Albumin Creatinine Ratio Calculator

Background.

Albumin is the most abundant protein in blood, and healthy kidneys keep almost all of it there. When the kidney's filters start to leak, most often because of diabetes or high blood pressure, small amounts appear in the urine well before blood creatinine or eGFR changes. That is why a urine albumin test is part of routine check-ups for people with those conditions.

A concentration on its own is hard to read. The same leak gives a high albumin figure in concentrated morning urine and a low one after someone has drunk a litre of water. Creatinine fixes this. It comes from muscle and is excreted at a fairly steady daily rate, so its concentration shows how concentrated the sample is, and dividing albumin by creatinine cancels the dilution. Because an adult excretes roughly a gram of creatinine a day, a ratio in milligrams per gram approximates the milligrams of albumin lost per day.

That approximation is also the ratio's main weakness. A frail older adult with little muscle makes less creatinine, so their ratio reads high for the albumin actually lost; a very muscular person reads low.

The page does the division and nothing more. Albumin goes in as mg/L and creatinine as g/L, and the result is in mg/g, the unit used on US reports. Many laboratories elsewhere, including in the UK, report mg/mmol instead; one mg/mmol is about 8.84 mg/g. No category is attached to the number. The KDIGO guideline cited below grades albuminuria into categories A1 to A3, and a raised value is normally confirmed on repeat samples, because exercise, infection, fever and menstruation can push a single result up. Reading the result is a job for the clinician who ordered the test.

What is albumin creatinine ratio calculator?

The urine albumin-to-creatinine ratio, written ACR or UACR, is the mass of albumin in a urine sample divided by the mass of creatinine in the same sample. Both are measured as concentrations, so the urine volume cancels: milligrams of albumin per litre divided by grams of creatinine per litre gives milligrams of albumin per gram of creatinine. It is the usual way to screen for and follow albuminuria from a single spot sample instead of a 24-hour urine collection.

How to use this calculator.

1. 01Copy the urine albumin result in mg/L from the lab report; older reports may label it microalbumin. If it is given in mg/dL, multiply by 10.
2. 02Enter urine creatinine in g/L. US reports usually give mg/dL, so divide by 100: 120 mg/dL becomes 1.2 g/L. A result in mmol/L is converted by multiplying by 0.1131.
3. 03Take both values from the same sample, ideally a first-morning specimen, which the KDIGO guideline prefers. Never pair albumin from one day with creatinine from another.
4. 04If the lab has already printed a ratio, compare like with like: a value in mg/mmol must be multiplied by about 8.84 to match the mg/g shown here.

The formula.

ACR = albumin ÷ creatinine, with albumin in milligrams per litre and creatinine in grams per litre. The litres cancel and the result is milligrams of albumin per gram of creatinine. No constant is needed because the units were chosen to line up; with creatinine in mg/dL you would multiply by 100 instead, and with creatinine in mmol/L the answer would come out directly in mg/mmol. Creatinine sits in the denominator, so anything that lowers it raises the ratio. Dilution lowers albumin and creatinine together and cancels out, but a person with low muscle mass excretes less creatinine overall, and that does not cancel. Both inputs must be greater than zero, since a zero creatinine would make the division undefined. If the lab reported albumin as below its detection limit, entering that limit gives the highest the ratio could be. The page applies no category boundaries and returns the ratio only.

A worked example.

Frequently asked questions.

References& sources.

1. [1]KDIGO 2024 Clinical Practice Guideline for the Evaluation and Management of Chronic Kidney Disease.
2. [2]NIDDK, Assess Urine Albumin.
3. [3]BIPM, The International System of Units (SI Brochure), 9th ed., version 3.01, coherent derived units and quantity equations.