𧫠Protein/Creatinine Ratio
Spot urine proteinuria, quantified.
For informational purposes only, not medical advice. Consult a healthcare professional.
The spot urine protein-to-creatinine ratio divides urine protein by urine creatinine, both in mg/dL, and the result approximates grams of protein excreted per day. It replaces the 24-hour urine collection for most purposes: a ratio of 1.5 means roughly 1.5 grams per day. Dividing by creatinine corrects for how dilute or concentrated the sample is, which raw protein concentration cannot do. This calculator computes the ratio with the standard severity bands used in nephrology.
How to Use This Calculator
Enter protein and creatinine from the same spot urine sample in mg/dL. The ratio estimates 24-hour protein excretion.
Use protein and creatinine from the same void. The ratio corrects for urine concentration, which is its whole point.
Read the ratio. Under 0.2 is normal; above 3.5 is nephrotic range.
Confirm abnormal results with repeat testing and clinical context before acting on them.
How the Math Works
Divide urine protein in mg/dL by urine creatinine in mg/dL. Protein 120 over creatinine 80 gives 1.5, estimating 1.5 grams of daily protein excretion. The approximation works because average daily creatinine excretion is near 1 gram, so the ratio of the two concentrations mirrors the ratio of their daily excretions. Bands: under 0.2 normal, 0.2 to 3.5 abnormal proteinuria, above 3.5 nephrotic range. First-morning samples are preferred since orthostatic and exercise proteinuria fade overnight.
Worked Example
Urine protein 120 mg/dL with creatinine 80 mg/dL gives a ratio of 1.50, estimating daily excretion of about 1.50. The calculator grades this as ~1.5 g/day: abnormal and worth working up, but below the 3.5 nephrotic-range threshold. A repeat first-morning sample would confirm whether this is persistent proteinuria or a transient spike from exercise or fever.
Reading Your Result
Under 0.2 is normal and needs nothing. The 0.2 to 3.5 range is abnormal proteinuria: evaluate for glomerular disease, diabetic kidney disease, hypertension effects, and medications, with repeat testing to confirm persistence. Above 3.5 is nephrotic range, usually with edema and low albumin, and deserves prompt nephrology referral. Rising ratios on repeat testing matter more than any single value.
| PCR | Estimated daily protein | Band |
|---|---|---|
| Under 0.2 | Under 0.2 g | Normal |
| 0.2-3.5 | 0.2-3.5 g | Abnormal |
| Above 3.5 | Above 3.5 g | Nephrotic range |
Limitations
The ratio assumes average creatinine excretion, so very muscular or very slight patients deviate. Transient proteinuria from exercise, fever, or upright posture can spike a random sample; confirm with first-morning repeats. It estimates total protein, not albumin specifically, and does not identify the cause. Nephrotic-range results need clinical correlation, not just the number.
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For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is the protein creatinine ratio?
Urine protein divided by urine creatinine from a spot sample. It estimates 24-hour protein excretion in grams per day without the collection jug. Under 0.2 is normal; above 3.5 is nephrotic range.
Why divide by creatinine?
To correct for urine concentration. A dehydrated person has high protein concentration without more protein excretion; creatinine rises proportionally, so the ratio stays honest. It is the same trick behind many urine tests.
What is nephrotic range proteinuria?
Over 3.5 grams per day, usually with low albumin, edema, and high lipids: the nephrotic syndrome. It signals glomerular disease and needs nephrology evaluation, often including biopsy.
Is first-morning urine better?
Yes for confirmation. Random daytime samples catch orthostatic and exercise-related proteinuria that fades overnight. A first-morning ratio reflects the true baseline and is the preferred confirmatory sample.
What causes transient proteinuria?
Exercise, fever, dehydration, urinary tract infection, and prolonged standing. These resolve with the trigger, which is why persistence across repeats defines real kidney proteinuria.
What is microalbuminuria?
Slightly elevated albumin excretion, 30 to 300 mg per day, the earliest sign of diabetic kidney disease. The PCR detects total protein; dedicated albumin-to-creatinine ratio testing is more sensitive for this early stage.
How accurate is PCR versus 24-hour collection?
Correlations run 0.8 to 0.9 in most studies, good enough to replace collections for monitoring. At very high or very low muscle mass, or extreme proteinuria, the approximation weakens and timed collections still win.
Can dehydration cause proteinuria?
It raises protein concentration but the creatinine correction keeps the ratio stable, which is exactly why the ratio beats raw concentration. True dehydration rarely creates a falsely high PCR.
What workup follows abnormal PCR?
Repeat first-morning confirmation, then urine microscopy, kidney function labs, blood pressure review, diabetes screening, and medication review. Persistent or nephrotic-range findings go to nephrology.
Does treatment lower proteinuria?
Often: blood pressure control, ACE inhibitors or ARBs, diabetes management, and sodium restriction all reduce it, and falling proteinuria predicts better kidney outcomes. The ratio then becomes the monitoring tool.