Urine is a window into the kidneys and the rest of the body. A quick look and a dipstick give useful clues within minutes.
Color and clarity
Pale yellow urine is normal, dark yellow suggests concentrated urine, and red or brown can mean blood, muscle breakdown or some foods and drugs. Cloudy urine can come from infection, crystals or mucus.
Specific gravity
Specific gravity shows how concentrated the urine is, normally about 1.005 to 1.030. A high value fits dehydration, and a fixed low value can mean the kidney cannot concentrate.
The dipstick
The dipstick checks for glucose, ketones, protein, blood, leukocyte esterase, nitrite, pH and bilirubin. Each positive result points to a different problem.
Microscopy and culture
Under the microscope, red cell casts suggest glomerular disease and white cell casts suggest kidney infection. A culture confirms which bacteria cause an infection.
| Finding | Normal | Can suggest |
|---|---|---|
| Nitrite and leukocyte esterase | Negative | Urinary tract infection |
| Glucose | Negative | High blood glucose, diabetes |
| Ketones | Negative | Fasting, diabetic ketoacidosis |
| Protein | Negative or trace | Kidney damage, preeclampsia |
| Blood | Negative | Stones, infection, tumor, glomerular disease |
At the bedside
A clean-catch midstream sample avoids contamination, and urine should be tested or refrigerated within about 2 hours. Normal adult output is at least 0.5 mL/kg per hour.
Related guides
Written by Making Synapses. Topic reference: OpenStax, Anatomy and Physiology 2e (no text adapted).