Hypermagnesemia: Causes, Symptoms & Treatment

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  • 0:01 Magnesium Must Be in Balance
  • 1:08 Hypermagnesemia
  • 2:10 Causes & Symptoms
  • 3:20 Treatments
  • 3:55 Lesson Summary
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Lesson Transcript
Instructor: Catherine Konopka

Catherine has taught various college biology courses for 5 years at both 2-year and 4-year institutions. She has a Ph.D. in cell and molecular biology.

Magnesium is a mineral that you just don't hear much about, but it is vital to our health. In this lesson, you will learn about the roles of magnesium in our body as well as the causes and consequences of having too much magnesium.

Magnesium Must Be in Balance

Magnesium isn't often talked about. Typically, sodium and calcium get all the attention in health and medical forums. But without magnesium, you would not be watching this right now. Magnesium is a cofactor for over 300 enzymes. In other words, without magnesium, 300 different kinds of enzymes in your body would not work…period! For instance, some of these enzymes are involved in protein and DNA synthesis. So without magnesium, your cells cannot divide and tissues cannot be repaired.

However, having too much magnesium in the body can also cause havoc as well. Magnesium ions (Mg2+) can block the channels that transport calcium ions (Ca2+) during muscle contraction. While imbalances in magnesium affect all cells, neurons and muscle cells are the most critical.

Magnesium is a little like electricity. It's something that we use every day and probably don't really notice it. But if we don't have enough (like when we lose power to our house) or there is too much (like when a power surge fries the electronics in our house), it disrupts our daily lives.


We have a lot of magnesium in our body, but most of it is inside our cells or stored in our bones. Less than 1% of our body's magnesium is circulating in our serum, the liquid portion of our blood; and almost half of that is bound to blood proteins. The concentration of free (unbound) magnesium in our blood ranges from 1.5 to 2.5 mg/dL. Magnesium must be kept within its normal range just like all other electrolytes, or ions, in the body.

Hypermagnesemia is abnormally high magnesium levels in the extracellular fluid, or the fluid outside the cells. This is in contrast to hypomagnesemia , which is abnormally low levels of magnesium. Hypermagnesemia occurs when serum values are greater than 5 mg/dL. To remember the difference between the prefixes, for 'hyper-' you can visualize a hyper child that has had too much sugar. Its opposite, 'hypo-', meaning too little, ends in an 'o' which looks a lot like a zero (0).

Causes and Symptoms

Hypermagnesemia is very uncommon because, generally, our kidneys do a very good job at eliminating excess magnesium. Thus, the most prevalent cause of hypermagnesemia is renal failure, or when kidneys don't work properly. Some antacids, such as Maalox, Rolaids, and Mylanta, contain magnesium, and taking these in excess could also lead to hypermagnesemia. However, typically there must be an underlying kidney condition for hypermagnesemia to develop.

Most of the symptoms of hypermagnesemia are caused by excess Mg2+ blocking calcium channels in all smooth, skeletal, and/or cardiac muscle cells. In addition, the severity of symptoms is correlated with magnesium levels. In other words, the higher your serum magnesium levels, the worse the symptoms. The most common symptoms are listed here:

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