Zimnitsky test: normal range, high and low

In shortThe Zimnitsky test measures urine density in eight portions collected every three hours. A typical density range across the day is 1.005–1.030, with a daytime share exceeding the nighttime one. Flattened fluctuations suggest impaired concentrating ability.

Reference ranges

Group	Reference range
Density across portions — typical range (international reference, not a national standard)	1.005–1.030
Pattern	daytime urine volume exceeds nighttime; at least one portion above 1.020

Values from the MedlinePlus Medical Encyclopedia and laboratory references (international typical range, not a national standard).

Check your value

Enter the number from your lab report — see how it compares with the typical range. Mind the units shown in the chosen row.

A rough comparison with a typical range, not a diagnosis. Reference ranges vary between laboratories — check the range on your own report and let a clinician interpret the result.

What this marker is

Healthy kidneys vary urine density widely: concentrated at night, more dilute by day. The test maps this rhythm portion by portion, revealing early tubular dysfunction before blood tests change.

It also estimates daily urine volume and the day/night balance — useful in evaluating nocturia, edema, and chronic kidney disease.

When it is high

Dehydration and glucosuriaPersistently high density occurs with fluid restriction and with glucose in the urine.

When it is low

Impaired concentrating abilityFixed low density (isosthenuria) points to chronic tubulointerstitial disease.

Excess fluid intake or diabetes insipidusCopious dilute urine across all portions.

What can skew the result

These factors can shift the value without any disease — worth considering before a retest:

Fluid intakeDiureticsAccuracy of the collection schedule

How to prepare

Normal drinking and eating; eight portions are collected strictly every three hours, including nighttime, into labeled containers.

When a retest makes sense

If the schedule was broken, the test is repeated; interpretation goes together with creatinine and eGFR.

Who usually reviews this result

A result outside the reference range is usually reviewed by: your GP or primary care doctor; a nephrologist for persistent abnormalities. Bring your lab report and any previous results to the appointment.

Names used on lab reports

Your report may use any of these names:
Zimnitsky testUrine concentration test

Units

Measured in: relative density

Several markers on your report?

See how MedProtect explains results in the app: the whole report, a check of the recognized values, and a clear breakdown.

Get your results explained See an example

Frequently asked questions

Do I have to wake up at night?

Yes — the night portions are the point of the test, since concentration peaks overnight.

Can I drink as usual?

Yes, normal fluid intake is required; deliberate restriction or overload invalidates the pattern.

What does a flat density profile mean?

Kidneys unable to vary concentration — seen in chronic tubulointerstitial diseases; the doctor interprets it with other kidney tests.

Sources

Urine concentration test: MedlinePlus Medical Encyclopedia — MedlinePlus. Accessed: August 31, 2026.

Zimnitsky test