Urine specific gravity: what a high or low specific gravity of urine means
Urine specific gravity (SG) · Urinalysis · reported in Unitless ratio compared with water (1.000), reported to three decimal places, e.g. 1.015
Urine specific gravity (SG) is a measure of how concentrated your urine is: the weight of your urine compared with the same volume of pure water, which has a specific gravity of exactly 1.000. Urine carries dissolved salts, urea and other waste, so it is always a little heavier than water. On a random sample the usual range is 1.005 to 1.030, and most people land between 1.010 and 1.025. The number is really a readout of two things at once: how much water you have been drinking, and how well your kidneys can concentrate or dilute urine to match.
A high specific gravity (above 1.025 to 1.030) most often means concentrated urine from not drinking enough, sweating, vomiting, diarrhea or fever. It is also pushed up by glucose, protein or X-ray contrast dye in the urine, which is why a value above 1.035 is almost never dehydration alone. A low specific gravity (below 1.005 to 1.010) usually means you drank a lot of fluid or took a diuretic, but it can also mean the kidneys have lost the ability to concentrate urine, as happens in advanced kidney disease or in diabetes insipidus (now also called arginine vasopressin deficiency or resistance).
On its own a single specific gravity rarely diagnoses anything. Clinicians read it with the rest of the urinalysis, with blood sodium and creatinine, and sometimes with a urine osmolality, which measures the same property more precisely. A specific gravity that stays stuck around 1.010 no matter how much or little you drink is the finding that matters most, because it means the kidneys are no longer adjusting.
SG at a glance
- What it is: the density of urine relative to water (1.000); a quick gauge of urine concentration and hydration.
- Normal (random sample): about 1.005–1.030; most values fall between 1.010 and 1.025. Labs and dipsticks differ slightly in their printed range.
- After an overnight fast, healthy kidneys concentrate to 1.020 or higher; sports-medicine groups call 1.020 or below well hydrated and above 1.030 significantly dehydrated.
- High (above 1.030) usually means dehydration; above 1.035 suggests glucose, protein or contrast dye in the urine rather than water loss alone.
- Low (below 1.005) means very dilute urine: a lot of fluid, diuretics, or a concentrating problem such as diabetes insipidus; a fixed 1.010 that never changes suggests advanced kidney disease.
- Next step: repeat with a first-morning sample after a normal day's fluids; if still abnormal, blood sodium, creatinine and a urine osmolality.
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What SG measures
Specific gravity reflects the total mass of dissolved solids in urine. The kidneys filter about 180 liters of plasma a day and then reabsorb nearly all of the water, adjusting the final amount under the control of antidiuretic hormone (vasopressin). When you are short of water, vasopressin rises, the collecting ducts reabsorb more water and the urine becomes concentrated (high SG, dark color, small volume). When you have plenty, vasopressin falls and the urine becomes dilute (low SG, pale, large volume). A healthy kidney can range from about 1.001 (near pure water) to about 1.035 to 1.040 at maximum concentration.
On a dipstick, the specific gravity pad contains a polymer whose acidity changes with the concentration of charged ions (sodium, potassium, chloride) in the urine, and an indicator dye shifts color in 0.005 steps from 1.000 to 1.030. Because it responds only to ions, the dipstick barely registers glucose, protein or contrast, and it reads about 0.005 too low in alkaline urine (pH 6.5 or higher), which some manufacturers tell you to correct for. A refractometer, used by many labs and in sports medicine, bends light through a drop of urine and is more precise, but it is pushed up by glucose, protein and contrast (roughly 0.004 per gram per deciliter of glucose and 0.003 per gram per deciliter of protein).
Specific gravity is a rough stand-in for urine osmolality, the gold-standard measure of concentration. As a rule of thumb 1.010 corresponds to about 300 mOsm/kg (the same as blood), 1.020 to about 600 to 700, and 1.030 to about 900 to 1,200 mOsm/kg; the relationship is loose, and when the exact number matters, for example in suspected diabetes insipidus or low blood sodium, osmolality is measured directly. Specific gravity is highest in the first-morning sample and lowest an hour or two after a large drink, so the time of collection changes the result.
