⚕️ Educational content only. This article explains what urinalysis measures and what the results generally indicate. It is not medical advice. Speak with your doctor or healthcare provider for interpretation in the context of your personal health.
Urinalysis (UA) — also called a urine test or dipstick test — is one of the most versatile and frequently performed tests in clinical medicine. It involves examining the physical appearance, chemical composition, and (in a full microscopy) the cellular content of a urine sample. Despite being a relatively simple and inexpensive test, urinalysis can provide important clues about kidney function, urinary tract infection, diabetes, liver disease, and several other conditions.
Key Takeaways
- Urinalysis has three components: physical assessment (colour, clarity, smell), chemical dipstick testing, and microscopic examination.
- Dipstick tests screen for protein, glucose, ketones, blood, nitrites, leukocyte esterase, bilirubin, urobilinogen, and pH.
- Protein in urine (proteinuria) is an important early marker of kidney damage, particularly in diabetes and hypertension.
- Nitrites and leukocyte esterase are the key dipstick markers of urinary tract infection (UTI).
- Glucose in urine typically indicates blood glucose above the renal threshold (≈10 mmol/L) — an important clue for undiagnosed diabetes.
- A positive dipstick result usually requires confirmation with urine microscopy and/or culture.
Physical Assessment
Normal urine is pale to dark yellow, clear, and without strong odour. Abnormal colour can indicate pathology: red or pink urine may suggest haematuria (blood), though it can also result from certain foods (beetroot) or medications; cloudy urine often indicates infection or the presence of cells and protein; very dark urine may indicate dehydration or bilirubinuria (bile pigments, suggesting liver disease); frothy urine can indicate significant proteinuria. Colour changes alone are non-specific, but they prompt further investigation.
Dipstick (Chemical) Testing
A urine dipstick is a plastic strip with chemically treated pads that change colour in the presence of specific substances. Results are read by comparing colour changes to a reference chart or using an automated reader. Key dipstick parameters include the following.
Protein: Normally, very little protein passes through the kidney’s filtration barrier. Persistent proteinuria indicates glomerular damage and is a key marker of chronic kidney disease, diabetic nephropathy, and hypertensive nephropathy. The dipstick is most sensitive to albumin. The albumin-to-creatinine ratio (ACR) on a urine sample provides a more quantitative assessment of proteinuria. Glucose: Glucose appears in urine (glycosuria) when blood glucose exceeds the kidney’s reabsorption threshold (approximately 10 mmol/L). Glycosuria can signal uncontrolled diabetes but can also occur in pregnancy (lower renal threshold) or in rare tubular disorders. Ketones: Ketones are produced when fat is broken down for energy. Ketonuria occurs in diabetic ketoacidosis (DKA), prolonged fasting, starvation, or a very low carbohydrate diet. Blood (haematuria): The dipstick detects the peroxidase activity of haemoglobin and myoglobin. True haematuria (red blood cells in urine) may indicate kidney stones, urinary tract infection, glomerulonephritis, or bladder cancer. A positive dipstick for blood must be confirmed by microscopy, as false positives occur with myoglobinuria (muscle breakdown) and haemoglobinuria. Nitrites: Many bacteria (particularly gram-negative organisms such as E. coli) convert urinary nitrates to nitrites. A positive nitrite result strongly suggests bacterial infection. Leukocyte esterase: An enzyme released by white blood cells (neutrophils). A positive result indicates pyuria (white cells in urine), suggesting infection or inflammation. Together, positive nitrites and leukocyte esterase are the key dipstick indicators of UTI. Bilirubin and urobilinogen: Bilirubin in urine indicates conjugated hyperbilirubinaemia (liver or biliary tract disease). Elevated urobilinogen occurs in haemolytic anaemia and liver disease. pH: Urine pH normally ranges from 4.5 to 8.0. Persistently alkaline urine can indicate infection with urease-producing organisms, renal tubular acidosis, or certain dietary patterns. Specific gravity: Reflects urine concentration. Low specific gravity indicates dilute urine (possible diabetes insipidus or excess fluid intake); high specific gravity indicates concentrated urine (dehydration or high ADH activity).
Urine Microscopy
When dipstick results are abnormal, urine microscopy examines the sediment after centrifugation to identify cells, casts, crystals, and organisms. Red blood cells may be dysmorphic (distorted, suggesting glomerular origin) or normal in shape (suggesting lower urinary tract bleeding). White blood cells confirm pyuria. Casts are cylindrical formations moulded in the renal tubules; red cell casts are highly specific for glomerulonephritis and are an important diagnostic finding. Bacteria seen on microscopy, combined with positive nitrites and leukocyte esterase, are strong evidence of UTI. Urine culture is required to identify the organism and determine antibiotic sensitivity.
References
- National Library of Medicine. Urinalysis. MedlinePlus. https://medlineplus.gov/lab-tests/urinalysis/
- NHS. Urine tests. https://www.nhs.uk/conditions/urine-tests/
- Simerville JA, Maxted WC, Pahira JJ. Urinalysis: a comprehensive review. American Family Physician. 2005;71(6):1153–1162.
- NICE Guideline NG109. Urinary tract infection (lower): antimicrobial prescribing. 2018.
- Kidney Disease: Improving Global Outcomes (KDIGO). Clinical practice guideline for the evaluation and management of chronic kidney disease. Kidney International Supplements. 2013;3(1):1–150.