You can take iron and magnesium on the same day, and a simple split keeps them out of each other's way: iron in the morning on an empty stomach or as prescribed, magnesium in the evening. The concern is mostly about form. In lab tests, poorly soluble magnesium compounds used as antacids (magnesium oxide and magnesium trisilicate) neutralized acid and drastically cut the amount of dissolved iron, while a soluble magnesium salt did not. The human data are milder: a liquid aluminum and magnesium hydroxide antacid did not significantly reduce iron absorption in a 1986 study, while calcium carbonate cut the rise in plasma iron by 67%. MedlinePlus advises waiting at least 2 hours after an antacid before taking iron. We found no study testing magnesium glycinate with iron. Adult upper limits: 45 mg a day for iron, 350 mg a day for supplemental magnesium.
This content is for informational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always consult your physician or qualified healthcare provider before starting any supplement regimen.
Pair checker
Can I take these together?
Yes, on the same day, but take them at different times: magnesium oxide and magnesium antacids may bind iron.
Why
Neither NIH fact sheet lists iron and magnesium as an interaction. In lab tests, poorly soluble antacid forms (magnesium oxide, trisilicate) neutralized acid and sharply cut dissolved iron while a soluble magnesium salt did not, and a 1986 human study found a magnesium and aluminum hydroxide antacid did not significantly reduce iron absorption.
Timing
Take iron in the morning on an empty stomach and magnesium in the evening. If your magnesium is oxide or an antacid, MedlinePlus advises waiting at least 2 hours after antacids before taking iron.
Sources
Check your whole list, not just one pair
Supplement Tracker checks every supplement you take against the others and reminds you of each dose at its own time.
A low ferritin result brings an iron tablet into the routine, and the magnesium glycinate that was already there for sleep or cramps is not going anywhere. So the question is a practical one: can you take iron and magnesium together, or do they need separate times?
You can take both on the same day. The real answer depends on which magnesium you mean. Magnesium oxide and magnesium antacids may bind iron in the gut, while for a soluble form such as glycinate we found no study showing a problem. Because iron does best in the morning and magnesium is usually taken in the evening, giving each its own time of day costs nothing and settles the question.
Do Iron and Magnesium Interfere?
Neither NIH fact sheet lists the other mineral as an interaction. The NIH iron fact sheet names calcium: experts recommend taking calcium and iron supplements at different times to avoid potential interference with iron absorption. It also says proton pump inhibitors can potentially reduce iron absorption. The NIH magnesium fact sheet lists interactions with medications such as oral bisphosphonates, tetracyclines, and quinolone antibiotics, not with iron.
What the magnesium fact sheet does point out is that magnesium is an ingredient in some medicines, including heartburn remedies and laxatives. That matters here, because the research on magnesium and iron is almost entirely about the antacid forms.
The mechanism is about acid. Iron salts dissolve and stay available best in an acidic stomach. Magnesium oxide and magnesium trisilicate neutralize acid, which is exactly why they are sold as antacids, and poorly soluble particles like these can also bind iron on their surface.
What the Research Says
Lab tests point at the antacid forms. A 1994 in vitro study by Disch and colleagues mixed ferrous gluconate with three magnesium compounds under conditions that simulated the changing pH of the gut. The two poorly soluble antacid compounds, magnesium oxide and magnesium trisilicate, had a potent neutralizing effect and caused a drastic drop in the amount of dissolved iron. A readily soluble salt, magnesium aspartate hydrochloride, barely shifted the pH and caused no drop. The authors concluded that poorly water-soluble magnesium compounds have a high capacity to adsorb iron and so interfere with its absorption. This was a test tube, not a person.
Human studies are milder. A 1986 JAMA study by O'Neil-Cutting and Crosby used a small-dose iron tolerance test to compare iron taken alone and with antacids. A liquid antacid containing aluminum hydroxide and magnesium hydroxide did not significantly decrease iron absorption. Sodium bicarbonate and calcium carbonate did: the rise in plasma iron was 50% and 67% smaller than in the control trials. A 1999 randomized trial in 16 healthy men gave a large iron dose followed by magnesium hydroxide half an hour later and found no difference in serum iron levels. That trial tested an overdose scenario, not an ordinary supplement.
