How will taking magnesium threonate affect magnesium levels in individuals already taking magnesium glycinate?

Additive Magnesium Supplementation: Combining Threonate with Glycinate

Taking magnesium threonate in addition to magnesium glycinate will increase your total elemental magnesium intake and overall magnesium levels, as both forms are bioavailable organic magnesium salts that contribute to systemic magnesium stores. 1

Understanding Magnesium Bioavailability

Both magnesium threonate and magnesium glycinate are organic magnesium salts with superior bioavailability compared to inorganic forms like magnesium oxide or hydroxide. 1 The key principle is that organic magnesium compounds (including citrate, glycinate, aspartate, lactate, and threonate) are readily absorbed and contribute to total body magnesium stores. 1

• Magnesium threonate has been specifically shown to raise magnesium levels in brain tissue and neurons effectively, with confirmed bioavailability based on dissociation studies, animal models, and human trials. 2
• Magnesium glycinate is an amino acid-bound compound that increases serum and tissue magnesium levels when administered orally. 3
• Both forms dissociate in the body to release elemental magnesium, which then contributes to your total magnesium status. 2

Calculating Total Magnesium Exposure

The critical factor is your total daily elemental magnesium intake from all sources combined. 1 When combining supplements:

• Calculate the elemental magnesium content from each product (not the total compound weight)
• Add these amounts together to determine your total supplemental magnesium intake
• The upper limit (UL) for supplemental magnesium from readily dissociable salts is 250 mg/day for adults. 2

For example, if you're taking magnesium glycinate providing 200 mg elemental magnesium and add magnesium threonate providing 250 mg elemental magnesium, your total supplemental intake would be 450 mg/day—which exceeds the established UL and increases risk of osmotic diarrhea and other gastrointestinal effects. 1, 4

Practical Dosing Strategy

Spread magnesium doses throughout the day rather than taking a single large dose to optimize absorption and minimize gastrointestinal side effects. 1 This approach is particularly important when combining multiple magnesium forms:

• All magnesium forms can cause loose stools through osmotic effects, drawing water into the intestines. 4
• Higher total doses increase the likelihood of diarrhea, bloating, and other GI symptoms. 1
• Dividing high doses (e.g., 405 mg/70 kg split into two 202.5 mg doses every 12 hours) does not sufficiently increase tissue magnesium levels compared to appropriate single dosing. 3

Safety Considerations and Monitoring

Avoid all magnesium supplementation if creatinine clearance is <20 mL/min due to hypermagnesemia risk. 1, 4 Additional precautions include:

• Monitor for gastrointestinal effects (diarrhea, bloating) which indicate excessive dosing. 1
• Be aware that patients are at increased risk of developing hypocalcemia after magnesium supplementation, requiring calcium level monitoring. 1
• Use caution in elderly patients, those with heart failure, or those taking medications that interact with magnesium. 1
• Ensure adequate hydration and sodium intake, as depletion causes secondary hyperaldosteronism which increases urinary magnesium losses. 4

Clinical Decision Algorithm

For patients already taking magnesium glycinate who want to add threonate:

1. Calculate current elemental magnesium intake from glycinate supplementation
2. Determine if additional magnesium is needed based on clinical indication (deficiency, specific symptoms, therapeutic goals)
3. If total supplemental magnesium would exceed 250 mg/day, consider replacing rather than adding—switch partially or completely to threonate if brain-specific benefits are the goal 5
4. If staying below 250 mg/day total, adding threonate is safe but monitor for GI effects 2
5. Ensure renal function is adequate (CrCl >20 mL/min) before any supplementation 1

Special Considerations for Magnesium Threonate

Magnesium threonate (Magtein®) was specifically developed to raise brain magnesium levels and has demonstrated cognitive benefits in clinical trials. 5 The standard dose studied is 2000 mg/day of the compound (providing approximately 250 mg elemental magnesium and 2730 mg L-threonate). 2 If cognitive enhancement is your primary goal, threonate may be preferable to glycinate, suggesting replacement rather than addition makes more clinical sense. 5

The L-threonate component itself has been evaluated for safety at intakes up to 2700 mg/day and is considered safe at this level. 2 However, the elemental magnesium content still contributes to your total magnesium load and associated risks of osmotic diarrhea when combined with other magnesium sources. 1