What Type of Magnesium Should I Take: Forms and Selection Guide

How Magnesium Forms Differ

Magnesium in dietary supplements comes in several distinct chemical forms. Specifically, the ODS identifies magnesium aspartate, magnesium citrate, magnesium lactate, and magnesium chloride as forms that are more easily absorbed by the body. The ODS reports that roughly 30% to 40% of the dietary magnesium consumed is typically absorbed by the body. The ODS fact sheet does not list magnesium glycinate, magnesium threonate, magnesium oxide, magnesium malate, or magnesium taurate among its identified more absorbable forms. If you want to evaluate two commonly discussed options, review our breakdown on magnesium glycinate vs citrate. For questions about testing or signs of low intake, review our articles on magnesium levels and magnesium deficiency symptoms.

How Much Magnesium Adults Need

Daily requirements vary by age and sex:

• Men aged 19 to 30 years require an RDA of 400 mg per day.
• Men aged 31 years and older require an RDA of 420 mg per day.
• Women aged 19 to 30 years require an RDA of 310 mg per day.
• Women aged 31 years and older require an RDA of 320 mg per day.

Requirements during pregnancy and lactation differ, and individuals in those life stages should consult the NIH ODS: Magnesium fact sheet for health professionals for exact targets. As noted in our guide on vitamin D and K2, magnesium is necessary to activate vitamin D in the body. Dietary sources that supply magnesium include leafy greens, nuts, seeds, legumes, and whole grains. The upper limit does not apply to magnesium from food.

Matching a Form to Your Goal

Selecting a magnesium supplement depends primarily on your individual objective, digestive sensitivity, and whether you want a form verified by the ODS as more easily absorbed. If higher gastrointestinal absorption is your priority, selecting among the forms named by the ODS (magnesium aspartate, magnesium citrate, magnesium lactate, or magnesium chloride) is one place to start. For dedicated explorations of individual topics, see our related guides:

• For threonate, read about magnesium threonate benefits.
• For sleep, visit our guide on magnesium for sleep.
• For cramps, see our guide on magnesium for leg cramps.
• For glycinate versus citrate, check our page on magnesium glycinate vs citrate.

Side Effects and Dose Limits

The Tolerable Upper Intake Level (UL) for magnesium from dietary supplements and medications is 350 mg per day for adults. This limit applies strictly to supplements and medications. It does not apply to magnesium from food. High doses of magnesium from supplements or medications often cause diarrhea, which may be accompanied by nausea and abdominal cramping. The ODS warns that very large doses of magnesium-containing laxatives and antacids, typically exceeding 5,000 mg per day, have been directly associated with magnesium toxicity.

Medicines and Conditions That Change the Choice

Certain prescription medications interact with supplemental magnesium. The ODS outlines specific separation windows and interactions:

• Oral bisphosphonates and magnesium-rich supplements should be separated by at least 2 hours.
• Tetracycline and quinolone antibiotics should be taken at least 2 hours before or 4 to 6 hours after taking a magnesium-containing supplement.
• Loop and thiazide diuretics can increase urinary magnesium loss.
• Proton pump inhibitors taken for prolonged periods, typically more than a year, can cause low blood magnesium levels.

Healthy kidneys remove excess magnesium in urine. The risk of magnesium toxicity increases in people with impaired kidney function or kidney failure. Anyone with kidney disease should only take magnesium supplements under direct medical supervision.