eMedicine Specialties > Pediatrics: General Medicine > Endocrinology

Hypomagnesemia: Differential Diagnoses & Workup

Author: James E Springate, MD, Associate Professor of Pediatrics, State University of New York at Buffalo; Attending Physician, Department of Pediatrics, Division of Pediatric Nephrology, Women & Children's Hospital of Buffalo
Coauthor(s): Gunjeet K Kala, MD, Clinical Instructor, Division of Pediatric Nephrology, University of Buffalo State University of New York School of Medicine and Biomedical Sciences, Women and Children's Hospital of Buffalo
Contributor Information and Disclosures

Updated: Sep 18, 2009

Differential Diagnoses

Hypocalcemia
Hypokalemia

Other Problems to Be Considered

Hypomagnesemia often leads to hypocalcemia, a phenomenon largely explained by inhibition of parathyroid hormone bioactivity. Hypocalcemia does not resolve until the magnesium deficiency has been corrected.

Workup

Laboratory Studies

Although the total serum magnesium concentration is the most practical and commonly used measure of magnesium status, it represents less than 1% of total body magnesium and may not provide an accurate reflection of true total body magnesium content.

Magnesium deficiency is frequently associated with other electrolyte abnormalities, such as hypokalemia, hypocalcemia, hypophosphatemia, and acidosis. Once hypomagnesemia is found, serum potassium, bicarbonate, calcium, and phosphate concentrations should be measured.

In patients with hypomagnesemia, measurement of urinary magnesium excretion helps distinguish renal magnesium wasting from intestinal losses. In the presence of magnesium deficiency, the 24-hour magnesium excretion rate should be less than 2 mEq. A simpler but less accurate test for renal magnesium wasting is to calculate the fractional excretion of magnesium [FE Mg ] - U Mg  X P Cr /P Mg  X U Cr x 100%; the result should be less than 2% in the setting of hypomagnesemia.

Other Tests

Hypomagnesemia may be associated with nonspecific ECG changes, including ST-segment depression, altered T waves, or loss of voltage. Severe magnesium deficiency may cause PR prolongation or widened QRS complexes. Tachycardia, premature beats and fibrillation have also been reported. 

More on Hypomagnesemia

Overview: Hypomagnesemia
Differential Diagnoses & Workup: Hypomagnesemia
Treatment & Medication: Hypomagnesemia
Follow-up: Hypomagnesemia
Multimedia: Hypomagnesemia
References
Further Reading
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References

  1. Tong GM, Rude RK. Magnesium deficiency in critical illness. J Intensive Care Med. Jan-Feb 2005;20(1):3-17. [Medline].

  2. Curiel-Garcia JA, Rodriguez-Moran M, Guerrero-Romero F. Hypomagnesemia and mortality in patients with type 2 diabetes. Magnes Res. Sep 2008;21(3):163-6. [Medline].

  3. Guerrera MP, Volpe SL, Mao JJ. Therapeutic uses of magnesium. Am Fam Physician. Jul 15 2009;80(2):157-62. [Medline].

  4. Naderi AS, Reilly RF Jr. Hereditary etiologies of hypomagnesemia. Nat Clin Pract Nephrol. Feb 2008;4(2):80-9. [Medline].

  5. Agus ZS. Hypomagnesemia. J Am Soc Nephrol. Jul 1999;10(7):1616-22. [Medline].

  6. Konrad M. Disorders of magnesium metabolism. In: Geary D, Shaefer F. Comprehensive Pediatric Nephrology. Philadelphia PA: Mosby Elsevier; 2008:461-475.

  7. Martin KJ, Gonzalez EA, Slatopolsky E. Clinical Consequences and Management of Hypomagnesemia. J Am Soc Nephrol. Jan 30 2008;[Medline]. [Full Text].

  8. [Best Evidence] Mouw DR, Latessa RA, Hickner J. Clinical inquiries. What are the causes of hypomagnesemia?. J Fam Pract. Feb 2005;54(2):174-6. [Medline]. [Full Text].

