MAGENT

Urine protein creatinine ratio from a spot sample (Ginsberg 1983)

The urine protein creatinine ratio (UPCR) divides the total protein in a single urine sample by the creatinine in the same sample. Ginsberg and colleagues showed in 1983 that this ratio, in mg of protein per mg of creatinine, tracks the grams of protein lost in a day. Magent's calculator returns the ratio, the same number as an estimate of daily protein in g/day, and the Ginsberg band.

Not a medical device. Not a diagnosis or dosing recommendation.

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What is the urine protein creatinine ratio?

Measuring protein loss directly means collecting every drop of urine for a day, which is slow and often incomplete. Creatinine leaves the body in urine at a fairly steady rate through the day. Dividing protein by creatinine in one sample corrects for how concentrated or dilute that sample happens to be.

Ginsberg 1983 compared single voided samples with timed collections and found the ratio estimated daily protein well. A ratio of 1.0 mg/mg corresponds to about 1.0 g of protein a day, which is why the calculator reports the rounded ratio twice: once as the ratio and once as estimated_g_day.

The calculator uses total protein, not albumin.

The urine protein creatinine ratio formula

UPCR (mg/mg) = urine protein (mg/dL) / urine creatinine (mg/dL)
estimated protein (g/day) ≈ UPCR

band   UPCR < 0.2          lt_0_2       (within normal limits)
       0.2 to 3.5          0_2_to_3_5
       UPCR > 3.5          gt_3_5       (nephrotic range)

Exact expression the calculator uses:

protein_creatinine_ratio = urine_protein_mg_dl / urine_creatinine_mg_dl

Inputs

InputMeaningUnitRange
urine_protein_mg_dlUrine total proteinmg/dL0.1 to 2000
urine_creatinine_mg_dlUrine creatininemg/dL1 to 500
urine_creatinine_umol_lUrine creatinine, alternativeµmol/L88 to 44210

Protein is required. Creatinine is required in one of its two units.

How the calculation works

  1. Put creatinine in mg/dL. A µmol/L value is divided by 88.42.
  2. Divide. Protein in mg/dL over creatinine in mg/dL gives a ratio in mg/mg. Because both are in the same unit, the dL cancels.
  3. Round. The ratio is rounded to 2 decimals. The same number is returned as the g/day estimate.
  4. Band. Below 0.2 is lt_0_2. Above 3.5 is gt_3_5. Everything from 0.2 to 3.5, including exactly 0.2 and exactly 3.5, is the middle band, because the paper says "less than" 0.2 and "more than" 3.5.

Units

The ratio here is mg of protein per mg of creatinine. Many labs print the same measurement in mg/g, which is the mg/mg number multiplied by a thousand, and labs in some countries print mg/mmol, which is a different number again. Check which unit a report uses before comparing it with the Ginsberg bands, and don't mix them. In Magent's reference cases, a urine creatinine of 8842 µmol/L converts to 100.0 mg/dL.

Worked examples

These use Magent's own expected values for the calculator.

Example 1: protein and creatinine both 100 mg/dL

  1. Urine protein 100 mg/dL, urine creatinine 100 mg/dL.
  2. 100 / 100.
  3. UPCR 1.0 mg/mg, estimated 1.0 g/day. Middle band (0_2_to_3_5).

Example 2: low protein

  1. Urine protein 10 mg/dL, urine creatinine 100 mg/dL.
  2. 10 / 100.
  3. UPCR 0.1. Below 0.2, so lt_0_2.

Example 3: high protein

  1. Urine protein 400 mg/dL, urine creatinine 100 mg/dL.
  2. 400 / 100.
  3. UPCR 4.0. Above 3.5, so gt_3_5, the nephrotic-range band.

Example 4: creatinine reported in µmol/L

  1. Urine protein 100 mg/dL, urine creatinine 8842 µmol/L.
  2. 8842 / 88.42 gives 100.0 mg/dL of creatinine. Then 100 / 100.
  3. UPCR 1.0, the same as Example 1.

History of the urine protein creatinine ratio

Ginsberg JM, Chang BS, Matarese RA and Garella S published the method in the New England Journal of Medicine in 1983. Their paper, titled for estimating quantitative proteinuria from single voided samples, set out the ratio and the cut-points below 0.2 and above 3.5 that the calculator reports.

When it's used

The ratio is worked out when a spot urine sample has been tested for total protein and creatinine and an estimate of daily protein loss is wanted without a timed collection.

Where it's used

Clinics, wards and laboratories where urine protein and creatinine are measured on the same sample.

Who uses it

Clinicians reading urine results, especially in kidney care. The calculator does the division, the unit change and the band.

Limits of the calculation

  • It is an estimate. It is not a measured 24-hour collection.
  • It uses total protein. It isn't interchangeable with the albumin/creatinine ratio or albuminuria staging.
  • The bands are published cut-points, not a label for any condition.
  • This page doesn't say what a result means for a particular person.

Clinical decisions belong to a qualified clinician who knows the patient.

  • FENa uses sodium and creatinine in blood and urine to give a fractional excretion. UPCR uses urine alone.
  • FEUrea does the same with urea. Neither measures protein.
  • eGFR estimates filtration from blood creatinine. UPCR estimates protein loss in urine.

Glossary

  • Spot sample: a single urine sample collected at one time.
  • Total protein: all protein in the urine, not just albumin.
  • Nephrotic range: the label for a ratio above 3.5 in Ginsberg's bands.
  • mg/mg: milligrams of protein per milligram of creatinine.

Common mistakes

  • Mixing units. A mg/g result is a thousand times the mg/mg ratio. A mg/mmol result is different again.
  • Entering protein and creatinine in different units. Both go in as mg/dL (or creatinine in µmol/L, which the calculator converts).
  • Using an albumin result. The calculator needs total protein.
  • Treating 0.2 or 3.5 as outside the middle band. Exactly 0.2 and exactly 3.5 are in the middle band.

Source

Ginsberg JM, et al. Use of single voided urine samples to estimate quantitative proteinuria. N Engl J Med. 1983;309(25):1543-1546. DOI: 10.1056/nejm198312223092503. PMID: 6656849

Frequently asked questions

What is a normal urine protein creatinine ratio?

Ginsberg 1983 treated a ratio below 0.2 mg/mg as within normal limits.

What ratio counts as nephrotic range?

Above 3.5 mg/mg in Ginsberg's bands.

Is the protein/creatinine ratio the same as the albumin/creatinine ratio?

No. This ratio uses total protein. The albumin/creatinine ratio measures albumin and uses different thresholds.

Why can the ratio stand in for grams per day?

In Ginsberg's comparison, the mg/mg ratio from a spot sample matched the daily protein loss in grams closely enough to serve as an estimate.

Can I enter creatinine in µmol/L?

Yes. The calculator divides it by 88.42 to get mg/dL first.