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How Long Does Magnesium Stay in Your Body?

4 min read
How long does magnesium stay in your body

How Long Does Magnesium Stay in Your Body?

4 min read

Medically reviewed by

Let’s start at the beginning.

Magnesium is an essential mineral. 

When we say essential, we mean exactly that – it’s responsible for over 300 enzymatic reactions in our bodies. 

Because of this, a shortage of magnesium takes a huge toll on the body: deficiencies can cause or worsen all kinds of symptoms and health conditions, from anxiety to PCOS.

Most of our magnesium is stored in our bones – 60%, to be precise. The remainder is found in soft tissue, primarily in muscle. 

But if magnesium is primarily stored in our bones, does this mean the mineral lingers in our system for a long time? How much time does it take to expel excess magnesium from our bodies? And does this affect how long magnesium takes to work?

In this article, we explore the following:

  • How long does magnesium stay in your body?
  • Does magnesium build up in your system?
  • How does magnesium leave your body?

In this guide:

How long does magnesium stay in your body?

How long do magnesium supplements actually remain in our bodies? 

Well, most magnesium will stay in your system for anywhere between 12 and 48 hours. Within hours of taking a magnesium supplement, most people will have excreted around. 70% of that magnesium content.

Magnesium levels will slowly build up over time, but it’s not a quick-fix type supplement – unfortunately, you cannot expect to take one dose and reap the rewards immediately.

What factors affect how long magnesium stays in your system?

Many factors influence how long magnesium stays in your system. Let’s take a look. 

The form of magnesium you take

There are a number of different forms of magnesium. 

Most are compounds created to increase bioavailability or target certain areas or processes. 

As different forms of magnesium can activate and impact different parts of the body – and are different compounds with magnesium bonded to various other minerals – it makes sense that the type of magnesium you consume might have a (small) impact on how magnesium stays in your system.

Take magnesium L-threonate, for example. This form of magnesium is unique in its ability to cross the blood-brain barrier readily – meaning all of the magnesium’s neuroprotective-associated benefits are released and can take effect differently than other types of magnesium.

The ingestion method

Ingesting magnesium orally is different from applying magnesium topically (to the skin) or absorbing it transdermally.

The reason for this is simple.

When you take magnesium orally, it is absorbed through the digestive system, while applying it to the skin means it will be absorbed through the skin receptors. 

Naturally, this leads to different amounts of magnesium being absorbed, and how long magnesium stays in your system will also be different. 

A study published by the  European Journal for Nutraceutical Research suggests that transdermal application of magnesium may be more effective in raising magnesium levels over a short time period. 

However, there’s little empirical evidence that details whether applying to this skin (transdermally) will cause magnesium to stay in the body longer. 

Another common method of using magnesium (especially those using magnesium for muscle pain or cramps)  is bathing in Epsom Salt, also known as magnesium sulfate. 

However, there is no evidence that magnesium is actually ingested into the body. So while it may be a relaxing ritual, it’s not the best way to build up magnesium in your system.

Does magnesium build up in your system?
The ingestion method impacts how much magnesium is absorbed and how long it is stored in the body.

The level of magnesium deficiency

If you’re ingesting magnesium to correct a severe deficiency, the way your body processes the mineral may be impacted. If you’re deficient in magnesium, your body will try to hold onto more of the mineral, and for longer, in order to relieve that deficiency. 

Any medical conditions you might have

People living with chronic illnesses or digestion issues may process and excrete magnesium at a different rate than the norm. 

Note there isn’t one singular way for this to manifest: a health condition may make your body hold on to magnesium for longer, or vice versa.

Does magnesium build up in your system?

So, does your body store magnesium?

Yes, magnesium builds up in your system over time. 

This is why you need to consistently take magnesium (at product-specified dosages, within approved guidelines) in order to correct a deficiency. 

Large doses of magnesium – i.e. significant overdoses – may cause too much magnesium to build up in the body. 

While magnesium is generally safe, overdoses may result in serious side effects. These include low blood pressure, confusion, and slowed breathing. 

Significant overdoses of magnesium can also be fatal for this reason. NHS guidelines state that ingesting 400mg of magnesium (or less) per day is “unlikely to do you any harm”.

Does the body store magnesium?
Taking magnesium daily and consistently is the best way to increase your magnesium levels.

Does the body flush out excess magnesium?

Now that we know understand how the body stores magnesium, the final question is what happens to excess magnesium? How does magnesium leave the body

Well, the body naturally attempts to flush out excess magnesium

This is what leads to some of the more minor side effects of taking too much magnesium – such as vomiting. It’s the body’s natural way of trying to get rid of the magnesium it doesn’t need and cannot use. 

As well as these side effects being unpleasant, this is another reason to avoid taking more magnesium than prescribed or recommended – excess doses simply won’t benefit you!

Do note that extra magnesium from food is safe because, in this case, the kidneys go to work and eliminate excess amounts of magnesium through urine.

The verdict

As is often the case in the world of supplements and health, there isn’t a one-size-fits-all answer that applies to the length of time magnesium stays in your body. 

While the answer tends to be somewhere between 12 and 48 hours, supplements vary in their absorption profile. 

The type of magnesium you take, the way you consume it, the reason you are taking it, and the presence of any health condition will have a varying impact on your body’s magnesium absorption rate. 

The one thing, though, is certain. Magnesium must be taken regularly and at the appropriate dosage for anyone to receive its benefits. 

Like most things in life, consistency is key!