Is it safe for an adult to take magnesium glycinate with vitamin D3 (Cholecalciferol), vitamin B12 (Cobalamin), and iron supplements?

Safety of Taking Magnesium Glycinate with Vitamin D3, B12, and Iron Supplements

Yes, it is generally safe for healthy adults to take magnesium glycinate with vitamin D3, vitamin B12, and iron supplements, but you should separate the magnesium and iron doses by at least 2 hours to optimize absorption of both nutrients. 1

Key Timing Consideration: Separate Magnesium and Iron

The most important practical consideration is that calcium and iron should be taken 2 hours apart from magnesium, as one may inhibit absorption of the other. 1 While this guideline specifically mentions calcium and iron, the same principle applies to magnesium and iron interactions.

• Research confirms that magnesium can inhibit iron absorption when taken simultaneously 2, 3
• A case report documented refractory iron deficiency anemia in a patient overusing magnesium laxatives despite oral iron supplementation 3
• Take your iron supplement at a different time of day than your magnesium glycinate—for example, iron in the morning and magnesium at night 1

No Interactions Between Other Combinations

The other supplement combinations pose no absorption or safety concerns:

• Vitamin D3 and magnesium can be taken together safely 1
• Vitamin B12 and magnesium have no known interactions 1, 4
• Vitamin D3 and vitamin B12 can be taken together 1, 4
• Vitamin D3 and iron can be taken together—in fact, vitamin C (often found with iron) may enhance iron absorption 1

Dosage Safety Parameters

Ensure your supplement doses fall within safe ranges:

Magnesium Glycinate

• Recommended daily intake: 320 mg for women, 420 mg for men 1, 4
• Upper limit from supplements: 350 mg/day 1, 4
• Recent evidence suggests doses above 350 mg/day are well-tolerated without significant diarrhea risk 5
• Magnesium glycinate is better absorbed and causes fewer gastrointestinal side effects than magnesium oxide 6

Vitamin D3

• Recommended intake: 600-800 IU for adults under 70 years; 800-1000 IU for adults over 70 years 4
• Safe upper limit: 4,000 IU/day without medical supervision 1, 4
• Target serum 25-hydroxyvitamin D levels of 30-80 ng/mL 1

Vitamin B12

• Recommended intake: 2.4 µg/day 1, 4
• No established upper limit due to low toxicity risk 1

Iron

• Recommended intake: 8 mg/day for men and postmenopausal women; 18 mg/day for premenopausal women 1, 4
• Upper limit: 45 mg/day 1, 4
• Higher doses can cause gastrointestinal disturbances 1

Special Precautions

Renal Function

Check your kidney function before starting magnesium supplementation—magnesium is absolutely contraindicated if creatinine clearance is below 20 mL/min due to risk of life-threatening hypermagnesemia 1, 6

Medication Interactions

• If you take diuretics, digoxin, or proton pump inhibitors, discuss magnesium supplementation with your physician as these medications can affect magnesium levels 6
• Fluoroquinolone antibiotics may have interactions with magnesium 6

Monitoring

• For healthy adults taking standard doses, no routine monitoring is needed 4
• If you have gastrointestinal disorders, kidney disease, or take medications affecting mineral absorption, check magnesium levels 2-3 weeks after starting supplementation 6

Practical Administration Strategy

Optimal timing to maximize absorption and minimize interactions:

1. Morning: Take iron supplement with vitamin C or citrus juice (enhances iron absorption) 1
2. Evening: Take magnesium glycinate with vitamin D3 and vitamin B12 1, 6
3. Separate doses by at least 2 hours 1

Taking magnesium at night has the added benefit of potentially improving sleep quality and maximizing absorption when intestinal transit is slowest 6

Common Pitfalls to Avoid

• Don't take iron and magnesium together—this is the single most important interaction to avoid 1, 2, 3
• Don't exceed the upper limit of 350 mg/day for supplemental magnesium unless under medical supervision 1, 4
• Don't assume you need supplements—most healthy adults can obtain adequate vitamins and minerals through diet alone 1, 4
• Don't take magnesium if you have severe kidney disease (creatinine clearance <20 mL/min) 6

When Supplementation May Be Beneficial

Certain populations may benefit from this supplement combination 1, 4:

• Older adults over 65 years (all four supplements) 4
• Strict vegetarians (B12, iron, potentially magnesium) 1, 4
• Individuals on calorie-restricted diets (<1,500 kcal/day) 1, 4
• Premenopausal women (iron 18 mg/day) 4
• Those with limited sun exposure (vitamin D3) 1, 4