What is Urinalysis?

Michael Pollick
Michael Pollick

Whenever a medical professional orders a urine sample from a patient, the collected urine is often sent directly to a lab for a procedure called urinalysis. Depending on the physician's orders, the lab technologist will examine everything from the color and temperature down to the most microscopic crystal formations or blood cells. Urinalysis can detect pregnancy, recreational drug use, diabetes, kidney diseases or evidence of infections elsewhere.

Scientist placing a test tube of urine in a centrifuge.
Scientist placing a test tube of urine in a centrifuge.

One of the first elements a lab technologist will check during urinalysis is color. Normal urine should be a pale yellow to amber color, but anything closer to the red spectrum can be a warning flag. The discoloration may only be caused by eating red beets or ingesting food coloring, but it can also be related to excessive shedding of red blood cells. Cloudiness may indicate crystal formation or an infection. Dark yellow or orange urine is usually a sign of extreme dehydration.

Poppy seeds can throw off a urinalysis test.
Poppy seeds can throw off a urinalysis test.

After the color and clarity have been noted, another urinalysis test may measure specific gravity. Roughly speaking, this would be the relative 'thickness' of the urine sample. Normal urine is only slightly denser than pure water because of the additional minerals and cell tissues dissolved in it. If the urinalysis reveals a significantly higher specific gravity, the patient may have excessive levels of glucose. This could indicate a blood sugar imbalance requiring immediate medical attention.

A urine sample.
A urine sample.

Most of us only encounter urinalysis during job screenings or routine physical exams. An in-home pregnancy test can also be considered a form of urinalysis, since the user's urine is checked for a reaction to chemicals. If urine samples are to be checked in bulk or a quick yes/no analysis is required, the technologist may use urinary dipsticks. Each dipstick for urinalysis contains a specific chemical or combination of chemicals. The stick is dipped into the urine, causing a chemical reaction which may or may not change the color. A positive or negative result may be seen within minutes of the test.

A lab technician holding a urine sample.
A lab technician holding a urine sample.

Some urinalysis is performed under the microscope, because the individual cells or crystal formations may be too small to detect. A centrifuge may be used to separate solid materials from the liquid. These results could reveal the presence of kidney stones, shed cancer cells or other chronic conditions.

Eating beets can affect the color of urine.
Eating beets can affect the color of urine.

The use of urinalysis for job screenings has been controversial for many years. The test is primarily used to detect recreational drug use, not other potential health problems. Many illegal and prescription drugs can remain in the urine for a few days, resulting in a positive reading and difficulty in the hiring process.

Some urinalysis is performed under a microscope, in order to detect crystal formations or individual cells.
Some urinalysis is performed under a microscope, in order to detect crystal formations or individual cells.

But urinalysis techniques cannot always discriminate between illegal drug ingestion and ingestion of a poppy seed muffin or over-the-counter medications. There is always a possibility of a 'false positive' when using a quick dipstick urinalysis. Some have argued that a drug-screening urinalysis system should not be the only criteria for determining suitability for employment. Positive results should be referred for more accurate tests involving blood or hair samples.

A home pregnancy test can be considered a form of urinalysis.
A home pregnancy test can be considered a form of urinalysis.
Michael Pollick
Michael Pollick

A regular wiseGEEK contributor, Michael enjoys doing research in order to satisfy his wide-ranging curiosity about a variety of arcane topics. Before becoming a professional writer, Michael worked as an English tutor, poet, voice-over artist, and DJ.

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Discussion Comments

anon44875

very informative.

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