Magnesium in Whole Blood or Urine

Clinical Information

Magnesium is another mineral abundant in the body, majority of which is in the skeleton and the remainder is distributed between muscle and nonmuscular soft tissues1,2.

Similar to calcium, magnesium is essential for the excitability of muscles and nerves3. In addition, it serves as cofactor in over 300 enzymatic reactions needed for protein synthesis, blood glucose control, blood regulation, and metabolism of food components1,3. It also contributes to body structure4.

Signs and Symptoms of Deficiency or Toxicity

Magnesium deficiency is not common among healthy individuals consuming balanced diets. However, the risk to magnesium deficiency increases when a person has prolonged diarrhea, Chron’s disease, celiac disease, diabetes and has long-term use of diuretics. Chronic alcoholism4.

Signs of magnesium deficiency include loss of appetite, nausea, vomiting, fatigue, numbness, tingling, muscle contractions and cramps, seizures, personality changes, abnormal heart rhythms, and coronary spasms. Severe deficiencies can also compromise calcium and potassium levels1.

Adverse effects of excess intakes of magnesium salts can lead to diarrhea, hypotension, lethargy, confusion, muscle weakness, and difficulty of breathing. Severe elevation of magnesium in the blood may result in cardiac arrest4.

Supplementation Guide

No published guidelines for supplementation for the general public. However, when magnesium supplements are taken, it should be with meals. If not, diarrhea may be experienced. Following are frequently used dosages of actual magnesium for the prevention of a deficiency7.

  • Adult and teenage males: 130 to 400 mg/day;
  • Adult and teenage females: 135 to 210 mg/day;
  • Pregnant females: 195 to 320 mg;
  • Breastfeeding females: 245-355 mg;
  • Children, 7-10 years: 100 to 170 mg;
  • Children 4-6 years: 65 to 120 mg.

Following are the established upper limits for magnesium per age group8.

  • For children,  1-3 y.o.: 65 mg; 4-8 y.o.:110 mg;13-18 y.o.:350 mg
  • For adults (19 years and older), pregnant/lactating women: 350 mg

Magnesium can interact with medications such as loop diuretics and thiazides, cytotoxic drugs, aminoglycosides, digoxin, and steroids9. Meanwhile, the absorption of magnesium is hindered by phytates, fibre, alcohol, or excessive calcium and phosphates6.

Food Sources

The richest sources of magnesium are whole seeds, unmilled grains, green leafy vegetables, legumes and nuts6.

(1) Office of Dietary Supplements-National Institutes of Health. (n.d.). Magnesium. Fact Sheet for Health Professionals. Retrieved from
(2) Gibson, R.M. (2005). Principles of Nutritional Assessment. New York: Oxford University Press, Inc.
(3) Huskisson E, Maggini S, Ruf M. The role of vitamins and mineral in energy metabolism and well-being. The Journal of International Medical Research 2007; 35: 277-289
(4) Higdon J, Drake VJ, Delage Barbara. (May 2014). Linus Pauling Micronutrient Information Center. Magnesium. Retrieved from
(5) Noronha JL, Matischak GM. Magnesium in critical illness: metabolism, assessment, and treatment. Intensive Care Med 2002; 28:667-679. doi:10.1007/s00134-002-1281-y
(6) Saris N-EL, Mervaala E, Karpannen H, Khawaja JA, Lewenstam A. Magnesium: An update on physiological, clinial and analytical aspects. Clinica Chimica Acta 2000; 294(1-2): 1-26.
(7) Micromedex. (n.d.). Drugs and Supplements. Magnesium Supplement (Oral Route, Parentral Route). Retrieved from
(8) Philippine Dietary Reference Intakes. 2015. Department of Science Technology-Food and Nutrition Research Institute.
(9) Abdulsahib HT. Determination of magnesium in whole blood and serum of Ischemic Heart Disease (IHD) patients by flame atomic absorption spectrometry. American Journal of Analytical Chemistry 2011; 2:996-1002.