The decisive distinction
On a U.S. Supplement Facts panel, Magnesium 500 mg (as magnesium glycinate) means 500 mg elemental magnesium for the stated serving. That exceeds the general adult upper limit of 350 mg/day from supplements and medicines. A front-label statement of 500 mg magnesium glycinate might instead describe the compound’s mass; do not assume it delivers 500 mg of the nutrient. Read the panel and serving size. [1]
Why the limit is not the dietary requirement
The magnesium RDA includes food, whereas the 350 mg adult upper limit excludes naturally occurring food magnesium. Supplemental excess can cause diarrhea, nausea and cramps. Impaired kidney function increases the risk of toxicity. The glycinate name does not remove these considerations or establish that a high dose is suitable for sleep or another symptom. [1]
A two-capsule example
Imagine the panel says 200 mg magnesium per two-capsule serving while the front advertises a larger compound amount. One capsule supplies 100 mg elemental magnesium, and two supply 200 mg. This example explains the denominator; it does not recommend that dose. Include magnesium-containing antacids and laxatives when reviewing nonfood intake, and discuss prescribed replacement separately. [1]
| Hypothetical statement | Interpretation |
|---|---|
| Magnesium 500 mg per serving | 500 mg elemental; above adult nonfoodUL |
| Magnesium 200 mg per two capsules | 100 mg elemental per capsule |
| 500 mg whole compound only | Elemental amount unresolved |
Sources for this article
- Magnesium - Health Professional Fact Sheet
Source consulted: 2026-09-20. This is a reference resource, not a claim that we conducted the studies or tested a product.