What is the safe dosage of magnesium glycerin (magnesium supplement) for oral administration?

Safe Dosage of Magnesium Glycinate

For general supplementation, start with the recommended daily allowance of 320 mg elemental magnesium for women and 420 mg for men, which can be increased gradually based on tolerance and clinical need. 1

Standard Dosing Guidelines

The FDA-approved dosing for magnesium supplements (including glycinate formulations) provides clear parameters:

• Adults and children ≥12 years: 2-4 chews (or equivalent dose) daily 2
• Children 6-12 years: 1-2 chews daily 2
• Children <6 years: Consult physician 2
• Maximum: Do not exceed recommended daily dose in 24 hours 2

Always drink a full glass (8 oz) of liquid with each dose, and the dose may be taken as a single daily dose or divided throughout the day. 2

Condition-Specific Dosing

For Chronic Constipation

The American Gastroenterological Association recommends magnesium oxide (not glycinate) at 400-500 mg daily initially, titrating based on symptom response, with clinical trials using up to 1,000-1,500 mg daily. 3 However, magnesium glycinate can be used at equivalent elemental magnesium doses (320-420 mg daily) with better GI tolerance than oxide formulations. 1

For Malabsorption Conditions

In patients with inflammatory bowel disease or short bowel syndrome, oral requirements may reach 700 mg/day of elemental magnesium depending on severity of malabsorption. 4 For short bowel syndrome specifically, 12-24 mmol daily (approximately 480-960 mg elemental magnesium) is recommended, preferably administered at night when intestinal transit is slowest. 1

For Erythromelalgia

Start at the recommended daily allowance (350 mg for women, 420 mg for men) and increase gradually according to tolerance. 1 Liquid or dissolvable magnesium products are better tolerated than pills. 1

Critical Safety Considerations

Absolute Contraindications

Avoid magnesium supplementation entirely if creatinine clearance is <20 mL/min due to life-threatening hypermagnesemia risk. 3, 1 This is the single most important safety consideration that supersedes all other dosing recommendations.

Relative Contraindications

• Use with caution in renal insufficiency and pregnancy 3
• Check renal function before initiating any magnesium supplementation 1
• In patients on continuous renal replacement therapy, hypomagnesemia occurs in up to 65% of cases, requiring dialysis solutions containing magnesium 1

Bioavailability and Formulation Considerations

Organic magnesium salts (glycinate, citrate, aspartate, lactate) have superior bioavailability compared to inorganic forms (oxide, hydroxide). 1 Research demonstrates that magnesium glycinate, as an amino acid-bound compound, shows dose-dependent absorption with better tissue penetration than some other forms. 5

Magnesium glycinate causes less osmotic diarrhea than magnesium oxide due to better absorption, making it preferable for general supplementation when laxative effects are not desired. 1

Dosing Algorithm

1. Assess renal function first: If CrCl <20 mL/min, do not supplement 3, 1

2. Correct volume depletion: In patients with diarrhea, high-output stomas, or electrolyte depletion, rehydrate with IV saline first to address secondary hyperaldosteronism before magnesium supplementation 1

3. Start with RDA dosing: 320 mg for women, 420 mg for men 1

4. Titrate based on indication:

   • General supplementation: Maintain at RDA
   • Constipation: Increase to 400-500 mg daily 3
   • Malabsorption: May require up to 700-960 mg daily 1, 4

5. Monitor for side effects: Common adverse effects include diarrhea, abdominal distension, and GI intolerance 3, 1

6. Divide doses if needed: Split daily dose into 2-3 administrations throughout the day for better tolerance 1

Common Pitfalls to Avoid

• Do not supplement magnesium without first checking renal function - this can cause fatal hypermagnesemia 1
• Do not attempt to correct magnesium deficiency without first addressing volume depletion in patients with diarrhea or high-output stomas, as ongoing aldosterone-mediated renal losses will exceed supplementation 1
• Do not exceed the Tolerable Upper Intake Level of 350 mg/day from supplements for general health maintenance to avoid adverse effects 1
• Do not assume serum magnesium accurately reflects total body stores - less than 1% of magnesium is found in blood, and 24-hour urinary excretion is a more sensitive index 1, 4
• Be aware that quality varies significantly - studies show 58.7% of magnesium supplements contain amounts outside permissible tolerance limits, with patients potentially receiving 98-304% of declared content 6