Urine concentration test
Water loading test; Water deprivation testA urine concentration test measures the ability of the kidneys to conserve or excrete water.
How the Test is Performed
For this test, some or all of the specific gravity of urine, urine electrolytes, and urine osmolality are measured before and after one or more of the following:
Specific gravity of urine
Urine specific gravity is a laboratory test that shows the total concentration of all chemical particles in the urine.
Urine electrolytes
The electrolytes - urine test measures specific chemicals called electrolytes in urine. It most often measures the levels of calcium, chloride, pota...
Urine osmolality
The osmolality urine test measures the concentration of chemicals in urine. Osmolality in the blood can be measured using a blood test.
- Water loading. Drinking large amounts of water or receiving fluids through a vein.
- Water deprivation. Not drinking fluids for a certain amount of time.
- Antidiuretic hormone (ADH) administration. Receiving ADH, which should cause the urine to become concentrated.
After you provide a urine sample, it is tested right away. For urine specific gravity, your health care provider uses a dipstick made with a color-sensitive pad. The dipstick color changes and tells the provider the specific gravity of your urine. The dipstick test gives only a rough result. For a more accurate specific gravity result or measurement of urine electrolytes or osmolality, your provider will send your urine sample to a lab.
If needed, your provider will ask you to collect your urine at home over 24 hours. Your provider will tell you how to do this. Follow instructions exactly.
Collect your urine at home over 24 hour
The urine 24-hour volume test measures the amount of urine produced in a day. The amounts of creatinine, protein, and other chemicals released into ...
How to Prepare for the Test
Eat your normal diet for several days before the test. Your provider will give you instructions for water loading or water deprivation.
Your provider will ask you to temporarily stop any medicines that may affect the test results. Be sure to tell your provider about all the medicines you take, including dextran and sucrose. Do not stop taking any medicine before talking to your provider.
Also tell your provider if you recently received intravenous dye (contrast medium) for an imaging test such as a CT scan or MRI scan. The dye can also affect test results.
CT scan
A computed tomography (CT) scan is an imaging method that uses x-rays to create pictures of cross-sections of the body. Related tests include:Abdomin...
MRI
A magnetic resonance imaging (MRI) scan is an imaging test that uses powerful magnets and radio waves to create pictures of the body. It does not us...
How the Test will Feel
The test involves only normal urination. There is no discomfort.
Why the Test is Performed
This test is most often done if your provider suspects central diabetes insipidus, a condition where there is an abnormality with ADH that regulates the concentration of the urine. The test can help tell that disease from nephrogenic diabetes insipidus, a condition where there is an abnormality in the kidney that prevents ADH from correctly regulating the concentration of the urine.
Central diabetes insipidus
Central diabetes insipidus is a rare condition that involves extreme thirst and excessive urination.
Nephrogenic diabetes insipidus
Nephrogenic diabetes insipidus (NDI) is a disorder in which a defect in the small tubes (tubules) in the kidneys causes a person to pass a large amou...
This test may also be done if you have signs of syndrome of inappropriate ADH (SIADH).
Syndrome of inappropriate ADH
Syndrome of inappropriate antidiuretic hormone secretion (SIADH) is a condition in which the body makes too much antidiuretic hormone (ADH). ADH is ...
Normal Results
In general, normal values for specific gravity are as follows:
- 1.005 to 1.030 (normal specific gravity)
- 1.001 after drinking excessive amounts of water
- More than 1.030 after avoiding fluids
- 50 percent rise in specific gravity after receiving ADH
Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples. Talk to your provider about the meaning of your specific test results.
What Abnormal Results Mean
Increased urine concentration may be due to conditions, such as:
- Glucose (a type of sugar) in the urine
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Heart failure
Heart failure
Heart failure is a condition in which the heart is no longer able to pump oxygen-rich blood to the rest of the body efficiently. This causes symptom...
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Loss of body fluids (dehydration) from diarrhea, vomiting, or excessive sweating
Loss of body fluids
Dehydration occurs when your body does not have as much water and fluids as it needs. Dehydration can be mild, moderate, or severe, based on how much...
ImageRead Article Now Book Mark Article - Narrowing of the kidney artery (renal arterial stenosis)
- SIADH
Decreased urine concentration may indicate:
- Diabetes insipidus
- Drinking too much fluid
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Kidney failure (loss of ability to reabsorb water)
Kidney failure
Acute kidney failure is the rapid (less than 2 days) loss of your kidneys' ability to remove waste and help balance fluids and electrolytes in your b...
ImageRead Article Now Book Mark Article - Severe kidney infection (pyelonephritis)
Risks
There are no risks with this test.
References
Navarro D, Fonseca NM, Garigali G, Fogazzi GB. Urinalysis. In: Johnson RJ, Floege J, Tonelli M, eds. Comprehensive Clinical Nephrology. 7th ed. Philadelphia, PA: Elsevier; 2024:chap 4.
Riley RS, McPherson RA. Basic examination of urine. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 29.
Verbalis JG. Posterior pituitary. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 206.
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Urine concentration test - illustration
The urine concentration test is a test that measures whether the kidneys are conserving or excreting water properly. A sample of urine is retrieved and tested for its specific gravity.
Urine concentration test
illustration
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Female urinary tract - illustration
The female and male urinary tracts are relatively the same except for the length of the urethra.
Female urinary tract
illustration
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Male urinary tract - illustration
The male and female urinary tracts are relatively the same except for the length of the urethra.
Male urinary tract
illustration
-
Urine concentration test - illustration
The urine concentration test is a test that measures whether the kidneys are conserving or excreting water properly. A sample of urine is retrieved and tested for its specific gravity.
Urine concentration test
illustration
-
Female urinary tract - illustration
The female and male urinary tracts are relatively the same except for the length of the urethra.
Female urinary tract
illustration
-
Male urinary tract - illustration
The male and female urinary tracts are relatively the same except for the length of the urethra.
Male urinary tract
illustration
Review Date: 8/20/2023
Reviewed By: Jacob Berman, MD, MPH, Clinical Assistant Professor of Medicine, Division of General Internal Medicine, University of Washington School of Medicine, Seattle, WA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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