Normal range for SG
Reference ranges vary between labs and by age, sex and pregnancy. Use the range printed on your own report.
| Group | Typical range (Unitless ratio compared with water (1.000), reported to three decimal places, e.g. 1.015) | Notes |
|---|---|---|
| Random sample, usual range | 1.005–1.030 | Most adults fall between 1.010 and 1.025. Dipsticks read in 0.005 steps; refractometers are more precise. Labs differ slightly. |
| Dilute urine | Below 1.010 | Expected after drinking a lot of fluid, with caffeine or alcohol, or on a diuretic. Persistent values below 1.005 regardless of intake need an explanation. |
| Normal concentrating ability (first-morning or after overnight fluid restriction) | 1.020 or higher (many labs use 1.022–1.025) | Shows the kidneys can concentrate urine. Equivalent to a urine osmolality above about 800 mOsm/kg. |
| Hydration bands (sports medicine) | 1.020 or below well hydrated; 1.021–1.030 dehydrated; above 1.030 significantly dehydrated | National Athletic Trainers' Association categories, used with urine color and body-weight change. |
| Isosthenuria | Fixed at about 1.008–1.012 whatever you drink | The kidneys can neither concentrate nor dilute; seen in advanced chronic kidney disease and in acute tubular necrosis. |
| Diabetes insipidus (vasopressin deficiency or resistance) | Usually below 1.005 (urine osmolality below 300, often below 200 mOsm/kg) with large volumes | Diagnosed with paired blood and urine osmolality and a supervised water-deprivation test, not specific gravity alone. |
| Above 1.035 | Glucose, protein or contrast dye | Values above 1.040 on a refractometer are almost always from X-ray contrast or heavy glucose; dehydration alone rarely passes 1.035. |
| Newborns and infants | 1.001–1.020 | Immature kidneys concentrate less; infants rarely exceed 1.025. |
High urine specific gravity
A high specific gravity means your urine is concentrated: there is relatively little water for the amount of dissolved waste. By far the most common reason is that your body is short of water and your kidneys are holding on to it, which is what should happen after a night's sleep, a hot day, exercise, vomiting, diarrhea or a fever. A single value of 1.025 to 1.030 in someone who feels well and has not been drinking much is normal physiology, and it should fall to 1.010 or below a few hours after a large drink.
The size of the number helps. Values above 1.035 cannot be explained by water loss alone, because healthy kidneys top out around 1.035 to 1.040; something heavy is in the urine. Glucose is the usual culprit (check the glucose pad and blood sugar), large amounts of protein in nephrotic syndrome come next, and intravenous contrast from a recent CT scan can push a refractometer reading above 1.050 for a day or two.
A high specific gravity is also informative when blood tests look wrong. If blood sodium is low yet the urine is concentrated (SG above about 1.010 with osmolality above 100 mOsm/kg), the kidneys are retaining water inappropriately, which is the pattern of the syndrome of inappropriate antidiuretic hormone (SIADH), heart failure, cirrhosis or adrenal insufficiency. In early acute kidney injury, a high specific gravity (above 1.020) with a low urine sodium points to a prerenal cause, poor blood flow to the kidney, rather than tubular damage.
Common causes
Dehydration from low intake, sweating, fever, vomiting or diarrhea
Loss of water or simply not drinking triggers vasopressin and the kidneys concentrate urine to 1.025 or more. This is the most common cause and reverses within hours of rehydrating.
First-morning or fasting sample
After eight hours without fluid, specific gravity of 1.020 to 1.030 is expected and is in fact the sign of a healthy kidney; the same value at midday after normal drinking means something different.
