Protein in Urine

Protein that slips through the kidneys’ filters into urine.

Healthy kidneys keep almost all protein in the blood, where it belongs. When more than a trace shows up in urine — a finding called proteinuria — it can be temporary and harmless, or an early sign the kidneys’ filters need attention. The difference usually comes down to whether it persists.

What it means

The kidneys filter your entire blood volume many times a day, holding onto the things your body needs — including proteins like albumin. A urine strip detects when protein is slipping through that filter in more than trace amounts.

Why it happens

Temporary proteinuria is common and usually benign: intense exercise, fever, dehydration, and stress can all cause it. Persistent proteinuria is different — it’s one of the earliest measurable signs of kidney strain, and it’s linked to conditions that quietly affect the kidneys over time, like diabetes and high blood pressure. In pregnancy, new protein in urine is something providers monitor closely.

What a result can tell you

A negative result is the expected finding. A single positive is worth a calm retest a few days later, once you’re rested and hydrated. Protein that shows up repeatedly is meaningful — caught early, kidney strain is far more manageable, and your provider can confirm with a lab test and look for the cause.

What it can’t tell you

A strip can’t tell temporary from persistent protein — only repeat testing can — and it can’t identify the cause or measure kidney function. Very dilute or very concentrated urine can also skew readings. Use it as an early-warning check, and let a provider take it from there.