Do not simply continue an intolerable magnesium supplement to get used to it. At the same time, diarrhea does not automatically mean severe magnesium poisoning. Amount, route of use, kidney function and other products determine how the situation should be assessed.
Distinguish digestive symptoms from hypermagnesemia
Oral magnesium supplements can cause diarrhea, nausea and abdominal cramps. Markedly elevated blood magnesium, or hypermagnesemia, can instead involve pronounced weakness, low blood pressure, breathing problems and abnormal heart rhythms, among other signs. Risk increases particularly when kidney excretion is impaired. [1]
| Information | What to record | Why it matters |
|---|---|---|
| Product | Name and complete label | The compound and additional ingredients become clear |
| Elemental magnesium | Milligrams per unit and number taken | The compound's weight is not the same measurement |
| Other sources | Other supplements and magnesium-containing medicines | Individual packages do not show the combined total |
| Personal circumstances | Symptoms, time of intake and known kidney problems | An identical amount may have different significance |
What the BfR recommendation of 250 milligrams means
Germany's Federal Institute for Risk Assessment recommends no more than 250 milligrams of magnesium per recommended daily supplement serving, divided into at least two intakes for better digestive tolerance. This guidance is neither a personal intake target nor a threshold at which acute poisoning definitely begins. Magnesium naturally present in food is not assessed in the same way as the additional supplement amount. [2]
Our calculation example: two capsules each providing 100 milligrams of elemental magnesium plus another product providing 150 milligrams yield 350 milligrams from preparations. This is not dosing advice. It simply illustrates how different product names can conceal overlapping intake.
Medicines belong on the list too
Some laxatives and antacids contain magnesium. Interactions with other medicines also need consideration. Tell your practice or pharmacist about more than supplements alone. With kidney disease, additional intake should be assessed individually beforehand. [1]
If new diarrhea develops after starting a self-selected supplement, pausing and obtaining advice is more appropriate than increasing the dose again. Discuss prescribed treatments with the treating practice rather than changing them without explanation.
Respond appropriately to a suspected overdose
After an accidentally much-too-large or unclear intake, particularly by a child, promptly contact a poison information service or medical help and keep the package available. Do not wait for a particular symptom list. With breathing difficulty, collapse or severe heart-related symptoms, call emergency services immediately; in the EU, call 112. Do not induce vomiting or use homemade antidotes.
Frequently asked questions
Does diarrhea already mean severe magnesium poisoning?
Not automatically. Persistent or severe symptoms still require assessment.
Does all the weight of magnesium citrate count as magnesium?
No. The declared elemental amount is what matters for intake.
Are 250 milligrams an acute poisoning threshold?
No. The BfR recommendation concerns additional daily supplementation and tolerance.
Who needs particular caution?
People with impaired kidney function and those using several magnesium-containing products.
Further reading
Comparing magnesium forms and elemental amounts and considering timing and medicines.
Sources
Editorially updated: September 28, 2026. Not an individual poisoning assessment or treatment.