Glucose in the urine (uncontrolled diabetes)
Each gram per deciliter of glucose adds about 0.004 on a refractometer. Glycosuria also pulls water into the urine (osmotic diuresis), so the person is frequently dehydrated as well.
Heavy protein loss (nephrotic syndrome)
Protein above 3 g a day raises specific gravity by about 0.003 per gram per deciliter and gives foamy urine; a 3+ or 4+ protein pad alongside a high SG is the clue.
X-ray contrast dye
Iodinated contrast from a CT scan or angiogram makes urine very dense for 24 to 48 hours, commonly above 1.040 and sometimes above 1.050 on a refractometer; dipsticks are less affected.
Syndrome of inappropriate antidiuretic hormone (SIADH)
Too much vasopressin from lung disease, brain injury, cancers or drugs such as SSRIs and carbamazepine keeps the urine concentrated while blood sodium falls below 135 mmol/L.
Heart failure, cirrhosis and adrenal insufficiency
Reduced effective blood flow to the kidneys and low cortisol both raise vasopressin, giving concentrated urine with low blood sodium and often swelling.
Prerenal acute kidney injury
Bleeding, severe dehydration or low blood pressure reduce kidney blood flow; the tubules still work and conserve water, so SG is above 1.020 with a urine sodium under 20 mmol/L and a BUN-to-creatinine ratio above 20.
Sweating during exercise and heat exposure
Athletes commonly show 1.025 to 1.035 after training in heat; this is why sports teams screen urine before practice, with 1.020 as the usual cut-off.
Symptoms that can go with it
- Dark yellow or amber urine passed in small amounts
- Thirst, dry mouth and dry lips
- Light-headedness on standing, a fast heart rate or headache
- Fatigue, muscle cramps or reduced sweating
- New confusion, drowsiness or reduced urine output in older adults (dehydration can be serious)
- Foamy urine and ankle swelling if the cause is heavy protein loss
- Excessive urination and thirst if the cause is glucose from uncontrolled diabetes
Low urine specific gravity
A low specific gravity (below about 1.005 to 1.010) means your urine is dilute: mostly water with little dissolved waste. In most people this simply reflects a large fluid intake in the hours before the test, a coffee or alcoholic drink (both suppress vasopressin), or a diuretic. It is the expected response to being well hydrated, and a value of 1.003 after you drank a liter of water to produce the sample is not a problem.
A low value becomes meaningful when it does not change. Someone who has gone all night without fluid should concentrate to 1.020 or more; if the first-morning urine is still 1.005, the kidneys are either not receiving the signal to conserve water (central diabetes insipidus, from the pituitary) or not responding to it (nephrogenic diabetes insipidus, from lithium, high calcium, low potassium or an inherited defect). These people pass 3 to 20 liters of pale urine a day and are intensely thirsty.
A specific gravity fixed at about 1.010 (isosthenuria), the same as blood plasma, is a different signal: the tubules have lost both their concentrating and diluting ability. It is a feature of advanced chronic kidney disease, acute tubular necrosis and sickle cell disease, and it is read together with creatinine and eGFR. Persistent dilute urine without obvious cause also occurs in primary (psychogenic) polydipsia, where the kidneys are healthy but the person habitually drinks far more than needed.
Common causes
High fluid intake before the test
Drinking a large volume to produce a sample dilutes it below 1.005 within an hour; this is the most common cause and needs no action beyond a repeat on a first-morning sample.
Diuretics, caffeine and alcohol
Furosemide, thiazides and SGLT2 inhibitors increase water loss; alcohol and, to a lesser degree, caffeine suppress vasopressin, so urine passed in the hours after them is dilute.
Central diabetes insipidus (vasopressin deficiency)
Damage to the pituitary or hypothalamus from surgery, head injury, tumors or inflammation stops vasopressin release; urine osmolality stays below 300 mOsm/kg despite a high blood sodium.
Nephrogenic diabetes insipidus (vasopressin resistance)
The kidney ignores vasopressin. Lithium is the leading acquired cause (affecting up to 20 to 40 percent of long-term users), followed by high blood calcium, low potassium and rare inherited forms.
