Urine Test [en Español]
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A urine test checks different components of urine, a waste product made by the kidneys . A regular urine test may be done to help find the cause of symptoms. The test can give information about your health and problems you may have.
The kidneys take out waste material, minerals, fluids, and other substances from the blood to be passed in the urine. Urine has hundreds of different body wastes. What you eat and drink, how much you exercise, and how well your kidneys work can affect what is in your urine.
More than 100 different tests can be done on urine. A regular urinalysis often includes the following tests:
- Color. Many things affect urine color, including fluid balance, diet, medicines, and diseases. How dark or light the color is tells you how much water is in it. Vitamin B supplements can turn urine bright yellow. Some medicines, blackberries, beets, rhubarb, or blood in the urine can turn urine red-brown.
- Clarity. Urine is normally clear. Bacteria, blood, sperm, crystals, or mucus can make urine look cloudy.
- Odor. Urine does not smell very strong, but it has a slightly "nutty" odor. Some diseases cause a change in the odor of urine. For example, an infection with E. coli bacteria can cause a bad odor, while diabetes or starvation can cause a sweet, fruity odor.
- Specific gravity. This checks the amount of substances in the urine. It also shows how well the kidneys balance the amount of water in urine. The higher the specific gravity, the more solid material is in the urine. When you drink a lot of fluid, your kidneys make urine with a high amount of water in it, which has a low specific gravity. When you do not drink fluids, your kidneys make urine with a small amount of water in it, which has a high specific gravity.
- pH. The pH is a measure of how acidic or alkaline (basic) the urine is. A urine pH of 4 is strongly acidic, 7 is neutral (neither acidic nor alkaline), and 9 is strongly alkaline. Sometimes the pH of urine is affected by certain treatments. For example, your doctor may instruct you how to keep your urine either acidic or alkaline to prevent some types of kidney stones from forming.
- Protein. Protein normally isn't found in the urine. Fever, hard exercise, pregnancy, and some diseases, especially kidney disease, may cause protein to be in the urine.
- Glucose. Glucose is the type of sugar found in blood. Normally there is very little or no glucose in urine. When the blood sugar level is very high, as in uncontrolled diabetes, the sugar spills over into the urine. Glucose can also be found in urine when the kidneys are damaged or diseased.
- Nitrites. Bacteria that cause a urinary tract infection (UTI) make an enzyme that changes urinary nitrates to nitrites. Nitrites in urine show a UTI is present.
- Leukocyte esterase (WBC esterase). Leukocyte esterase shows leukocytes ( white blood cells [WBCs] ) in the urine. WBCs in the urine may mean a UTI is present.
- Ketones. When fat is broken down for energy, the body makes substances called ketones (or ketone bodies). These are passed in the urine. Large amounts of ketones in the urine may mean a very serious condition, diabetic ketoacidosis , is present. A diet low in sugars and starches (carbohydrates), starvation, or severe vomiting may also cause ketones to be in the urine.
Microscopic analysis. In this test, urine is spun
in a special machine (centrifuge) so the solid materials (sediment) settle at
the bottom. The sediment is spread on a slide and looked at under a microscope.
Things that may be seen on the slide include:
- Red or white blood cells. Blood cells aren't found in urine normally. Inflammation, disease, or injury to the kidneys, ureters, bladder, or urethra can cause blood in urine. Strenuous exercise, such as running a marathon, can also cause blood in the urine. White blood cells may be a sign of infection or kidney disease.
- Casts. Some types of kidney disease can cause plugs of material (called casts) to form in tiny tubes in the kidneys. The casts then get flushed out in the urine. Casts can be made of red or white blood cells, waxy or fatty substances, or protein. The type of cast in the urine can help show what type of kidney disease may be present.
- Crystals. Healthy people often have only a few crystals in their urine. A large number of crystals, or certain types of crystals, may mean kidney stones are present or there is a problem with how the body is using food ( metabolism ).
- Bacteria, yeast cells, or parasites. There are no bacteria, yeast cells, or parasites in urine normally. If these are present, it can mean you have an infection.
- Squamous cells. The presence of squamous cells may mean that the sample is not as pure as it needs to be. These cells do not mean there is a medical problem, but your doctor may ask that you give another urine sample.
Why It Is Done
A urine test may be done:
- To check for a disease or infection of the urinary tract . Symptoms of a urine infection may include colored or bad-smelling urine, pain when urinating, finding it hard to urinate, flank pain, blood in the urine (hematuria), or fever.
- To check the treatment of conditions such as diabetes, kidney stones, a urinary tract infection (UTI), high blood pressure ( hypertension ), or some kidney or liver diseases.
- As part of a regular physical examination.
