The urinalysis (UA) is one of the most frequently ordered labs across every setting — ER, ICU, inpatient floors, urgent care, and outpatient offices. In many cases, correctly reading the UA is what makes the diagnosis.
Many labs add urine microscopy, which quantifies the contents of the urine and gives you exact detail. This guide walks through the initial bedside assessment, every dipstick parameter, and the key microscopy findings — crystals, cells, and casts.
Before you even run the dipstick, you can learn a lot just by using your senses — color, turbidity, and smell.
Color
Urine color is the easiest read on a patient's hydration status — the less hydrated, the more concentrated and dark; the more hydrated, the more dilute and clear-yellow. The first void of the morning is normally darker. Color can also flag other problems:
Amber / Yellow
Normal range, from clear yellow to dark amber. Darker means more concentrated (less hydrated).
Red or Pink
Think blood (cystitis, stones, malignancy, trauma, menses). As little as 1 mL can change the color. Non-bloody: rhabdo (myoglobin); foods (beets, blackberries, rhubarb); meds (propofol, chlorpromazine, Ex-Lax).
Orange
Rifampin (TB antibiotic) or phenazopyridine (Pyridium / OTC AZO).
"Purple Urine Bag Syndrome" — very rare. UTIs with certain gram-negative bacteria in alkaline urine; amitriptyline or methylene blue; high-tryptophan diet.
Turbidity (Cloudiness)
Cloudy urine often suggests infection — which may be accurate — but cell casts or cellular debris from kidney damage can also cloud it.
Smell
Strong = dehydration. Foul = infection (urea-splitting bacteria form ammonia). Sweet = glucose from hyperglycemia. Feculent odor suggests an enteric-urinary fistula.
A Gross Bit of History
Clinicians used to taste urine to detect glucose. Sweet urine meant "diabetes mellitus" — literally "honey-sweet." Thankfully, the dipstick replaced that.
The Urinalysis Dipstick
Once you've assessed the urine with your senses, run the dipstick. There are three common ways to interpret it:
1
Manual Dipstick
Dip the strip and compare each pad to the color chart printed on the bottle.
2
Automated Analyzer
Insert the strip into an automated urine analyzer, which prints out the results.
3
Send to Lab
The lab runs the UA and uploads results to the EMR, performing microscopy when indicated.
Glucose & Bilirubin
Glucoseglucosuria
Glucose spills into urine (glucosuria) once the renal threshold of about 180 mg/dL is reached — useful for spotting hyperglycemia in undiagnosed diabetics when no blood work is available. Stress or fever can cause mild glucosuria in non-diabetics, and SGLT2 inhibitors (e.g., Farxiga) raise urine glucose even with normal serum levels. Note: ascorbic acid (vitamin C) can cause false-negatives.
Bilirubinliver / bilirubin metabolism
Low amounts can be normal; elevated levels point to abnormal bilirubin metabolism or liver dysfunction. Practically, it doesn't add much diagnostic information on its own. Specimens must be tested promptly — bilirubin is unstable in light.
Ketones & Ascorbic Acid
Ketonesnormal: none (<0.3 mg/dL)
Ketonuria indicates ketosis — classically from uncontrolled diabetes or DKA. It can also come from acute illness, physiologic stress, strenuous exercise, nausea/vomiting, and low-carb/keto diets. Note: levodopa (Parkinson's) can cause a false positive.
Ascorbic Acid (Vitamin C)normal: not present
High urinary vitamin C causes false-negatives for heme, glucose, leukocyte esterase, and protein. Some dipsticks add a chemical to neutralize this effect.
Specific Gravity & Heme
Specific gravity tells you how dilute or concentrated the urine is — a good proxy for hydration status.
Normal
1.005–1.030
specific gravity
Low (<1.005)
Dilute
DI, renal failure
High (>1.030)
Concentrated
dehydration, SIADH
Low SG may indicate diabetes insipidus, renal failure, pyelonephritis, glomerulonephritis, psychogenic polydipsia, or malignant hypertension. High SG may indicate severe dehydration, hepatorenal syndrome, heart failure, renal artery stenosis, shock, or SIADH. Protein, ketones, glucose, and recent IV contrast can falsely elevate SG; diuretics (like Lasix) also affect it.
Hemenormal: negative
Detects blood in the urine. Causes include UTIs, kidney/glomerular damage, trauma, stones, malignancy, vaginal contamination, and coagulopathies. In patients over 50 with persistent hematuria, rule out malignancy. The test is very sensitive (down to 1–2 RBCs/HPF), so a negative dipstick effectively excludes blood.
Heme false positives: myoglobin (rhabdomyolysis), semen (recent ejaculation), alkaline urine >9.0, contamination from hemorrhoids or vaginal blood, and oxidizing perineal cleaners. A positive heme dipstick requires urine microscopy to confirm true hematuria.
pH & Protein
pHnormal ~6 (range 4.6–8)
Acidic urine (<7.0):metabolic or respiratory acidosis, or an E. coli UTI. Basic urine (>7.0): most kidney stones, urea-splitting bacteria (Proteus, Klebsiella), renal tubular acidosis, or potassium depletion. Diet matters — cranberries and high-protein diets acidify; citrus and low-carb diets alkalinize. Sodium bicarbonate and thiazides raise pH.