Chronic kidney disease
As nephrons are lost the kidney can no longer concentrate, and nocturia with pale urine is often an early symptom; SG settles around 1.010 and eGFR is reduced.
Acute tubular necrosis and interstitial nephritis
Damaged tubules cannot reabsorb water; SG is about 1.010 with a urine sodium above 40 mmol/L, which distinguishes it from a prerenal cause.
Sickle cell disease and trait
Sickling in the low-oxygen inner kidney damages the concentrating mechanism early in life, so a maximum SG of only 1.010 to 1.015 is typical even in people with the trait.
Primary polydipsia
Habitual intake of many liters a day, sometimes with psychiatric illness or dry-mouth medications, washes out the kidney's concentrating gradient; a supervised water-deprivation test separates it from diabetes insipidus.
Symptoms that can go with it
- None if you are simply well hydrated
- Passing large volumes of pale urine day and night (more than about 3 liters a day) with constant thirst in diabetes insipidus
- Waking to urinate several times a night (nocturia)
- Craving cold water in particular, a classic feature of central diabetes insipidus
- Dehydration, dizziness and confusion if water intake is restricted in someone who cannot concentrate urine
- Fatigue, poor appetite, itching or swelling with chronic kidney disease
Read it alongside
- Urine osmolality — the precise measure of concentration; ordered when specific gravity is persistently low or blood sodium is abnormal.
- Serum sodium and serum osmolality — low blood sodium with concentrated urine suggests SIADH; high blood sodium with dilute urine suggests diabetes insipidus.
- Creatinine, eGFR and BUN — a fixed SG of 1.010 with a raised creatinine points to kidney disease; a high BUN-to-creatinine ratio with concentrated urine points to dehydration.
- Urine glucose and protein pads — explain a specific gravity above 1.035 and change how the number is interpreted.
- Urine sodium (and fractional excretion of sodium) — separates prerenal kidney injury (urine sodium below 20 mmol/L, SG above 1.020) from tubular damage (above 40 mmol/L, SG 1.010).
- Urine color — pale straw usually matches an SG below 1.015 and dark amber above 1.025; a useful home check between tests.
- Hematocrit and albumin — both rise with dehydration (hemoconcentration) and support a high SG being due to water loss.
- Blood glucose and A1C — if glucose is present in the urine.
What usually happens next
- If the value was high and you had not been drinking much, drink normally for a day and repeat; a value that falls to 1.015 or below confirms it was simply concentration.
- If the value was low, repeat on a first-morning sample while drinking as you normally do; a result of 1.020 or higher shows the kidneys can concentrate urine. It does not close the question on its own: glucose, protein or recent contrast dye can raise specific gravity without normal concentrating ability, so if you are still passing unusually large volumes or are constantly thirsty, see your clinician regardless of the repeat value. Do not restrict fluids to test yourself: if you are passing large volumes of urine, going without water can dehydrate you within hours, which is why any water-deprivation test is done under supervision with weight, urine and blood checks.
- A specific gravity above 1.035, or any high value with glucose or 3+ protein on the dipstick, leads to blood glucose and kidney function tests and, for protein, a urine protein-to-creatinine ratio.
- A persistently low value (below 1.005) with large urine volumes and thirst is investigated with paired blood and urine osmolality, blood sodium and calcium, a medication review (especially lithium) and sometimes a supervised water-deprivation test.
- A fixed value around 1.010 is interpreted with creatinine and eGFR; if those are abnormal, expect a referral to a kidney specialist.
- Ask: was this a first-morning or random sample, did I have contrast or a lot of fluid beforehand, and what do my sodium and creatinine show?
Diet, lifestyle and natural levers with evidence
What can move SG once the cause is known. Nothing here replaces finding the cause.