How To Prepare
Do not eat foods that can color the urine, such as blackberries, beets, and rhubarb, before the test. Do not exercise strenuously before the test.
Tell your doctor if you are menstruating or close to starting your menstrual period. Your doctor may want to wait to do the test.
Your doctor may ask you to stop taking certain medicines that color the urine. These include vitamin B, phenazopyridine (Pyridium), rifampin, and phenytoin (Dilantin). Be sure to tell your doctor if you are taking diuretics , which may affect the test results.
Talk to your doctor any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form (What is a PDF document?) .
How It Is Done
A routine urine test can be done in your doctor's office, clinic, or lab. You may also be asked to collect a urine sample at home and bring it with you to the office or lab for testing.
Collecting a urine sample from a small child or baby is done by using a special plastic bag with tape around its opening. The bag is placed around the child's genitals until he or she urinates. Then you carefully remove the bag. To collect a urine sample from a very sick baby, a doctor may use a urinary catheter through the urethra or a needle through the baby's belly directly into the bladder (suprapubic tap).
Clean-catch midstream one-time urine collection
- Wash your hands to make sure they are clean before collecting the urine.
- If the collection cup has a lid, remove it carefully and set it down with the inner surface up. Do not touch the inside of the cup with your fingers.
- Clean the area around your
- A man should retract the foreskin, if present, and clean the head of his penis with medicated towelettes or swabs.
- A woman should spread open the genital folds of skin with one hand. Then she can use her other hand to clean the area around the urethra with medicated towelettes or swabs. She should wipe the area from front to back so bacteria from the anus is not wiped across the urethra.
- Begin urinating into the toilet or urinal. A woman should hold apart the genital folds of skin while she urinates.
- After the urine has flowed for several seconds, place the collection cup into the urine stream and collect about 2 fl oz (60 mL) of this "midstream" urine without stopping your flow of urine.
- Do not touch the rim of the cup to your genital area. Do not get toilet paper, pubic hair, stool (feces), menstrual blood, or anything else in the urine sample.
- Finish urinating into the toilet or urinal.
- Carefully replace and tighten the lid on the cup, and then return it to the lab. If you are collecting the urine at home and cannot get it to the lab in an hour, refrigerate it.
Double-voided urine sample collection
This method collects the urine your body is making right now.
- Urinate into the toilet or urinal. Do not collect any of this urine.
- Drink a large glass of water, and wait about 30 to 40 minutes.
- Then get a urine sample. Follow the instructions above for collecting a clean-catch urine sample.
Return the urine sample to the lab. If you are collecting the urine at home and cannot get it to the lab in an hour, refrigerate it.
24-hour urine collection
Your doctor may ask you to collect your urine for 24 hours.
- The collection period usually starts in the morning. When you first get up, urinate—but don't save this urine. Write down the time that you urinated to mark the beginning of your 24-hour collection period.
- For the next 24 hours, collect all your urine. Your doctor will usually provide you with a large container that holds about 1 gal (4 L) and has a small amount of preservative in it. Urinate into a smaller, clean container, and then pour the urine into the large container. Avoid touching the inside of the container with your fingers.
- Keep the large container in the refrigerator during the collection period.
- Urinate for the final time at or just before the end of the 24-hour period. Add this urine to the large container, and write down the time.
- Avoid getting toilet paper, pubic hair, stool (feces), menstrual blood, or other foreign matter in the urine sample.
Return the urine sample to the lab.
How It Feels
There is no discomfort in collecting a urine sample.
There is no chance for problems in collecting a urine sample.
A urine test checks different components of urine, a waste product made by the kidneys .
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
Normal: Pale to dark yellow
Abnormal: Many foods and medicines can affect the color of the urine. Urine with no color may be caused by long-term kidney disease or uncontrolled diabetes . Dark yellow urine can be caused by dehydration . Red urine can be caused by blood in the urine.
Normal: Slightly "nutty" odor
Abnormal: Some foods (such as asparagus), vitamins, and antibiotics (such as penicillin) can cause urine to have a different odor. A sweet, fruity odor may be caused by uncontrolled diabetes. A urinary tract infection (UTI) can cause a bad odor. Urine that smells like maple syrup can mean maple syrup urine disease, when the body can't break down certain amino acids .
Normal: 1.005–1.030 footnote 1
Abnormal: A very high specific gravity means very concentrated urine, which may be caused by not drinking enough fluid, loss of too much fluid (excessive vomiting, sweating, or diarrhea), or substances (such as sugar or protein) in the urine. Very low specific gravity means dilute urine, which may be caused by drinking too much fluid, severe kidney disease, or the use of diuretics .