Proteinnormal: undetectable
The dipstick is specific for albumin. Any damage to the glomerular basement membrane lets albumin through. Normal urine has <150 mg/day and reads undetectable; the dipstick turns positive above roughly 300 mg/day. Benign causes: dehydration, stress, fever, heat injury, inflammation, intense activity, acute illness, orthostatic proteinuria. Glomerular causes: diabetic nephropathy, lupus nephritis, preeclampsia, HIV/hep B/post-strep GN, certain cancers and drugs. Tubular causes: interstitial cystitis, sickle cell, NSAID/aminoglycoside nephrotoxicity.
Correlate Protein with Specific Gravity
Very dilute urine underestimates protein; very concentrated urine overestimates it. The dipstick is a crude screen — a 24-hour urine specimen is the standard of care for ongoing proteinuria, and a nephrology consult is warranted if a renal cause is found.
Nitrites & Leukocyte Esterase
Nitritesnormal: negative
Enterobacteriaceae (E. coli, Klebsiella, Proteus, Enterobacter, Citrobacter, Pseudomonas) make nitrate reductase, which converts urinary nitrate to nitrite. A negative result means little; a positive result makes infection highly likely. The reaction needs dwell time in the bladder — up to 4 hours — so urinary frequency or a Foley can produce false-negatives. False-positives: azo dyes, bilirubin, and urine left sitting too long.
Leukocyte Esterasenormal: negative
Released when WBCs lyse. Its presence supports a UTI (and can also signal autoimmune disease, STDs, stones, or intra-abdominal infection). If it's absent, infection is essentially ruled out. False-negatives: proteinuria, glycosuria, very concentrated urine, tetracycline. False-positives: vaginal discharge contamination, ampicillin, salicylate toxicity, strenuous exercise.
Urine Microscopy
Microscopy looks at the urine under the microscope to characterize the cells, crystals, and casts present.
Crystals
Crystals are crystallizations within the urine. They can be normal when composed of substances normally found in urine; type and quantity depend on the urine's pH and the underlying cause.
Amorphous
Form as urine cools, more often in acidic urine. Just precipitated electrolyte salts — no clinical significance.
Uric Acid
Associated with gout; also stones, tumor lysis syndrome, or chemotherapy.
Calcium Oxalate
Acidic urine, linked to kidney stones, dehydration, high oxalate intake, and antifreeze ingestion.
Calcium Carbonate
May follow excessive calcium supplementation; also associated with kidney stones.
Calcium Phosphate
Precipitate in alkaline urine; rarely from hypoparathyroidism.
Triple Phosphate (Struvite)
Magnesium ammonium phosphate, in alkaline urine. Linked to stones and UTIs with urea-splitting bacteria (Proteus mirabilis, Pseudomonas).
Hippuric Acid
Rare; found in normal or acidic urine.
Cystine
Acidic urine in patients with the genetic condition cystinuria.
Bacteria & Cells
Bacteria are not normally found in urine — it should be sterile. When present, they usually mean infection or contamination, and they multiply rapidly if the specimen sits at room temperature.
Bacteria
Leukocyte esterase and/or nitrites with <15–20 epithelial cells/HPF make infection highly likely. Consider empiric antibiotics if symptomatic, and culture for confirmation.
Red Blood Cells
Normal is <2 RBCs/HPF. Microscopic hematuria = ≥3 RBCs/HPF, and confirms a heme-positive dipstick.
White Blood Cells
Normal is <2–5 WBCs/HPF. >5 suggests infection, inflammation, or contamination — mostly neutrophils when infectious.
Epithelial Cells
Squamous cells from the external urethra. >15–20/HPF indicates contamination — recollect to rule out infection.
Casts
Casts are tube-like protein structures made of various cells. Low urine pH, low flow rate, and high salt concentration promote their formation. Any cast other than a hyaline cast represents pathology within the kidney itself.
Hyaline Casts
Can be normal and nonspecific — seen after exercise, dehydration, or with diuretic use.
RBC Casts
Indicate glomerulonephritis or vasculitis.
WBC Casts
Seen with tubulointerstitial nephritis and acute pyelonephritis; also renal TB and vaginal infections.
Muddy-Brown Casts
Diagnostic of acute tubular necrosis, the leading cause of AKI.
Waxy Casts
Consistent with acute or chronic renal failure.
Broad Casts
Consistent with advanced renal failure.
Fatty Casts
Indicate nephrotic syndrome.
Renal Tubular Epithelial Casts
Seen in acute tubular necrosis, interstitial nephritis, and proliferative glomerulonephritis.
Clinical Pearls
1
Vitamin C is the great masker. Ascorbic acid causes false-negatives for heme, glucose, leukocyte esterase, and protein — always consider it.
2
A positive heme needs microscopy. Confirm true hematuria with ≥3 RBCs/HPF before chasing it; rule out myoglobin.
