Citrates are normal products from citric acid metabolism (endogenous and derived from diet or supplements). The vast majority of urinary kidney stones are composed of poorly soluble calcium oxalate and phosphate salts. The accumulation of these insoluble salts in the kidneys leads to the formation of crystals and possibly stones. Citrates have the property of binding to calcium in the form of soluble salts capable of preventing the formation and growth of crystals and calcium salt stones. Citrates therefore act as protective agents against the formation of calcium stones. The results are expressed in millimoles of citrate per day (mmol/d).
Citrate levels should be interpreted along with calcium, phosphate and urinary oxalate levels. Low citrate levels in urine are a risk factor for the formation of stones. Several metabolic disorders and conditions that lower urine pH are associated with decreased urinary citrates (metabolic acidosis, consumption of acidic products, low potassium or magnesium levels in the blood). There are treatments for increasing urinary citrate levels such as the correction of pH, potassium or magnesium levels, or adding potassium citrate to the diet.