How to treat magnesium deficiency?

Magnesium Repletion Protocol

For magnesium deficiency, oral organic magnesium salts should be used as first-line therapy due to their superior bioavailability, with dosing spread throughout the day to optimize absorption. 1

Assessment of Magnesium Status

• Serum magnesium levels are not entirely reliable as less than 1% of magnesium is in the blood (remainder is in bone, soft tissue, and muscle) 1
• Clinical symptoms of deficiency include:
  • Abdominal cramps
  • Impaired healing
  • Fatigue
  • Bone pain
  • Muscle weakness
  • Cardiac arrhythmias

Oral Repletion Protocol

First-Line Therapy:

1. Preferred formulations: Organic magnesium salts 1

   • Magnesium citrate
   • Magnesium lactate
   • Magnesium aspartate
   • Avoid magnesium oxide due to poor bioavailability (only 4% absorption) 2

2. Dosing:

   • Standard dose: 12-24 mmol (300-600 mg elemental magnesium) daily 1
   • For severe deficiency: Up to 12 mmol magnesium oxide (4 mmol × 3 doses) daily 1
   • Best administered at night when intestinal transit is slowest 1

3. Administration strategy:

   • Divide doses throughout the day to maximize absorption 1
   • Target serum level >0.6 mmol/L (although this is an imperfect marker) 1
   • Continue until symptoms resolve and magnesium levels normalize

Special Considerations:

• In patients with diarrhea or high-output stomas:

  • Correct water and sodium depletion first (to address secondary hyperaldosteronism) 1
  • Consider adding 1-alpha hydroxy-cholecalciferol (0.25-9.00 μg daily) if oral supplements don't normalize levels 1
  • Monitor serum calcium to avoid hypercalcemia when using vitamin D supplements 1

• For patients with malabsorption:

  • Avoid excessive dietary fat which can worsen magnesium absorption 1

Parenteral Repletion Protocol

Indications for IV/IM administration:

• Severe symptomatic hypomagnesemia
• Failure of oral therapy
• Malabsorption syndromes
• High-output intestinal losses that cannot be managed orally

IV/IM dosing:

1. Mild deficiency: 3

   • 1 g magnesium sulfate (8.12 mEq) IM every 6 hours for 4 doses
   • Total: 32.5 mEq over 24 hours

2. Severe deficiency: 3

   • Up to 250 mg/kg (approximately 2 mEq/kg) IM within 4 hours
   • OR 5 g (approximately 40 mEq) added to 1 L of 5% Dextrose or 0.9% Sodium Chloride for slow IV infusion over 3 hours

3. For patients on continuous renal replacement therapy:

   • Use dialysis solutions containing magnesium to prevent hypomagnesemia 1

Monitoring during parenteral repletion:

• Monitor serum magnesium levels every 12-24 hours
• Watch for signs of hypermagnesemia (hypotension, respiratory depression)
• Adjust dosing based on renal function

Important Considerations and Pitfalls

1. Bioavailability issues:

   • Organic magnesium salts have significantly better bioavailability than magnesium oxide 2
   • Inorganic salts like magnesium chloride may have equivalent bioavailability to some organic salts 2

2. Medication interactions:

   • Proton pump inhibitors can worsen magnesium deficiency 1
   • Diuretics can increase magnesium excretion 1

3. Renal considerations:

   • Avoid magnesium supplementation in patients with severe renal insufficiency 1
   • Maximum dosage in severe renal insufficiency: 20 g/48 hours with frequent monitoring 3

4. Side effects management:

   • Oral magnesium can worsen diarrhea - consider nighttime dosing 1
   • Parenteral administration can cause hypotension if given too rapidly 3

5. Vitamin D connection:

   • Magnesium is required for vitamin D activation and metabolism 4
   • Consider vitamin D status when treating magnesium deficiency

By following this structured approach to magnesium repletion, clinicians can effectively address deficiency while minimizing side effects and optimizing absorption.