Calculate the elemental magnesium you actually absorb from glycinate, citrate, oxide, and other forms. Two products labeled “500 mg magnesium” can deliver wildly different elemental amounts. Math, not medical advice.
Your situation
400 mg/day
Target elemental magnesium for your situation
2,857 mg
Equivalent dose of magnesium glycinate on the label
magnesium glycinate is ~14% elemental magnesium. To get 400 mg of actual Mg you need 2,857 mg of the compound on the label.
Reference: elemental magnesium content by form
| Form | Elemental Mg % | Best for | Trade-offs |
|---|---|---|---|
| Glycinate | ~14% | Sleep, anxiety, sensitive stomach | Lower elemental — needs larger pills |
| Citrate | ~16% | General use, mild constipation | Mild laxative effect at higher doses |
| Malate | ~15% | Energy, fibromyalgia symptom support | Limited human RCT data |
| L-Threonate | ~8% | Cognition (crosses blood-brain barrier in vitro) | Expensive; cognitive RCTs limited |
| Taurate | ~9% | Cardiovascular, blood pressure adjunct | Few comparative trials |
| Orotate | ~7% | Athletic performance (limited data) | Most expensive; lowest elemental |
| Oxide | ~60% | Cheapest source of elemental Mg, occasional constipation | ~4% bioavailable orally; mostly laxative |
| Chloride | ~12% | Topical (sprays, baths) and oral | Salty taste; topical absorption claims weak |
| Lactate | ~12% | Slow-release, lower GI distress | Avoid with kidney disease |
| Sulfate (Epsom) | ~10% | Baths, IV use only — NOT for oral supplementation | Strongly laxative orally |
RDA reference (Institute of Medicine)
| Group | RDA mg/day | UL (supplemental only) |
|---|---|---|
| Males 14-18 | 410 | 350 |
| Males 19-30 | 400 | 350 |
| Males 31-50 | 420 | 350 |
| Males 51+ | 420 | 350 |
| Females 14-18 | 360 | 350 |
| Females 19-30 | 310 | 350 |
| Females 31-50 | 320 | 350 |
| Females 51+ | 320 | 350 |
| Pregnant 14-18 | 400 | 350 |
| Pregnant 19-30 | 350 | 350 |
| Pregnant 31-50 | 360 | 350 |
| Lactating 14-18 | 360 | 350 |
| Lactating 19-50 | 320 | 350 |
UL applies to supplemental magnesium only. Magnesium from food has no UL because food sources don’t cause the GI distress that supplements do at the same elemental dose.
Use-case adjustments
- Sleep: Most RCTs use 200-400 mg elemental Mg in the evening. Glycinate is the most-cited form (gentle, well-absorbed, no laxative effect). Threonate is marketed for cognition during sleep but human trials are very limited.
- Migraine prevention: American Headache Society includes magnesium oxide 400-600 mg/day or magnesium citrate 600 mg/day as Level B evidence for migraine prophylaxis (as elemental Mg). Effect typically takes 2-3 months.
- Constipation: Oxide and citrate at higher doses (300-600 mg) provide laxative effect. Glycinate does NOT — wrong form for this use case.
- Muscle cramps: Evidence is mixed. A 2020 Cochrane review found no clear benefit for nocturnal leg cramps. Reasonable to try 200-300 mg elemental Mg as glycinate or citrate; reassess after 4 weeks.