  9. Rodriguez-Hernandez H, Gonzalez JL, Rodriguez-Moran M, Guerrero-Romero F. Hypomagnesemia, insulin resistance, and non-alcoholic steatohepatitis in obese subjects. Arch Med Res. Jul-Aug 2005;36(4):362-6. [Medline].

  10. Topf JM, Murray PT. Hypomagnesemia and hypermagnesemia. Rev Endocr Metab Disord. May 2003;4(2):195-206. [Medline].

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Keywords

hypomagnesemia, magnesium, Mg, infectious diarrhea, steatorrhea, inflammatory bowel disease, GI neoplasms, diabetic ketoacidosis, irritability, disorientation, depression, psychosis, treatment, diagnosis, low magnesium levels, treatment, diagnosis

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Contributor Information and Disclosures

Author

James E Springate, MD, Associate Professor of Pediatrics, State University of New York at Buffalo; Attending Physician, Department of Pediatrics, Division of Pediatric Nephrology, Women & Children's Hospital of Buffalo
James E Springate, MD is a member of the following medical societies: American Academy of Pediatrics, American Physiological Society, American Society of Pediatric Nephrology, International Pediatric Transplant Association, and Society for Pediatric Research
Disclosure: Nothing to disclose.

Coauthor(s)

Gunjeet K Kala, MD, Clinical Instructor, Division of Pediatric Nephrology, University of Buffalo State University of New York School of Medicine and Biomedical Sciences, Women and Children's Hospital of Buffalo
Gunjeet K Kala, MD is a member of the following medical societies: American Academy of Pediatrics, American Society of Pediatric Nephrology, and American Society of Pediatric Nephrology
Disclosure: Nothing to disclose.

Medical Editor

Karl S Roth, MD, Professor and Chair, Department of Pediatrics, Creighton University School of Medicine
Karl S Roth, MD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Pediatrics, American College of Nutrition, American Pediatric Society, American Society for Clinical Nutrition, American Society of Nephrology, Association of American Medical Colleges, Medical Society of Virginia, New York Academy of Sciences, Sigma Xi, Society for Pediatric Research, and Southern Society for Pediatric Research
Disclosure: MDS Pharma Salary Employment

Pharmacy Editor

Mary L Windle, PharmD, Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy, Pharmacy Editor, eMedicine
Disclosure: Pfizer Inc Stock Investment from financial planner; Avanir Pharma Stock Investment from financial planner ; WebMD Salary and stock Employment and investment from financial planner

Managing Editor

George P Chrousos, MD, FAAP, MACP, MACE, FRCP(London), Professor and Chair, First Department of Pediatrics, Athens University Medical School, Aghia Sophia Children's Hospital, Greece
George P Chrousos, MD, FAAP, MACP, MACE, FRCP(London) is a member of the following medical societies: American Academy of Pediatrics, American College of Endocrinology, American College of Physicians, American Pediatric Society, American Society for Clinical Investigation, Association of American Physicians, Endocrine Society, Lawson-Wilkins Pediatric Endocrine Society, and Society for Pediatric Research
Disclosure: Nothing to disclose.

CME Editor

David Pallares, MD, Clinical Assistant Professor, Department of Pediatrics, Division of Allergy and Immunology, University of Louisville
David Pallares, MD is a member of the following medical societies: American Academy of Allergy Asthma and Immunology
Disclosure: Nothing to disclose.

Chief Editor

Stephen Kemp, MD, PhD, Professor, Department of Pediatrics, Section of Pediatric Endocrinology, University of Arkansas and Arkansas Children's Hospital
Stephen Kemp, MD, PhD is a member of the following medical societies: American Academy of Pediatrics, American Association of Clinical Endocrinologists, American Pediatric Society, Endocrine Society, Phi Beta Kappa, Southern Medical Association, and Southern Society for Pediatric Research
Disclosure: Genentech, Inc. Honoraria Speaking and teaching; Pfizer, Inc. Honoraria Consulting

 
 
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