Urine Specific Gravity
How concentrated your urine is compared with plain water. It mostly reflects how much fluid you've had and how well your kidneys balance water.
AI-verified against cited sources. Awaiting expert reviewAlso called SG, USG, Sp GrLOINC 5811-5
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What it is
Specific gravity compares the weight of your urine with the weight of plain water, which is 1.000. The more salts, urea and other waste dissolved in urine, the higher the number. Very dilute urine reads close to 1.000, and concentrated urine reads above about 1.020. It is usually measured with a dipstick as part of a urinalysis. Some labs use a device called a refractometer instead.
Why it matters
Your kidneys keep or release water to keep your body in balance, and specific gravity gives a quick picture of that. It tends to rise when you are short on fluid and fall when you have had a lot to drink. It also helps your clinician read the rest of a urinalysis. A very dilute sample can hide small amounts of protein, and a very concentrated one can make them look bigger.
If it’s low
A lower reading means your urine is dilute. The most common reason is simply drinking a lot of fluid. Readings that stay very low, or stay near 1.010 whatever you drink, can be linked to how well the kidneys concentrate urine, so clinicians look at them alongside other tests.
Common causes
- Drinking a lot of fluid
- Water pills (diuretics) and other medicines that make you pass more urine
- Diabetes insipidus, a rare condition that makes the body lose too much water (it is not the same as diabetes mellitus)
- Kidney conditions that reduce the ability to concentrate urine
- Low blood sodium, or a hormone condition involving the adrenal glands
What can help
- Think back to how much you drank in the hours before the sample, and mention it to your clinician
- Ask whether repeating the test with a first-morning sample, or adding a urine osmolality test, would help
- Bring up constant thirst or passing very large amounts of urine
If it’s high
A higher reading usually means your urine is concentrated, most often because you are low on fluid. Sugar or protein in the urine, or recent X-ray contrast dye, can also push the number up. Less often, a higher reading is linked to a hormone, heart or kidney-artery condition that makes the body hold on to water.
Common causes
- Not drinking enough, or losing fluid through sweat, fever, vomiting or diarrhea
- A first-morning sample, which is often the most concentrated of the day
- Sugar in the urine, as can happen with high blood sugar
- Protein in the urine
- Recent X-ray contrast dye or dextran IV fluids
- Less often, SIADH (a condition where the body holds on to too much water), heart failure or narrowing of a kidney artery
What can help
- Drink fluids regularly through the day, unless a clinician has told you to limit them
- Tell the lab or your clinician if you were fasting, exercising hard or sweating a lot before the sample, or had recent imaging with contrast dye
- Ask whether a repeat sample or a urine osmolality test would be useful
Usual ranges
What labs print as the reference range, by who was tested. Ranges differ a little between labs, so the range on your own report is the one your result is judged against.
For adults: 1.005–1.03 SG. Source: Labcorp, MedlinePlus Medical Encyclopedia (NIH National Library of Medicine), Quest Diagnostics, American Family Physician, Practical Laboratory Medicine, Cureus (urinalysis table with the treating hospital's reference intervals).
- Adults (this one applies)1.005–1.03 SG
Sources: Labcorp, MedlinePlus Medical Encyclopedia (NIH National Library of Medicine), Quest Diagnostics, American Family Physician, Practical Laboratory Medicine, Cureus (urinalysis table with the treating hospital's reference intervals)
What can affect your result
- How much you drank and how much you sweated before the sample
- Time of day: a first-morning sample is usually more concentrated
- Heat, exercise, fever, vomiting or diarrhea
- Water pills (diuretics) and other medicines that change urine volume
- Sugar or protein in the urine, and recent X-ray contrast dye
- Method: a dipstick gives a rough value in coarse steps, while a refractometer or osmolality test is more precise
- The usual range differs a little between labs
- Recent X-ray contrast dye and dextran IV fluids can push the reading up.
- Protein or sugar in the urine raises the reading on a refractometer.
- Very alkaline urine can make a dipstick read lower than the true value.
- Water pills (diuretics) and other medicines that change how much urine you make.
A first-morning sample is usually the most concentrated. Later samples depend on how much you have had to drink. Hours. It follows how much you drink, sweat and urinate on the day of the test.
When to talk to a clinician
A single reading outside your lab's range is common and usually reflects what you drank. Talk with a clinician if readings stay below about 1.003, or stay fixed near 1.010 whatever you drink. Also talk with one if you are very thirsty or passing large amounts of urine. Get urgent care for confusion, fainting, or no urine for many hours.
Questions you could ask
- How does my specific gravity fit with the rest of my urinalysis and my kidney blood tests?
