You CAN have too much magnesium.
More Info: Though it is very rare to get too much magnesium from food sources, you can get too much magnesium if you are taking supplements, milk of magnesia, or Epsom salts.
How Much Magnesium Is Too Much?
According to the National Institutes for Health Office of Dietary Supplements, the upper limit (UL) for magnesium supplementation for a healthy adult, both male and female) is 350 milligrams per day. Your physician may prescribe higher does to treat specific medical problems.
There is not set upper limit for dietary intake of magnesium, only for supplementation.
What Are the Symptoms of a Magnesium Overdose?
The initial symptoms of a magnesium overdose can include an upset stomach and diarrhea. Additional symptoms can include nausea, vomiting, a slowed heart rate, a drop in blood pressure, confusion, and cardiac arrhythmias.
A magnesium overdose can cause serious health risks including respiratory paralysis, cardiac arrest, coma, and death. Ingesting too much magnesium is especially problematic for anyone with kidney problems.