Relation between total and ionized serum calcium concentrations
- Alan S L Yu, MB, BChir
Alan S L Yu, MB, BChir
- Harry Statland and Solon Summerfield Professor of Medicine
- University of Kansas Medical Center
- Jason R Stubbs, MD
Jason R Stubbs, MD
- Associate Professor of Medicine
- Division of Nephrology & Hypertension
- University of Kansas Medical Center
- Section Editors
- Stanley Goldfarb, MD
Stanley Goldfarb, MD
- Editor-in-Chief — Nephrology
- Section Editor — Mineral and Bone Metabolism; Renal Ureteral Stones
- Professor of Medicine
- University of Pennsylvania School of Medicine
- Mitchell E Geffner, MD
Mitchell E Geffner, MD
- Section Editor — Pediatric Endocrinology
- Professor of Pediatrics
- Keck School of Medicine, University of Southern California
The plasma (or serum) calcium concentration is usually reported in units of mg/dL in the United States, in mmol/L in many other countries, and in meq/L by some laboratories. The relationship between these units is defined by the following equations:
mmol/L = [mg/dL x 10] ÷ mol wt
meq/L = mmol/L x valence
Since the molecular weight of calcium is 40 and the valence is +2, 1 mg/dL is equivalent to 0.25 mmol/L and 0.5 meq/L. Thus, the normal range of total serum calcium concentration of 8.8 to 10.3 mg/dL is equivalent to 2.2 to 2.6 mmol/L and 4.4 to 5.2 meq/L.
DETERMINANTS OF THE SERUM CALCIUM CONCENTRATION
The total serum calcium concentration consists of three fractions [1,2]:
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- DETERMINANTS OF THE SERUM CALCIUM CONCENTRATION
- Change in total but not ionized calcium
- - Hypoalbuminemia
- - Hyperalbuminemia
- - Multiple myeloma
- Change in ionized fraction but not total calcium
- - Acid-base disorders
- - Parathyroid hormone
- - Hyperphosphatemia
- MEASURING THE SERUM CALCIUM IN PATIENTS WITH CKD