Drink enough fluid, spread through the day
Strong evidenceSpecific gravity tracks water intake closely. In a study of free-living adults, low drinkers (about 1.3 liters of total fluid a day) had a mean 24-hour urine osmolality near 750 mOsm/kg (specific gravity roughly 1.020), while high drinkers (over 3 liters) averaged about 370 mOsm/kg (roughly 1.010). For most adults 2 to 3 liters of total fluid a day, more in heat or with exercise, keeps urine pale and specific gravity at or below 1.020.
People with heart failure, advanced kidney disease or on fluid restriction should follow their clinician's limit; drinking many liters in a short time can lower blood sodium.
If you form kidney stones, keep urine dilute (target below about 1.010)
Strong evidenceIn a five-year randomized trial of 199 first-time calcium stone formers, those told to drink enough to pass more than 2 liters of urine a day had a recurrence rate of 12 percent versus 27 percent in controls, and the time to a new stone was more than doubled. American Urological Association guidance is a urine volume of at least 2.5 liters a day, which corresponds to a specific gravity under about 1.010 on most samples.
Use urine color as a day-to-day check
Moderate evidenceUrine color on an eight-shade chart correlates with specific gravity (correlation about 0.8 in validation studies), and a pale straw color generally corresponds to an SG at or below 1.020. Trials in healthy adults show urine color tracks changes in daily water intake within a day, making it a practical guide between lab tests.
B vitamins, beets, rifampin and phenazopyridine color urine and make the chart unreliable; a very dilute color is not a goal in itself.
Replace fluid and salt during long or hot exercise
Moderate evidenceSports-medicine guidelines use a pre-exercise specific gravity above 1.020 to flag dehydration and recommend drinking to limit body-weight loss to under 2 percent during activity, which prevents the SG rise to 1.025 to 1.035 seen after training in heat. Including sodium in drinks during sessions longer than about two hours helps retain the fluid rather than passing it as dilute urine.
Overdrinking plain water during endurance events can cause exercise-associated hyponatremia; drink to thirst rather than to a schedule.
Limit alcohol and very high-protein or high-salt meals before a test
Preliminary evidenceAlcohol suppresses vasopressin and produces dilute urine for several hours, while a large protein or salt load raises urea and sodium excretion and increases specific gravity. Neither changes kidney function, but both can make a single reading misleading, so keep the evening before a urinalysis ordinary.
When to see a clinician promptly
- Signs of significant dehydration: unable to keep fluids down, no urine for 8 hours or more, dizziness on standing, confusion, a fast heart rate or sunken eyes, especially in infants and older adults; this needs same-day care.
- Passing very large volumes of pale urine (more than 3 liters a day) with constant thirst, particularly after a head injury, pituitary surgery or while taking lithium.
- A specific gravity above 1.035, or any high value with glucose on the dipstick, with thirst, weight loss or blurred vision (possible uncontrolled diabetes).
- Dilute urine together with a low blood sodium, headache, nausea or confusion, which can signal water intoxication or SIADH and needs prompt assessment.
- A fixed specific gravity around 1.010 with reduced urine output, swelling, or a raised creatinine, suggesting acute or chronic kidney disease.
- Dehydration symptoms in a child with vomiting or diarrhea who has had fewer than three wet diapers in 24 hours or no tears when crying.
Frequently asked questions
What is a normal urine specific gravity?
On a random sample, about 1.005 to 1.030, with most people between 1.010 and 1.025. A first-morning sample is normally 1.020 or higher because you have not had fluids overnight. Labs print slightly different ranges, and a dipstick only reads in steps of 0.005, so 1.015 and 1.020 are effectively the same result.
Is a specific gravity of 1.030 bad?
Not usually. A value of 1.030 means concentrated urine and in most people reflects not having drunk much, sweating, or a first-morning sample. It should fall below 1.015 after a few glasses of water. It matters if it persists despite drinking normally, if the dipstick also shows glucose or heavy protein, or if you have symptoms of dehydration or of uncontrolled diabetes.
