“The first signs are usually lack of appetite, nausea, tiredness or weakness. More severe depletion can cause muscle cramps, twitching, tingling or numbness. Severe deficiencies may lead to seizures or irregular beating of the heart.”
These symptoms are real warning signs, but they are not a magnesium test. Fatigue, for example, can also occur with anaemia, thyroid problems, poor sleep and several other conditions. According to MedlinePlus, the US National Library of Medicine, very low magnesium can also occur alongside low calcium or potassium.
An irregular heartbeat with fainting, or a seizure, needs urgent medical attention. Food or supplements should not be used as a substitute for emergency care.