Protein/Creatinine Ratio: What a Normal Result Looks Like, and When It Isn't

At a Glance

Your result is a ratio: protein in the urine divided by creatinine in the same sample.

The reference ranges for this component are not the same for everyone. For the protein/creatinine ratio on test 757 — the part of this panel that produces your number — Quest publishes these in its East service area (Eastern PA, MD, DE, VA, NY, NJ, Southern CT), which is the area checked for this page:

That is a 50% difference, and a single range cannot carry both. A woman with a result between 100 and 150 mg/g is inside the published interval for women even where a single-number range flags her. It is the first thing to check. Quest gates these figures by service area, so another area may print different ones — which is why the interval on your own report is what counts.

Separately from the reference interval, Quest's clinical guidance defines proteinuria as a "urinary total protein-creatinine ratio ≥150 mg/g". A reporting interval and a clinical threshold are different objects and need not agree.

Why sex can affect the ratio

Two things are worth keeping apart: a general piece of physiology, and a decision Quest has made.

Creatinine comes from muscle, and StatPearls gives the excretion figures: "for healthy adult males, the creatinine excretion ranges from 20 to 25 mg/kg/24 hours, whereas females excrete about 15-20 mg/kg/24 hours." Divide the same amount of protein by a smaller quantity of creatinine and the ratio comes out larger — so sex can move this number through the denominator, without anything differing in what the kidneys are doing.

Quest's decision is separate. It publishes different male and female reference intervals for this component, and its directory does not state how those limits were set. The physiology above is not an account of Quest's reasoning, and this page does not offer one.

Worth knowing alongside it: clinical category schemes are not always sex-specific. KDIGO's 2024 albuminuria categories — a different analyte, but the comparable scheme — use one set of cutoffs for everyone.

What this panel contains

Your result comes from Quest test 38944, "Protein, Total and Protein Electrophoresis, 24 Hour Urine and Immunofixation", which bundles three tests:

Electrophoresis and immunofixation evaluate the kind of protein rather than the amount, and together they are how a laboratory identifies a monoclonal protein — an immunoglobulin, or a free immunoglobulin light chain, produced by a single clone of cells. Their presence does not tell you why the panel was ordered in your case.

One thing is specific to a timed collection: this panel measures total protein directly across the full 24 hours — Quest's interval for that line is under 150 mg per 24 hours — so the ratio sits alongside a direct measurement rather than substituting for one. Quest asks for a 24-hour collection in an unpreserved plastic container, instructs that the total volume be recorded, and rejects acidified urine.

A missed hour affects those two figures differently. The mg-per-24-hour totals depend on collecting the whole day, so an incomplete collection makes them unreliable. The ratio is more robust: protein and creatinine come from the same urine, so the amount collected divides out of both. What can still shift it is which hours were missed, since the two are not excreted evenly through the day.

How to read your result

No row here is a diagnosis, and none of them is read without the rest of the report.

If you remember only one thing

Check which reference range your result was measured against. The published intervals are under 100 mg/g for men and under 150 mg/g for women, and a single range cannot be both.

A raised result still needs looking at. Ordinary things raise it temporarily, but what happens next depends on how high it is and what else is going on.

Two people, same result

Two people, a man and a woman, both have a protein/creatinine ratio of 120 mg/g.

For the man, the published interval is under 100 mg/g, so 120 sits above it and the question is what is behind it and whether it persists.

For the woman, the published interval is under 150 mg/g, so 120 sits inside it.

Same number, same test, same laboratory. What separates them is which of the two published intervals applies — exactly what a single range cannot show.

What this result cannot tell you

Which protein it was. The total is a sum; sorting it is what the electrophoresis line is for.

Whether your kidneys are damaged. Raised urinary protein is a reason to look at kidney function, not a measurement of it. Creatinine, eGFR and your history are.

Whether the cause is lasting. One collection cannot separate a temporary rise from a persistent one.

How your number compares with someone else's. Intervals differ by sex, by laboratory and by service area, and some report in mg/mmol.

Common interpretation mistakes

Reading a single range as sex-neutral. There are two published intervals, fifty per cent apart, and a woman between 100 and 150 mg/g is the case this mistake hurts.

Treating a laboratory interval as a clinical threshold. An interval describes what the laboratory reports; Quest's ≥150 mg/g proteinuria definition is a clinical line.

Treating albumin and total protein as the same measurement. Quest gives albuminuria as "a urine ACR ≥30 mg/g" against 150 mg/g for total protein — different analytes, five times apart.

Reading a result just over the line as a severe one. Nephrotic range begins above 3,500 mg in 24 hours.

Assuming the panel was ordered as a kidney test — or that it wasn't. The components say what was measured, not what the clinician was asking.

