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Magnesium normal range (and what it means for nurses)

Normal serum magnesium is 1.6 to 2.6 mg/dL at UW Medicine (University of Washington Medicine), a range the MagstoneRN app's lab tool uses. Low magnesium can cause cramps and dysrhythmias; high magnesium slows the pulse and the reflexes. Some textbooks use mEq/L, a different unit. Use the range on the patient's report.⁠[1][2][3]

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Quick facts

Serum magnesium reference range
TestRangeUnitApplies to
Magnesium (serum or plasma)⁠[1]1.6-2.6mg/dLAll ages
Hypomagnesemia (low)⁠[1][2]Below 1.6mg/dLAll ages
Hypermagnesemia (high)⁠[1][2]Above 2.6mg/dLAll ages

Loop diuretics, alcohol, and a poor diet cause low magnesium

  • Hypomagnesemia usually comes from too little magnesium in the diet or from loop diuretics, which excrete it. Alcohol use disorder and long-term proton pump inhibitor use are other causes.⁠[2]
  • Signs include nausea, vomiting, lethargy, weakness, leg cramps, tremor, dysrhythmias, and tetany, which is linked to the low calcium that can come with low magnesium.⁠[2]
  • Hypomagnesemia, like hypokalemia, can increase the risk of digoxin toxicity, and loop diuretics such as furosemide cause magnesium losses along with potassium.⁠[4]

High magnesium usually comes from kidney failure or extra magnesium

  • Hypermagnesemia usually comes from kidney failure, too much magnesium replacement, or magnesium-containing laxatives or antacids.⁠[2][5]
  • Signs include bradycardia, a weak and thready pulse, lethargy, hyporeflexia, and muscle weakness, and it can progress to cardiac arrest.⁠[2]

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How it shows up on nursing exams

  • Hyporeflexia and bradycardia point to high magnesium; leg cramps and tetany point to low magnesium.⁠[2]
  • A patient taking furosemide can lose potassium and magnesium together, and low levels of either raise the risk of digoxin toxicity.⁠[4]

Practice question

An adult patient with alcohol use disorder who takes furosemide has a serum magnesium of 1.2 mg/dL. The laboratory reference range is 1.6 to 2.6 mg/dL. Which assessment finding should the nurse expect?

  1. A. Hyporeflexia and a heart rate of 52 beats per minute
  2. B. Cramping legs and muscle tetany
  3. C. Constipation and increased thirst
  4. D. A weak, thready pulse
Show the answer and why

Correct answer: B. Cramping legs and muscle tetany

  • A. Incorrect. Hyporeflexia and bradycardia are signs of high magnesium. This patient's magnesium is low.
  • B. Correct. 1.2 mg/dL is below 1.6. Leg cramps and tetany are signs of hypomagnesemia (tremor can come with high or low magnesium), and both furosemide and alcohol use disorder are common causes.
  • C. Incorrect. Constipation and increased thirst are signs of high calcium, not low magnesium.
  • D. Incorrect. A weak and thready pulse is listed with high magnesium, along with bradycardia and hyporeflexia.

Sources for this question: ⁠[1][2]

Memory hook: High magnesium slows the pulse and the reflexes; low magnesium cramps the legs and can cause dysrhythmias.

Questions about magnesium

What is a normal magnesium level?

It is 1.6 to 2.6 mg/dL at UW Medicine, a range the MagstoneRN app's lab tool uses. Textbooks print other ranges, some in mEq/L, a different unit. Compare a result only with a range in the same unit, and use the range on the patient's report.⁠[1][2][3]

What causes low magnesium?

Too little magnesium in the diet, loop diuretics, alcohol use disorder, and long-term proton pump inhibitor use are common causes.⁠[2]

Study this topic in MagstoneRN

MagstoneRN's Lab values tool lists magnesium in mg/dL from UW Medicine and in mEq/L from the teaching table in Open RN's Health Alterations, a free nursing textbook, and lists the sources for each range.

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Sources for this page

All 5 sources
  1. Magnesium, default method (reference interval effective September 14, 2026) (opens in a new tab). UW Medicine Laboratory Test Guide. License: Not openly licensed; reference values cited as facts, no text reused. Accessed October 18, 2026.
  2. Nursing Fundamentals, 2nd edition, Chapter 15: Fluids and Electrolytes (opens in a new tab). Open RN, Chippewa Valley Technical College (2024). License: CC BY 4.0. Accessed October 18, 2026.
  3. How to Understand Your Lab Results (updated September 4, 2025) (opens in a new tab). MedlinePlus, National Library of Medicine. License: Public domain (U.S. government work). Accessed October 18, 2026.
  4. Nursing Pharmacology, 2nd edition, Chapter 6: Cardiovascular and Renal Systems (opens in a new tab). Open RN, Chippewa Valley Technical College (2023). License: CC BY 4.0. Accessed October 18, 2026.
  5. Magnesium Blood Test (updated October 25, 2023) (opens in a new tab). MedlinePlus, National Library of Medicine. License: Public domain (U.S. government work). Accessed November 13, 2026.

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Sources: 5 entries, from government health agencies and reputable secondary sources, last accessed November 13, 2026.