetes is the condition most likely to be quietly damaging the filters. Where creatinine and eGFR estimate how well the kidneys filter, the uACR is the one number in the group that reports whether the filter is leaking, which is what lets it move first. Labs report this ratio in mg/g, and a result above 30 can signal early kidney damage through microalbumin leakage even while filtration numbers stay normal.
It is also the kidney test most people with diabetes or high blood pressure are supposed to get every year and many never do, partly because nothing about early kidney damage feels like anything. The seep does not hurt. And because the uACR is itself a ratio that only makes sense read against eGFR rather than on its own, knowing how to weigh one kidney number beside another is what turns a result like this into a finding. This is a test built to be read before anything feels wrong.
Sources
- Microalbumin Creatinine Ratio — MedlinePlus, National Library of Medicine
- Urine Albumin-Creatinine Ratio (uACR) — National Kidney Foundation
- Chronic Kidney Disease (CKD) Tests & Diagnosis — NIDDK, National Institutes of Health
- Diabetic Kidney Disease — NIDDK, National Institutes of Health
Written and reviewed by BloodSight Editorial Team · Last updated
See your Albumin-to-Creatinine Ratio on one timeline.
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In your personal range
Normal ranges
| Group | Range | Unit |
|---|---|---|
| Adult Male | 0–30 | mg/g |
| Adult Female | 0–30 | mg/g |
Reference ranges may vary by laboratory and individual factors.
Albumin-to-Creatinine Ratio — Common Questions
What is a normal albumin-to-creatinine ratio?
Is the albumin-to-creatinine ratio a blood test or a urine test?
Can I have a high albumin-to-creatinine ratio with a normal eGFR?
Why does one high uACR need to be repeated?
What does an albumin-to-creatinine ratio of 50 mean?
Disclaimer
This content is for informational and educational purposes only. It is not intended as medical advice, diagnosis, or treatment recommendation. Reference ranges may vary by laboratory. Always discuss your results with a qualified healthcare professional.
Related Tests
eGFR is a kidney-filtration figure no machine ever measured. A formula draws it from your creatinine, age, and sex, which makes it a useful map of filtration and a misleading one in a few predictable places.
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BUN is the protein-waste reading on your metabolic panel, and the easiest kidney number to push around without touching the kidneys. A dry day or a big protein meal can lift it while your creatinine sits still.
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Fasting glucose is the same blood sugar as any other glucose reading, measured under one strict rule: nothing but water for at least eight hours. That rule is what lets one morning's number be compared to the next.
Creatinine clearance is the one kidney test the patient performs: a full day of urine in a jug, paired with a blood draw. The collection is the test, and a single missed trip to the toilet quietly biases the answer.
The kidney test that goes high while the famous filtration numbers still look fine — and why a little albumin in urine is never supposed to be there at all.