Magnesium Supplements: Benefits, Forms, Dosage and Safety
Magnesium is a mineral your body uses in more than 300 enzyme reactions. Supplements reliably fix low magnesium and relieve constipation, and they may modestly lower blood pressure and help prevent migraines. Most adults who supplement need 100–200 mg a day, and supplements alone shouldn't exceed 350 mg.
Evidence at a glance
| Use | Grade | What the research shows |
|---|---|---|
| Correcting low magnesium | A | Supplements raise levels in people with low intake or losses from medication. |
| Constipation (citrate, oxide) | A | Osmotic laxative effect is well established. |
| Lowering blood pressure | B | Meta-analyses show small reductions, larger in people who are deficient. |
| Migraine prevention | B | Included in some headache society guidance; evidence is moderate. |
| Sleep quality | C | Small trials, mostly in older adults; effects are modest. |
A: strong, consistent human evidence · B: moderate · C: limited or mixed · D: good evidence of no benefit.
Magnesium sits behind a surprising number of everyday functions: muscle contraction, nerve signals, heart rhythm, blood sugar control and bone structure. About half of US adults get less than they need from food, which is why magnesium is one of the most popular supplements.
What magnesium does
- Muscles and nerves: helps muscles relax after contracting and keeps nerve signals steady.
- Energy: needed to make and use ATP, the body's energy currency.
- Blood sugar: supports insulin signaling.
- Bones: about 60% of the body's magnesium is stored in bone.
Forms compared
| Form | Absorption | Gut effects | Typical use |
|---|---|---|---|
| Glycinate | Good | Gentle | Daily supplementing |
| Citrate | Good | Mild laxative | Daily use, constipation |
| Oxide | Low | Strong laxative | Constipation, antacid |
| Malate | Good | Gentle | Daily use |
| L-threonate | Moderate | Gentle | Marketed for brain health; early evidence |
For a deeper look at the two most popular forms, read magnesium glycinate vs citrate.
How much to take
Your target from food and supplements combined is 310–420 mg a day depending on age and sex. Supplements alone should stay at or below 350 mg unless a doctor recommends more. See the full table in how much magnesium per day.
Safety and interactions
The most common side effect is diarrhea, usually at higher doses. People with kidney disease shouldn't supplement without medical advice. Magnesium can bind to some antibiotics (tetracyclines, quinolones) and osteoporosis drugs (bisphosphonates), so separate them by at least 2 hours. Long-term proton pump inhibitors and some diuretics can lower magnesium levels.
Sources
This page is for education and is not a substitute for advice from your doctor. Read our medical disclaimer.