All you need to know about magnesium

Find out all you need to know about the underdog of macrominerals – magnesium.

Magnesium is involved in over 300 processes in the body. But, despite its importance, many people don’t consider it when looking at their health. 

In this blog, we discuss: 

What is magnesium?

Magnesium is a macromineral which is involved in almost all the body’s major processes, and therefore is needed by the body in relatively large amounts, compared to other nutrients. 

Magnesium is essential for: 

  • Maintaining healthy bones 
  • Energy production  
  • Nerve and muscle function 
  • Blood pressure regulation 
  • Blood sugar regulation  
  • Aiding in production of DNA  

Magnesium may also have a role in insulin secretion. And studies show that low levels of magnesium are associated with diabetes. 

How much magnesium do you need?

The NHS recommends 300 mg of magnesium a day for men (19-64 years) and 270 mg a day for women (19-64 years) [1].  

What are the symptoms of low magnesium?

Because the symptoms of low magnesium are not unique to a magnesium deficiency, low magnesium levels can be very difficult to pinpoint and diagnose. 

Signs and symptoms of magnesium deficiency include: 

  • Muscle cramps 
  • Fatigue 
  • Eye twitches 
  • Irregular heartbeat 
  • High blood pressure 
  • Problems sleeping 
  • Low mood 

Many people with magnesium deficiency go undiagnosed for a long while as severe symptoms don’t often appear until levels are extremely low. 

What causes a low magnesium level?

A low magnesium level (also known as hypomagnesemia) can be caused by several different factors. 

Causes of low magnesium include: 

  • Inadequate dietary intake  
  • Kidney disorders  
  • Chronic alcohol abuse  
  • Diabetes  
  • High levels of calcium in the blood (hypercalcemia) 
  • Overactive parathyroid glands  
  • Gut autoimmune diseases – such as Crohn’s disease or Colitis 
  • Certain medications  

The most common cause of a low magnesium level is inadequate dietary intake, so it’s important to ensure you are getting enough magnesium in your diet. You can do this by eating foods such as wholegrains, lentils, and nuts (such as almonds and cashews).  

What causes a raised magnesium level?

A high magnesium level (also known as hypermagnesemia) is rare, but can be caused by things such as: 

  • Kidney dysfunction  
  • Excessive magnesium intake (usually from supplements) 
  • Adrenal insufficiency (caused by things such as Addison’s disease)  
  • Severe dehydration  

Though rare, it’s more likely for you to have a raised magnesium level if you have an underlying health condition. Excessive magnesium can be dangerous, so it is important that if you supplement, you take the recommended amount and no more. 

What is a normal serum magnesium level?

The most common way of measuring magnesium levels is with a blood test (serum magnesium). Some laboratories define a normal value between 0.7 and 1 mmol/L, but reference ranges vary significantly [2].  

Studies have shown that magnesium levels at the lower end of normal may actually mask a true deficiency, known as chronic latent magnesium deficiency. For this reason, some labs suggest a lower cut-off 0.85 mmol/L. 

You can read more about how laboratories set their ranges in our blog; understanding your blood results.  

Why should I test my magnesium level?

As low magnesium levels often go unrecognised, many people suffer from the symptoms of a deficiency when something as simple as increasing their dietary intake of magnesium could really help them feel better. 

How can I test my magnesium level?

There are lots of ways of measuring magnesium levels in the body.  

The easiest and most convenient way is with a blood test. You can test your levels at home with our Magnesium (Serum) Blood Test.  

Unfortunately, blood tests can't accurately assess the body's total magnesium content. So, a magnesium deficiency can sometimes be masked by a normal blood test result, especially if your result is low-normal. 

Magnesium RBC vs magnesium serum

Most magnesium in the body is distributed in the bone (60%) and tissues (40%). Only a very small proportion (less than 1%) is present in blood. For this reason, blood tests can only give a proxy measure of total body magnesium, but not a direct measurement.  

There are two different types of blood tests for measuring magnesium levels:  

  • Serum magnesium test - this measures the concentration of magnesium in the liquid portion of your blood. It's the most common test for assessing magnesium levels.  
  • Red blood cell (RBC) magnesium test - this measures the concentration of magnesium in the red blood cells.  

The concentration of magnesium is higher in red blood cells than in serum, so RBC magnesium is sometimes said to be a more sensitive measure.  
Although RBC magnesium may be a better measure for sudden drops in magnesium than serum, either test could miss a long-term magnesium deficiency (where levels may be low within bone and tissues but appear normal in a blood test).  

Can magnesium help you sleep?

Magnesium could promote better sleep and improve sleep quality, as it is involved in several biochemical processes, including some promoting relaxation.  

Magnesium also helps to regulate gamma-aminobutyric acid (GABA), which has calming and sedative effects. And it helps in the production of melatonin (a hormone that helps to regulate the sleep-wake cycle). 

Though magnesium can potentially help you get better sleep, it is not a guaranteed solution for everyone.  

If you aren’t getting great quality sleep, give our top tips for a better night’s sleep a try.  

How can I increase my magnesium level?

You can increase your magnesium level through simple lifestyle and dietary changes.  

Dietary and lifestyle changes that can increase your magnesium level include: 

  1. Adjusting your diet – try to incorporate magnesium-rich foods into your meals. Foods such as nuts, seeds, legumes, wholegrains, and fish are all good sources.  
  2. Reduce alcohol and caffeine intake – excessive alcohol and caffeine consumption has been associated with the depletion of magnesium. 
  3. Manage stress – chronic stress has been associated with the depletion of magnesium levels. Struggling to de-stress? Try our unconventional ways to reduce stress.  
  4. Get enough vitamin D – vitamin D aids in the absorption and utilisation of magnesium in the body.  
  5. Review medication – some medications (such as certain diuretics and protein pump inhibitors) may affect magnesium absorption or increase magnesium excretion. If you suspect your medication could be contributing to low magnesium levels, speak with your doctor.  

Should I take a magnesium supplement?

Whether a supplement is right for you will depend on several factors, including your magnesium levels and the reason they're low. Most people can get the magnesium they need from their diet, but some may benefit from supplements, especially if they have a condition that reduces their levels.  

Supplements containing less than 400mg are unlikely to cause harm [1], but if you have kidney problems, it's important to discuss any supplements with your doctor first. 


  1. Vitamins and minerals (no date) NHS choices. Available at: (Accessed: 13 July 2023).
  2. Workinger, J., Doyle, Robert. and Bortz, J. (2018) ‘Challenges in the diagnosis of magnesium status’, Nutrients, 10(9), p. 1202. doi:10.3390/nu10091202.

Related tests

Magnesium (serum) Blood Test

A test to measure magnesium levels in the blood serum

  • Results estimated in 3 working days
  • 1 biomarkers