𧫠ACR Calculator
Screen for kidney damage from a spot urine sample.
Albumin-to-creatinine ratio
For informational purposes only, not medical advice. Consult a healthcare professional.
Healthy kidneys keep albumin, an important blood protein, out of the urine. When the kidney's filters start leaking, albumin slips through long before standard blood tests show a problem. The albumin-to-creatinine ratio (ACR) from a simple spot urine sample is the earliest practical screen for that leak.
Dividing by creatinine corrects for how concentrated the urine is, which is why a random sample works instead of a 24-hour collection. This calculator converts your lab's albumin and creatinine numbers into the ACR and maps it to the KDIGO categories doctors use.
How to use this calculator
Take the urine albumin and urine creatinine values from your lab report. Most US labs report both in mg/dL for a spot urine sample.
Enter urine albumin in mg/dL from your lab report.
Enter urine creatinine in mg/dL from the same sample.
Read your ACR in mg/g and its KDIGO category, and note whether a repeat test is needed.
The formula and categories
ACR is albumin divided by creatinine, scaled to mg of albumin per gram of creatinine. Because both come from the same sample, hydration cancels out.
The older terms microalbuminuria (30 to 300) and macroalbuminuria (above 300) are still widely used and mean exactly the same thing as A2 and A3. Either vocabulary is fine as long as the numbers match.
Worked example
A lab reports urine albumin 4.5 mg/dL and urine creatinine 120 mg/dL. ACR = 4.5 / 120 x 1000 = 37.5 mg/g. That lands in A2, moderately increased. For a person with diabetes, this is the classic early signal of diabetic kidney disease, and guidelines call for a repeat test to confirm, tighter blood pressure and glucose control, and usually an ACE inhibitor or ARB.
Contrast a report of albumin 0.8 mg/dL with creatinine 150 mg/dL: ACR = 0.8 / 150 x 1000 = 5.3 mg/g, comfortably A1 and normal. Same test, very different story, which shows why the ratio matters more than either number alone.
What your result means
A1 (below 30): normal. If you have diabetes or hypertension, repeat yearly, since risk evolves. A2 (30 to 300): early kidney damage. This stage is where intervention pays off most: blood pressure control, glucose control, and kidney-protective medications can halt or reverse progression. A3 (above 300): significant damage needing active nephrology care.
ACR pairs with eGFR (the blood-test measure of filtering function) to stage chronic kidney disease fully. Either one can be abnormal while the other is fine, so both get checked. For blood sugar context, our blood sugar converter and diabetes risk calculator complement this screen.
When ACR misleads
Several everyday things raise ACR temporarily: vigorous exercise in the past 24 hours, fever, urinary tract infection, menstruation, and even prolonged standing. That is why guidelines require confirmation: two of three abnormal samples over 3 to 6 months before diagnosing persistent albuminuria.
Very muscular people excrete more creatinine, which can dilute the ratio downward, while frail elderly people excrete less, nudging it up. Neither effect usually changes the category, but borderline A2 results near 30 deserve a repeat under standard conditions: rested, afebrile, and infection-free.
Protecting your kidneys after an A2 result
An A2 result is the best bad news in kidney medicine: early enough that intervention changes the trajectory. Blood pressure control leads, with a target usually under 130/80 and an ACE inhibitor or ARB as the preferred agent, since these drugs lower pressure inside the kidney's filters specifically, not just in the arm cuff.
Glucose control comes next for people with diabetes: every point of A1C reduction slows albuminuria progression. Sodium under 2 grams a day, steady weight loss if overweight, and quitting smoking each add independent benefit. Newer drug classes, SGLT2 inhibitors and finerenone, have strong trial evidence for slowing decline once albuminuria is established; ask your doctor whether they fit your case.
Recheck ACR every 3 to 6 months after an abnormal result, alongside eGFR. What you want to see is stability or regression into A1. Albuminuria can genuinely improve with treatment, which is rare enough in chronic disease to be worth celebrating.
ACR vs protein/creatinine ratio
Labs offer two urine ratios and they are not interchangeable. ACR measures albumin specifically, the protein that leaks earliest in diabetic and hypertensive kidney disease. The protein-to-creatinine ratio (PCR) measures all protein, which suits glomerular diseases where larger proteins spill, like nephrotic syndrome.
| Feature | ACR | PCR |
|---|---|---|
| Measures | Albumin only | Total protein |
| Best for | Diabetes, hypertension screening | Known glomerular disease, nephrotic range |
| Sensitivity | Detects 30 mg/g and up | Misses early albuminuria |
| Guideline role | CKD screening standard | Monitoring established proteinuria |
For screening, ACR wins: it catches disease a stage earlier. For tracking heavy proteinuria already diagnosed, PCR is cheaper and sufficient. Your lab report usually shows whichever your doctor ordered, and now you know why.
For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is a normal ACR level?
Below 30 mg/g (category A1). This is the normal range for a spot urine sample, though people with diabetes or hypertension should still repeat screening yearly.
What does an ACR of 30 to 300 mean?
Moderately increased albuminuria (A2), formerly called microalbuminuria. It signals early kidney damage, most often from diabetes or hypertension, and it is the stage where treatment prevents the most harm.
What does an ACR above 300 mean?
Severely increased albuminuria (A3), formerly macroalbuminuria. This indicates significant kidney damage and calls for prompt, active kidney care with a nephrologist involved.
Why divide albumin by creatinine?
Urine concentration varies wildly with hydration. Creatinine is excreted at a fairly steady rate, so the ratio cancels out dilution and lets a random spot sample substitute for a 24-hour collection.
Can exercise affect ACR results?
Yes. Vigorous exercise within 24 hours, fever, urinary tract infection, and menstruation can all raise ACR temporarily. Abnormal results should be confirmed with a repeat test under normal conditions.
How is ACR different from a urine dipstick?
Dipsticks detect protein only above roughly 300 mg/g and miss the entire A2 range. ACR is far more sensitive and is the recommended screen for early kidney disease.
How often should ACR be checked?
Yearly for people with diabetes, hypertension, or other kidney risk factors. After an abnormal result, repeat in 3 to 6 months to confirm persistence before acting on it.
What lowers a high ACR?
Blood pressure control (especially ACE inhibitors or ARBs), glucose control in diabetes, weight management, less sodium and alcohol, and smoking cessation. In studies these measures slow or reverse albuminuria progression.