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Human Urine Sample

Steven C. Campbell, M.D., Ph.D. Associate Editor(s)-in-Chief: Yazan Daaboul, M.D.
Synonyms and keywords: Urinary findings; Urinary abnormalities; Findings on urine exam; Urine; Urine composition; Urine output


Urine is a fluid produced by humans through the kidney, collected in the bladder, and excreted through the genital urethra. Urine formation helps to maintain the balance of minerals and other substances in the body. Urinary findings may be qualitative or quantitative. Qualitative urinary findings are often analyzed on urinalysis and urine culture. Quantitative urinary findings depends on urine output. A urinalysis (U) is an array of tests performed on urine and is one of the most common methods of medical diagnosis. A part of a urinalysis can be performed by using urine dipsticks, in which the test results can be read as color changes.

Composition of Urine

Urea structure

The following is a list of normal urine constituents:

Algorithm of Common Urinary Findings

Urinary Findings
Quality (Composition)
Quantity (Volume)
Urine culture
Urine output
High urine output
Low urine output
Urine odor
Color and Turbidity
Specific gravity or osmolality
Urinary pH
Casts and Crystals

Urine Odor

Urine is usually odorless but can produce pungent smells following the consumption of certain foods (e.g. asparagus)

Urine Color and Turbidity


Below is a table that lists common urine discolorations and their associated conditions.

Urine Color Associated Conditions
Clear or Light Yellow Normal urine color
Dark Yellow Dehydration, vitamin B12 administration
Greenish/Yellow Vitamin B administration
Yellow-Red Laxatives
Orange Rifampicin, nitrofurantoin, pyridium
Dark / Black Alkaptonuria, porphyria, sarcoma
Milky Lymphatic fistulas
Opaque Bacteria, Cells
Dark Red/Pink Concentrated, hematuria, hemoglobinuria, myoglobinuria, Ingestion of certain foods (colored candy, berries, or beets)
Yellowish-Brown Hyperbilirubinemia
Pale Polyuria, chronic kidney disease
Foamy or Frothy Proteinuria
With sediment Precipitation of urate salts
Cloudy Pyuria, tissue components
With intestinal contents Intestinal fistulas

To view a complete comprehensive list of causes that are are associated with urine discoloration, click here


  • Normal urine is usually clear
  • Turbid urine may be a manifestation of urinary bacterial infection, hematuria, proteinuria, pyuria, or presence of crystals and casts.

Urine Specific Gravity and Osmolality

Urine Specific Gravity

  • Normal urine specific gravity (density) ranges between 1.003 and 1.035 g.cm-3.
  • Specific gravity outside the normal range may sometimes be associated with urinary disorders.

Urine Osmolality

  • In healthy individuals with restricted fluid intake, urine osmolality should be > than 800mOsm/kg.
  • 24-hour urine osmolality normally ranges between 500 and 800 mOsm/kg.
  • Random urine osmolality normally ranges between 50 and 1400 mOsm/kg.

Increased urine osmolality

Decreased urine osmolality

Urinary pH

  • The pH of urine is normally close to neutral pH = 6 to 7 (Range: 4.5 to 8.2).
  • Strongly acidic or alkaline urine may be manifestations of the following:

Renal and urologic diseases

  • Urinary tract infection
  • Acute kidney injury
  • Chronic kindey disease
  • Renal tubular acidosis

Systemic diseases

Drug administration



Pyuria is defined as the presence of 10 or more white cells per cubic millimeter in a urine specimen, 3 or more white cells per high-power field of unspun urine, a positive result on Gram’s stain of an unspun urine specimen, or a urinary dipstick test that is positive for leukocyte esterase[1]

Pyuria may first be classified based on gross/microscopic examination

Pyuria may also be classified based on the presence/absence of detectable infection

  • Bacteriuria (detectable bacteria in urine)
  • Sterile pyuria (non-infectious cause or an infection that is undetected on regular gram-stain and urine culture)


  • Albuminuria
    • Microalbuminuria
    • Macroalbuminuria
  • Paraproteinuria


  • Benign
  • Malignant

Casts and Crystals


To view a comprehensive list of urinary cast types and the characteristics of each cast type, click here

Acellular casts

  • Hyaline casts
  • Granular casts
  • Waxy casts
  • Fatty casts
  • Pigment casts
  • Crystal casts

Cellular casts

  • RBC casts
  • WBC casts
  • Bacterial casts
  • Epithelial cell casts


  • Struvite crystals (magnesium-ammonium-phosphate)
  • Bilirubin crystals
  • Calcium carbonate crystals
  • Amorphous crystals
  • Calcium oxalate dihydrate crystals
  • Cystine crystals


Urinary beta-HCG (urinary pregnancy test)






To view a comprehensive list of causes of eosinophiluria, click here

Bacterial antigens


Urinary drug concentration

  • Drug testing uses urinalysis to test for certain chemicals which are typically present in the urine only after recreational drug use.
  • These tests must be requested specifically or as part of a toxicology screen, and are not part of a routine urinalysis.

Dissolved electrolytes or heavy metals

Calciuria (urinary calcium) differential diagnosis:


Parameter Upper reference range in the urine per 24 hours
Norepinephrine 23-105 micrograms/24 hours
Dopamine 190-450 micrograms/24 hours
Metanephrine 74-297 micrograms/24 hours
Normetanephrine 105-354 micrograms/24 hours
Vanillic acid 3.3-6.5 mg/24 hours
Vanillyl mandelic acid 17-33 micromol/liter (3.3-6.5 mg/24 hour)

Differential Diagnosis of urinary catecholamines

Urine Culture

Normal urine is sterile. Presence of microorganisms in urine culture may be associated with urinary infections or colonization.

Urine Quantity (Volume)

  • The amount of urine produced depends on hydration (volume of fluid intake), physical activity, environmental factors, body surface area, and general health condition.
  • In adult humans, the average urine production is approximately 1 L to 2 L per 24 hours.

High Urine Output

  • Polyuria: Excessive urinary production > 2.5 L per 24 hours

Low Urine Output

Low urine output may be either oliguria or anuria:

  • Oliguria: Urine production < 400 mL / 24 hours in adults. A more specific definition includes the following:
    • Infants: oliguria is defined as urine output < 1 mL/kg/hr[2]
    • Children: Oliguria is defined as urine output < 0.5 mL/kg/hr.
    • Aduults: Oliguria is defined as urine output < 17 to 21 ml/hr.

For a detailed explanation of oliguria, click here.

  • Anuria: Urine production < 100 mL / 24 hr in adults.

For a detailed explanation of anuria, click here.


  1. Horan, Teresa C.; Andrus, Mary; Dudeck, Margaret A. (2008-06). "CDC/NHSN surveillance definition of health care-associated infection and criteria for specific types of infections in the acute care setting". American Journal of Infection Control. 36 (5): 309–332. doi:10.1016/j.ajic.2008.03.002. ISSN 1527-3296. PMID 18538699. Check date values in: |date= (help)
  2. Klahr S, Miller S (1998). "Acute oliguria". N Engl J Med. 338 (10): 671–5. doi:10.1056/NEJM199803053381007. PMID 9486997. Free Full Text.

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