A urine test is a painless way for your doctor to check your health and test for abnormalities. One thing your doctor may check for in your urine sample test, or urinalysis, is specific gravity.
Urine that’s too concentrated could mean your kidneys aren’t functioning properly, or that you aren’t drinking enough water.
The main role of your kidneys is to filter your blood and maintain normal electrolyte balance. Testing urine specific gravity is a quick way for your doctor to tell if your kidneys are trying to compensate for some abnormality.
Specific gravity testing is useful if your doctor thinks you have any of the following conditions:
- Dehydration or hydration
- Heart failure
- Diabetes insipidus, a rare condition causing thirst and the excretion of large amounts of diluted urine
- Kidney failure
- Kidney infection
- Urinary tract infection
- Hyponatremia, or low sodium levels
- Hypernatremia, or elevated sodium levels
You may have to take a urine specific gravity test several times in one day. This will help your doctor to see how well your kidneys are compensating.
A sample for a urine specific gravity test contains at least 1 to 2 ounces of urine. The best time to get a sample is first thing in the morning when your urine is the most concentrated.
Your doctor will give you a cup to collect a urine sample. For the best sample, you should use an antibacterial wipe to clean the area around your urethra. This will reduce the likelihood that bacteria will contaminate the sample.
Urinate a small amount and then place the cup under your urine stream. Urinate into the cup until you have a large enough sample, then finish urinating into the toilet. This is known as the clean-catch or midstream method.
Your doctor will send the urine sample to a laboratory while it’s fresh. This will ensure the best results. A lab technician will use a refractometer to project light into the sample and determine its density. This is more reliable than the dipstick method where a stick placed in the urine to measure how much it sinks or floats.
While there are home tests, the results won’t be as accurate as those conducted by a professional in a sterile environment. Home tests are more susceptible to contamination.
Another benefit of taking the test at your doctor’s office is that they can send the sample to the lab for more detailed testing and analysis.
Osmolality tests are sometimes used to evaluate how the kidneys dilute and concentrate, with osmolality being the index of a concentration. Knowing the osmolality of your urine can help your doctor diagnose certain conditions.
Urine specific gravity is a more precise measurement of your urine’s overall concentration than looking at the color of your urine alone.
Your doctor will look at the ratio of the density of your urine to the density of water. To put it another way, the specific density of water would be 1.000. Ideally, urine specific gravity results will fall between 1.002 and 1.030 if your kidneys are functioning normally.
Specific gravity results above 1.010 can indicate mild dehydration. The higher the number, the more dehydrated you may be.
High urine specific gravity can indicate that you have extra substances in your urine, such as:
Your doctor will use the results from your urine specific gravity test, along with other urinalysis results, to come up with a diagnosis. Abnormal specific gravity results could indicate:
- Excess substances in the blood
- Kidney disease
- Infection, such as a urinary tract infection
A urinalysis can also measure the concentration of various cells. White blood cells can indicate an infection. And glucose can point to glucose intolerance or diabetes.