Can You Take Magnesium and Vitamin C Together? The Short Answer

Since last winter's cold, a 1,000 mg vitamin C tablet has been part of your breakfast. Last month you added magnesium citrate, and to keep things simple, both go down with the same glass of water. Now your stomach gurgles by mid-morning. Can you take magnesium and vitamin C together, or is one of them working against the other?

Yes, you can take them together. We found no study showing that either one blocks the other's absorption, and no study that tested the pair at all: no evidence of a clash, and none of a special benefit. Magnesium and vitamin C do meet in one place, your gut. At high doses, both can cause diarrhea, nausea and cramps, so if your stomach objects, the amount you take in one sitting is the first thing to look at.

Do Magnesium and Vitamin C Interfere?

Not in any way we could find. Vitamin C does have a known absorption effect, but on a different mineral: the vitamin C fact sheet from the NIH Office of Dietary Supplements (ODS) notes that it improves the absorption of nonheme iron (our iron and vitamin C page covers that pairing). We found no study showing that vitamin C does anything similar for magnesium, or that magnesium changes how much vitamin C you absorb.

For magnesium, the ODS magnesium fact sheet ties absorption to the form instead. Forms that dissolve well in liquid are absorbed better, and the aspartate, citrate, lactate and chloride forms "tend to have higher bioavailability than magnesium oxide and magnesium sulfate." The interactions ODS flags for magnesium involve medicines, which we cover under dosage below.

So for magnesium and vitamin C, timing comes down to your stomach and your schedule, not to absorption.

Where They Overlap: Diarrhea and Cramps

The two fact sheets describe nearly the same side effects. ODS says that "high doses of magnesium from dietary supplements or medications can cause diarrhea, nausea, and abdominal cramping," and that "high doses of vitamin C can lead to diarrhea, nausea, abdominal cramps, and other gastrointestinal disturbances."

We found no study that measured the two together, so nobody can say whether those effects add up. Still, if you take vitamin C and magnesium together in large doses and your stomach complains, the shared side effect is the obvious first suspect, and the dose per sitting is the easiest thing to change.

It deserves extra thought if you take magnesium citrate partly to stay regular (our guide to magnesium citrate for constipation covers that use). You are already counting on magnesium to loosen things, and a large vitamin C dose on top may push in the same direction.

What Each One Does

Neither needs the other to do its job.

Magnesium plays a role in moving calcium and potassium across cell membranes, a process ODS describes as important for nerve signals, muscle contraction and a normal heart rhythm. Recommended intakes for adults range from 310 to 420 mg a day. Citrate is only one of the forms sold; our magnesium glycinate page covers another.

Vitamin C "plays an important role in immune function," according to ODS, and it helps with nonheme iron, as above. One popular habit does not hold up, though: ODS notes that vitamin C taken after cold symptoms start does not appear to affect how long the cold lasts or how severe it gets. Our article on vitamin C and colds goes through what it can and cannot do.

Practical Recommendations

None of this has been tested as a routine; it follows from the two fact sheets.

• Take them together if one reminder suits you. We found nothing that calls for a gap between them or ties either one to a particular hour. For magnesium's own timing questions, see our guide to the best time to take magnesium.
• Add up every source. A multivitamin or blend that lists magnesium or vitamin C counts toward the daily limits below.
• If your stomach complains, split them first. Try vitamin C with breakfast and magnesium with dinner or at bedtime, and change one thing at a time so you can tell which change helped. If that is not enough, take the magnesium as two smaller doses instead of one large one.
• Look at the form if you take citrate for regularity. If loose stools are the problem, ask a pharmacist whether a different form would suit you better. Our comparison of magnesium glycinate and oxide explains how the common forms differ.
• Skip the extra vitamin C when a cold starts. A few extra grams at the first sniffle can take you past the adult limit, and by the ODS account a late start does not appear to shorten the cold anyway.
• If you also take iron, pair the vitamin C with the iron. That is where ODS describes an absorption benefit for it.

Dosage Considerations

Magnesium: the magnesium upper limit for adults is 350 mg a day, per the ODS magnesium fact sheet, and 65 to 350 mg for children and adolescents, depending on age. It covers magnesium from supplements and medicines, not from food, which is why it can sit below the recommended intake. Any medicine that lists magnesium among its ingredients counts toward it.

Vitamin C: the vitamin C upper limit is 2,000 mg a day for adults, per the ODS vitamin C fact sheet, and lower at younger ages (as low as 400 mg, depending on age). A 1,000 mg tablet is half the adult limit, so a second one at the first sign of a cold uses up the rest.

Who should check first:

• People with kidney disease. The kidneys regulate magnesium, so ask your doctor before taking it.
• People who have had kidney stones. ODS mentions kidney stones and excess iron absorption as concerns with vitamin C, and says they are "not generally considered a risk in healthy individuals." That reassurance is written for healthy people. If you have had a stone, or have been told you absorb too much iron, ask your doctor before taking high doses.
• People on certain medicines. ODS notes that magnesium may interact with oral bisphosphonates and with tetracycline and quinolone antibiotics, so ask your pharmacist how far apart to take them. Diuretics and proton pump inhibitors can affect magnesium status, so tell the prescriber about your magnesium supplement.

Key Takeaway

You can take magnesium and vitamin C together: we found no conflict between them and no study of the pair. The one place they overlap is your gut, since high doses of either can cause diarrhea, nausea and cramps. For adults, keep supplemental magnesium within 350 mg a day and vitamin C within 2,000 mg. If your stomach still objects, split them between morning and evening before you drop either one.

Track Your Timing

Supplement Tracker sorts your supplements into time-of-day slots, each with its own reminder time, so vitamin C can sit in the morning and magnesium in the evening if you split them. Check off each dose as you take it, and the dated history shows what you took on the days your stomach complained.