Our Members Asked:
How much magnesium do I need and how much magnesium from supplements is too much?
How much magnesium do I need and how can I get enough?
A healthy diet can provide the recommended daily intake of magnesium, which, for men and women age 30 or older, is 420 mg and 320 mg, respectively, per day (use the table below for recommended intakes for all ages).
- Dietary Reference Intakes (DRIs): Recommended Dietary Allowances and Adequate Intakes from the National Academies
- Daily Values from FDA Food Labeling: Revision of the Nutrition and Supplement Facts Labels 2016
- ULs (Tolerable Upper Intake Levels) from Dietary Reference Intakes (DRIs): Tolerable Upper Intake Levels, Vitamins from the National Academies
- * - Adequate Intake (AI)
- mg - milligram (1,000 milligrams = 1 gram)
- mcg - microgram (1,000 micrograms = 1 milligram)
- NE - DV not established
- ND - UL not determined
- m - male; f - female
- lact - lactating (breast feeding); preg - pregnant
- Age ranges are in years
Good sources of dietary magnesium include nuts such as almonds and peanuts, and foods such as spinach, black beans, and potatoes. See a list of foods that provide magnesium in our Magnesium Supplements Review.
However, if you are not getting enough magnesium from your diet, it may be beneficial to take a supplement that will provide, for example, 200 mg to safely get you to the recommended intake. See our Top Picks among magnesium supplements.
Having low and/or deficient blood levels of magnesium may increase the risk of osteoporosis, elevated blood pressure, and heart disease.
Early signs of magnesium deficiency include loss of appetite, nausea, vomiting, fatigue, and weakness. Low serum magnesium levels can also result in serious adverse events including muscle spasm (tetany), irregular heartbeat (arrhythmias), and convulsions (seizures); however, patients do not always have these symptoms. Severe magnesium deficiency is rare. See the What It Does section of our Magnesium Supplements Review for more information.
Tests for magnesium deficiency
There are a number of tests designed to measure magnesium levels, however, most (including the most common test, serum magnesium concentration, or SMC) do not provide a complete assessment of magnesium status. For this reason, doctors use a combination of testing and evaluation of symptoms to diagnose magnesium deficiency. These include the serum magnesium concentration (SMC) test, the red blood cell (RBC) test, the magnesium loading test, the 24-hour excretion test, and others. You can find more information about these tests in the ConsumerTips section of the Magnesium Supplements Review.
Risks of getting too much magnesium
The daily Tolerable Upper Intake Level (UL) for magnesium for adults is 350 mg. However, the magnesium one consumes from food does not count toward the UL; only magnesium from supplements and medicine can cause adverse effects and counts toward this limit. So, as long as you're not getting more than 350 mg of magnesium per day from supplements and/or medicine and are getting some magnesium from foods (like whole grains, nuts, beans, and green leafy vegetables) you can satisfy the RDA without exceeding the UL.
Even at moderate doses, magnesium from supplements can cause side effects such as stomach upset, nausea, vomiting and diarrhea. This does not happen with magnesium obtained naturally from foods.
Know that slightly high blood levels of magnesium have been associated with cardiovascular risks, and very high blood levels of magnesium, known as hypermagnesemia, can cause more serious symptoms such as low blood pressure and slowed breathing, and can be fatal. Although uncommon, hypermagnesemia can occur with excessive intake of magnesium-containing laxatives or supplements, and has also been reported in people ingesting or gargling with large quantities of Epsom salt (magnesium sulfate). Magnesium supplements can be dangerous in people with kidney disease and should only be used with physician supervision.
If you are not taking magnesium specifically for its laxative effect, there are forms which are less likely to cause diarrhea. Also, be aware magnesium-containing supplements and laxatives can interact with certain medications.