Normal: 4.6–8.0 footnote 1
Abnormal: Some foods (such as citrus fruit and dairy products) and medicines (such as antacids) can affect urine pH . A high (alkaline) pH can be caused by severe vomiting, a kidney disease, some urinary tract infections, and asthma . A low (acidic) pH may be caused by severe lung disease ( emphysema ), uncontrolled diabetes, aspirin overdose, severe diarrhea, dehydration, starvation, drinking too much alcohol, or drinking antifreeze (ethylene glycol).
A one-time urine collection, if normal, will be negative for glucose. footnote 1
Abnormal: Intravenous (IV) fluids can cause glucose to be in the urine. Too much glucose in the urine may be caused by uncontrolled diabetes, an adrenal gland problem, liver damage, brain injury, certain types of poisoning, and some types of kidney diseases. Healthy pregnant women can have glucose in their urine, which is normal during pregnancy.
Abnormal: Ketones in the urine can mean uncontrolled diabetes, a very low-carbohydrate diet, starvation or eating disorders (such as anorexia nervosa or bulimia ), alcoholism, or poisoning from drinking rubbing alcohol (isopropanol). Ketones are often found in the urine when a person does not eat (fasts) for 18 hours or longer. This may occur when a person is sick and cannot eat or vomits for several days. Low levels of ketones are sometimes found in the urine of healthy pregnant women.
Normal: Very few or no red or white blood cells or casts are seen. No bacteria, yeast cells, parasites, or squamous cells are present. A few crystals are normally seen.
Red blood cells in the urine may be caused by kidney or bladder injury, kidney stones , a urinary tract infection (UTI), inflammation of the kidneys ( glomerulonephritis ), a kidney or bladder tumor, or systemic lupus erythematosus (SLE). White blood cells (pus) in the urine may be caused by a urinary tract infection, bladder tumor, inflammation of the kidneys, systemic lupus erythematosus (SLE), or inflammation in the vagina or under the foreskin of the penis.
Depending on the type, casts can mean inflammation or damage to the tiny tubes in the kidneys, poor blood supply to the kidneys, metal poisoning (such as lead or mercury), heart failure , or a bacterial infection .
Large amounts of crystals, or certain types of crystals, can mean kidney stones, damaged kidneys, or problems with metabolism . Some medicines and some types of urinary tract infections can also increase the number of crystals in urine.
Bacteria in the urine mean a urinary tract infection (UTI). Yeast cells or parasites (such as the parasite that causes trichomoniasis) can mean an infection of the urinary tract.
The presence of squamous cells may mean that the sample is not as pure as it needs to be. These cells do not mean there is a medical problem, but your doctor may ask that you give another urine sample.
What Affects the Test
Reasons you may not be able to have the test or why the results may not be helpful include:
- If you are having your menstrual period.
- Taking medicines, such as diuretics, erythromycin, trimethoprim (Trimpex), or high doses of vitamin C (ascorbic acid) taken with an antibiotic , such as tetracycline.
- Having an X-ray test with contrast material in the past 3 days.
- Not getting the urine sample to the lab in 1 hour.
What To Think About
- Some urine tests can be done using a home test kit.
- Other substances that may be checked during a urine test
- Bilirubin . This is a substance formed by the breakdown of red blood cells. It is passed from the body in stool. Bilirubin is not found in urine. If it is present, it often means that the liver is damaged or that the flow of bile from the gallbladder is blocked. To learn more, see the topic Bilirubin .
- Urobilinogen. This is a substance formed by the breakdown of bilirubin. It is also passed from the body in stool. Only small amounts of urobilinogen are found in urine. Urobilinogen in urine can be a sign of liver disease ( cirrhosis , hepatitis ) or that the flow of bile from the gallbladder is blocked.
- Bence Jones protein. This is an abnormal protein found in the urine of about 50% of people with a rare type of cancer called multiple myeloma . A urine test is often done when multiple myeloma is suspected. The protein test done during a regular urine test does not check for Bence Jones protein.
- To lower the chance of contaminating the urine sample with bacteria, a health professional may collect a urine sample by using a urinary catheter. A catheter may be used to collect urine from a person in the hospital who is very ill or who can't give a clean-catch sample. Using a catheter allows a clean sample to be collected.
- If an abnormal result is found during a urine test, more tests may be done, such as a urine culture, X-ray of the kidneys ( intravenous pyelogram [IVP] ), or cystoscopy .
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
Other Works Consulted
- Chernecky CC, Berger BJ (2008). Laboratory Tests and Diagnostic Procedures, 5th ed. St. Louis: Saunders.
- Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.
- Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.
Primary Medical Reviewer Adam Husney, MD - Family Medicine
Specialist Medical Reviewer Avery L. Seifert, MD - Urology
Current as ofFebruary 19, 2016
Current as of: February 19, 2016
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