Magnesium Glycinate to Magnesium Oxide Conversion
When converting from magnesium oxide to magnesium glycinate, use a 1:5 ratio of elemental magnesium content, as magnesium oxide contains approximately 60% elemental magnesium while magnesium glycinate contains only about 14% elemental magnesium.
Bioavailability Comparison
Magnesium supplements differ significantly in their elemental magnesium content and bioavailability:
- Magnesium Oxide: Contains approximately 60% elemental magnesium but has very poor bioavailability at only about 4% absorption 1
- Magnesium Glycinate: Contains approximately 14% elemental magnesium but has significantly higher bioavailability
This difference in bioavailability is crucial when determining equivalent dosing. Despite magnesium oxide having higher elemental magnesium content, its poor absorption makes it less effective at raising serum magnesium levels compared to more bioavailable forms like magnesium glycinate.
Conversion Formula
To convert from magnesium oxide to magnesium glycinate:
- Calculate the elemental magnesium in the current magnesium oxide dose
- Divide by the percentage of elemental magnesium in magnesium glycinate
- Adjust for the higher bioavailability of magnesium glycinate
Example Calculation:
- 500 mg magnesium oxide contains approximately 300 mg elemental magnesium (60%)
- To get 300 mg elemental magnesium from magnesium glycinate (14% elemental content), you would need approximately 2,143 mg of magnesium glycinate
- However, due to magnesium glycinate's superior bioavailability compared to magnesium oxide (4% absorption), the actual equivalent dose would be lower
Clinical Considerations
Gastrointestinal Effects: Magnesium oxide is more likely to cause diarrhea due to its osmotic effect in the intestines 2. Magnesium glycinate is generally better tolerated and less likely to cause digestive disturbances 3.
Renal Function: Always consider renal function when prescribing any magnesium supplement. Patients with CKD grade 4 are at higher risk of hypermagnesemia 4.
Dosing Schedule: Smaller, divided doses throughout the day may improve absorption compared to a single large dose 2.
Monitoring: Check serum magnesium levels periodically, especially when changing formulations or in patients with compromised renal function.
Practical Recommendation
For a patient currently taking 400 mg of magnesium oxide daily (providing approximately 240 mg elemental magnesium):
- Convert to approximately 800-1000 mg of magnesium glycinate
- Consider dividing the dose to improve absorption and reduce potential gastrointestinal effects
- Monitor for clinical response and adjust as needed
This conversion ensures the patient receives similar therapeutic benefits while potentially reducing gastrointestinal side effects due to the better tolerability of magnesium glycinate.