Specimen Collection

Sample stability:

• 7 days at 15-25 ^o C
• 7 days at 2-8 ^o C
• 1 year at -20 ^o C

4.5 mL PST Blood (Preferred)

0.5 mL Paediatric Micro-PST Blood (Preferred)

5 mL Heparin Blood

4 mL Plain Blood

3.5 mL SST Blood

0.5 mL Paediatric Microsample Blood

0.5 mL Paediatric Micro-heparin Blood
Reference Intervals

Units: mmol/L

Reference range:

Child and Adult:	0.70 - 1.00

Uncertainty of Measurement: 8% at the level of 0.5 mmol/L

4% at levels of 1.5 mmol/L and higher

Turnaround Time: Within 3 hours
Assay Method

Principle : Colorimetric

Reagents: Roche MG2 kit

Analyser: Cobas c702

Diagnostic Use and Interpretation

Hypomagnesemia may be due to GIT or renal losses:

• diarrhoea / malabsorption
• proton pump inhibitor therapy in susceptible patients (impairs GIT absorption)
• diuretics
• alcoholism
• renal tubular disorders

Urine magnesium is useful in distinguishing GIT from renal loss: Urine Mg should be <1 mmol/L in hypomagnesemia due toGIT loss.

Hypokalaemia is a frequent finding in patients with hypomagnesaemia; magnesium deficiency causes an inability of the kidney to conserve potassium.

Hypocalcaemia may be secondary to magnesium deficiency, which impairs both the release and action of PTH.

Hypermagnesemia

May occur with magnesium supplementation in patients with renal failure, and as therapy in eclampsia, as hyermagnesemia has anticonvulsant and hypotensive effects.

Effects of hypermagnesemia include neuromuscular depression, somnolence, and hypotension.

Deep tendon reflexes may disappear at plasma Mg levels above 2 mmol/L, and respiratory depression above 4 mmol/L.

Please be aware that prices may change. If required, confirmation of the current price can be obtained from Elaine McGrath .

Contact Information

The chemical pathology team can be reached via email: chemicalpathologist@adhb.govt.nz or via Lablink (09) 307 4949 ext 22000 or 09-3078995

Emails will receive priority attention from the on-call chemical pathologist. Include the patients NHI.

After-hours: contact Lablink (Auckland City Hospital ext. 22000 or 09-3078995) or hospital operator for on duty staff after hours .

• Dr Samarina Musaad (Clinical Lead) : SamarinaM@adhb.govt.nz ext. 22402
• Dr Cam Kyle : CampbellK@adhb.govt.nz ext 22052
• Dr Weldon Chiu : WeldonC@adhb.govt.nz ext. 23427
• Dr Campbell Heron : CHeron@adhb.govt.nz ext. 23427
• Dr Sakunthala Jayasinghe Saku.Jayasinghe@adhb.govt.nz
• Dr Owen Yi WenyiYi@adhb.govt.nz

Last updated at 11:42:03 16/01/2026