Serum magnesium concentration: time for a standardised and evidence-based reference range.

Total serum magnesium concentration is rarely determined in clinical practice. Moreover, there is currently no standardised and evidence-based reference range for serum magnesium. The aim of this communication is to propose a reference range that is evidence-based and reflects the preventive potential of optimal magnesium levels. A literature search was conducted in the PubMed database using the terms "serum magnesium", "reference interval", "reference range", and "hypomagnesemia". Additionally, citations from relevant studies were consulted. There is considerable variation between laboratories with regards to the lower limit of magnesium in serum. The majority of limits are considerably below the 0.85 mmol/L (2.07 mg/dL) threshold proposed by expert groups. The rationale for this limit is that lower levels are associated with an increased risk of diseases such as type 2 diabetes and cardiovascular diseases. To prevent health risks associated with low magnesium levels, the lower limit of serum magnesium should be raised to 0.85 mmol/L and standardised between laboratories. At least, laboratory reports should note that levels below 0.85 mmol/L are associated with an increased risk of disease. Furthermore, the determination of serum magnesium should be afforded the same importance in routine laboratory diagnostics as the determination of other electrolytes.