What does a specific gravity of 1.005 or lower mean?
It means your urine is very dilute, which is the expected result if you drank a lot of fluid, had coffee or alcohol, or take a diuretic. It is a concern only when a first-morning sample after a night without fluid is still 1.005 or below, or when you are passing more than about 3 liters of urine a day with thirst, both of which raise the question of diabetes insipidus and need blood and urine osmolality tests.
What does urine specific gravity tell you about hydration?
It is one of the most practical hydration measures. Sports-medicine bodies classify 1.020 or below as well hydrated, 1.021 to 1.030 as dehydrated and above 1.030 as significantly dehydrated. A single reading is affected by what you drank in the previous few hours, so a first-morning sample or several readings over a day are more reliable than one midday test.
What is the difference between urine specific gravity and urine osmolality?
Both measure concentration. Specific gravity compares the weight of urine with water and is affected by the size of the dissolved particles, so glucose, protein and contrast inflate it. Osmolality counts the number of particles regardless of size and is the gold standard. As a rough guide, 1.010 corresponds to about 300 mOsm/kg and 1.030 to about 900 to 1,200 mOsm/kg. When precision matters, as in diabetes insipidus or low sodium, osmolality is used.
Does specific gravity show kidney disease?
It can hint at it. Healthy kidneys swing the value widely between about 1.003 and 1.030 depending on fluid intake. Kidneys that have lost most of their function settle at a fixed 1.008 to 1.012 (isosthenuria) whatever you drink. A single value cannot diagnose kidney disease; creatinine, eGFR and the urine albumin-to-creatinine ratio are the tests that do.
Can diabetes raise urine specific gravity?
Yes, in two ways. Glucose spilling into the urine is dense and adds about 0.004 for every gram per deciliter on a refractometer, and the sugar drags water out with it, so the person is also dehydrated. A specific gravity above 1.035 with a positive glucose pad is a reason to check blood glucose and A1C the same day.
Why was my specific gravity different on two tests?
Because it changes hour by hour with fluid intake. A sample given after drinking a liter of water to fill the cup might read 1.003 while a first-morning sample the next day reads 1.025; both are normal. Contrast dye, a new diuretic, alcohol the night before and heavy exercise also shift it. Compare samples taken at the same time of day under similar conditions.
References
- Urinalysis. MedlinePlus, US National Library of Medicine (2023)View source
- Urinalysis. Mayo Clinic (2023)View source
- Simerville JA, Maxted WC, Pahira JJ. Urinalysis: a comprehensive review. American Family Physician (2005)
- Urinalysis. Merck Manual Professional Version (2024)
- Armstrong LE, Maresh CM, Castellani JW, et al.. Urinary indices of hydration status. International Journal of Sport Nutrition (1994)
- Perrier E, Vergne S, Klein A, et al.. Hydration biomarkers in free-living adults with different levels of habitual fluid consumption. British Journal of Nutrition (2013)
- McDermott BP, Anderson SA, Armstrong LE, et al.. National Athletic Trainers' Association position statement: fluid replacement for the physically active. Journal of Athletic Training (2017)
- Borghi L, Meschi T, Amato F, Briganti A, Novarini A, Giannini A. Urinary volume, water and recurrences in idiopathic calcium nephrolithiasis: a 5-year randomized prospective study. Journal of Urology (1996)
- Voinescu GC, Shoemaker M, Moore H, Khanna R, Nolph KD. The relationship between urine osmolality and specific gravity. American Journal of the Medical Sciences (2002)
- Chadha V, Garg U, Alon US. Measurement of urinary concentration: a critical appraisal of methodologies. Pediatric Nephrology (2001)
- Diabetes insipidus. National Institute of Diabetes and Digestive and Kidney Diseases (2021)View source
- Verbalis JG, Goldsmith SR, Greenberg A, et al.. Diagnosis, evaluation, and treatment of hyponatremia: expert panel recommendations. American Journal of Medicine (2013)
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