Magnesium: Do You Need a Supplement?

Magnesium supplements are marketed for almost everything: sleep, stress, cramps, headaches and energy. That makes it hard to tell whether you need one or whether you are paying for a tablet your diet already covers.

This article explains what magnesium does, how much you need, who is more likely to run low, what supplements can and cannot do, and how to take one safely. It can help you decide on a next step, but it cannot tell you whether your own levels are low.

What does magnesium do in the body?

Magnesium is a mineral your body uses in hundreds of chemical reactions. According to the NIH Office of Dietary Supplements (ODS), it helps regulate muscle and nerve function, blood sugar, blood pressure, and the making of protein, bone and DNA.

Most of the magnesium in your body is stored in your bones, and only a small share circulates in your blood. Your kidneys keep blood levels in a narrow range by holding on to more or letting more go. That is one reason a blood test can look normal even when your body stores are on the low side.

Magnesium is one of many nutrients that work together. For a broader look at eating patterns that cover your needs, see our nutrition and wellness guide.

How much magnesium do you need each day?

Adult men need about 400 to 420 mg of magnesium a day, and adult women need about 310 to 320 mg, according to the Recommended Dietary Allowances (RDAs) published by ODS. Needs are slightly higher during pregnancy.

There is also a Tolerable Upper Intake Level (UL), the most you can take daily without likely harm. For adults, the UL is 350 mg a day from supplements and medicines. It does not apply to magnesium in food, because the kidneys clear extra dietary magnesium in healthy people.

Which foods are high in magnesium?

Nuts, seeds, beans, leafy greens and whole grains are the richest everyday sources. ODS lists pumpkin seeds, chia seeds, almonds, spinach, cashews, peanuts, black beans, edamame, soy milk, and whole wheat bread among good sources.

• Seeds and nuts: pumpkin seeds, chia seeds, almonds, cashews, peanuts and peanut butter.
• Beans and soy: black beans, kidney beans, edamame, tofu and soy milk.
• Leafy greens: spinach and other dark greens.
• Whole grains: oatmeal, brown rice, whole wheat bread and some fortified breakfast cereals.
• Other foods: potatoes with skin, yogurt, bananas, avocado and salmon.

Many of these foods are also high in fiber, and refining grains strips much of their magnesium. Our piece on the fiber most people are missing shows how the same swaps raise both. The Dietary Guidelines for Americans note that many people fall short on magnesium-rich foods, so a handful of nuts or a bowl of beans is often the simplest fix.

Who is more likely to run low on magnesium?

Healthy people rarely develop a true deficiency, because the kidneys limit how much is lost in urine. A long period of low intake, or a condition that increases losses, is usually needed. ODS names several groups at higher risk.

If you are in one of these groups, ask your doctor whether your magnesium has been checked. A supplement may be reasonable, but the underlying cause matters more.

What are the signs of low magnesium?

Early low magnesium may cause loss of appetite, nausea, vomiting, fatigue and weakness. As it gets worse, symptoms can include numbness, tingling, muscle cramps, seizures, personality changes, and abnormal heart rhythms.

Many of these early signs are vague and have dozens of other causes. Night cramps, for example, are common and usually not caused by low magnesium; our article on leg cramps at night covers the more likely reasons. Low magnesium can also make low calcium and low potassium harder to correct, which is one reason doctors often check them together.

Do not try to diagnose a deficiency from symptoms alone. A blood test is the usual starting point, and your doctor can interpret it alongside your health history and medicines.

Can a magnesium supplement help with sleep, cramps or migraine?

The evidence is mixed. Magnesium is often promoted for sleep, muscle cramps, anxiety and migraine, but good-quality studies do not show a clear benefit for most people who already get enough from food.

