Quick answer

Yes. In a one-week pilot of eight adults, urine magnesium, a rough sign of absorption, rose by 33.6 mg a day when magnesium was taken with meals against 21.8 mg when fasting. Magnesium oxide needs stomach acid to dissolve, and some foods lower magnesium uptake while others raise it.^1,2,3

Key facts

Even at peak stomach acid levels, only 43% of magnesium oxide dissolved in laboratory tests, while citrate dissolved well in plain water.²
One L-threonate trial let people take their capsules with or without food.⁴
Protein and some carbohydrates, such as inulin, raise magnesium uptake; phytate and oxalate lower it.³
Zinc in very high doses, 142 mg a day in one study, can interfere with magnesium absorption.⁵

With a meal or fasting?

In a one-week pilot study of eight adults under medical care, urine magnesium rose by 33.6 mg a day in those who took magnesium with meals and by 21.8 mg in those who took it fasting, a rough sign of more absorption with meals.¹

That pilot is the only direct comparison we found. It was tiny, lasted a week and measured urine rather than blood, so it is a hint rather than proof. We found no study that compared stomach upset with and without food.¹

The classic study of how much magnesium the gut takes up gave it with a standard meal, and the trials of individual forms differed: one L-threonate trial allowed either way, while one comparison of forms used an overnight fast.^4,6,7

Magnesium oxide and stomach acid

In laboratory tests, magnesium oxide barely dissolved in water and only 43% dissolved at peak stomach acid levels, while magnesium citrate dissolved well even in plain water.²

Oxide has to be dissolved by stomach acid before its magnesium can be absorbed, and that study found it both less soluble and less well absorbed than citrate. In another study only about 4% of the magnesium in oxide was absorbed.^2,8

Citrate, which dissolved well even in plain water, depends far less on stomach acid. Oxide, by contrast, is sold as an antacid in its own right.^2,9

What in a meal changes uptake

What else is in a meal changes how much magnesium is taken up. Phytate, oxalate, some kinds of fiber and high doses of other minerals lower uptake; protein, medium-chain fats and some carbohydrates, such as inulin and resistant starch, raise it.³

Very high doses of zinc from supplements, 142 mg a day in one study, can interfere with magnesium absorption.^5,10

In the same absorption study that tested almonds, magnesium from an enteric-coated magnesium chloride tablet was absorbed much less well than from a dissolved salt.⁶

The same review names the dose as one of the biggest factors in how much is absorbed, which is easier to control than what is on the plate.³

Citrate, malate and L-threonate on an empty stomach

We found no study that tested citrate, malate or L-threonate with and without food. Citrate dissolves without acid, so an empty stomach should matter less for it than for oxide, and liquid citrate laxative labels ask for a full glass of liquid with each dose.^2,11

What's in ours

What’s in ours

Magnesium Glycinate: Magnesium, 275 mg per serving, from the label
Men's Multi: Magnesium, 50 mg per serving, from the label
Creatine + Electrolytes: Magnesium, 60 mg per serving, from the label

Food does not fix medicine timing

Food is not a substitute for spacing. NIH's advice on antibiotics and bisphosphonates, and the antacid warnings on the gabapentin and levothyroxine labels, are about timing, so ask your pharmacist how to fit magnesium around those medicines.^10,12,13

Long-term use of acid reducers called proton pump inhibitors can itself lower blood magnesium, so tell your doctor if you take one along with magnesium.^5,14

Questions people ask

Should I take magnesium with food to avoid an upset stomach?

No study we found tested that. Loose stools and stomach upset become more likely as the dose rises, so a smaller dose is the step with evidence behind it.⁵

Can I take magnesium with milk or coffee?

The sources here do not test either. Milk itself provides 27 mg of magnesium a cup.⁵

See what we make

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See the Full Measure line Creatine + Electrolytes Magnesium Glycinate Men's Multi

Sources

This page is information, not medical advice. Talk to your doctor or pharmacist about your own situation.