Magnesium Menu: Which Form Fits You?

With so many magnesium supplements on the shelf, it's hard to know whether you need one and which form to choose. This guide explains common forms, how to read the label dose and which side effects to watch for. 

Food first, well-dosed supplements second

Magnesium supports muscle and nerve function, and most people can get much of what they need from their regular diet. Ideally, food is your primary source of magnesium, with nuts, seeds, leafy greens and beans covering many people's needs and offering other nutritional benefits.

For adults, daily magnesium needs from food plus supplements are about 310-320 mg for women and 400-420 mg for men, depending on age. Needs are slightly higher during pregnancy. To put that in perspective, a banana, 8 ounces of low-fat yogurt, a quarter cup of peanuts, and a half cup each of cooked spinach, black beans and brown rice add up to about 317 mg, roughly what most women need in a day.

Magnesium supplements can fill gaps when you don’t get enough from food, but not everyone needs one. For adults, the daily upper limit from supplements and magnesium-containing medicines is 350 mg, unless a health care professional recommends otherwise. This limit does not include magnesium naturally found in food. 

“Too much magnesium from supplements or medicines can cause diarrhea, nausea and cramping,” said Edward Dix, Pharm.D., a pharmacist and system director of Pharmacy Services at Inspira Health. “Check the ‘magnesium’ amount per serving in the Supplement Facts panel. That is the elemental magnesium—the amount that counts toward your intake. Check the serving size, too, and include magnesium in any multivitamins, antacids or laxatives you use. Those with kidney disease are at higher risk of magnesium buildup and should talk to their health care professional before taking magnesium supplements or medicines.”

Different forms of supplements

Before putting a magnesium supplement into your routine, it helps to know what you're buying. Here's a clear look at the most widely available forms:

1. Magnesium glycinate: a common option

This form is often marketed as easy on the stomach and for sleep and relaxation. Some studies suggest a small sleep benefit, but evidence is still limited. It has not been shown to work better for sleep than other magnesium forms.

“If you need a supplement, magnesium glycinate may be an option to discuss with your pharmacist,” said Dr. Dix. “The dose and how well you tolerate it matter. No form is guaranteed to prevent stomach upset.”

2. Magnesium citrate: absorbed well, with a laxative effect

Magnesium citrate is generally absorbed better than magnesium oxide. It draws water into the intestines, so it is also used in medicines for occasional constipation. It may not be a good choice if loose stools are a problem for you. 

3. Magnesium oxide: budget-friendly but poorly absorbed

For an inexpensive option, some people turn to magnesium oxide.

“While this type is very common and often sold as an antacid or for constipation, it is poorly absorbed and can cause diarrhea,” shared Dr. Dix. “It can still be useful, but when the goal is to raise magnesium levels, a form that is more easily absorbed may be a better choice.”

4. Other forms: malate, threonate and chloride

Malate and threonate are marketed for various benefits, including muscle comfort and brain health. Human research has not established that they offer better health outcomes than other forms. Magnesium chloride is available in both oral and topical products. Oral chloride is generally absorbed better than oxide; evidence that topical sprays or creams reliably raise magnesium levels is lacking.

As with all supplements, you should avoid paying a premium for claims that outpace the research.

Before you buy: medication interactions and other considerations

Magnesium can reduce the absorption of certain antibiotics, such as tetracyclines and quinolones, and oral bisphosphonates for bone health. Ask your pharmacist how far apart to take them. The interval depends on the specific medicine, so one timing rule does not fit all situations. 

Some diuretics (water pills) and long-term use of proton pump inhibitors (acid reflux medicines) can lower magnesium levels. Ask your health care professional whether you need a blood test for magnesium. Bring your supplement bottle and a list of your medicines to your pharmacist to check for interactions. 

Taking magnesium with food may help limit stomach upset. Follow the product directions and any medication-spacing instructions from your pharmacist.

Talk with a pharmacist, physician or registered dietitian before starting a supplement, especially if you have kidney disease or take regular medicines. If you are pregnant, breastfeeding or considering a supplement for a child, ask your health care professional about the right dose. 

Learn more about the right supplements for your health with Inspira Nutrition Counseling.