CWeak evidence, or evidence againstMineral
The short answer
Sold hard for sleep, cramps and anxiety on evidence that is thin. No authorised EU sleep claim exists for it. Deficiency is real and worth correcting; the rest is marketing.
Who this is actually for
People with a diagnosed deficiency, on long-term proton pump inhibitors or diuretics, or with poorly controlled diabetes.
What it is legally allowed to claim
Quoted from the EU register of authorised health claims, Regulation (EU) 432/2012. A product may only make these claims if it supplies enough of the nutrient to qualify.
- Magnesium contributes to normal energy-yielding metabolism
- Magnesium contributes to normal muscle function
How much is too much
No EFSA upper level for food magnesium. Supplemental doses above roughly 250 milligrams commonly cause diarrhoea.
Cautions and interactions
Magnesium oxide is poorly absorbed and mostly a laxative. Reduce the dose in kidney impairment. Separate from antibiotics and levothyroxine.
Ask a pharmacist before you start anything. Interactions with prescribed medicines are the most common way supplements cause harm, and they are easy to check. Bring the actual packet, or a photo of the ingredients panel, because doses and forms vary enormously between products. Nothing here is a substitute for advice about your own situation.