Assuming a normal ratio clears the kidneys. It is one measurement, across one collection.

Questions your doctor may ask

Which reference range was this result compared against?

Were you unwell, feverish or dehydrated around the collection, and had you exercised hard in the day or two before?

Was the collection complete — did you miss any of the 24 hours, and was the total volume recorded?

Do you have diabetes or high blood pressure, and how long have you had them?

What did the electrophoresis and immunofixation lines show?

Read together with

Creatinine and eGFR — filtration itself. A urine protein result is read alongside them rather than instead of them.

Microalbumin/Creatinine Ratio — a related test measuring albumin rather than total protein, with a threshold five times lower.

Total Protein, Urine — the protein figure before it is divided by creatinine.

Creatinine, Random Urine — the denominator, measured on a spot sample.

Protein/Creatinine Ratio (random urine) — the same ratio measured on a single sample rather than a timed collection.

Clinical pearls

Quest's directory publishes no reference interval for the bundled panel, test 38944 — with no service area selected the entry reads "See Laboratory Report". The component that produces the ratio, test 757, does publish intervals once a service area is chosen, and in the East area they are sex-specific.

The units are a trap. StatPearls says "a UPCR value greater than 15 mg/mmol should raise suspicion and warrant further investigation". On KDIGO's conversion factor of 0.113 that is about 133 mg/g — close to Quest's figures but identical to neither, which is why a number lifted from one source and compared against another's units will not line up.

Orthostatic proteinuria is worth knowing about in younger people: protein appears after a long period upright and is absent from the early-morning sample. StatPearls calls it "rare in patients more than 30 years of age".

Clinical Takeaway

The protein/creatinine ratio divides urinary total protein by urinary creatinine. On Quest test 757 — the component of this panel that produces the number — the reference intervals published for the East service area are sex-specific: under 100 mg/g creat for males and under 150 mg/g creat for females, with the same figures expressed as under 0.100 and under 0.150 mg/mg. Quest gates these by service area and only that area was checked. Sex can affect the ratio through its denominator: StatPearls gives creatinine excretion as 20 to 25 mg/kg/24 hours in healthy adult males against 15 to 20 in females. How Quest arrived at these particular limits is not stated in its directory. Separately, Quest's clinical guidance defines proteinuria as a "urinary total protein-creatinine ratio ≥150 mg/g" — a clinical threshold rather than a reporting interval. The analyte is total protein, not albumin; Quest's albuminuria threshold is a urine ACR ≥30 mg/g and the two are not interchangeable. StatPearls gives normal excretion as "Less than 150 mg/24 hour or 15 mg/mmol" and nephrotic range as "More than 3500 mg/24 hour or more than 350 mg/mmol". Transient causes — fever, acute illness, exercise, dehydration, emotional stress and orthostatic proteinuria — can raise the figure, so a repeat may be appropriate; StatPearls nonetheless states that a raised value "should be further evaluated for underlying reasons", and whether a repeat alone is the right next step depends on the degree of proteinuria and the rest of the clinical picture. The panel bundles this component with a urine protein electrophoresis and an immunofixation, which evaluate the protein pattern and can identify a monoclonal protein — an immunoglobulin or a free light chain from one clone of cells; their presence establishes what was measured and not the ordering indication.

In one sentence

A protein/creatinine ratio measures urinary protein against urinary creatinine, and Quest's East service area publishes two different reference ranges for it — under 100 mg/g for men and under 150 for women — so the first question about any result is which one it was read against.

Bottom line

Your result is urine protein divided by urine creatinine, reported in milligrams per gram.

The first thing to check is which range it was measured against. In Quest's East service area the published intervals for this component are under 100 mg/g for men and under 150 mg/g for women — a difference of fifty per cent, and a single range beside your result cannot be both. A woman with a result between 100 and 150 is the case most likely to look abnormal without being outside the published interval for her. Sex can affect the ratio because creatinine excretion tends to be lower in women; how Quest arrived at these particular limits is not something its directory states.

Separately from that interval, Quest's clinical guidance treats a ratio of 150 mg/g or above as proteinuria. That is a different kind of number — a clinical line rather than a reporting range — and the two need not agree.

A raised result means protein was in the urine across this collection. It does not say why. Fever, acute illness, hard exercise, dehydration and emotional stress can all raise it, so a repeat is often sensible — but a raised result still deserves to be looked at rather than filed, and how much it matters depends on how high it is and what else is going on. Nephrotic-range loss, above 3,500 mg in a day, is a separate category.

This panel also runs a protein electrophoresis and an immunofixation, which look at what kind of protein is present rather than how much. Take the report to the clinician who ordered it, ask which reference range it was compared against, and bring any earlier protein results.