Magnesium deficiency: symptoms and when to test

What does your body need magnesium for?

Magnesium is involved in over three hundred enzyme reactions. It plays a role in, among other things:

• The contraction and relaxation of muscles
• The transmission of signals between nerve cells
• The production of energy in every cell of the body
• Bone formation
• A steady heart rhythm
• The regulation of blood sugar

Magnesium works closely with other minerals such as calcium and potassium: when one shifts, the other often moves with it. It is precisely this broad role that allows a deficiency to show itself in many different ways, and precisely why it is so easily missed.

Which complaints can point to a magnesium deficiency?

The muscles and nerves usually speak up first. Think of:

• Muscle cramps, often at night in the calves or feet
• A twitching or pulling eyelid
• Muscle tremors elsewhere in the body
• Tingling
• A tense and stiff feeling in the muscles

These complaints fit disturbed nerve signalling, exactly the territory where magnesium is active. Many people know the twitching eyelid as a harmless sign of stress or lack of sleep, and it usually is. If it persists for weeks or comes together with other muscle complaints, it is a signal to take seriously.

There are also more general complaints:

• Persistent fatigue and listlessness
• Difficulty falling asleep or restless sleep
• Irritability
• Headaches

With a larger deficiency, palpitations or an irregular feeling in the chest can occur; always take those complaints seriously and discuss them with your GP.

All of these signals are non-specific. They can just as easily fit stress, lack of sleep, an iron deficiency or an underactive thyroid. From the complaints alone you cannot tell whether magnesium is the problem.

Causes: taking in too little or losing too much

Magnesium is mainly found in wholegrain products, nuts, seeds, legumes, green leafy vegetables and dark chocolate. Anyone who eats a lot of processed food and little from these food groups slowly builds up a tight intake. Strict dieting or a one-sided eating pattern can also limit the supply. A deficiency rarely appears overnight; it creeps in over months or years.

Medication is a second route, and one that is often missed. These factors increase the chance of a deficiency:

• Long-term use of acid-reducing medication, which can reduce absorption in the gut
• Diuretics for high blood pressure or heart conditions, which increase excretion through the kidneys
• Excessive alcohol use
• Bowel conditions with reduced absorption, such as coeliac disease or Crohn's disease
• Poorly controlled diabetes

If you use one of these medicines long term and recognise the complaints above, that is a reason to be more alert than average.

Finally, you lose magnesium through sweat. Anyone who trains intensively, especially in warm weather or during long endurance sessions, loses more and also uses more for energy production and muscle recovery.

For most recreational athletes this is easily covered by a normal diet. With a high training load combined with cramps or stalling recovery, a measurement can certainly provide insight.

Why blood magnesium only tells part of the story

An honest caveat is in order here. Only around one per cent of all the magnesium in your body circulates in the blood. The rest is stored in the bones and in the cells.

The body also keeps the blood value as stable as possible, if necessary by drawing on that reserve. A clearly lowered blood value is therefore a meaningful signal. But a value within the laboratory's range does not fully rule out a reserve that is running low.

Does that make testing pointless? No. A measurement:

• Makes a pronounced deficiency visible
• Provides a starting point for tracking the effect of changes in diet or medication
• Helps weigh other explanations for your complaints

Our doctors always assess your value in the context of your complaints, diet, medication and exercise habits, and indicate when a conversation with your GP is sensible. The result is a building block, not the whole building.

When does testing make sense?

A measurement is especially worth considering when complaints and risk factors come together. For example: you have recurring muscle cramps or a twitching eyelid, and you use acid-reducing medication or a diuretic long term. Or you train intensively, eat few wholegrains, nuts and green vegetables, and feel persistently tired.

If you already take a magnesium supplement, bear in mind that this influences the measured value. If you want to know your baseline, ideally test before you start a supplement, or discuss with a doctor how to read the result in your situation.

Prefer a broader picture?

Because the complaints of a magnesium deficiency strongly overlap with those of other deficiencies, many people opt for a broader measurement in a single blood draw. The Vitamins, minerals and electrolytes package combines magnesium with the most important vitamins, minerals and electrolytes. That way you see where you stand in one go, instead of ticking off deficiency after deficiency with separate tests.

At Bloodworks you arrange a magnesium test without a referral. You have your blood drawn at one of over 750 affiliated collection points across the Netherlands, a doctor reviews your result and you receive a clear PDF report, typically within 2 working days. No subscription, no hidden costs.