- Could this simply reflect how much I was drinking, or should we repeat it?
- Would a urine osmolality test or a blood sodium check add anything?
- Could how much I was drinking, or any medicines I take, explain such dilute urine?
- Would repeating the test with a first-morning sample or adding a urine osmolality test help?
Questions people ask
Why does my specific gravity change from one test to the next?
It follows how much you drank, how much you sweated and the time of day, so it can move quite a bit in a single day. One reading mostly shows your hydration at that moment.
What does a reading of 1.010 mean?
A reading near 1.010 is close to the concentration of the fluid your kidneys filter from the blood. It is often seen when your fluid balance is about right. If readings stay at 1.010 no matter how much or how little you drink, it can mean the kidneys are not concentrating or diluting urine well, and your clinician may look into it.
Does a high reading mean I am dehydrated?
Often it does, especially above about 1.020. But sugar, protein and X-ray contrast dye can also raise it, so a high number on its own doesn't settle the question. Thirst, urine color and how much you have been drinking help fill in the picture.
Is a dipstick specific gravity as accurate as a lab test?
A dipstick gives a rough result. If your clinician needs a better measure of how concentrated your urine is, a refractometer reading or a urine osmolality test is more precise.
Show the science and sources
Is a change real?
Specific Gravity naturally varies about 0.4% from test to test in the same healthy person. Between two results from the same lab, a change of roughly 1% or more is unlikely to be day-to-day noise or lab variation (95% reference change value). Source: Desirable Biological Variation Database specifications, 2014 update (Minchinela J, Ricos C, et al.; the 'Ricos database', a compilation of median published CVI/CVG).
For clinicians and researchers
Urine specific gravity (USG) is the ratio of urine density to the density of water and tracks total dissolved solute, so it correlates with osmolality but is not the same thing. Reagent strips respond to ionic strength (a pKa shift in the indicator), whereas refractometers respond to refractive index, which rises with every solute. In one validation study, SG rose with added albumin, creatinine, glucose, hemoglobin, sodium chloride and urea (Wyness 2016), and refractometers are generally more accurate than strips. Strip results are read from a color chart in coarse steps, so they are approximate. Dextran solutions, IV radiopaque dyes and proteinuria raise readings, and alkaline urine can lower them (AAFP). In intrinsic renal insufficiency USG becomes fixed near 1.010, the value of glomerular filtrate (AAFP 2005). Near 1.010 suggests euvolemia, above 1.020 relative dehydration (or glucosuria or SIADH) and below 1.003 marked dilution, as in diabetes insipidus, water intoxication, impaired renal function or adrenal disease (AAFP 2022). Urine osmolality is the more specific measure of concentrating ability. Sources disagree on adrenal insufficiency: AAFP (2005, 2022) lists it with low USG, while MedlinePlus lists Addison disease with high USG, alongside heart failure, renal artery stenosis, shock and hypernatremia. Published and lab-printed intervals differ: 1.005–1.030 (Labcorp report, MedlinePlus), 1.001–1.035 (Quest 5463), 1.003–1.030 (AAFP 2005), 1.0020–1.0300 (Tietz random-urine interval verified for a refractometer, Wyness 2016) and 1.001–1.035 or 1.003–1.035 on some hospital tables.
LOINC 5811-5 (primary), 53326-5, 5810-7, 50562-8, 2965-2. Specimen: urine.
Sources
- Urinalysis, Routine With Microscopic Examination on Positives: sample report (test 003038), Labcorp (2026)
- 003038: Urinalysis, Routine With Microscopic Examination on Positives, Labcorp
- Urinalysis, Complete (test code 5463), Quest Diagnostics
- Urine specific gravity test, MedlinePlus Medical Encyclopedia (NIH National Library of Medicine) (2025)
- Urinalysis: A Comprehensive Review, American Family Physician (2005)
- Office-Based Urinalysis: A Comprehensive Review, American Family Physician (2022)
- Evaluation and analytical validation of a handheld digital refractometer for urine specific gravity measurement, Practical Laboratory Medicine (2016)
- An Emerging Human Pathogen: Raoultella Planticola, Cureus (urinalysis table with the treating hospital's reference intervals) (2025)
- Median Arcuate Ligament Syndrome Beyond the Classic Demographic: Celiac Artery Compression in a 62-Year-Old Man With Cardiovascular Risk Factors, Cureus (urinalysis table with the treating hospital's reference intervals) (2026)
AI-verified against cited sources. Awaiting expert review. Last reviewed 2026-10-03. How we build and check these pages.