• Sleep: some small studies, mostly in older adults, suggest a possible modest benefit, but the research is limited. Sleep habits usually matter more; see our guide to why you cannot sleep.
• Muscle cramps: reviews have generally found magnesium unlikely to help typical leg cramps in older adults. Evidence in pregnancy is mixed.
• Migraine: some people with migraine have lower magnesium levels, and magnesium is sometimes used as part of migraine prevention. Talk to your doctor before trying it, especially if you are pregnant.
• Blood pressure and blood sugar: studies suggest a possible small effect, mainly in people who were low to begin with. A supplement is not a replacement for prescribed treatment.

If a supplement makes you feel better, that is worth discussing with your doctor rather than assuming a deficiency caused your symptoms.

What types of magnesium supplements are there?

Supplements come in several forms, and the amount your body absorbs varies. ODS notes that some studies find magnesium aspartate, citrate, lactate and chloride are absorbed more completely than magnesium oxide and sulfate.

Check the label for elemental magnesium, the amount of the mineral itself, rather than the total weight of the compound. Many multivitamins contain some magnesium, so add that in. If you are wondering whether a broader product makes more sense, see our article on whether you need a multivitamin.

The FDA does not approve dietary supplements for safety or effectiveness before they are sold. Look for a third-party quality seal, such as USP, which checks that the product contains what the label says.

Is it possible to take too much magnesium?

Yes. Too much magnesium from supplements or medicines commonly causes diarrhea, nausea and stomach cramps. Very high doses can lead to magnesium toxicity, with symptoms such as low blood pressure, facial flushing, muscle weakness, confusion, irregular heartbeat and, rarely, cardiac arrest.

People with kidney disease are at highest risk, because their kidneys cannot remove the excess. Large doses of magnesium-containing laxatives and antacids have caused toxicity, so count those products toward your total.

Magnesium can also interact with medicines. It can reduce absorption of some antibiotics (tetracyclines and quinolones) and bisphosphonates used for osteoporosis, so separate the doses as your pharmacist advises. Some diuretics and long-term acid-reducing drugs can lower magnesium, while others can raise it.

When should you talk to your doctor?

Talk to your doctor or pharmacist before starting a magnesium supplement if you have kidney disease, heart rhythm problems, a gut condition, or take prescription medicines. A registered dietitian (RD or RDN) can help you plan meals that cover your needs from food.

See your doctor if you have ongoing fatigue, weakness, numbness, tingling or muscle twitching. These symptoms have many possible causes, and a simple blood test can check magnesium along with calcium, potassium and other markers.

Call 911 or go to the emergency room if you have a seizure, a fast or irregular heartbeat with dizziness or fainting, chest pain, severe muscle weakness, or confusion, especially after taking large doses of magnesium supplements, laxatives or antacids.

How can you get more magnesium from food?

The easiest way is to swap in a few magnesium-rich foods you already like, rather than overhauling your diet. Small, regular changes add up over a week.

• At breakfast: choose oatmeal or a whole grain cereal, and top it with a spoonful of chia or pumpkin seeds.
• At lunch: use whole wheat bread instead of white, and add spinach or other dark greens to a sandwich or salad.
• At dinner: add black beans, kidney beans, tofu or edamame to a stir-fry, soup or bowl, and try brown rice in place of white.
• For snacks: a small handful of almonds, cashews or peanuts, a banana, or yogurt.

MyPlate suggests making half your grains whole grains and varying your protein foods to include beans, nuts and seeds. Following that pattern naturally raises magnesium along with fiber and potassium. Food also carries no risk of the diarrhea that larger supplement doses often cause in healthy people.

So, do you need a magnesium supplement?

For most healthy adults, the answer is probably no. A varied diet with nuts, seeds, beans, greens and whole grains usually meets the RDA without a pill.

A supplement may be worth discussing if you have a condition or take medicines that lower magnesium, if you are older and eat little, or if a blood test shows a low level. If you do take one, keep supplemental magnesium under 350 mg a day unless your doctor advises a different amount, and tell your doctor and pharmacist so they can check for interactions.