A freshly voided specimen is pale yellow, straw-colored, or amber, depending on its concentration.
Urine is darker than normal when it is scanty and concentrated. Urine is lighter than normal when it is excessive and diluted. Certain drugs, such as cascara, l-dopa, and sulfonamides, alter the color of urine. Some foods can alter the color; for example, beets can cause urine to appear red in color.
Odor
Normal urine smell is aromatic. As urine stands, it often develops an ammonia odor because of bacterial action.
Some foods cause urine to have a characteristic odor; for example, asparagus causes urine to have a strong, musty odor. Urine high in glucose content has a sweet odor. Urine that is heavily infected has a fetid odor.
Turbidity
Fresh urine should be clear or translucent; as urine stands and cools, it becomes cloudy.
Cloudiness observed in freshly voided urine is abnormal and may be due to the presence of red blood cells, white blood cells, bacteria, vaginal discharge, sperm, or prostatic fluid.
pH
The normal pH is about 6.0, with a range of 4.6 to 8. (Urine alkalinity or acidity may be promoted through diet to inhibit bacterial growth or urinary stone development or to facilitate the therapeutic activity of certain medications.) Urine becomes alkaline on standing when carbon dioxide diffuses into the air.
A high-protein diet causes urine to become excessively acidic. Certain foods tend to produce alkaline urine, such as citrus fruits, dairy products, and vegetables, especially legumes. Certain foods, such as meats, tend to produce acidic urine. Certain drugs influence the acidity or alkalinity of urine; for example, ammonium chloride produces acidic urine, and potassium citrate and sodium bicarbonate produce alkaline urine.
Specific gravity
This is a measure of the concentration of dissolved solids in the urine. The normal range is 1.015 to 1.025.
Concentrated urine will have a higher-than-normal specific gravity, and diluted urine will have a lower-than-normal specific gravity. In the absence of kidney disease, a high specific gravity usually indicates dehydration, and a low specific gravity indicates overhydration.
Constituents
Organic constituents of urine include urea, uric acid, creatinine, hippuric acid, indican, urine pigments, and undetermined nitrogen. Inorganic constituents are ammonia, sodium, chloride, traces of iron, phosphorus, sulfur, potassium, and calcium.
Abnormal constituents of urine include blood, pus, albumin, glucose, ketone bodies, casts, gross bacteria, and bile.