Serum vs RBC magnesium - how should I check for magnesium deficiency?

Low mood, fatigue, muscle cramps – if this sounds familiar, you could be one of the 20% of people in the UK with insufficient magnesium levels.

Magnesium plays a role in over 300 enzymatic processes in the body, yet many people with a magnesium deficiency go undiagnosed.

So, what causes low magnesium levels? And are magnesium blood tests accurate?

This article explores:

• Why do we need magnesium?
• How do I know if I have magnesium deficiency?
• How can I test my magnesium level?
• What’s a normal magnesium serum level?
• How can I increase my magnesium levels?

Why do we need magnesium?
 

Magnesium is a mineral involved in almost all of the body’s major functions. So it’s needed in relatively large quantities, compared to other nutrients.

Magnesium is essential for:

• Healthy bones
• DNA and energy production
• Nerve and muscle function
• Regulation of blood pressure and blood sugar levels

There are also many studies suggesting health benefits of magnesium. 
These may include:

• Supporting good sleep [1]
• Improved cognitive performance [2]
• Mood regulation and reduced depression and anxiety [3]
• Fighting migraines [4]
• Reducing premenstrual syndrome (PMS) symptoms [5]

How do I know if I have a magnesium deficiency?
 

Despite its importance, magnesium deficiency (hypomagnesemia) can be difficult to diagnose as the symptoms aren’t unique to magnesium deficiency. Additionally, the causes of magnesium deficiency are often linked to other conditions.

Symptoms of magnesium deficiency

Signs and symptoms of magnesium deficiency vary. 
The most common are:

• 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.

Causes of magnesium deficiency

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, such as water tablets (furosemide), antibiotics (gentamicin), and proton pump inhibitors (omeprazole)

How can I test my magnesium level?
 

So, you think you might have a magnesium deficiency – how can you go about testing to find out?
There are a few different ways to check your magnesium levels, some more convenient than others.

1. Magnesium blood tests

The most convenient and cost-effective option is of course, magnesium blood testing. Two most common types of blood test are serum and red blood cell (RBC) tests.

Both involve taking a small sample of blood and sending it to a lab for analysis.

Serum magnesium vs. RBC magnesium

• 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. 
• 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. But in general, serum magnesium tests are less expensive and more popular.

Best for: Initial investigation of magnesium deficiencies

2. Urine magnesium test

As your magnesium levels fluctuate depending on what you eat and drink, a urine test can show the amount of magnesium your body is excreting (which can range between 5-70%).

The drawback with a magnesium urine test is over 24 hours you must collect your urine, so it’s not as convenient as a home blood test.

Best for: Detecting magnesium deficiency due to kidney failure

3. Hair mineral analysis

Did you know your hair can provide insights to your health history?
Each hair grows from a follicle. And each hair follicle has tiny little blood vessels feeding into it, nourishing the follicle with nutrients and encouraging growth.

The theory is by analysing the hair composition, you can determine a person’s nutritional intake.

Best for: Although this is a common technique used in forensic science, it works much better for toxicology and drug detection than for detecting nutritional deficiencies.

4. Tissue or muscle biopsy

Around 53% of magnesium is stored in your bones, 27% in muscle, and 19% in other organs. Just 1% of magnesium is present in your bloodstream. To investigate a deficiency in your bones or tissues, a biopsy is necessary.

Best for: A muscle or tissue biopsy can give a definitive diagnosis of magnesium deficiency. But it’s extremely unlikely that you would be offered this, as it’s costly, invasive, and impractical.

 

There are lots of ways to check your magnesium levels.

But the most convenient way you can test your magnesium levels at home is with a blood test such as our Magnesium (Serum) Blood Test.

If you feel like a more comprehensive health check is in order, our Optimal Health Blood Test might be just the thing you need.

What is a normal serum magnesium level?
 

References ranges can vary between laboratories, but the accepted normal value is between 0.7 and 1 mmol/L.

Although magnesium levels can fluctuate in women due to periods, pregnancy, and menopause, this is still the accepted normal magnesium level for women [6].

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. 

If you need help understanding your blood results, check out our helpful blog.

While a step towards getting better health insights, blood tests don’t always reflect total magnesium content in the body. A deficiency can sometimes be masked by a normal result, especially if it’s on the low end of normal. If your results are within range, but you still experience symptoms of magnesium deficiency – reach out to your GP.

How can I increase my magnesium levels?
 

Providing your low magnesium levels aren’t caused by an underlying health condition, you can increase your magnesium levels with some simple lifestyle adjustments.

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. Find out how to increase your vitamin D levels.
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.
6. Consider supplementation – most people can get the magnesium they need from diet, but if this is something you struggle with supplements may be for you. Our blog can help you decide which magnesium supplement is best for you. Supplements with less than 400 mg are recommended, but if you have kidney problems you should consult with your doctor first.

 

---

 

References