Is it safe to take magnesium and calcium supplements together?

Is It Safe to Take Magnesium and Calcium Supplements Together?

Yes, it is safe to take magnesium and calcium supplements together, and they are routinely combined in clinical practice, including in parenteral nutrition formulations and oral supplements. 1

Evidence from Clinical Guidelines

Combined Administration is Standard Practice

• Calcium and magnesium are regularly administered together in parenteral nutrition for infants, children, and adults, with established dosing ratios that ensure optimal absorption and bone mineralization. 1

• The ESPGHAN/ESPEN guidelines explicitly recommend providing appropriate amounts of calcium, phosphorus, and magnesium simultaneously to ensure optimal growth and bone mineralization. 1

• Organic calcium and phosphorus salts are recommended when compounding solutions together to prevent precipitation, and magnesium sulfate has few compatibility issues when combined with calcium. 1, 2

The Calcium-to-Magnesium Ratio Matters More Than Separation

• The optimal calcium-to-magnesium intake ratio appears to be between 1.7 and 2.6 (by weight), rather than whether they are taken together or separately. 3, 4

• Ratios below 1.7 or above 2.8 may be detrimental to health outcomes. 5

• Current US dietary patterns show a mean Ca:Mg ratio exceeding 3.0 from food alone, which is already suboptimal. 5, 3

Clinical Implications for Supplementation

• When calcium supplementation is needed, consider adding magnesium to maintain a favorable ratio, especially since most Americans have high calcium-to-magnesium ratios from diet alone. 3

• For oral calcium supplementation, the maximum dose should not exceed 500 mg of elemental calcium at one time for optimal absorption, and divided doses are recommended if daily supplementation exceeds 500 mg. 6

• Magnesium oxide at 12-24 mmol daily is recommended for mild hypomagnesemia, typically given at night, though organic magnesium salts (aspartate, citrate, lactate) have higher bioavailability. 2

Potential Interactions and Considerations

Absorption Dynamics

• Magnesium complexes with oxalate in the gastrointestinal tract, potentially reducing calcium oxalate supersaturation in urine and decreasing oxalate absorption. 1

• While calcium and magnesium may compete for absorption at very high doses, this is not clinically significant at recommended supplementation levels. 5

Kidney Stone Risk

• The combination of calcium and magnesium may actually be beneficial for kidney stone prevention, as magnesium can reduce calcium oxalate crystallization. 1, 7

• Magnesium and citrate exert a synergistic effect on lowering the relative supersaturation of brushite (calcium phosphate), suggesting protective interactions. 7

• Higher dietary magnesium was associated with a 30% lower risk of stone formation in men. 1

Cardiovascular and Mortality Considerations

• High calcium-to-magnesium ratios (>2.6) have been associated with increased risk for cardiovascular disease, metabolic syndrome, and some cancers. 3, 8

• The Women's Health Initiative trial showed increased nephrolithiasis risk with 1000 mg calcium plus 400 IU vitamin D3 daily (hazard ratio 1.17), but this study did not include magnesium supplementation. 1

Practical Recommendations

For General Supplementation

• Take calcium and magnesium together without concern, focusing instead on maintaining an appropriate ratio between the two minerals. 1, 3

• If taking calcium carbonate (which requires gastric acid), take it with meals; calcium citrate can be taken without food. 6

• Aim for a total dietary plus supplemental Ca:Mg ratio between 1.7 and 2.6 to optimize health outcomes. 3, 4

Dosing Strategy

• Do not exceed 500 mg elemental calcium per dose for optimal absorption. 6

• Total calcium intake (diet plus supplements) should not exceed 2,000-2,500 mg/day. 6

• Consider magnesium supplementation of 146 mg/day (the mean dose used by Americans who supplement) when taking calcium supplements. 3

Special Populations

• In parenteral nutrition, calcium and magnesium are routinely given together with established safety profiles across all age groups. 1

• For patients with kidney stone history, the combination may be particularly beneficial due to magnesium's protective effects against calcium oxalate crystallization. 1, 7

Common Pitfalls to Avoid

• Do not focus on separating calcium and magnesium doses—this is unnecessary and not supported by clinical evidence. 1

• Avoid very high calcium supplementation without adequate magnesium, as this creates an unfavorable ratio associated with adverse health outcomes. 5, 3

• Do not use acidic calcium solutions packaged in glass vials (like some calcium gluconate preparations) due to aluminum contamination. 1, 2