The practical guidance treats antacids as a timing issue. MedlinePlus says milk, calcium, and antacids should not be taken at the same time as iron supplements, and advises waiting at least 2 hours after them before taking iron. A 2025 practical guide to oral iron dosing likewise lists antacids among the things that reduce iron absorption and recommends a morning dose on a fasting stomach.
The gap in the evidence. We found no study that tested magnesium glycinate, citrate, or any other ordinary magnesium supplement taken together with iron. The lab finding for a soluble magnesium salt is reassuring, but it is one salt in one test-tube setup.
Practical Recommendations
This is our suggested routine, not a tested protocol.
- Take iron in the morning on an empty stomach, or on the schedule your prescriber gave you. MedlinePlus notes that a small amount of food is fine if iron upsets your stomach. Vitamin C or orange juice with the iron may help; see our iron and vitamin C page.
- Take magnesium in the evening. That suits most reasons people take it, and our guide to the best time to take magnesium covers the details by form.
- Treat magnesium oxide and magnesium antacids like an antacid. If your magnesium is oxide, a heartburn tablet, or milk of magnesia, wait at least 2 hours after it before taking iron, as MedlinePlus advises for antacids.
- Check combination products. Some magnesium supplements also contain calcium. Calcium is the mineral the NIH does recommend keeping apart from iron; our iron and calcium page covers that spacing.
- Watch the medications. Iron, magnesium, or both can interact with levothyroxine, tetracycline and quinolone antibiotics, and oral bisphosphonates. Ask your pharmacist for the gap that applies to your prescription.
Dosage Considerations
Iron: the upper limit for adults is 45 mg a day, according to the NIH iron fact sheet. If your iron was prescribed for a diagnosed deficiency, the dose and schedule are your prescriber's call.
Magnesium: the upper limit for supplemental magnesium is 350 mg a day for adults, according to the NIH magnesium fact sheet. The limit applies to supplements and medicines, not to magnesium from food. High doses can cause diarrhea, nausea, and abdominal cramping. The same fact sheet notes that citrate, chloride, lactate, and aspartate forms tend to be absorbed better than oxide and sulfate.
Who should check first:
- People with hemochromatosis or another form of iron overload. Talk to your doctor before taking any iron supplement.
- Anyone taking iron without a confirmed deficiency. Our guide to who actually needs iron supplements explains what to test first.
FAQ
Can you take iron and magnesium at the same time?
For a soluble form like glycinate, we found no study showing a problem, but we also found none testing the pair. With magnesium oxide or a magnesium antacid, lab data suggest it may bind iron, and MedlinePlus advises waiting at least 2 hours after an antacid before iron. Different times of day is the simple answer.
Can I take iron and magnesium glycinate together?
No study has tested magnesium glycinate with iron. In a lab test, a soluble magnesium salt did not reduce dissolved iron, unlike magnesium oxide. If you can, still take iron in the morning and glycinate in the evening.
Can I take iron and magnesium together at night?
Magnesium at night is a common choice. Iron is better taken in the morning on an empty stomach; a 2025 dosing guide notes that absorption is markedly reduced when iron is taken in the afternoon. If night is the only time you can take iron, take it as your prescriber advises and keep magnesium antacids out of that slot.
Does magnesium oxide block iron absorption?
In a test-tube study, magnesium oxide drastically reduced the amount of dissolved iron. A 1986 human study found that a liquid magnesium and aluminum hydroxide antacid did not significantly reduce iron absorption. The human data are limited, so spacing them is the cautious choice.
Key Takeaway
You can take iron and magnesium on the same day; it is the timing and the form that matter. Magnesium oxide and magnesium antacids may bind iron, so give them at least 2 hours before iron, the gap MedlinePlus advises for antacids. For magnesium glycinate there is no study either way. Iron in the morning and magnesium in the evening keeps both clear of the question.
Track Your Timing
Supplement Tracker lets you schedule iron as a morning dose and magnesium as an evening dose, each with its own reminder. Your history then shows how consistently you took each one, which is useful when the next blood test comes back.
