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About 50% of Americans get less magnesium than the estimated average requirement. Researchers report this in a review of magnesium in the blood.[1]
On this page, you can read what magnesium is, what the guidelines say about a value that is too low or too high, what affects your value and which other values are best read alongside it.
Also known as: Mg, serum magnesium. At the lab: MG.
Magnesium is a mineral. Your body absorbs it at the end of the small intestine. Your body absorbs 20 to 60% of the magnesium in your food. The more magnesium in your food, the lower that percentage.[2]
Only 1% of the magnesium in your body is in your blood. About half is in your bones and teeth. The rest is in your cells, muscles, organs and nerve tissue.[2]
Magnesium helps your muscles work properly. It makes sure a large number of enzymes work properly. Enzymes are substances that make processes in your body possible. Magnesium also plays a part in how your cells produce energy.[2]
If you are deficient, you may feel listless or tired or get muscle cramps. In extreme cases, your heart rhythm can be disturbed. It is hard to tell whether a deficiency is the cause of symptoms like these.[2]
In studies in animals and humans, researchers see a magnesium deficiency go hand in hand with several long-term conditions. These include conditions of the heart and blood vessels, of the bones and of the metabolism, and conditions involving inflammation.[1]
The lab uses a reference value for magnesium of 0.71 to 0.98 mmol/l. The lab calls a level between those limits normal.[3]
| Value | What it can mean | Who it is for |
|---|---|---|
| Below 0.75 mmol/l[1] | Below the current reference interval; may point to a deficiency | The population the interval is based on (NHANES I, 1974) |
| 0.75 to 0.95 mmol/l[1] | Within the current reference interval; a hidden deficiency can still exist | The population the interval is based on (NHANES I, 1974) |
| Above 0.95 mmol/l[1] | Above the current reference interval | The population the interval is based on (NHANES I, 1974) |
Source: Costello and colleagues, Adv Nutr. The current reference interval for serum magnesium, derived from the spread of values in a general population rather than from health outcomes.[1]
A low level can point to a magnesium deficiency. A deficiency like this can develop if your kidneys or gut are not working well. Even so, your blood level is not a good measure of a deficiency, because there is only a little magnesium in your blood. Researchers write that a hidden deficiency can also exist when your level is within the current interval.[2, 1]
A level above the interval in the table is higher than what was measured in the general population. On intake, the Voedingscentrum writes that you only take in too much magnesium through supplements, magnesium salts or mineral water high in magnesium.[2, 1]
BioProfile is working on its own zones for each value, from risk to optimal. A doctor reviews those zones before they appear in your result.
Magnesium is found in wholemeal bread and other wholegrain products, vegetables, nuts, milk and dairy products, and meat. Water can also contribute. A 25 gram handful of unsalted nuts contains 54 milligrams of magnesium.[2]
You can only get too much magnesium from supplements, magnesium salts or mineral water that is high in magnesium. If you take in more than 250 milligrams a day on top of your food, gut problems such as diarrhoea can occur.[2]
Your gut absorbs magnesium from your food. If your kidneys or gut are not working well, a magnesium deficiency can develop.[2]
Magnesium is included in all five packages, from BioProfile 31 to BioProfile 150.[4]
The BioProfile editorial team wrote this page on 5 October 2026 from the sources below, which we read on 5 October 2026. Every number on this page appears in one of those sources, with that source's number next to it. An expert has yet to review this page; once that review is done, the expert's name and the date of the review will appear at the top. This page explains and does not diagnose. Discuss a value outside the normal range with your GP.
