Test ID: CITR
Citrate Excretion, Urine
Useful For 
Suggests clinical disorders or settings where the test may be helpful
Diagnosing risk factors for patients with calcium kidney stones
Monitoring results of therapy in patients with calcium stones or renal tubular acidosis
Clinical Information Discusses physiology, pathophysiology, and general clinical aspects, as they relate to a laboratory test
Urinary citrate is a major inhibitor of kidney stone formation due in part to binding of calcium in urine. Low urine citrate levels are considered a risk for kidney stone formation.
Several metabolic disorders are associated with low urine citrate. Any condition which lowers renal tubular pH or intracellular pH may decrease citrate, (eg, metabolic acidosis, increased acid ingestion, hypokalemia, or hypomagnesemia).
Low urinary citrate promotes kidney stone formation and growth, and is subject to therapy by correcting acidosis, hypokalemia, or hypomagnesemia by altering diet or using drugs such as citrate and potassium.
Reference Values Describes reference intervals and additional information for interpretation of test results. May include intervals based on age and sex when appropriate. Intervals are Mayo-derived, unless otherwise designated. If an interpretive report is provided, the reference value field will state this.
0-19 years: not established
20 years: 150-1,191 mg/specimen
21 years: 157-1,191 mg/specimen
22 years: 164-1,191 mg/specimen
23 years: 171-1,191 mg/specimen
24 years: 178-1,191 mg/specimen
25 years: 186-1,191 mg/specimen
26 years: 193-1,191 mg/specimen
27 years: 200-1,191 mg/specimen
28 years: 207-1,191 mg/specimen
29 years: 214-1,191 mg/specimen
30 years: 221-1,191 mg/specimen
31 years: 228-1,191 mg/specimen
32 years: 235-1,191 mg/specimen
33 years: 242-1,191 mg/specimen
34 years: 250-1,191 mg/specimen
35 years: 257-1,191 mg/specimen
36 years: 264-1,191 mg/specimen
37 years: 271-1,191 mg/specimen
38 years: 278-1,191 mg/specimen
39 years: 285-1,191 mg/specimen
40 years: 292-1,191 mg/specimen
41 years: 299-1,191 mg/specimen
42 years: 306-1,191 mg/specimen
43 years: 314-1,191 mg/specimen
44 years: 321-1,191 mg/specimen
45 years: 328-1,191 mg/specimen
46 years: 335-1,191 mg/specimen
47 years: 342-1,191 mg/specimen
48 years: 349-1,191 mg/specimen
49 years: 356-1,191 mg/specimen
50 years: 363-1,191 mg/specimen
51 years: 370-1,191 mg/specimen
52 years: 378-1,191 mg/specimen
53 years: 385-1,191 mg/specimen
54 years: 392-1,191 mg/specimen
55 years: 399-1,191 mg/specimen
56 years: 406-1,191 mg/specimen
57 years: 413-1,191 mg/specimen
58 years: 420-1,191 mg/specimen
59 years: 427-1,191 mg/specimen
60 years: 434-1,191 mg/specimen
>60 years: not established
Interpretation Provides information to assist in interpretation of the test results
Any value less than the mean for 24 hours represents a potential risk for kidney stone formation/growth. Patients with low urinary citrate, and new or growing stone formation may benefit from adjustments in therapy known to increase urinary citrate excretion. (See Clinical Information).
Very low levels (<150 mg/24 hours) suggest investigation for the possible diagnosis of metabolic acidosis (eg, renal tubular acidosis).
Cautions Discusses conditions that may cause diagnostic confusion, including improper specimen collection and handling, inappropriate test selection, and interfering substances
Drugs that lower systemic pH, potassium, and/or magnesium lower urine citrate and are to be avoided in patients with tendency to calcium stones.
Conversely, drugs that raise systemic pH, potassium, and/or magnesium may raise urine citrate and should be considered in treating patients or interpreting results.
Clinical Reference Provides recommendations for further in-depth reading of a clinical nature
Hosking DH, Wilson JW, Liedtke RR, et al: The urinary excretion of citrate in normal persons and patients with idiopathic calcium urolithiasis (abstract). Urol Res 1984;12:26
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