Magnesium, whole blood

Magnesium, whole blood
B-Mg ATK 7004

Similar to potassium, most of the magnesium in the body is intracellular. Only 1% of the magnesium is in the extracellular compartment, making plasma magnesium level an inefficient marker for the magnesium status of the whole body.

Magnesium is needed for the energy metabolism of the body and cellular production processes. It works as a regulator and activator of complex reactions in several cells and cell membranes, and is essential for approximately 300 enzymatic reactions. Magnesium is vital in muscles and nerve impulse transmission. Magnesium plays many roles in protein synthesis, and is an important factor in the production of antibodies. It has various effects on immune system function.


Investigating magnesium levels in the body. Suspected magnesium deficiency in fluid therapy, parenteral nutrition, malabsorption, renal insufficiency, diuretic therapy. Cardiac arrhythmias, tachycardia, changes in ECG (prolonged QT interval). Increased neuromuscular excitability (tetany, muscle twitches).


5 mL of lithium or sodium heparin blood. Mix the sample well. The tube must not contain any clots. Take trace element samples last in order to cleanse the sampling needle of possible trace element residues. If this is the only test requisition, first take one extra tube. 

No fasting is needed. No trace element supplements 12 hours before sampling. The result is normalised to whole blood haematocrit (Hkr) value (B-PVK). The client should determine the haematocrit prior to shipping the sample and write the result on the test requisition. Without a measured Hkr value, standard Hkr is used.

Storage and delivery

Ship at room temperature on sampling day (shipping Mon-Thu). Store frozen over the weekend, ship at room temperature.



Turnaround time

10 weekdays

Reference ranges, calculated

women 1.14 – 1.62 mmol/L (Hkr 0.39)
​men 1.19 – 1.71 mmol/L (Hkr 0.42)

The Hkr value affects the reference ranges. The same sample can be used to measure Cu, K, Mn, P, Se and Zn.