Magnesium is a mineral that is essential for energy production, muscle function, nerve function and maintenance of strong bones. The body gets magnesium through the diet, and it is absorbed by the small intestine and large intestine. Magnesium is stored in the skeleton, cells and tissues. The magnesium concentration in the blood is normally just approx. 1 per cent of the body's total magnesium, which makes it difficult to measure the total magnesium level correctly from just blood samples. That said, however, testing for magnesium in blood samples is still useful as a way of evaluating the magnesium status of a person; in order to find out whether someone has a magnesium deficiency, for example.
A range of different foods contain small amounts of magnesium, particularly green vegetables such as spinach, as well as wholegrain and nuts. Foods containing dietary fibre are usually good sources of magnesium, too. The body maintains its magnesium level by regulating how much it absorbs and how much it excretes or retains in the kidneys.
Magnesium deficiencies (hypomagnesaemia) can be seen in undernourished individuals, people suffering from diseases causing malabsorption and people suffering excess loss of magnesium via the kidneys. Excess magnesium (hypermagnesaemia) can be seen in people taking supplements containing magnesium and people with reduced renal function.
People with a mild to moderate magnesium deficiency may have one or more non-specific symptoms. Prolonged or severe deficiencies may cause nausea, loss of appetite, fatigue, confusion, muscle cramps, spasms, changes in heart rate and numbness or tingling. They may also affect the calcium metabolism and worsen calcium deficiencies. Symptoms of excess magnesium may resemble the symptoms of magnesium deficiency, such as nausea, muscle weakness, loss of appetite and irregular heart rate.
A magnesium sample is used to measure the level of magnesium in the blood (or, sometimes, in the urine). Magnesium is an important component in the body's metabolism, and a deficiency in this mineral has a part to play in many disorders. Abnormal levels of magnesium are most common in conditions or disorders causing reduced or excessive metabolism of magnesium via the kidneys, or causing impaired absorption in the intestines. Magnesium levels can be checked as part of an assessment of serious kidney problems and/or uncontrolled diabetes, and can assist in the diagnosis of gastrointestinal disorders.
As a low magnesium level may lead to ongoing low calcium and potassium levels over time, it can be checked in order to diagnose problems with calcium, potassium and phosphorus. Magnesium levels can be measured frequently in order to monitor the results of oral or intravenous magnesium supplements.
High levels are seen in patients with chronic renal insufficiency, the use of antacids containing magnesium (milk-alkali syndrome), hypothyroidism, and sometimes hyperparathyroidism.
Osteoporosis, headaches (migraines), spasms, digestive problems, stunted growth, nerve problems, depression, functional cardiac disorders, kidney problems, sleep problems (such as waking up too often and too early), memory problems, asthma, constipation, etc. are all potential symptoms of magnesium deficiency. Deficiencies are also linked with metabolic syndrome: high blood pressure, cardiovascular disease, high levels of bad LDL cholesterol, diabetes and excess weight due to impaired insulin sensitivity.