Magnesium (Mg/Mag) (Xylidyl Blue)

Clinical definition of the Magnesium (Xylidyl Blue) test
This test is done to check the amounts of Magnesium in the body. Magnesium is mostly found in the bone and inside cells of body tissues and organs. It is necessary for almost all the processes in the body. It helps maintain normal muscle and nerve function, keeps the bones strong, controls the heart beat, and helps regulate blood pressure. Magnesium also controls blood sugar levels and helps support the body's defense (immune) system. Green vegetables such as spinach; whole grains, and nuts are a rich source of Magnesium.

Why is the Magnesium (Xylidyl Blue) test done?
The Magnesium test is used to for the quantitative determination of Magnesium in the blood using the reagent xylidyl blue. Altered levels of magnesium are seen in persons suffering from diabetes, alcoholism, diuretics, hyperthyroidism, hypothyroidism, malabsorption, hyperalimenation, myocardial infarction, congestive heart failure, liver cirrhosis, renal failure, Addison’s disease, and vitamin D intoxication. Hence this test helps in the diagnosis and the treatment of the above conditions.

What are the common signs/symptoms when the Magnesium (Xylidyl Blue) test is done?

  • Weakness
  • Irritability
  • Cardiac arrhythmia
  • Nausea
  • Diarrhea due to excess or shortage of magnesium
  • Abnormal calcium or potassium levels
  • Loss of appetite
  • Fatigue
  • Confusion
  • Muscle cramps
  • Seizures  
  • Abnormal heart rate
  • Numbness or tingling sensation

Who should do the Magnesium (Xylidyl Blue) test (Target population)?
This test is done as a follow up test for persons suffering from chronically low levels of calcium and potassium.

What should I do before the Magnesium (Xylidyl Blue) test?

Specimen type

Specimen collection procedure

Preparatory instructions before the test *

Serum (Blood Sample)

Venipuncture - Collection of blood from a vein, usually from the arm.

Fasting Required.

Fasting samples have to be collected after a minimum 8-hour overnight fasting status.

Clear fluids like water is allowed during this period. Refrain from consumption of early morning beverages like tea, coffee and milk until specimen collection is completed.

In case of diabetics on oral or injectable hypoglycemic agents, consult your physician about continuing with these medications prior to specimen collection.

*Subjects suffering from any illness or on oral or injectable medications are advised to consult their physician prior to requesting any tests or procedures.

How do I interpret my Magnesium (Xylidyl Blue) test results?

Reference Range*


1.7 to 2.2 mg/dL


‘*A Reference range is a set of values which helps the healthcare professional to interpret a medical test. It may vary with age, gender, and other factors. Reference ranges may also vary between labs, in value & units depending on instruments used and method of establishment of reference ranges’

Diseases/conditions related to the Magnesium (Xylidyl Blue) test

  • Addison's disease
  • Chronic renal failure
  • Dehydration
  • Diabetic acidosis
  • Oliguria
  • Alcoholism
  • Chronic diarrhea
  • Delirium tremens
  • Hemodialysis
  • Hepatic (liver) cirrhosis
  • Hyperparathyroidism
  • Hypothyroidism
  • Pancreatitis
  • Toxemia of pregnancy
  • Ulcerative colitis

Other tests related to the Magnesium (Xylidyl Blue) test

  • Calcium
  • Potassium
  • Phosphorus
  • Parathyroid hormone (PTH)
  • 25-OH VITAMIN D3
  • 25-Hydroxyvitamin D
  • Vitamin B-12
  • Holotranscobalamin (Active Vitamin B12)