Serum magnesium - testMagnesium - blood
A serum magnesium test is a measurement of how much magnesium there is in the blood.
How the Test is Performed
Blood ismost oftendrawn from a vein. The veinusually used is on the inside of the elbow or the back of the hand.
The procedure is done in the following way:
- The site is cleaned with germ-killing medicine (antiseptic).
- The health care provider wraps an elastic band around the upper arm to apply pressure to the area and make the vein swell with blood.
- A needle is gently inserted into the vein.
- The blood collects into an airtight vial or tube attached to the needle.
- The elastic band is removed.
- The needle is removed.
- The puncture site is covered with an adhesive stripto stop any bleeding.
Forinfants or young children, a sharp tool called a lancet may be used to puncture the skin and make it bleed. The blood collects into a small glass tube called a pipette, or onto a slide or test strip. Afterward, abandage may be placed over the area if there is any bleeding.
How to Prepare for the Test
No special preparation is needed.
How the Test Will Feel
When the needle is inserted to draw blood, you may feelslight pain, or a prick or stinging. Afterward, there may be some throbbing.
Why the Test is Performed
This test is done when yourhealth care providersuspects you may have an abnormal level of magnesium in your blood.
About half of the body's magnesium is found in bone. The other half is found inside cells of body tissues and organs.
Magnesium is needed for nearly all chemical processes in the body. It helps maintain normal muscle and nerve function, andkeeps the bones strong. Magnesium is also needed for the heart to function normally and tohelp regulate blood pressure. Magnesium alsohelps the body controlblood sugar level and helps support the body's defense (immune) system.
1.7 to 2.2 mg/dL
Normal value ranges may vary slightly among different laboratories. Talk to yourhealth care providerabout the meaning of your specific test results.
What Abnormal Results Mean
A high magnesium level may indicate:
A low magnesium level may indicate:
- Chronic diarrhea
- Delirium tremens
- Hepatic (liver) cirrhosis
- Too much insulin
- Toxemia of pregnancy
- Ulcerative colitis
There is very little risk in having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Taking blood from some people may be more difficult than from others.
Other risks may include:
- Excessive bleeding
- Fainting or feeling light-headed
- Hematoma (blood accumulating under the skin)
- Infection (a slight risk any time the skin is broken)
Klemm KM, Klein MJ. Biochemical markers of bone metabolism. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 22nd ed. Philadelphia, PA: Elsevier Saunders; 2011:chap 15.
Mason JB. Vitamins, trace minerals, and other micronutrients. In: Goldman L, Schafer AI, eds. Goldman's Cecil Medicine. 24th ed. Philadelphia, PA:Elsevier Saunders; 2011:chap 225.
Review Date: 1/22/2013
Reviewed By: Linda J. Vorvick, MD, Medical Director and Director of Didactic Curriculum, MEDEX Northwest Division of Physician Assistant Studies, Department of Family Medicine, UW Medicine, School of Medicine, University of Washington. Also reviewed by A.D.A.M. Health Solutions, Ebix, Inc., Editorial Team: David Zieve, MD, MHA, David R. Eltz, Stephanie Slon, and Nissi Wang.