A complete safety, timing, and dosage guide for combining Selenium with Magnesium (Citrate, Glycinate, Oxide, Threonate) — including how the two supplements interact, the best time of day to take each, and which populations should be careful.
Yes, you can take magnesium and selenium together safely. They have no significant interaction, and combining them is common in mineral supplements.
Magnesium (Citrate, Glycinate, Oxide, Threonate) and Selenium together are safe to combine. There is no evidence that they affect each other's absorption or function, so you can take them in the same daily routine without concern.
Magnesium is absorbed mainly in the small intestine through transient receptor potential channels (TRPM6/7), while selenium is absorbed as selenomethionine, selenocysteine, or selenite via amino acid and other transporters. These pathways are independent, so there is no competition for absorption. Once inside the body, magnesium acts as a cofactor for ATP and enzyme reactions, while selenium is incorporated into selenoproteins like glutathione peroxidase and thioredoxin reductase. Neither mineral requires the other for its activation, and they do not share a common rate-limiting step. As a result, taking both together does not create a meaningful biochemical interaction.
If you are taking both daily, the simplest approach is to take them together with a balanced meal — breakfast or lunch works well. For magnesium, choose a form like citrate or glycinate and take it with food to minimize stomach upset; for selenium, take it as selenomethionine with the same meal. If you prefer a split routine, take selenium in the morning with breakfast and magnesium in the evening with dinner or before bed. There is no required spacing, but if you are taking a multivitamin or separate zinc/iron/calcium supplements, aim to take those at a different time of day, ideally at least two hours apart from magnesium. If you miss a dose, just resume at your next scheduled time; do not double up. When you refill, compare labels so your combined selenium intake from supplements stays under 200 mcg daily unless your healthcare provider directs otherwise.
The form of magnesium you take — citrate, glycinate, oxide, or threonate — changes how well it is absorbed and tolerated, but it does not affect selenium handling. If you choose magnesium oxide, note that it is less bioavailable and more likely to cause loose stools, while glycinate and threonate tend to be gentler and better absorbed. Selenium form also matters on its own: selenomethionine is absorbed more efficiently than sodium selenite, but this is unrelated to magnesium. For both supplements, absorption and safety depend on the specific salt or chelate, not on the presence of the other mineral.
In clinical practice, magnesium and selenium are not a classic pairing, but both frequently appear in broad-spectrum multivitamins, trace mineral formulas, and thyroid support products. You will also see them together in bone health and cardiovascular formula stacks, though usually with calcium, vitamin D, or zinc.
Yes, you can take them at the same time. They do not compete for absorption, and taking them together with a meal is totally fine. I often recommend this for simplicity.
Yes, it is safe to combine them daily. Both are essential minerals with recommended daily intakes, and there is no known interaction between them. Just keep total selenium from all sources below 400 mcg per day.
You do not need to wait any specific time between them. Since they do not interfere with each other, you can take them at the same meal or a few hours apart, whichever is more convenient.
No, they do not compete for absorption. Magnesium uses TRPM6/7 channels in the small intestine, while selenium is absorbed through separate amino acid and anion transporters. Their pathways are independent, so taking both is unlikely to reduce the amount you absorb.
Most people can take them together safely. However, if you have advanced kidney disease, you should avoid magnesium supplements unless your doctor approves. Also, if you have a history of selenium toxicity or thyroid cancer, discuss selenium supplementation first, since high doses can be risky.
I recommend taking both with food. Magnesium, especially oxide, can cause stomach upset or diarrhea on an empty stomach, and selenium is better absorbed when eaten with a meal that contains protein. If you take them together, a balanced meal works well.
Reviewed by Caroline M. on April 27, 2026 for accuracy against the sources listed above. This page is educational and is not a substitute for professional medical advice.
The matrix has 86 supplements and 7310 pairwise interactions. Click any cell to see the full breakdown.