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Relation between total and ionized serum calcium concentrations

Alan S L Yu, MB, BChir
Jason R Stubbs, MD
Section Editors
Stanley Goldfarb, MD
Mitchell Geffner, MD
Deputy Editor
Albert Q Lam, MD


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.


The total serum calcium concentration consists of three fractions [1,2]:


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Literature review current through: Sep 2016. | This topic last updated: Mar 11, 2016.
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