Urinary calcium is calcium

Calcium in biology

Calcium plays a pivotal role in the physiology and biochemistry of organisms and the cell. It plays an important role in signal transduction pathways, where it acts as a second messenger, in neurotransmitter release from neurons, contraction of all muscle cell types, and fertilization...

 in the urine

Urine

Urine is a typically sterile liquid by-product of the body that is secreted by the kidneys through a process called urination and excreted through the urethra. Cellular metabolism generates numerous by-products, many rich in nitrogen, that require elimination from the bloodstream...

. It is termed -calcuria or -calciuria as a suffix

Suffix

In linguistics, a suffix is an affix which is placed after the stem of a word. Common examples are case endings, which indicate the grammatical case of nouns or adjectives, and verb endings, which form the conjugation of verbs...

.

Normal amount

In a urinalysis

Urinalysis

A urinalysis , also known as Routine and Microscopy , is an array of tests performed on urine, and one of the most common methods of medical diagnosis...

, the normal amount of urinary calcium can be measured in amount per time (commonly per 24 hours). It can also be measured in amount per mass of creatinine

Creatinine

Creatinine is a break-down product of creatine phosphate in muscle, and is usually produced at a fairly constant rate by the body...

, which avails for estimating the urinary calcium excretion in a spot urine sample, because urinary creatinine clearance is relatively unaffected by differences in free water clearance

Free water clearance

In the physiology of the kidney, free water clearance is the volume of blood plasma that is cleared of solute-free water per unit time. An example of its use is in the determination of an individual's state of hydration.-Overview:...

 which occurs, for example, in dehydration

Dehydration

In physiology and medicine, dehydration is defined as the excessive loss of body fluid. It is literally the removal of water from an object; however, in physiological terms, it entails a deficiency of fluid within an organism...

 and which would distort the interpretation of the urinary calcium in a spot urine sample.

Normally, in an average adult, the amount of calcium excreted in the urine is 100–250 mg (15–20 mmol) over a 24 hour period. For those on low-calcium diets, there is normally 50–150 mg/24 hours, while those on a calcium-free diet will have 5–40 mg/24 hours.

The following reference range

Reference range

In health-related fields, a reference range or reference interval usually describes the variations of a measurement or value in healthy individuals...

s are for persons with average calcium intake (600–800 mg/day for adults):

Individual	Lower limit	Upper limit	Unit
Females	20	275	mg calcium / 24 hours
Males	25	300
Age 0–12 months		2,100	mg calcium / g creatinine
Age 13–24 months		450
Age 25 months-5 years		350
Age 6–10 years		300
Age 11–18 years		260
Age > or =19 years		220

Disorders

An abnormally high amount of urinary calcium is called hypercalciuria

Hypercalciuria

Hypercalciuria or hypercalcinuria is the condition of elevated calcium in the urine. Chronic hypercalcinuria may lead to impairment of renal function, nephrocalcinosis, and renal insufficiency....

 and an abnormally low amount is called hypocalcuria.