Urine Test

Urine represents the excretory product of the kidneys, through which waste or harmful metabolic products present in the blood are eliminated from the body. Once produced by the kidneys, urine flows through the ureter and collects in the bladder, a hollow organ designed for its storage. Urine is then expelled through the urethra during urination.

The urine test is of considerable importance in medical practice because it allows the diagnosis not only of diseases affecting the kidneys and the excretory system, but also of relevant and common conditions involving other organs and systems.

The test must be carried out using the first urine excreted in the morning, which is more concentrated than urine collected at other times of the day. For accurate execution of the test, it is necessary that it be performed shortly after collection, in order to avoid alterations of the content.

In a healthy adult, the normal urine volume over 24 hours is approximately 1.2–1.5 liters, although amounts between 600 mL and 2 L are also considered normal. Values above the norm (polyuria) may be caused by alcoholism, diabetes, hypertension, hyperparathyroidism, kidney damage, and the use of corticosteroids or diuretics. A decrease in urine output (oliguria) may result from dehydration, diarrhea, hypotension, trauma, burns, vomiting, kidney disease, or heart failure.

During the urine test, several parameters are analyzed, including: appearance, color, density, pH, the presence of proteins, glucose, ketone bodies, urobilinogen, bilirubin, nitrites, leukocytes, traces of blood, and ascorbic acid.

Appearance

Urine is normally clear, but after some time, slight cloudiness may appear, which is non-pathological and due to the precipitation of poorly soluble salts (such as phosphates, carbonates, urates, etc.). However, cloudy urine with sediment may indicate the presence of pus, mucus, bacteria, blood, crystals, or desquamated cells that may signal an ongoing urinary tract infection.

Color

The normal color of urine can vary from pale yellow to amber, depending on the person’s diet and the degree of concentration. However, color changes are not always pathological: for example, taking multivitamin supplements containing riboflavin (vitamin B2) can cause a bright yellow-green urine color, which lasts until discontinuation; various drugs can also cause a transient change in urine color. 

In some cases, though, color changes may signal specific problems. Any red hue in urine, whether light or dark, may indicate the abnormal presence of blood, which can originate from the kidneys (e.g., due to kidney stones) or the bladder (e.g., in case of cystitis). For this reason, care must be taken to avoid contamination from menstrual blood. An orange-red urine color, similar to egg yolk, may suggest excess urobilinogen, a compound normally present only in trace amounts; its increase may indicate liver or blood disorders (e.g., hepatic dysfunction, hepatitis, liver cirrhosis, severe anemia). Finally, a green-brown color may be due to bilirubin, a waste product of the liver, and may suggest altered liver function or gallbladder stones.

Foam

Evaluating the presence of surface foam in urine may be important. The appearance of abundant, whitish foam indicates decreased surface tension, often related to the presence of proteins. Yellow-green or dark orange foam may indicate the presence of bilirubin.

Density (Specific Gravity - SG)

Urine density (or specific gravity) is a good indicator of kidney function: if this parameter falls within normal values, it means the kidneys can perform their functions and eliminate waste. Normal values range from 1.003 to 1.035 g/cm³. Increased density may be due to a reduced urine volume (oliguria) or, in the case of diabetes mellitus, the presence of glucose in the urine. Low values may result from excessive fluid intake, renal failure, diabetes insipidus, or diuretic use.

pH

Urine pH reflects one of the kidney's most important functions: acid-base balance regulation. Normal values range from 4.6 to 8 and are influenced by diet: a protein-rich diet tends to lower urine pH, while a vegetarian diet raises it. A pH above 7 may be caused by metabolic or respiratory alkalosis, urinary infections, vomiting, the use of antacids, or certain diseases. A pH below 5 indicates acidosis, which may be due to fasting, intense physical exercise, diabetes mellitus, or chronic renal failure.

Proteins (PRO)

Normally, the kidneys do not allow proteins to pass into the urine or do so only in minimal amounts (less than 150 mg in 24 hours). The presence of higher amounts of proteins is called proteinuria and is an important sign of kidney damage. However, proteinuria may also result from anemia, diabetes, cystitis, gout, pregnancy, fever, intense physical effort, or prolonged exposure to cold.

Glucose (GLU)

Glucose is normally absent or present only in trace amounts in urine. However, certain pathological conditions may lead to an increase. The most common cause is diabetes mellitus, although other disorders (e.g., hyperthyroidism) can also lead to glucosuria.

Ketone Bodies (KET)

Ketones are normally present in urine in only small amounts. Physiological increases in adults may occur during low-carb diets, intense physical activity, or pregnancy (slight increase). Pathological increases are found in uncontrolled diabetes mellitus and can be dangerous if untreated.

Urobilinogen (URO)

Urinary urobilinogen levels can provide important information about liver and biliary tract health. Normal levels range between 0.1 and 1.8 mg/dL; higher concentrations may indicate liver damage (hepatitis, tumors) or increased red blood cell breakdown, as in hemolytic anemia or large hematomas undergoing resorption. Lower levels may be seen in obstructive jaundice or after prolonged antibiotic treatment.

Bilirubin (BIL)

The presence of bilirubin in urine is almost always pathological, as in normal conditions only very small amounts (<0.02 mg/dL) are present — usually undetectable. Its presence gives urine a dark yellow to green-brown color, which may also appear foamy. Increased bilirubin occurs in obstructive jaundice (but not in hemolytic jaundice).

Nitrites (NIT)

Normally, only small amounts of dietary nitrites are found in urine. However, their concentration can increase significantly during urinary infections, as certain bacteria (e.g., E. coli, Klebsiella, Pseudomonas, Enterococci, Staphylococci, etc.) can convert nitrates into nitrites. The nitrite test is more accurate when performed on the first morning urine. Still, a negative result does not exclude infection, as some bacteria lack this conversion capability.

Ascorbic Acid (ASA)

The presence of ascorbic acid (vitamin C) in urine is not pathological. However, detecting it is important because excessive concentrations can interfere with the testing of other parameters (e.g., pH, glucose, urobilinogen, blood, leukocytes), potentially causing false-negative results. For this reason, it is recommended not to take multivitamins or consume vitamin C-rich foods (e.g., citrus fruits) in the 24 hours before the test.

Blood (BLD)

Normally, there is no blood in urine. Its presence (hematuria) causes a more or less intense red coloration of urine. Blood can originate from any part of the urinary tract and may be caused by kidney, ureteral, or bladder stones, cystitis, foreign bodies, glomerulonephritis, tumors (prostate, kidney, bladder), papillomas, urethritis, etc. In women, the blood may also be genital in origin. To determine the source, the “three-glass test” may be performed: collect urine in three portions — initial, midstream, and final. Blood in the first sample indicates a prostatic origin; in the third, a bladder origin; in all three, a renal origin. This simple method can help localize the bleeding.

Leukocytes (LEU)

Leukocytes are normally present in urine only in minimal amounts. An increase (>10/mL) is a general sign of inflammation somewhere in the urinary tract. Leukocyturia is common in cystitis, ureteritis, and pyelonephritis. It can also result from trauma, dehydration, stress, fever, diabetes mellitus, and kidney tumors.

Test Preparation

To prepare for the urine test:

Avoid foods that may alter the color of urine (e.g., blackberries, beets, rhubarb).

Do not take multivitamins or vitamin C-rich foods (e.g., citrus fruits) in the 24 hours before the test.

Avoid intense physical activity the day before.

Collect the first morning urine, ideally midstream, and perform the test shortly afterward to avoid alteration of the sample.

Wait a few seconds after urination begins before collecting the sample in the container.

Test cost: €6